ALBERT

Notizen: The sequence of palaeosols and intervening loess units in North China provides a sensitive, detailed record of global climatic changes over the last 2.5 million years. Although various depth functions of properties, notably magnetic susceptibility, have been successfully correlated with oxygen isotope records from the deep oceans, there is a need to improve our understanding of such proxy measures used to infer past climates. For instance, pedologists are well placed to address some of the uncertainties surrounding the origin of the enhanced magnetic susceptibility (MS) values in palaeosols, and the reconstruction of palaeoprecipitation patterns by application of MS climofunctions. There are few published field descriptions of the soils buried in the loess, and those available often fail to recognize their accretionary and polycyclic nature. Field and micromorphological techniques enable finely detailed reconstructions of the pedogenic and sedimentary signals held in both palaeosol and loess units. Micromorphology, in particular, has provided detailed environmental information on successive pedosedimentary developmental stages at several sites in the Loess Plateau of China. This approach re-focuses attention on the local, climatically sensitive mechanisms that underpin the inferred global patterns of climate.

Notizen: The hierarchical nature of soil structure is examined by measuring the physical properties of a range of aggregate sizes obtained using repetitive fracture. Fractals are used to assess the change with aggregate size of the specific volume, the proportion of pre-existing cracks which link to form the aggregate failure surface, and the aggregate failure stress. The pore size distribution, evaluated using mercury porosimetry and the application of the box counting algorithm to thin sections and thick sections, is also used to obtain a fractal dimension, D. Our results show that D depends upon the measurement approach for mass fractal scaling. This finding may limit the application of fractals to predict the scaling behaviour of soil physical properties.

Notizen: Laboratory experiments were conducted on artificially weathered mudrocks (i) to measure changes in the roughness following cycles of freezing and thawing, and (ii) to find a simple method to calculate roughness as an alternative method to standard deviation methods. Surface roughness was measured with a laser profile meter and the resulting measurements were analysed by a program written for the purpose. The analysis is based on calculation of the fractal dimension of the profile for selected ranges of scale, and estimated by linear regression. Results revealed distinct micro- and macrotopographic variations of artificially weathered surface samples.

Notizen: La diversité des conditions d’environnement (roche-mère, climat, végétation) prévalant dans un massif de moyenne montagne (Vosges, France) nous a permis d’établir leur rôle dans la manifestation à des degrés divers des propriétés andiques dans le sol. Nous avons examiné un lot de 13 profils sélectionnés à partir de critères lithologiques, climatiques et morphologiques présumés favorables à l’expression de ces propriétés andiques: roches-mères basiques d’origine volcanique ou non, climat montagnard très humide, abondance de matière organique sur une grande profondeur. Ces profils se subdivisent en deux populations. Quatre d’entre eux peuvent être classés comme des Andisols (Alic Fulvudands) alors que les autres ont des propriétés andiques trop faiblement exprimées pour appartenir à cet ordre et doivent être classés comme des Andic Haplumbrepts. Tous ces sols sont dépourvus d’allophanes. Dans cet environnement de moyenne montagne, les facteurs favorables à la manifestation de propriétés andiques sont d’une part, les altitudes et les expositions qui induisent de faibles températures et de fortes précipitations et d’autre part, l’altérabilité des roches-mères déterminée par leur composition chimique et minéralogique. Comme les vieux matériaux volcaniques sur lesquels se développent la plupart des sols étudiés sont pauvres en verres, voire complètement dévitrifiés, les Andisols vosgiens présentent beaucoup d’analogies avec les Andisols non-allophaniques non-volcaniques identifiés dans d’autres environnements. Leurs propriétés andiques sont faiblement exprimées et elles sont dues à la présence de complexes organo-métalliques associée à des teneurs élevées en carbone organique.The diverse environmental conditions (parent material, climate, vegetation) in the Vosges Mountains (France) allow us to investigate their role in the development of soils with varying degrees of andic properties. We studied 13 profiles selected on the basis of lithological, ecological and morphological criteria assumed to favour the formation of andic properties, i.e. basic parent materials of volcanic and other origins, wet montane climates and accumulation of thick layers of organic matter. The profiles belong to two classes: four are Andisols, more precisely Alic Fulvudands, and the others are Andic Haplumbrepts with only weakly expressed andic properties. In this montane environment the factors favouring the andic properties seem to be on the one hand height and exposure inducing cold and humid microclimates, and on the other the chemical and mineralogical composition controlling the weatherability of the soil’s parent materials. For example, the old volcanic rocks on which most of the soils occur are poor in glassy material or are even completely devitrified. Accordingly, Andisols in the Vosges are like those of non-volcanic, non-allophanic Andisols elsewhere in the world: their andic properties are weakly expressed and are caused by organo-metallic complexes associated with their upper organic-rich horizons rather than by allophanes.

Notizen: Increasing cropping intensity (i.e. number of crops per year) of irrigated rice seems to cause an accumulation of phenolic compounds in the soil organic matter (SOM). We have studied the chemical nature of SOM in a broad range of soil types at different sites with long-term double- and triple-crop irrigated rice trials. Accumulation of phenols, as measured by 13C nuclear magnetic resonance spectroscopy, was found in both the mobile humic acid (MHA) and calcium humate (CaHA) fractions at all sites, regardless of soil type, hydrology during the fallow, and with and without inorganic fertilizer or green manures. Although phenols accumulated consistently in MHA and CaHA, the C, N and hydrolysable amino acid concentrations, degree of humification and amounts of MHA and CaHA were significantly altered by crop management, and they varied from site to site. Our results are consistent with the hypothesis that the accumulation of phenols is a characteristic of the anaerobic, or nearly anaerobic, soil conditions that exist at the initial stages of SOM formation in submerged irrigated rice soils. By contrast, other SOM properties are additionally influenced by soil conditions that govern the degradation and turnover of existing SOM. The chemical properties of MHA and CaHA indicated that they are labile, and the quantities of these HA fractions were more sensitive to recent management than were total soil C or N.

Notizen: The effects of levels of application of potassium (K) fertilizer, and its interactions with both nitrogen (N) fertilizer and the growth interval between fertilizer application and harvesting on ryegrass herbage yield and chemical composition, and the fermentation, predicted feeding value, effluent production and dry-matter (DM) recovery of silage were evaluated in a randomized block design experiment. Twenty plots in each of four replicate blocks received either 0, 60, 120, 180 or 240 kg K ha−1, each at either 120 or 168 kg N ha−1. Herbage from the plots was harvested on either 24 May or 8 June and ensiled (6 kg) unwilted, without additive treatment, in laboratory silos. Immediately after harvesting, all plots received 95 kg N ha−1 and were harvested again after a 49-day regrowth interval. From the primary growth, herbage DM yields were 6·31, 6·57, 6·74, 6·93 and 6·93 (s.e. 0·091) t ha−1, herbage K concentrations were 15·5, 16·2, 19·1, 22·4 and 26·1 (s.e. 1·06) g kg−1 DM and herbage ash concentrations were 57, 63, 71, 73 and 76 (s.e. 0·9) g kg−1 DM, and for the primary regrowth herbage DM yields were 2·56, 2·73, 2·83, 2·94 and 2·99 (s.e. 0·056) t ha−1 for the 0, 60, 120, 180 and 240 g K ha−1 treatments respectively. Otherwise, the level of K fertilizer did not alter the chemical composition of the herbage at ensiling. After a 120-day fermentation period the silos were opened and sampled. The level of K fertilization had little effect on silage fermentation and had no effect on estimated intake potential, in vitro DM digestibility (DMD), DM recovery or effluent production. Increasing N fertilizer application increased silage buffering capacity (P 〈 0·05) and the concentrations of crude protein (P 〈 0·001), ammonia N (P 〈 0·01) and effluent volume (P 〈 0·01), and decreased ethanol concentration (P 〈 0·05) and intake potential (P 〈 0·05). Except for the concentrations of lactate and butyrate, delaying the harvesting date deleteriously changed the chemical composition (P 〈 0·001) and decreased intake potential (P 〈 0·001) and DMD (P 〈 0·001) of the silages. It is concluded that, other than for K and ash concentration, increasing the level of K fertilizer application did not alter the chemical composition of herbage from the primary growth or the resultant silage. Also, the level of K fertilizer application did not affect predicted feeding value, DM recovery or effluent production. Herbage yield increased linearly with increased fertilizer K application. Except for acetate and ethanol concentrations, there were no level of K fertilizer application by level of N fertilizer application interactions or level of K fertilizer application by harvest date interactions on silage fermentation or predicted feeding value. Increasing N fertilizer application from 120 to 168 kg ha−1 had a more deleterious effect on silage composition and feeding value than increasing K fertilizer application from 0 to 240 kg ha−1. Delaying harvesting was the most important factor affecting herbage yield and composition, and silage composition and had the most deleterious effect on silage feeding value.

Notizen: Twelve plots were laid down on an existing perennial ryegrass/white clover sward, one plot in each of six replicated blocks receiving 100 kg  N ha−1 (100N) and one plot receiving no N (0N). Biomass, canopy development (stratified cuts and point quadrat records at 2–4-week intervals) and changes in stolon population density were recorded during one 8-week regrowth period (25 July–23 September) to investigate the likely causes of N effects on white clover in mixed swards.Over the period, N fertilizer resulted in an increase of 74% in perennial ryegrass biomass and a reduction of 24% in white clover biomass. There was also a reduction of 44% in stolon growing point density, mainly due to lower density of younger stolon branches. White clover's contribution to the upper three leaf area index (LAI) units (taken as an estimate of the proportion of photosynthetically active radiation (PAR) intercepted) was, on average, 70% at 0N producing 74% of the sward biomass, compared with 46% contribution to interception and 37% contribution to biomass at 100N.While there was no evidence of overtopping, it is concluded that N fertilizer application increased the LAI of perennial ryegrass in the upper layers of the canopy thereby reducing the share of available PAR to white clover. This, coupled with a lower radiation use efficiency at high N and lower population density, results in white clover's reduced performance in mixed swards receiving N fertilizer.

Notizen: This work investigated the range of fatty acid concentrations in grass silages made from the regrowth of perennial ryegrass Lolium perenne using different techniques involving combinations of shading of the crop before cutting, wilting and the use of chemical additives. The effects of the different silage additives on overall fermentation were large, with many of the formic acid and formalin-treated silages having a very restricted fermentation. Nonetheless, effects on levels and proportions of fatty acids were numerically small. The major differences between silages were generated during field operations (shading and wilting), with little further changes in fatty acids within the silage clamp. The extended wilt had the most dramatic effect on fatty acids with a marked reduction in both total fatty acids (24·6 vs. 17·5 g kg−1 dry matter; s.e.d. = 0·65, P 〈 0·001) as well as in the proportion of total fatty acids as α-linolenic acid (C18:3n-3; 0·55 vs. 0·48; s.e.d. = 0·013, P 〈 0·01). Shading the grass with a black plastic sheet for 24 h before cutting had a similar effect.

Notizen: In official forage grass variety trials in the UK, herbage samples are dried at 100°C or more to facilitate quick drying of the large numbers of samples that are currently needed. When assessing herbage quality, however, 80°C has been recommended as the highest temperature that can be used during drying without serious deterioration. Herbage from six perennial ryegrass varieties, which were known to show a range of variation in in vitro concentration of digestible dry matter (DMD) and water-soluble carbohydrate concentration (WSC) during the vegetative phase of growth, was dried in an oven with forced ventilation at 100°C and at 80°C before analysis. Mean DMD over all varieties was slightly lower [6 g kg−1 dry matter (DM)] and mean WSC over all varieties was considerably lower (24 g kg−1 DM) at 100°C. Varieties differed in mean DMD over both drying temperatures by 37 g kg−1 DM and in mean WSC by 63 g kg−1 DM. There was, however, no significant interaction between variety and drying temperature for either DMD or WSC. Although drying at the higher temperature underestimated both DMD and WSC, it did not significantly alter the ranking of varieties or the range among them.

Notizen: The effects on the production from dairy cows of two annual stocking rates (2.5 and 3.0 cows ha−1) and two systems (grass and maize+rye) were examined. The experiement included three treatments: Treatment A was a grass system with an annual stocking rate of 2.5 cows ha−1 and Treatments B and C were maize+rye systems with a stocking rate of 2.5 and 3.0 cows ha−1 respectively. There were twenty cows per treatment and the total area of the system was 22 ha. Treatment A had 4.05 ha of grass silage area, Treatment B had 0.8 ha of grass silage area and 3.2 ha designated to silage crops (maize+rye), whereas Treatment C had 0.4 ha of grass silage area and 2.7 ha of silage crops. Maize silage had a higher nutritive value that the rye or grass silage. The greter production from the maize+rye crops allowed the silage needs of the cows to be met in systems with a seasonal herbage production when stocking rates are higher than for grass-only systems. Rye plus maize system allowed higher stocking rates (2.7 cows per ha) than grass-only system (2.1 cows per ha) because of more efficident use of land resources. Lower stocking rates and grass-only systems increased milk production per cow but not per hectare in comparison with rye plus maize systems.

Notizen: The effect of N-(n-butyl) thiophosphoric triamide (nBTPT)-amended urea on herbage dry-matter yield and nitrogen offtake by perennial ryegrass (Lolium perenne) was studied in fifteen grassland experiments at two sites in Northern Ireland between 1994 and 1996. The dry-matter yield and N offtake with applied urea was only significantly lower than that with applied calcium ammonium nitrate (CAN) on four occasions. On these occasions nBTPT increased the yield from the application of urea making it almost as effective as CAN. There was no evidence of any adverse effect on grass production with repeated applications of nBTPT-amended urea over a 3-year period and no indication that its efficacy to reduce NH3, loss from ureatreated swards declined when used repeatedly on the same soil.

Notizen: The relationship between rate of water loss of Italian ryegrass (Lolium multiflorum) and crop properties, weather conditions and mechanical treatments were studied on a field scale, as was the importance of the variables and their combined effects on influencing the wilting process.Eleven forage-drying experiments were performed between 1992 and 1994 on diploid and tetraploid cultivars cut at different growth stages, ranging from early elongation to flowering, under environmentally variable conditions. The rate of drying was measured until a moisture content of 1 g water g−1 dry matter (DM) (500 g kg−1) was reached, or for a maximum of 2 days by calculating the rate of water loss from two consecutive hourly weights of swath portions placed on trays. Multiple regression analysis was used to correlate the drying rate (k) with crop properties and with meteorological and mechanical treatment variables.The interaction between potential evapotranspiration (ET0) and the moisture content of grass at cutting (Mgrass appeared to be the most important variable, from the twenty-one tested, in influencing K. This variable shows that the same quantity of energy available for evaportaion acts in different ways when the water content of the crop at cutting differs. The rate of water loss is also influenced by the Mgrass itself, surgacae density of the swath, tedding and the weather conditions on the first day of drying.The value of Mgrass at cutting is greatly greatly dependent on crop maturity and ploidy. The tetraploid cultivars, with a higher inital moisture content, lost water more slowly than diploid cultivars did. Because the date of cutting cannot be delayed, owing to the decline in nutrive value, it is helpful to select for cultivars with low moisture contents at cutting, as well as applying mechanical treatment (spreading and tedding), in order to keep the wilting period as short as possible.A validated drying model can be useful for operational purposes to understand the drying process and to assess technological choices for forage drying.

Notizen: Nitrogen fertilization affect growth and yield of timothy (Phleum Pratense L.), but there are conflicting report on its effect on nutritive value. Two experiments were conducted to describe changes in nutritive value of field-grown timothy fertilized with four rates of N fertilizer during spring and summer growth cycles, and to analyse relationships between parameters of nutritive value and the leaf to weight ratio (LWR). Early in the regrowth cycles when the harvestabe shoot biomass was approximately 200 g dry matter (DM) m−2 and under non-limiting N and water conditions, the in vitro true digestibility (IVTD) of DM was greater in spring than in summer because the concentration of neutral-detergent fibre (NDF) was lower and its in vitro cell wall digestibility (IVCWD) was greater. However, the rates of decline in IVTD and IVCWD and the rate of increase in NDF were greater in spring than in summer. Nitrogen deficiency decresed IVTD and IVCWD, and increased NDF concentration early in the regrowth cycles. Nitrogen deficiency, however, reduced the rate of change in the three parameters of nutritive value. By the end of growth cycles, IVTD was 59 and 42 g kg−1 DM greater when no N was applied than with non-limiting N conditions in spring and summer respectively. When no N was applied, the IVCWD was 76 and 52 g kg−1 NDF greater, whereas the NDF concentration was 35 and 42 g kg−1 DM less than under non-limiting N conditions in spring and summer respectively. The N deficiency increased the proportion of leaves in the biomass, which can explain for the most part the positve effect of the N deficiency on the nutritive value of timothy. This positive effect of the N deficiency on nutritive value though the proportion of leaves in the biomass, however, was reduced by the negative effect of N deficiency on the nutritive value of leaves or stems or both.

Notizen: The effect of length of the allowed grazing time (Experiment 1), length of starvation time and placement in the rumen of inert bulk material before grazing (Experiment 2) on liquid and particulate rumen pool sizes, composition and fermentability was investigated. In Experiment 1, four lengths of allowed grazing time (1.00, 1.75, 2.50 and 3.25 h) after overnight starvation were compared. The allowed grazing time had no significant effect on total and liquid rumen pool sizes after grazing but did affect (P 〈 0.05) dry-matter (DM) and organic matter (OM) rumen pool sizes. The non-significant diferences between the volatile fatty acid (VFA) rumen pool sizes before and after 1 h of grazing may indicate a delay in the availability of the more rapidly fermentable substrate for the microorganisms. The total VFA remen pool sizes increased significantly (P 〈 0.01) with the allowed grazing time, which suggests that these fermentation products may be involved in the control of the grazing time in later stages during the day. Experiment 2 consisted of a factorial combination of two lengths of starvation before grazing (16.5 and 2.5 h) and the presence or absence in the rummen of 12.5 kg of a synthetic indigestible material. The duration of starvation before grazing did not affect significantly the particulate, ammonia and VFA rumen pool sizes after grazing except for propionic acid, which was reduced (P 〈 0.09) by the longer starvation time. The inclusion of inert bulk material in the rumen before grazing significantly reduced (P 〈 0.05) the total, Liquid DM, OM, and ammonia rumen pool sizes but not the VFA rumen pool sizes after grazing. High levels of ammonia as well as total rumen contents may be involved in the control of the grazing time in this experiment.

Notizen: The components of actual and potential seed yield were examined in field experiments on a wide range of varieties of white clover (Trifolium repens L.). The factors affecting seed yield under conditions typical of management regimes used in the production of commercial seed crops were assessed in two experiments. In the first, carried out on spaced plants, considerable diferences are shown between six varieties across the range of leaf sizes in the distribution and profuseness of inflorescence production through the flowering season. In the second, carried out in plots, typical on-farm criteria were used to choose a single harvest date. Significant variation was found between varieties, including representatives of different leaf size categories, for seed yield components that include number of inflorescences m−2, number of florets per inflorescence and harvestable seed weight. Large-leaved varieties tended to produce more seeds per floret and higher seed weights per inflorescence, whereas small-leaved varieties gave the highest number of inflorescences −2. However, the small-leaved variety AderDale, selected for strong peduncles, was exceptional, giving high values for all seed yield components. The impact of weather conditions on many seed yield components (e.g. total number of inflorescences) was demonstrated by the differences between the 2 years of the experiment. However, other characterstics, e.g. number of florets per inflorescence and number of seeds per floret, did not vary between years. Deviations from potential seed yield were assessed fromthe perspective of commerical seed production. The implications of these results for the production of white clover varieties with increased seed yields under UK conditions are discussed.

Notizen: The packing of elementary particles in soil largely determines the properties that depend on the textural soil pore space, but is studied little. The relations between packing and size and nature of soil particles were studied using fractions of clay, silt and sand, mixed when wet and then dried. Ternary mixtures (clay:silt:sand) were compared with binary mixtures (clay:silt, clay:sand). The pore space of the mixtures was studied using mercury porosimetry and scanning electron microscopy. In all the mixtures the textural pore space was divided into two compartments: (1) lacunar pores due to the presence of skeleton particles and to the shrinkage of the clay phase between these particles, and (2) the clay–fabric pores due to the packing of the clay. In the ternary mixtures, lacunar pores could be divided into two classes: (1) those due to sand particles within the clay–slit phase considered as a single phase, and (2) those due to silt particles within this same phase. For certain mixtures, lacunar pores, referred to as hidden lacunar pores, were not interconnected but were occluded. This occurred both for hidden pores caused by the presence of sand and occluded by the clay–slit phase, and for hidden pores caused by the presence of silt and occluded by the clay phase. The relations between these types of textural pores and the proportions of different size fractions in the mixtures provide guidelines for making optimum use of the particle-size characteristics of the soil to determine its properties.

Notizen: Carbon-13 (C-13) solid-state NMR spectroscopy was used to investigate the chemical nature of organic C in mineral topsoil sampled under grassland and adjacent recently established (10–17 years old) coniferous forest (Douglas fir, Pseudotsuga menziesii; Ponderosa pine, Pinus ponderosa; Corsican pine, Pinus nigra) at two sites (Craigieburn, Cave Stream) in the South Island of New Zealand. This involved using a Cross-Polarized/Magic-Angle Spinning (CP/MAS) technique to identify different chemical forms of soil organic C, whilst Proton Spin Relaxation Editing (PSRE) was used to determine different ‘pools’ of soil organic C. Results obtained from the Craigieburn soils (0–5 cm) were more promising than those obtained from the Cave Stream soils (0–10 cm) because the total Fe content was smaller, and indicated a shift towards more recalcitrant forms of organic C in soil under trees compared with grassland, which might reflect reduced inputs of fresh organic matter to the soil under trees.

Notizen: The balance of Si, Fe and Al in the soil solution determines more or less the course of soil formation in the tropics. We have tried to improve understanding of the processes by studying fluxes of dissolved Si, Fe and Al from the atmosphere, through the canopy and the soil, and to the groundwater, in two distinct Amazonian ecosystems, one a typical rainforest, developed on a Ferralsol, the other a so-called ‘Campinarana’ forest, developed on a Podzol. The Si, Fe and Al in the rain and the throughfall and the stemflow were measured throughout a year, and the leaching of Si, Fe and Al through the upper soil and at the groundwater level were estimated. The annual balance showed that stemflow inputs were negigible compared with the contributions from throughfall and rain. The inputs of Fe, Al and Si to the topsoil from the rain and from dust and biological release in the canopy were small but not negligible. These sources contributed more aluminium in the Campinarana than in the rainforest. The rainfall constituted the main input of dissolved Fe and Al to the topsoil in both ecosystems. The element balances in the soil horizons confirmed that the present functioning of the Ferralsol results in aluminization and desilicification. We also found that the elements are transported in micropore flow and on translocated particles, as well as in freely percolating water.

Notizen: In tropical cropping systems with few external inputs, efficient management of mineral N derived from added organic residues is essential for the proper functioning of the system. We studied the dynamics of mineral nitrogen (N) in the top 100 cm of soil with a system of tensiometers and suction cups after applying 15N-labelled Leucaena leucocephala and Dactyladenia barteri residues to bare and cropped microplots installed in the respective alley cropping systems, and followed the fate of the N for two maize-cowpea rotations (1992 and 1993).Fifty days after applying the residues (DDA), 20% of the added residue N was found in the soil profile of the bare Leucaena treatment, and 5% under Dactyladenia, compared with 5% and 1%, respectively, where cropped. All values decreased to about 1% after 505 days. In the cropped soil, no mineral N derived from the residues was lost by leaching during the first 6 weeks.As the maize grew, the soil profile was gradually depleted of nitrate to near Zero in the Dactyladenia treatment, whereas during the cowpea season the amount of nitrate N increased to 36 kg N ha−1 for the Leucaena treatment, and 26 kg N ha−1 for the Dactyladenia treatment. The soil of the bare microplots contained substantially more nitrate N (98 and 47 kg N ha-1 during the first year on average, under Leucaena and Dactyladenia, respetively) than that of the cropped microplots, except during the 1993 cowpea season. Nitrate residing in the subsoil (80–100 cm) in the bare treatments was not readily leached to deeper soil. The risk of losses of native mineral N was greatest during the first 50 DAA and to a lesser extent during the cowpea seasons. Improved management of the hedgerows could increase the potential of the hedgerow trees to recycle mineral N.

Notizen: Volatile fatty acids (VFAs) accumulate in animal manure when it is stored anaerobically, and they quickly decompose when the manure is applied to soil. In this study the influence of VFAs on the immobilization of N and mineralization of C in soil was investigated by incubating mixtures of acetate, propionate and butyrate in soils containing varying amounts of clay. The oxidation of VFAs (300 μg C g−1 soil) caused a significant increase in pH (0.6–2.2 pH units), with the largest increase in the most coarse-textured soil. The maximum net immobilization of N resulting from decomposition of the VFAs was 33–77 mg N g−1C and was maximal after 1–5 weeks of decomposition. After this time immobilized N was remineralized, and after 12 weeks the VFAs caused no net immobilization of N in the two most sandy soils. Despite this, the concentration of N in the microbial biomass was still greater in the soil amended with VFAs than in the control. After 12 weeks, the mineralization of C from the decomposition of the VFAs was equivalent to 60–113% of the applied C. It seems that mineralization of native soil C and N was stimulated by adding VFAs, except in the most clayey soil. This stimulation was presumably caused by the increase in the soil's pH as the VFAs oxidized.

Notizen: Trace gas fluxes of N2O and CH4 were measured weekly over 12 months on cultivated peaty soils in southern Germany using a closed chamber technique. The aim was to quantify the effects of management intensity and of soil and climatic factors on the seasonal variation and the total annual exchange rates of these gases between the soil and the atmosphere. The four experimental sites had been drained for many decades and used as meadows (fertilized and unfertilized) and arable land (fertilized and unfertilized), respectively. Total annual N2O-N losses amounted to 4.2, 15.6, 19.8 and 56.4 kg ha–1 year–1 for the fertilized meadow, the fertilized field, the unfertilized meadow and the unfertilized field, respectively. Emission of N2O occurred mainly in the winter when the groundwater level was high. At all sites maximum emission rates were induced by frost. The largest annual N2O emission by far occurred from the unfertilized field where the soil pH was low (4.0). At this site 71% of the seasonal variation of N2O emission rates could be explained by changes in the groundwater level and soil nitrate content. A significant relationship between N2O emission rates and these factors was also obtained for the other sites, which had a soil pH between 5.1 and 5.8, though the relation was weak (R2 = 15–27%). All sites were net sinks for atmospheric methane. Up to 78% of the seasonal variation in CH4 flux rates could be explained by changes in the groundwater level. The total annual CH4-C uptake was significantly affected by agricultural land use with greater CH4 consumption occurring on the meadows (1043 and 833 g ha–1) and less on the cultivated fields (209 and 213 g ha–1).

Notizen: A model of nitrogen release from ammoniacal fertilizers into soil (e.g. from a controlled release nitrogen (CRN) source) and subsequent nitrification has been developed to assess possibilities for reducing losses of N and environment pollution. Emphasis was placed on the effects of changes in ammonium concentration and pH on nitrification rates, and the interactions of these effects with the rate of release of N from fertilizers. The model considers ammonium release and transport from a spherical source, such as a coated granule of CRN or a nest containing either granules of CRN or an easily dissolved fertilizer (EDF). It is shown that the appearance of nitrate in the soil decreases as the size of the N source increases. This is due to both a decrease in the rate of nitrification, caused by accumulation of ammonium near the source, and a slower relative release (i.e. smaller ratio of N released per unit time to the total mass initially in the source, which is inversely proportional to the radius of a granule or nest). Placement of many CRN granules in a nest is shown to be an effective way to reduce nitrification, particularly in soils having low microbial activities. The less the mobility of ammonium in the soil, the slower will be the nitrification because ammonium accumulates close to the source. A CRN nest leads to more effective reduction of nitrification than an EDF nest and N in it is released more slowly into the soil.

Notizen: The weakest link between particles or aggregates determines the strength of soil. We have re-examined the theory and, as a result, have re-defined friability, F, as the coefficient of variation of soil tensile strength. The formal relationship between the parameter 1/α of the weakest link theory of strength, which has previously been used as a measure of friability, and the newly defined measure, F, is described by a simple equation which has an accuracy of within 2% over the range of interest. The quantity F is used to show that friability reaches maximum at water contents around the lower plastic limit, that mechanical disturbance of wet soil by tillage reduces the friability, and that friability is strongly positively correlated with the organic carbon content of the soil. These results show the merit of measuring friability for determining the optimum water content for tillage, for quantifying the damage done by different tillage practices, and as a theoretically based index of soil physical quality.

Notizen: Colorimetric and ion exchange methods are commonly used to distinguish and measure Al species in natural waters. Unfortunately they also include weakly complexed Al species in their ‘reactive' or ‘labile' Al fractions and thus are of limited value for the estimation of free Al3+. Capillary electrophoresis (CE) has the potential for direct measurement of Al3+, and its performance has been verified experimentally. The method also detected the stable and positively charged AlOx+ complex formed with oxalic acid. It was compared with a colorimetric and an ion exchange method by analysing artificial solutions containing low molecular weight organic acids as well as soil extracts and seepage waters and was found to be the only method closely matching the theoretically calculated values of free Al3+. In samples from the upper soil horizons of an acid forest soil less than 14% of total Al was present as free Al3+, whereas the colorimetric method found more than 65%, and the ion exchange method more than 80% of total Al in a ‘reactive' or ‘labile' form. The latter methods thus would seriously overestimate Al toxicity, whereas using CE Al toxicity is likely to be only slightly underestimated.

Notizen: Pollution of the environment by nitrogen (N) has emerged as a serious concern in agriculture, especially in the case of crops such as oilseed rape. To assess the effect of N fertilization on N dynamics, the movements of water and nitrate were determined in a rendzina near Châlons-en-Champagne (eastern France) cropped with oilseed rape with three levels of fertilizer N and in a bare control. From in situ micrometeorological measurements, actual evapotranspiration rates were computed with an energy budget and used to calibrate an evapotranspiration model based on meteorological data and crop leaf area index. Water flow below 120 cm was then deduced from periodic measurements of soil moisture contents and precipitation, and the associated nitrate leaching fluxes were calculated from the NO3 concentration measured at the same depth. Denitrification rates and ammonia volatilization were monitored in the field after fertilizer applications, and crop assimilation of nitrogen was determined frequently during the growth cycle. A nitrate budget gave an approximation of the in situ net mineralization fluxes.The water balance was influenced by the crop and its fertilization: the crop's canopy and roots enhanced the water loss by evapotranspiration and contributed to diminish the soil water storage, whereas drainage volumes were about the same for all cropped treatments, and significantly greater in the bare soil. The rainy winter was particularly favourable to leaching, and losses were much greater (+ 41%) under the over-fertilized crop than under the non-fertilized one, but remained less (– 42%) than those under the bare control soil. Bilans hydriques et azotés d'une culture de colza sur rendzine avec différentes doses d'engrais Les pollutions de l'environnement par l'azote sont devenues une préoccupation majeure en agriculture, particulièrement dans le cas des cultures comme le colza. Pour évaluer les effets de la fertilisation azotée sur la dynamique de l'azote, les transferts d'eau et de nitrate d'une rendzine ont été mesurés près de Châlons-en-Champagne (Est de la France) sur des parcelles expérimentales de colza avec trois niveaux de fertilisation azotée et sur une parcelle témoin en sol nu. A partir de mesures micrométéorologiques in situ, l'évapotranspiration réelle a été calculée par bilan énergétique de la surface du sol, et un modèle d'évapotranspiration ayant pour entrées des données météorologiques classiques et l'indice foliaire de la culture a été calibré. Le flux net d'eau sous 120 cm a été alors déduit de mesures périodiques de teneur en eau du sol et de précipitations, et les flux de nitrate associés ont été calculés à partir des concentration mesurées à la même profondeur. Les flux de dénitrification et la volatilisation d'ammoniac ont été mesurés au champ après les apports d'engrais; l'absorption d'azote par la culture a été déterminée fréquemment pendant le cycle de croissance. Enfin, un bilan azoté a donné l'ordre de grandeur de la minéralisation nette.Le bilan hydrique a été influencé par la culture et sa fertilisation: le couvert végétal et les racines ont accentué les pertes d'eau par évapotranspiration et par conséquent le stock d'eau, tandis que la lame d'eau drainée était à peu près la même pour tous les traitements cultivés, et significativement plus élevée pour le sol nu. L'hiver particulièrement pluvieux a été très favorable au lessivage, et les pertes ont été beaucoup plus fortes (+ 41%) sous la culture sur-fertilisée que sur la culture non-fertilisée, mais elles sont restées inférieures (– 42%) à celles sous sol nu. Nomenclature

Notizen: We have studied microstructural changes in montmorillonite and kaolinite, which were amended with organic debris (leaves of chestnut or beech), microbial inoculum and nutrients and subjected, for 30 days at 25°C, to alternate drying and wetting (D–W) or kept continuously moist at water-holding capacity (WHC). The objective was to evalute the interactions between the decomposition of plant residues and clay microstructural organization in different pore–water regimes. The microstructure was studied by Hg porosimetry, N adsorption at 77 K, and scanning electron microscopy. Decomposition was assessed by measuring residual C and N, the amount of humified material, the relative contents of humic (HA) and fulvic (FA) acids, and their molecular weight distribution. The structural organization at the end of the experiments was different for the two clays, and new classes of pores were found as the result of the microbial metabolism. The decomposition was also significantly affected by clay type. Decomposition of the organic matter (OM) was rapid in the montmorillonite. The humified material occured mainly as low molecular weight FAs. By contrast, transformation was slow in kaolinite, leaving much residual C, and more of the humified material consisted of HAs. Alternate D–W had little effect on microstructure and decomposition. Samples that were kept moist and amended with chestnut leaves produced the greatest amount of humified substances. The dynamics of the decomposition was significantly affected by the nature of the leaves as indicated by the differences in residual C, humified material and C/N ratio. By contrast, changes in pore size distribution (PSD) were litle influenced by the type of organic debris.

Notizen: The mechanisms responsible for stabilization of earthworm casts were investigated in a laboratory study. Earthworms (Aporrectodea caliginosa) were fed soil or soil amended with either ground wheat straw or lucerne hay. Cast material and uningested soil material were incubated for 56 days, and changes in aggregate stability (measured by wet sieving), soil biological activity and macronutrient availability were measured periodically. In general, aggregate stability and microbial biomass C tended to increase during the incubation for both cast and soil material, whereas hot-water extractable carbohydrate content declined. For amended treatments, basal respiration rate and microbial metabolic quotient were large at the first sampling (7 days) but declined rapidly thereafter. There was a transitory increase in extractable P in fresh casts compared with uningested material, a sustained increase in mineral N concentrations but no change in exchangeable K content. For unamended treatments, the casts were less stable than soil material, but this difference diminished during incubation. Drying aggregates before analysing them did not reverse this trend. The casts contained more microbial biomass C than soil material did, but the basal respiratory rate, respiratory quotient and hot-water extractable carbohydrate content were less. By contrast, for wheat- and lucerne-amended treatments casts were more stable than soil material, and the microbial biomass was less at all sampling times. For wheat treatments, respiratory quotient and hot-water extractable carbohydrate content were larger for cast than soil material, but the opposite was the case for lucerne treatments. We attribute the stability of casts in amended treatments to the intimate mixing of part-decomposed organic fragments with comminuted soil particles, binding by microbial mucilage associated with the organic fragments and linking and binding by fungal hyphae.

Notizen: The effects of soil pH on sorption of cadmium, zinc, nickel and cobalt were studied by changing the pH of a soil and measuring sorption. Results were compared with published results for effects of pH on sorption of cadmium, zinc and nickel by goethite. In a further experiment, the effects of pH on the uptake of zinc and cobalt by subterranean clover were measured.Effects of pH on sorption were described in terms of the concentration of metal ions required to produce equal sorption. Where the metal ions were incubated with the soil, unit increase in pH decreased the concentration of metal ions required about 10-fold for zinc, about 7-fold for nickel, about 6-fold for cobalt, and about 4-fold for cadmium. When the soil was mixed with a large volume of solution, the effects were similar for zinc and cadmium but slightly smaller for cobalt and slightly larger for nickel. In all cases, the magnitude of the effect varied somewhat with pH. Sorption was greater with a dilute background electroiyte than with a concentrated one and the effects of pH were greater. The effects for soil were smaller than effects of pH on sorption by iron oxides for which unit increase in pH can decrease the required concentration of Zinc 35-fold and cadmium 11-fold.These results are consistent with adsorption of divalent ions on a variable charge surface that is negatively charged. They are not consistent with the adsorption of monovalent metal ions on a variable charge surface. This mechanism requires at least a 10-fold effect of pH. They show that the change in electric potential with change in pH is smaller for reacting surfaces in soil than for goethite. The effects of changing pH on the amounts of zinc and cobalt fertilizer required for equal uptake by plants was even smaller with unit increase in pH, causing a 1.4-fold increase in the amount of fertilizer required, that is, a 1.4-fold decrease in fertilizer effectiveness.

Notizen: In experiments in lysimeters of sandy soil chlordane was transported in water flows only when sorbed on suspended soil material. A chlordane ‘concentration’ was calculated by dividing this sorbed chlordane by the volume of the water sample in which the suspended matter was carried. In all but one lysimeter the first peak in this ‘concentration’ appeared in the drainage well ahead of the first peak in the concentration of bromide applied at the same time as the chlordane. Chlordane also persisted in the drainage for less time than bromide. The transport of chlordane was most closely associated with that of the largest category of suspended soil material (〉 1.2 μm), possibly because that category contained the most organic matter. It was not associated with the transport of colloidal matter for either of the two possible size limits applied to the latter (〈 0.22 μm or 〈 0.45 μm). In the lysimeters to which pig slurry was applied the evidence that it enhanced the transport of chlordane was limited and equivocal; the chlordane was probably sorbed strongly by the soil's organic matter before the slurry was applied. The application of chlordane was 100 times greater than in normal agricultural practice and it was followed by a substantial volume of water. Nevertheless, only 0.00002% of it was transported from the lysimeters, and its ‘concentration’, calculated as above, never exceeded the EU limit of 0.1 μg1−1 for any one pesticide.

Notizen: Potential causes for changes in the amounts of carbon (C) stored in the soils of boreal forests were studied by measuring the C in the soil along a 5000-year chronosequence in coastal western Finland and using a simple dynamic model of decomposition. The amount of soil C stabilized at an age of about 2000 years. This suggests that the youth of many boreal soils does not make them sinks for atmospheric C. Simulated repeated fires kept the amount of soil C reduced by about 25%, but if fires were prevented then the C in the soil increased. Stored C may thus be less than the potential storage where fires are frequent, and it could be increased by preventing fires. Simulated clear-cutting caused a temporary 5–10% decrease in the amount of soil C over a 20-year period after the harvesting. It also caused a long-term decrease in the amount of soil C such that, after two 100-year rotations, the amount had been decreased by 14%. Stored C is almost certainly less than the potential storage and decreasing where forests are harvested.

Notizen: Organic acids have been implicated in many soil-forming and rhizosphere processes, but their fate in soil is poorly understood. We examined the sorption of four simple short-chain organic acids (citric, oxalic, malic and acetic) in five acid soils and on synthetic iron hydroxide (ferrihydrite). The results for both soils and ferrihydrite indicated that the sorption depended on concentration in the following order of strength: phosphate 〉〉 oxalate 〉 citrate 〉 malate 〉〉 acetate. The sorption reactions in soil were shown to be little influenced by pH, whereas for ferrihydrite, sorption of all ligands increased strongly with decreasing pH. The sorption of organic anions onto ferrihydrite was influenced to a lesser extent by the presence of metal cations in solution. From the results we calculated that when organic acids enter solution they rapidly become sorbed onto the soil's exchange complex (〉 80% within 10 min), and we believe that this sorption will greatly diminish their effectiveness to mobilize nutrients from the rhizosphere.

Notizen: Nitrous oxide is produced in soils by biological denitrification and nitrification. To improve the fundamental understanding of the processes leading to N2O fluxes from soils, the production of N2O from denitrification and nitrification in spruce forest, beech forest, riparian grassland, coastal grassland and an agricultural field were studied. Samples were taken at a high and a low position along a topographic gradient in each site in the spring and autumn when the largest N2O fluxes were expected. They were incubated after being amended with N, and C2H2 was used as biological inhibitor to distinguish nitrification and denitrification.The N2O production in the low landscape position varied between 32 and 121 ng N cm−3 h−1 in the riparian grassland. 9 and 26 ng N cm−3 h−1 in the coastal grassland, and 135 and 195 ng N cm−3 h−1 in the agricultural field which was 10–100 times more than in the high positions where rates ranged between 3 and 5 ng N cm−3 h−1, 0.3 and 0.4 ng N cm−3 h−1, and 7 and 10 ng N cm−3 h−1, respectively. These differences almost certainly arose because the soil in the low positions was wetter and contained more organic matter. In the two forests N2O production was less than 1 ng N cm−3 h−1, strongly inhibited by O2, and not influenced by landscape position. Nitrification contributed to more than 60% of total N2O production in the riparian grassland. In the agricultural field nitrification produced 13–74% of the total N2O in the low position, and 10–88% in the high position. Denitrification was the dominant source of N2O in the coastal grassland except at the low position in the autumn where nitrification produced 60% of the total N2O. In the two forests where the soil had small nitrification potentials denitrification was the only source of N2O. In the other sites nitrification and denitrification potentials were large and of identical magnitude. The results emphasize the need to separate nitrification and denitrification at the process level and to recognize topography at the field scale when modelling N2O effluxes from soil.

Notizen: The movement of bacterial-feeding nematodes (Caenorhabditis elegans) through sand was investigated using a range of sand sizes, equilibrated at a range of matric potentials, in the presence or absence of an attractant source (Escherichiacoli) at the distal end of a column. In the presence of E. coli there was significantly greater movement of the nematode population towards the E. coli population, and the extent of the movement depended on the matric potential of the sand. Over time, an increasing proportion of the C. elegans population responded to the presence of the E. coli. The processes controlling these effects are discussed with respect to taxis and kinesis mechanisms of the nematode population, and with regard to the diffusive characteristics of the physical structure of the sand.

Notizen: We have examined the charge characteristics, with special emphasis on the role of free Fe and organic matter, of humid tropical soils from Bambouto Mountains, Western Cameroon. The soils, which are formed from tuff, basalt and trachyte, are dominated by kaolinite and sesquioxides. The amounts of Fe oxides in them increase somewhat with depth. Open 2:1 phyllosilicates are present in trace amounts. The point of zero charge of the variable charge components, pH0, is around 4 in the topsoil (0–20 cm) and around 6 at 100–150 cm depth. In the subsoils, pH0 exceeds soil pH presumably because of large quantities of Fe oxides. Deferration increases both soil pH and pH0, but diminishes the anion exchange capacity. Oxides and oxyhydrates of Fe have positive surface charge, so their removal from the soils would result in overall loss of positive charge. Increases in soil pH would bring about an increase in the cation exchange capacity of the soils. Hence, management practices that reduce soil acidity should reduce loss of essential basic cations via leaching.

Notizen: With annual incorporation of straw, soil N mineralization is expected to increase whereby requirements for fertilizer N inputs may be reduced. Samples of whole soil, clay (〈 2 μm), silt (2–20 μm) and sand (20–2000 μm) sized organomineral separates from three soils with annual additions of straw ranging from 0 to 12 t ha–1 were leached after 0, 1, 2, 4, 8, 12 and 16 weeks of incubation at 20°C, to determine the content of NH4 + NO3. A three-pool model using first order kinetics and fixed rate constants (N1, k1 = 0.231 day–1; N2, k2 = 0.00693 day–1; N3, k3 = 0) was fitted to the mineralization data.The mineralizability of whole soil N (mg N g–1 N) differed among soil types. Straw generally increased the fast N1 and the passive N3 pool while the medium-term N2 pool was reduced in size. The N1, N2 and N3 averaged 0.8, 2.6 and 96.6% of the whole soil N, respectively.The N mineralizability increased in the order: sand 〈 silt 〈 clay. The lability of N in a given size separate was almost similar across soil types and straw managements. The active N pools (N1 + N2) averaged 7.1% of the clay N and 2.2% of the silt N. The main difference was related to the N2 pool, which accounted for 5.5% in clay and 1.2% in silt.Mineral N produced during incubation ranged from 63 to 105 kg N ha–1. Effects of straw disposal were small (〈 11 kg N ha–1). Maximum response was at 4 t straw ha–1; adding more straw diminished mineralization of N.Long-term annual incorporation of cereal straw contributes mainly soil N with a slow turnover.

Notizen: We investigated the effect of goethite and copper on almond β-glucosidase activity. The activity of β-glucosidase was found to be inhibited at dissolved copper concentrations exceeding 0.2 mm. Copper was most influential in the pH range 5–5.5, at which the enzyme activity was reduced by 50% or more at total copper concentrations of 0.2 mm compared with copper-free assays. At pH 4, the presence of 0.2 mm copper reduced the activity by 15% at most. Copper caused a shift of the pH optimum towards lower pH. Goethite did not influence β-glucosidase activity significantly, although up to 95% of the enzyme was adsorbed on its surface. The adsorption seemed to be caused principally by non-electrostatic forces which were too weak to affect the structure of the enzyme. Goethite reduced the inhibitory effect of copper because of the strong affinity of copper for goethite, as observed in batch adsorption experiments. The sorption of the enzyme on goethite was not competitive with copper at concentrations less than 0.2 mm; at larger concentrations, however, the presence of the enzyme reduced copper adsorption. The influence of copper on enzyme activity as well as the influence of copper in combination with goethite could be described with a model combining Michaelis–Menten enzyme kinetics with a simple conditionally first-order reaction law for the binding of copper by the enzyme.

Notizen: The analysis of X-ray diffraction (XRD) patterns by the Rietveld method was tested for characterizing quantitatively the mineralogical composition of a ferralitic soil from southern Mali. Quantitative analysis of two samples from this soil revealed kaolinite and quartz as major components and smaller amounts of haematite, goethite and anatase. Despite a strong overlap of the peaks, precise and reliable cell parameters and Al for Fe substitutions were determined. The quantitative results of the Rietveld refinement were verified by chemical analysis. This comparison revealed a strong influence of sample preparation on the quantitative mineralogical analysis by XRD.

Notizen: The use of forage brassicas, such as kale, in diets of ruminants is typically constrained by the presence of anti-metabolites that break down in the rumen to cause detrimental effects after absorption including haemolytic anaemia and tissue damage. Ensilage of kale before feeding may provide conditions that favour the degradation of potentially toxic anti-metabolites, thereby improving the nutritive value of the feed. An experiment was conducted with eighty Scottish Blackface housed lambs, in which four levels of kale silage were used to replace grass silage and in which the forage component comprised around 60% of the finishing diet. Productivity of lambs was not affected other than to increase the killing-out percentage of the lambs. Glucosinolate concentrations in kale were markedly reduced by the ensiling process. Haematological parameters, such as packed cell volume, haemoglobin concentration and the presence of Heinz−Ehrlich bodies, were not significantly affected by replacing grass silage with kale silage. Similarly, there were no significant effects arising from the dietary treatments on the blood plasma components, gamma-glutamyl transpeptidase, blood urea nitrogen, tri-iodothyroxine and thyroxine, which are conventional measures of glucosinolate toxicity.The results indicated that the ensilage of kale reduces its toxicity and hence removes constraints on the maximum inclusion levels in the diet. Also, it was possible to reduce the potential contamination of carcasses with soil by lambs not grazing the crop and thus keeping fleeces clean.

Notizen: Persistence of white clover (Trifolium repens) in mixtures was studied in a long-term experiment. Mixtures of two cultivars of perennial ryegrass (Lolium perenne) with contrasting growth habits and three white clover cultivars differing in leaf size were sown in 1991 and evaluated at two cutting frequencies. During 1995 and 1996 mixtures with large-leaved white clover cv. Alice had the highest dry-matter (DM) content, clover and N yield, and the highest white clover content, and mixtures with medium-leaved Retor the lowest, whereas mixtures with small-leaved Gwenda yielded most grass DM. In 1995 averaged over cutting treatments and mixtures, the mixtures yielded 11·8 t DM ha−1 with a white clover content of 0·6; the apparent N fixation was 393 kg N ha−1. In 1996 these values declined to 8·5 t DM ha−1, 0·48 white clover and 236 kg N ha−1. There was no significant effect of cutting frequency on DM yield or white clover content, whereas the effects of grass cultivar were not consistent.In spring there was a peak in the DM production of the mixtures, coinciding with a peak in production of the grass component. However, in summer and autumn the seasonal pattern of DM production of the mixtures was similar to that of the white clover component. Both cultivars of perennial ryegrass showed the same seasonal response, but the seasonal growth pattern of white clover differed slightly between clover cultivars and cutting treatments. In later years only one cutting frequency was imposed, and no yield measurements were taken. White clover was judged to have performed well during 1997; the clover content in September was very high (0·76), whereas in October 1998 it was 0·45. Mixtures with Alice contained most white clover. Despite fluctuations in white clover content during 1991–98, all clover cultivars had persisted 7 years after sowing, irrespective of companion grass cultivar, at both cutting treatments.

Notizen: The rates of litter decomposition, organic matter loss and nutrient release for Dactylis glomerata (Gramineae) and Vicia villosa (Leguminosae) were studied at two sites in north Greece, which differed in soil pH, soil particle distribution and nutrient availability.Climate, soil characteristics and taxonomic plant differences affected the rates of litter decomposition. Litter loss was higher at site A (neutral soil) than at site B (acid soil). Organic matter loss was generally low. Dry weather affected both parameters. Nitrogen release from litter was higher for both species at site A. The rate of P and K release was higher in the neutral soil than in the acid soil for both species, while that of Ca for both species and of Mg for Vicia was higher in the acid soil. Phosphorus, Ca and Na release from the litter of the leguminous species began earlier than from the graminaceous species. P mineralization from Vicia litter seemed to start just after its incorporation into the soil.

Notizen: This paper reports the effects of onset of phenological maturity on the nutritive value of white clover (Trifolium repens L.). The study comprised (i) examination of an extensive data set on nutritive value and (ii) investigation of the constituents of nutritive value, in vivo feeding value, protein degradability and metabolizable protein content of white clover harvested at three stages of maturity (early-flowering, full-flowering, ripe seed stages) during the primary growth phase in spring in Australia. The data set on nutritive value showed a consistent pattern of high nutritive value during cool season months, progressive decline through spring and uniformly lower nutritive value over summer. Results from laboratory determinations, in sacco degradability studies and a digestibility trial on white clover harvested at early-flowering, full-flowering and ripe seed stages were consistent with results from the data set on nutritive value. Onset of maturity during the primary growth phase in spring was accompanied by large changes in nutritive value: neutral-detergent fibre (NDF) increased from 184 to 301 g kg−1 dry matter (DM), nitrogen (N) declined from 36 to 20 g kg−1 DM, in vitro digestibility declined from 0·74 to 0·65 and metabolizable protein content declined from 144 to 67 g kg−1 DM from early-flowering to ripe seed stage. These nutritive value changes were accompanied by a decline of in vivo digestibility at the rate of 0·0032 d−1 and an 0·2 reduction in voluntary intake.

Notizen: Greyface (Border Leicester × Scottish Blackface) ewes, mated in October, were housed in winter and turned out after lambing in late March to one of four treatments replicated three times on perennial ryegrass (Lolium perenne)-dominated pastures. On three of the treatments the stocking rate was 12·5 ewes plus lambs ha−1 annum−1 (SR12·5), whereas on the fourth it was 15·0 ewes plus lambs ha−1 annum−1 (SR15·0). There were two levels of applied fertilizer nitrogen (N), 152 kg N ha−1 annum−1 (N152) and 205 kg N ha−1 annum−1 (N205). Three patterns of nitrogen application were used: predominantly in spring (E), predominantly in autumn (L), and mainly in spring and autumn (E + L). Grazed sward surface height was controlled within the range 3·5–5·5 cm during spring and summer, and supplementary feed was offered when sward height was below 3·5 cm.The effects on animal performance, yield of silage and requirement for supplementary feed were measured over 3 years (1986–88). Management of the sward height within the specified limits resulted in similar levels of individual animal performance for all treatments, but treatment SR15·0N205E + L produced a significantly (P 〈 0·05) greater output of lamb per hectare. There was no evidence to suggest that, by increasing the amount of N fertilizer applied in the autumn, ewe reproductive performance was increased. Neither the treatment with the lower level of N applied in the spring (SR12·5N152L) nor the high stocking rate treatment (SR15·0N205E + L) was self-sufficient in winter feed (silage) production. SR15·0N205E + L also required more supplementary feed in both the lactation (38·1 kg ewe−1) and the mating (9·1 kg ewe−1) periods. SR12·5N152L required the second greatest amount of supplementary feed during lactation (36·1 kg ewe−1), whereas SR12·5N205E + L required the least supplementary feed over both periods (27·8 kg and 4·8 kg ewe−1). Taking all treatments together, there were significant (P 〈 0·05) differences between years in lamb weaning weight (kg), lamb output (kg ha−1), yield of silage (kg ewe−1) and supplementary feed required (kg ewe−1), arising mainly from a lower level of herbage production in one year. Treatment SR12·5N152E generated the highest gross margin per hectare.

Notizen: Different procedures for autumn management in crops of Festuca pratensis grown for seed, in particular the possibility of combining seed production with the production of forage in autumn, were examined in eleven experiments conducted between 1993 and 1996 at various locations in south-east Norway. Methods without intensive use of regrowth, such a nitrogen (N) fertilizer application (40 Kg N ha−1) on 10 the September, either separately or preceded by cutting on the same date, generally stimulated the subsequent number of reproductive tillers and seed yield compared with untreated plots (no N, no cuting). However, cutting before N fertilizer application on 10th September tended to have a nagative effect on seed yield in 1995–96, when a mild autumn was followed by a winter with extremely low temp ratures and no, or very little, snow cover. Maximizing regrowth, by the application of 80 kg N fertilizer ha−1 immediately after seed harvest, never impaired seed yield when a forage harvest was taken on 10 September but did so in 1995–96, when a forage harvest was delayed to 10 October. Additional N (40 kg −1) after a forage harvest did not significantly affect seed yield, although negative and positive tendencies were observed after harvesting in September and October respectively.When forage harvesting was delayed from 10 September to 10 October, the average yields of dry matter (DM) increased, but the forage quality, especially the crude protein content, decreased. As a result of the high yields of DM obtained (on average 2250 kg −1 in September and 2610 kg−1 in October), use of regrowth may be of essential economic value for seed growers of Festuca pratensis.

Notizen: The n-alkane technique for estimating herbage intake and diet selection in dairy cows fed perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) herbages was evaluated. Pairs of animals were offered either 8, 10, 12 or 14 kg dry matter (DM) d−1 of herbage alone or with 2 kg DM d−1 of barley. Fresh herbage was cut daily from a perennial ryegrass/white clover sward and the appropriate amount was fed in four feeds during the day. Individual intakes and the white clover proportion of the diet were estimated during a 12-d period using the n-alkane technique. Animals were dosed twice daily with paper pellets containing dotriacontane (C32-alkane). Faecal grab samples were collected after the morning and afternoon milking. Three least-squares optimization methods were compared in calculating the white clover proportion in the diet; then, total DM intake was calculated. The different least-squares optimization methods gave similar predictions of the white clover content of the forage consumed. No significant (P 〈 0.05) effects of sampling routine, concentrate (barley) fed or interactions between the two were detected with respect to the difference between calculated and actual intake, the difference as a proportion of the total intake and estimated white clover content of the diet. The difference between the calculated and actual intake ranged from 139 to 366 g DM d −1, which resulted in a proportional difference ranging from 0.004 to 0.02 depending on sampling routine. The actual white clover content of the herbage mixture fed was 0.42 ± 0.008, whereas the estimated white clover content ranged from 0.41 ± 0.006 to 0.43 ± 0.008. The results suggest that accurate herbage intake estimates can be achieved in dairy cows grazing perennial ryegrass/white clover swards if representative samples from herbage consumed can be collected.

Notizen: The Argentinean semiarid Chaco region is climatically suitable for cattle raising and has an average annual rainfall of 550 mm, concentrated from November to February. There, large areas are affected by high salinity; thus, perennial forages suitable for this region must combine adequate salt and drought tolerance. Panicum coloratum is a C4 perennial grass adapted over a wide range of soil and rainfall conditions, and the purpose of this study was to evaluate the response of two cultivars (Klein Verde and Bambatsi) to salinity. Under controlled conditions, 100 and 200 mmol l−1 NaCl delayed germination and significantly reduced germination percentages and seedling survival in both cultivars. However, in the field, factors other than salinity (possibly drought) had a large impact on plant survival. In short-term experiments under controlled environmental conditions, the vegetative growth of cultivar Klein Verde was less affected by salinity than Bambatsi. The cumulative growth over one year in a saline plot was also higher in cultivar Klein Verde. This cultivar also had higher shoot K+/Na+ ratios under salinity, as a result of higher K+ concentrations, and accumulated more triglycerides in roots. These features have been associated with salt tolerance in other species.

Notizen: The distribution of length, diameter, surface area and volume of roots was measured in northern New South Wales, Australia, under temperate pasture that had been previously grazed at low and high stocking rates for 30 years; these root characteristics were compared with those of roots under ungrazed pasture. The ungrazed pasture was dominated by Phalaris (Phalaris Aquatica), whereas annual grasses and dicotyledons were a large component of the pasture at low and high stocking rates. A fine-meshed (0.250 mm) sieve was used for separating the roots from the soil, and the root characteristics were measured using image analysis techniques. With this sieve size, root length densities were many times higher than published data for astures where a larger mesh sieve had been used for sample preparation. The lengths of root per unit of soil volume (root length densities) were high for all stocking rates and averaged 91 cm cm−3 near the soil surface (0 – 5 cm) declining to 4.0 cm cm−3 at the deepest depth measured (65–75 cm). There was a greater proportion of roots near the soil surface at the higher stocking rates. A greater proportion of fine roots occurred at the higher stocking rates, which was probably due to the differences in botanical composition. Reciprocal, power and logarithmic functions best described the distribution of root length density, root surface area density and root volume density, root surface area density and root volume desnity with depth.

Notizen: Sixteen multiparous Holstein/Friesian cows were used to examine the effect on food intake and milk production of replacing 40% of the dry matter (DM) of first cut perennial ryegrass silage (G) with either maize silage (M), fermented (F) or urea-treated (U) wheat whole crop silage. In addition to the forage mixtures, the animals received 5.25 kg DM d −1 of a standard concentrate and 1.75 kg DM d −1 of soya bean meal. The experiment consisted of four periods, each of 4 weeks duration, in a Latin square design. The grass silage used was of high quality with an estimated metabolizable energy (ME) content of 11.4 MJ kg −1 DM and in vitro digestibility of 748 g kg −1 DM. DM intake was significantly increased (s.e.d. = 0.364, P 〈 0.01) with the inclusion of M, F and U. The resulting total DM intakes were 17.6, 18.4, 19.2 and 20.1 kg d −1 for treatments G, M, F and U respectively. None of the animal production variables was significantly affected by the treatments. Milk yield was 27.4, 26.4, 27.1 and 26.9 kg d −1 for treatments G, M, F and U respectively. Milk fat content was 48.9, 46.9, 49.0 and 48.1 g kg −1, and milk protein content was 34.1, 33.6, 34.0 and 34.3 g kg −1 for treatments G, M, F and U respectively. The results show that partly (40%) replacing a high-quality grass silage with forage maize, fermented whole crop wheat or urea-treated whole crop wheat will increase DM intake in dairy cows but is not accompanied by an increase in animal performance and therefore will result in decreased efficiency of forage DM utilization.

Notizen: Reduced inputs of fertilizer and lime to grasslands can result in decreased soil pH, increased aluminium concentration in the soil solution and, consequent upon these, inhinition of nitrogen acquisition by plannts. This study tested the hypothesis that under conditions of low pH and high aluminium concentrations a grass species more tolerant of acid conditions (Deschampsia flexuosa) maintains a greater total supply of nitrogen to growing leaves after defoliation from both root uptake and mobilization of stores than a less tolerant species (Lolium perenne). The grasses were grown without alumimium at pH values 3.5, 4.0, 5.0 or 5.5 and at a range of aluminium concentrations (0, 20, 100, 200 or 1000 mmol m−3) at pH 4.5. Labelling with 15NH415NO3 after defoliation allowed estimation of both root uptake and mobilization of stores in supplying nitrogen to growing leaves. The total amount of nitrogen supplied to the growing the leaves after defoliation by the combination of current root uptake and mobilization was maximal when aluminium was in the range 20–20 mmol m-3. The total nitrogen supplied to growing leaves the both species after defoliation was greater when the grasses were grwon at pH 5.0 and 5.5 than when grown at pH 4.0. L. perenned and D. flexuosa were affected similarly by both aluminium and pH with respect to the total nitrogen supplied to the leaves. The effects of aluminium an dpH upon the supply of nitrogen to growing leaves after defoliation my not be a dominant factor in the vegetation dynamics of grazed swards.

Notizen: Data from in vivo digestibility trial with four to six horses fed twenty-seven forage-based diets are used to calculate prediction equations for the digestibility of dry and organic matter, based on the crude ash (CA), crude protein (CP) and crude fibre (CF) contents of diets and faeces. The most precise prediction of dry-matter digestibility (r.s.d. = 0.032, R2= 0.80) was derived from a multiple regression including faecal (CP, CF) and dietary parameters (CF). Among faecal parameters, CP was the best single predictor of both digestibility (r.s.d) = 0.040, r2= 0.63) and dietary CP content (r.s.d = 0.028, r2= 0.59). For biological reasons we propose a non-linear model that allows prediction of dry- and organic-matter digestibility from faecal CP Content with reasonable Precision (r.s.d = 0.038, 0.036, r2= 0.65, 0.74, respectively). This will be adequate for many studies, especially for free-living animals in rangelands.

Notizen: We investigated the processes of mineral formation in three Alfisol profiles of Sierra Nevada (southern Spain), with special emphasis on the little-studied process of mica inheritance, particularly as regards its quantitative aspects. X-ray diffraction, conventional and high resolution transmission electron microscopy, selected-area electron diffraction, and geochemical analysis of the soil solution were used, and the granulometric fractions gravel, coarse sand, fine sand, silt and clay were studied, as was unaltered parent rock. Most interesting was inheritance of dioctahedral mica (illites) with small crystallochemical changes. The transition of mica from parent rock to clay was characterized by small crystallochemical changes affecting their structural formulae, reduction of the 2M1 polytype content, decrease in crystallite size, increase in crystal defects, and other changes in particle morphology. We propose the term ‘pedocrystallochemical evolution’ for the transition. The changes reverse the processes that take place in micas when rocks are formed by sedimentation, diagenesis and metamorphism. The kaolinite in the soils is a result of neoformation, and acts as the equilibrium phase within the chemical system. Reddening seems to have been caused by both inheritance and neoformation of iron oxides (haematite + goethite).

Notizen: We investigated the potential of montmorillonite, Al-montmorillonite and gravel sludge to immobilize polluting heavy metals in agricultural soil. Batch experiments showed that both Al-montmorillonite and montmorillonite immobilized zinc and cadmium. Zinc was bound specifically on Al-montmorillonite and became increasingly incorporated into the interlayer hydroxy-Al polymer, whereas there was no specific sorption on montmorillonite. Cadmium was bound on montmorillonite and Al-montmorillonite unspecifically by cation exchange, but there was no incorporation into the lattice.In pot experiments montmorillonite, Al-montmorillonite, or gravel sludge were added to a soil contaminated with zinc and cadmium. Increasing doses of these agents decreased the concentrations of NaNO3-extractable zinc and cadmium. Aluminium-montmorillonite and gravel sludge were more efficient than montmorillonite in immobilizing both zinc and cadmium. Remobilization tests at pH between 4 and 5.5 showed that cadmium and zinc desorbed more easily from montmorillonite than from Al-montmorillonite. Gravel sludge application increased the buffer capacity of the contaminated soil substantially. The binding agents decreased zinc concentrations in red clover (Trifolium pratense), and gravel sludge also reduced the cadmium concentrations.

Notizen: We investigated the possibility of inferring effective hydraulic properties of soil from the structure of the pore space. The aim was to identify structural properties, which are essential for water flow, so that physical experiments may be replaced by direct morphological measurements. The pore structure was investigated in three dimensions by serial sections through impregnated samples. The complex geometry of pore space was quantified in terms of two characteristics: pore-size distribution and pore connectivity. Only pores larger than 0.04 mm were considered. The results were used as input parameters for a pore-scale network model. The main desorption branch of the soil-water characteristic and the corresponding hydraulic conductivity function of the network model were calculated by numerical simulation. The simulation results, which are exclusively based on morphological investigations, were compared with independently measured results from a multi-step outflow experiment. This approach was demonstrated for two centrasting soil materials: the A and B horizons of a silty agricultural soil. The simulations were close to the experimental data, except for the absolute values of the hydraulic conductivity. The pore-size distribution and pore connectivity govern the shape of hydraulic functions and the applied morphometric methods are suitable for predicting essential characteristics of hydraulic soil properties.

Notizen: Siderite, calcite and goethite occur in a Low Moor Peat near Freising, southern Germany. Siderite is present mainly as microcrystalline ovoids which have a lamellar structure and are less than 5 μm long. Selected area electron diffraction and X-ray diffraction data suggest a crystal size less than that of the ovoids, probably as small as 20–50 nm. Siderite occurs interstitially between plant materials, predominantly of the genus Equisetum. Calcite, which is subordinate to siderite, occurs as pseudomorphs of plant cells. This suggests an earlier crystallization for calcite predating that of the siderite.The distribution of mineral morphologies and pH and Eh data suggest that siderite weathers by oxidation to goethite under mildly alkaline conditions, despite the probable production of protons. This process initially involves a pseudomorphism of the siderite ovoids by goethite. However, the goethite, comprising poorly acicular crystals with a mean coherence length of 11 nm normal to the 111 plane, eventually develops into a massive fabric.Calcite occurs with goethite in oxidized samples in the same location as in the unoxidized samples, but in decreased amount. Thus, calcite dissolution may act as a buffer to siderite oxidation.

Notizen: Mathematical morphology is an approach to image analysis based on set theory. It explores structures by examining the effect of transforming them by set operations. Such operations can be built up and combined into powerful tools for exploring, transforming and measuring the size, shape and connectivity of components of interest in images. Greylevel images are handled by regarding them as binary images in three dimensions. This paper reviews the basic ideas and illustrates them by application to studies of the size distribution of soil pores, the lengths and geometric patterns of cracks in drying soil, and the growth of fungal hyphae. It then extends them in an introductory way to random sets. Practical issues of scale, resolution, sampling, replication and noise in the use of images for soil measurement are described briefly.

Notizen: The structural voids in vertisols contain easily available water for plants and their volume can be calculated from the shrinkage curve. Access by plants to that water depends also on the geometric arrangement of the pores so that the water can flow through them. We have devised a method for studying the structural porosity by casting the pores in resin. The intraprism pore space of wet soil clods is impregnated with a UV fluorescent polyester resin under vacuum. When this has set we use the swelling properties of the clay to separate the clay matrix from the resin. A cast so obtained is the real three-dimensional solid reproduction of the structural porosity. This representation of the pore system is easier to study than results from computerized reconstitution of the three-dimensional space from two-dimensional images of soil in thin sections. Channels, packing pores and planar voids can be observed directly in three dimensions as the method saves the integrity and continuity of pores as small as 10 μm in diameter. The geometry of the cast shapes agrees with the interpretation of shrinkage and moisture characteristic curves. The method offers direct qualitative observation of pore organization and volume measurements of the intraprism structural porosity in vertisols.

Notizen: The adsorption of oxalate and fulvate and the competition for surface-adsorption sites between SO42–-oxalate and SO42–-fulvate on goethite and on a soil material from a podzol B horizon were studied in batch titration experiments. The adsorption and competition processes were evaluated with surface complexation modelling using the diffuse-layer model (DLM). Two different adsorption reactions were tested for oxalate and fulvate adsorption and the reaction giving the largest charge neutralization at the surface gave the best description of experimental data. In the soil solution an Al-oxalate complex induced a substantial decrease in oxalate adsorption when the pH fell below 4.5. No such effect was found in the soil-fulvate system. Adsorption constants obtained from binary systems (oxide-ligand) were used to model adsorption and competition in the two ternary systems oxide-SO42–-oxalate and oxide-SO42–-fulvate. Experimental data showed that oxalate and fulvate competed with SO42– for adsorption sites. The DLM produced acceptable descriptions of experimental data, although the model slightly underpredicted SO42– adsorption in ternary systems. The competition between adsorbates was attributed mainly to charge neutralization at the surface induced by adsorption of the ligands.

Notizen: Adsorption and desorption of the herbicides glyphosate [N-phosphonomethyl-aminoaceticacid], simazine [6-chloro-N,N′-diethyl-1,3,5-triazine-2,4-diamine] and atrazine [6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine] were studied in four sandy soils from Western Australia. Distribution coefficients (Kds) were calculated from breakthrough curves (BTCs) resulting from leaching step changes in concentrations through small saturated columns of soil at flow rates ranging from 0.3 to 30 m day–1. A comparison was made with Kds obtained after batch equilibrating solutions of the herbicides with the same soils. The Kds of herbicides in soils decreased with increasing flow rate and most strongly for glyphosate in soils rich in clay content. Resulting increases in mobility of about 40–50% were estimated for simazine and atrazine and 〉 50% for glyphosate at flow rates of 3 m day–1. Adsorption and desorption rates were estimated by fitting numerically simulated BTCs to experimental BTCs. Best fits were obtained with a time-dependent Freundlich adsorption equation. The resulting coefficient for time dependency in the equation suggests that the rates of adsorption and desorption are controlled mainly by diffusion in an adsorbing layer on or in soil particles.

Notizen: The Gaines–Thomas selectivity coefficient, K, was used to express the relation between the cations in solution and the cations in exchange sites in podzolic forest soils. Soil solution was obtained by centrifuging a fresh bulked soil sample. Exchangeable cations HX, AlX, CaX, MgX and KX and effective cation-exchange capacity, CECe, were determined with 0.1 m BaCl2. Apparent values of K indicated a preference of Ca2+ over Mg2+ and over Al3+ in O, A and B horizons (log KAl–Ca 〈 0 and log KMg–Ca 〈 0), whereas log KK–Ca and log KH–Ca exceeded zero. The horizons were similar with respect to log KH–Ca, and the differences in log KMg–Ca were small. Log KK–Ca and log KAl–Ca increased in the horizons in the order O 〈 A 〈 B. Log KAl–Ca was not significantly correlated with the fraction AlX/CECe. Log KMg–Ca was positively correlated with the fractions HX/CECe and AlX/CECe, and negatively correlated with log (CaX/MgX). The selectivity coefficient of binary cation exchange seemed to be applicable to in situ soil solutions. However, the fraction of each cation on exchange sites should be based on the CECe rather than on the sum of the two cations. The latter, also, seemed to be acceptable in cases of exchangeable cations with a large relative content in soil, e.g. in Al3+–Ca2+ exchange in A and B horizons, and in H+–Ca2+ exchange in O and A horizons.

Notizen: The OAh and Ah horizons of acid brown and podzolic forest soils are reported to fix more radiocaesium than the mineral B horizons beneath them. We determined the respective influence of organic matter and clay minerals on the magnitude of Cs+ retention in a strongly acid brown forest soil in Belgium. The soil contained mica throughout the profile. Vermiculite was identified in the OAh and Ah horizons, and hydroxy interlayered vermiculite (HIV) in the Bw horizon. The OAh and Ah clay fraction retained much more Cs+ than the Bw horizon. The extraction of Al interlayers by Na-citrate resulted in a marked increase in Cs+ fixation in the Bw clays as well as the collapse of the vermiculitic layers after K+ saturation. Organic matter had a strong but indirect effect on Cs+ fixation. In the Bw horizon, acid weathering of layer silicates releases free Al and produces HIV minerals in which Al polymers block the access of radiocaesium onto Cs+-specific sites. In OAh and Ah horizons, free Al is complexed by organic acids. Consequently, the interlayer specific sites remain accessible for Cs+ fixation.

Notizen: The effects of N applied in spring on the growth and development of white clover (Trifolium repens L.) in a mixed sward were investigated at Uppsala, Sweden. In early spring, the plots received 0 or 90 kg N ha−1 in the form of nitrochalk. The formation and loss of stolon branches were followed on marked stolons. The proportion of white clover in the total above-ground dry matter (DM) of the sward fell substantially in both treatments during the 8-week growth period, but more so in N fertilized than in unfertilized plots; fertilizer N increased the accumulation of grass DM, whereas it reduced the accumulation of white clover DM. Over time, there was a loss of white clover growing points and this loss was greatest in plots where N was applied. Branching occurred predominantly during the first half of the growth period and was unaffected by N application, whereas the loss of branches was more confined to the latter period and was increased in plots receiving N. Irrespective of node position, the size of the branches that died was comparatively small, and more branches were lost from young than from old node positions. It is concluded that the decline in the number of growing points in the N fertilized sward was mainly due to an increased loss of recently formed branches. As a consequence of its stimulating effect on grass growth, the N fertilized treatment initially led to a reduction in the R:FR ratio of light and subsequently also in the availability of photosynthetically active radiation within the canopy. These changes in the light environment of the sward caused morphological adjustments to be made by the white clover and may have contributed to the observed loss of branches.

Notizen: The effect of defoliation interval on growth patterns of contrasting perennial ryegrass (Lolium perenne)–white clover (Trifolium repens) mixtures was studied. The dynamics of increase in leaf area, light interception and dry-matter (DM) production were measured within successive regrowth periods. No N fertilizer was applied. During 1995 six mixtures were cut eight (F1) or six times (F2) at a stubble height of 5 cm. The stubble composition was stable throughout the growing season: after harvest about 50 g DM m−2 (with a white clover proportion of 0·52) was present with a leaf area index (LAI) of 0·5 (0·38 white clover). The percentage of intercepted radiation after cutting was 20–30% and increased during 3 weeks to about 95%.The relative growth rate of leaf area and DM was higher for white clover than for perennial ryegrass, with the proportion of clover in the LAI and DM increasing during each regrowth period. Mixtures with large-leaved white clover cv. Alice had a lower initial clover content after harvest, but a more rapid increase in clover LAI and DM than mixtures with the smaller leaved cvs Gwenda or Retor. Alice had the highest total and clover LAI and DM at harvest. Cutting frequency affected the change in white clover–perennial ryegrass ratio during regrowth. This was significantly higher in mixtures with Alice than in mixtures with Gwenda, but only under less frequent cutting (F2).In spring there was a mean white clover proportion of about 0·55 in the LAI and 0·45 in the total harvested DM. In summer the white clover proportion in the LAI and DM increased to 0·70–0·75. There was a decline during autumn, especially in F2 and in the mixtures with the small-leaved white clover cv. Gwenda and the medium-leaved cv. Retor. In contrast, grass DM and LAI declined from spring to summer. The decline in clover LAI in autumn was similar in Alice and Gwenda at frequent cutting (F1), but stronger in Gwenda in F2. Retor had the lowest clover specific leaf area (SLA). The SLA values of Alice and Gwenda were similar, SLA being similar between cutting treatments. No differences were found for leaf weight ratio (LWR) among the three white clover cultivars or between the grass cultivars, and LWR was not affected by cutting treatment. Defoliation interval had limited effects on the growth pattern and leaf characteristics of perennial ryegrass–white clover mixtures.

Notizen: Four groups of six spring-calving beef cows and their calves were allocated to two replicated grazing treatments on a Nardus stricta-dominated hill pasture in the UK during six consecutive summer grazing seasons. Treatments were applied by continuous variable stocking to maintain a sward height of either 4–5 cm (short) or 6–7 cm (tall) between tussocks of N. stricta.Cows on both treatments ingested a greater proportion of N. stricta than was present in the sward. The short treatment reduced the herbage intake of cows proportionally by 0·35 (P 〈 0·001) and reduced herbage digestibility by 0·03 (P 〈 0·01) compared with the tall treatment. Cows lost 0·02 kg d−1 live weight on the short treatment but gained 0·27 kg d−1 live weight on the tall treatment (s.e.d. 0·077; P 〈 0·001). Calf liveweight gains were 0·60 and 0·86 (s.e.d. 0·034; P 〈 0·001) kg d−1 for the short and tall treatments respectively. The greatest liveweight gains for both cows and calves occurred during the first 5–6 weeks of the grazing season and differences between treatments increased over the season. Cattle on the short treatment consistently grazed a higher proportion of N. stricta tillers more closely than those on the tall treatment, and the percentage cover of N. stricta declined more rapidly on the short treatment. After 6 years of grazing there was a considerably greater (P 〈 0·001) proportion of very small tussocks, i.e. less than 140 cm2 basal area, on the short treatment than on the tall treatment. The percentage cover of broad- and fine-leaved grasses also declined, in contrast to previous studies. This may have been due to lower soil fertility on the site of the current experiment.It is concluded that high levels of utilization of N. stricta are incompatible with high levels of individual animal performance in lactating cows, although short periods in early summer may give acceptable performance. Lower levels of utilization such as that achieved on the 6–7 cm treatment resulted in moderate levels of animal performance and also gradually reduced the cover of N. stricta, although it took longer for the effect to be established.

Notizen: Cereals grown for forage are increasing in importance in the rations of ruminants in the UK and have the potential to supply high proportions of energy-rich forage in their diets. However, such diets usually require some degree of protein supplementation. Crop mixtures, generally referred to as intercrops, have the potential to boost the forage protein content of diets as well as having a number of agronomic benefits. In this paper, the growth and utilization of annual intercrops is reviewed with particular reference, where feasible, to temperate regions. General agronomic and feeding issues associated with cereal intercrops are outlined together with the practicalities of field-scale management of intercrops in highly mechanized systems. A number of cereal-based intercrop combinations are also considered, concentrating specifically on their value for forage production. The future potential for different combinations is discussed and research recommendations made.

Notizen: The research goal was to determine whether crop damage from herbicides measured early in the growing season soon after treatment could be used to estimate relative crop yield loss. Percentage stunting was rated visually and percentage crop ground cover (i.e. percentage of the ground surface covered by vegetation) was determined from video photographs taken 2–4 weeks after sethoxydim-susceptible maize (Zea mays L.) was sprayed with sethoxydim at various rates plus crop oil concentrate. Averaged over 3 years, relative percentage maize yield was a negative sigmoidal function of relative sethoxydim rates from 0.065× to 0.5×, where the 1× rate was 420 g a.i. ha−1 (r2 = 0.80). Relative maize yield was positively linearly related to percentage crop ground cover and negatively linearly related to rated percentage stunting averaged over 3 years. Linear regression models of relative maize yield vs. percentage maize ground cover explained only slightly more data variability (r2 = 0.86) than did rated stunting (r2 = 0.82) over 3 years. The advantages and disadvantages of rated stunting and crop ground cover as scientific measurements are discussed.

Notizen: Avena fatua L. populations from numerous fields in Alberta have simultaneously developed resistance to recommended rates of two dissimilar herbicides, triallate and difenzoquat. We used exogenous applications of gibberellic acid (GA3) to investigate the possibility that endogenous gibberellins were involved in the A. fatua's resistance mechanism. For control plants, without applied GA3, shoots of the most resistant (R) populations emerged more rapidly and elongated faster than shoots of the susceptible (S) populations. Increases in shoot elongation in response to exogenous GA3 were significantly lower in R populations compared with S populations. This suggests that R populations may have elevated endogenous gibberellin levels, relative to S populations. Additionally, inhibition of S population shoot elongation and shoot anatomical abnormalities caused by relatively low concentrations of triallate and difenzoquat could be prevented by exogenous application of GA3. These results suggest that there may be a phytohormonal involvement in the mechanism of triallate/difenzoquat resistance in A. fatua. That is, higher endogenous gibberellin levels in R populations may result in meristematic growth that is rapid enough to preclude phytotoxic levels of these herbicides from reaching the shoot meristem, which is the likely site of action.

Notizen: Parthenium hysterophorus L. seeds were buried at a depth of 5 cm for periods of 2–24 months to determine their longevity. The majority (73.7%) of these seeds were still viable after 24 months of burial. The remainder could not be recovered (18.0%) or were no longer viable (8.3%). There was a log-linear decline in persistence of germinable seeds over time, which indicated a constant rate of loss and a half-life of about 6 years. Seedling emergence from surface-sown seeds was also studied. Although there was considerable rainfall (31 mm), seedlings did not emerge during the first month of this experiment. In the succeeding 3 months, there was substantial seedling emergence after rainfall, and 51.4% of seeds had germinated by the end of the fourth month. After 5 months had passed, further seedling emergence was not detected, and intact seeds could not be located. These findings suggest that seed incorporation into the soil is important to the long-term persistence of P. hysterophorus seeds. In an initial test of germination, unburied seeds from the same seed lot exhibited a degree of innate dormancy, and this may explain the delayed germination observed in the surface-sown seeds. In the seed burial and recovery experiment, innate dormancy was lost after 2 months of burial in the field, although in situ germination of buried seed remained low for at least 24 months. Therefore, it appears that more than one dormancy mechanism may contribute to the persistence of P. hysterophorus seeds.

Notizen: Germinability and emergence of Sisymbrium orientale Torn. seed susceptible and resistant to acetolactate synthase (ALS)-inhibiting herbicides was investigated. Freshly harvested seed from a field containing confirmed ALS-inhibiting herbicide-resistant (ALS resistant) plants and susceptible seed from a nearby field was found to exhibit strong innate dormancy initially. However, germinability of seed from both resistant and susceptible biotypes increased to 50% after 1 month, indicating that innate dormancy had been partly relieved. No significant differences in behaviour of resistant vs. susceptible biotypes were recorded over 3 years. Field experiments conducted over a 4-year experimental period, to determine seedbank longevity in the absence of fresh seed input to the seedbank, revealed S. orientale to have a short seedbank life. Cultivation stimulated seedling emergence compared with no-tillage seedling emergence. These findings establish that persistence of S. orientale in the seedbank is short if fresh seed production is prevented. This knowledge can be used to manage populations of S.␣orientale, especially in cases such as this where the population is herbicide-resistant.

Notizen: Growth and berry production of triazine-susceptible and -resistant Solanum nigrum L. in the field with and without a maize crop were studied over 3 years. Delayed transplanting reduced the final dry matter production and berry production greatly. In most of the experiments, the final total dry matter production and berry production of the triazine-resistant biotype were lower than those of the susceptible biotype. However, relative growth rates of both biotypes in a maize crop were similar during the exponential growth phase. One important determinant of final dry matter and berry production could be dry matter growth in the very young seedling phase. Although dry matter production and reproduction of the resistant biotype in a maize crop will be lower than that of the susceptible biotype in the absence of the selecting herbicide, management strategies to control resistant biotypes of S. nigrum should not only be based on this characteristic.

Notizen: A range of herbicides was evaluated for the control of Chromolaena odorata (L.) K & R in oil palm at the Nigerian Institute for Oil Palm Research. Glufosinate-ammonium quickly dessicated treated foliage but weed plants soon recovered. Glyphosate-isopropylamine and glyphosate-trimesium produced similar results, both formulations controlling treated vegetation and suppressing regrowth for up to 12 weeks after treatment. Triclopyr and hexazinone + diuron were effective for up to 20 WAT, whereas imazapyr controlled regrowth for up to 36 WAT. Regrowth of the weed from its roots was better suppressed when the foliage was left undisturbed for 4–7 days after herbicide treatment. Repeated annual applications of triclopyr, hexazinone + diuron, the two formulations of glyphosate or imazapyr progressively reduced the biomass of C. odorata in the plots. In particular, imazapyr effectively eliminated the weed after the second application. Taking crop tolerance into consideration, the most promising herbicide treatments were glyphosate at 2.4 kg a.i. ha−1 and low rates (0.5 kg a.i. ha−1 or less) of imazapyr.

Notizen: The potential accuracy of using airborne multispectral imaging to map weed patches rapidly in a fallow field has been evaluated. An image of a field of oilseed rape (Brassica napus L.) stubble interspersed with Panicum effusum R. Br. was acquired using a four-camera airborne digital imaging system; recording in the infrared, red, green and blue wavebands. The image was converted into georectified weed maps using supervised and unsupervised classification procedures. Comparison of the airborne-derived maps with an accurate weed map compiled from a detailed ground survey demonstrated that weed:non-weed classification and mapping accuracies of better than 87% are possible. The limitations of assessing the accuracy of classified imagery using ground-truth data of similar spatial resolution are discussed.

Notizen: The ability of barley to compete with Lolium rigidum Gaud. was evaluated in a replacement series competition experiment under glasshouse conditions. A similar, positive response to nitrogen applications on growth, seed production and nitrogen uptake by barley and L. rigidum was found. The nitrogen level did not alter the competitive relationship between the species. There was reciprocal competition between barley and L. rigidum but, because of earlier tillering and nitrate absorption by barley, the competition from the crop was greater. L. rigidum exhibited a prolonged period of tillering and nitrate absorption and competed less with the barley. The relative yield total in the mixture was greater than 1 as a result of the different time of nitrate absorption by both species. The role of nitrogen fertilizer in the competitive relationship between the species is considered in terms of the period of application and the nitrogen salt used.

Notizen: Field experiments were conducted from 1994 to 1997 at two locations to study the effectiveness of chlorsulfuron and triasulfuron applied through different irrigation methods (chemigation) for control of Orobanche aegyptiaca Pers. in tomato (Lycopersicon esculentum Mill). Three split applications of chlorsulfuron at 2.5 g a.i. ha−1 and of triasulfuron at 7.5 g a.i. ha−1, through conventional sprinkler irrigation systems, 10–14 days apart followed immediately by sprinkling with water, controlled O. aegyptiaca by about 90% and 80% and increased crop yield 25–47% and 30%, respectively, without any crop injury symptoms. Repeated applications of the same herbicides at half rates resulted in slightly higher O. aegyptiaca control and crop yield than only one herbicide application at double rate. Chemigation by the sprinkler systems (microsprinklers, 60 m3 ha−1) slightly increased the herbicide efficiency as compared with the high volume spray (800 m3 ha−1). O. aegyptiaca control from sulfonylureas applied by drip chemigation was poor, as this probably requires very accurate timing and the herbicide distribution in the soil was not uniform.

Notizen: The long-term economic benefits of `patch' spraying are likely to be related to the initial spatial distribution of the target weeds, the demographic characteristics of the species and the weed control and crop husbandry practices to which they are subjected. This paper describes a stochastic simulation model developed to investigate the interaction between weed seed dispersal and patch spraying. Simulated weed plant and seed populations are generated and compared with data from field observations. Lloyd's Patchiness index is used to quantify the patchiness of the weed density distribution, and the parameter k of the negative binomial distribution is used as a measure of distribution shape. A method of assessing the spatial scale of weed aggregation is proposed, in which spatial weed density information is transformed into the frequency domain, using a discrete two-dimensional Fourier transform. In this paper, we simulate `on/off' patch spraying (full or zero herbicide application rate). A quantitative analysis of the effects of sprayer resolution and weed seed dispersal range on the herbicide reduction and yield benefits from patch spraying is performed for three initial spatial seedbank distributions. The model is parameterized for the grass weed Alopecurus myosuroides Huds. Herbicide is applied in square areas (whose size is defined by the spatial resolution of the sprayer) in which mean weed density is greater than or equal to one plant m–2. For a system conforming to this specification we show that for the control of A. myosuroides, it is unlikely that patch spraying would be profitable in the long term if the control area is larger than 6 m × 6 m. In some circumstances higher resolution may be required.

Notizen: The capacitance probe is an attractive device for monitoring soil moisture automatically. However, its sphere of influence is rather small (a few cubic centimetres only). We have analysed the possibility of monitoring moisture at the field scale using only a few probes (≤3). We calibrated each probe by establishing a direct relation between the field average soil moisture θf and the signal given by the probe. As in earlier studies, we found that a linear relation is generally suitable. A classical statistical analysis was performed to assess the error of a single probe. When replicate probes were installed, we obtained replicate estimates of θf. We proposed an estimator θf that combines all replications optimally.Three experiments each lasting several months were carried out on bare tilled fields to evaluate the probe against gravimetric measurements. Our results show that the calibrations differ significantly from one probe to another. Once calibrated, the capacitance probe provided accurate soil moisture measurements (70% of the calibration relations had residual standard deviations 〈 0.02m3m−3), but it is advisable to have at least two replicate probes. Soil water storage was well estimated by combining four to seven probes to establish the moisture profile, despite the error induced by each probe. Moreover, the temporal variations in water storage were accurately measured by the probes. We found an error of 0.6 mm day−1 (standard deviation) in daily variation of the water storage, which partly involved the error made on the reference measurements (gravimetric method).

Notizen: Various extractants used in current analytical procedures for the fractionation of sulphur (S) in soils were compared with respect to their ability to dissolve Al hydroxy sulphate minerals of defined composition (basaluminite, K alunite, mixtures of basaluminite and Na alunite). The minerals were synthesized and aged in the laboratory at 20°C and 50°C. The dissolution kinetics at 20°C of these Al hydroxy sulphates in deionized water, 0.02M HCl and 0.02M NaOH were also investigated.The dissolution stability of the Al hydroxy sulphate minerals increased in the order basaluminite 〈 K alunite 〈 Na alunite. The dissolving power of the reagents used increased in the order H2O ≤ 0.016M KH2PO4≪ 0.02M HCl ≈ acidic NH4 oxalate ≈ 0.5M NaHCO3 〈 Na2 CO3/NaHCO3 〈 0.1M NH4F 〈 0.5M NH4F 〈 0.05M NaOH ≤ 0.05M LiOH. In Al hydroxy sulphate-containing soils, inorganic S is probably understimated and ester sulphate S overestimated, if the inorganic S pool is assessed by extraction with KH2PO4, Ca(H2PO4)2 or NaHCO3 solutions. The dissolution of all studied Al hydroxy sulphates, particularly that of K and Na alunite, in H2O and 0.02 M HCl is strongly delayed by kinetic restraints. Thus it seems unlikely that Al3+ or SO2−4 activites in soil solutions are strictly regulated by precipitation/dissolution equilibria of these minerals except for horizons with extraordinarily slow seepage water movement.

Notizen: Tea (Camellia sinensis L.) is generally grown in highly weathered acidic Ultisols of the humid tropics. The low pH, large P fixing capacity and moisture content of these soils favour the dissolution of phosphate rock. Plant species differ widely in their ability to take up P from phosphate rock, and we have compared phosphate mobilization in the rhizosphere of tea with that under calliandra (Calliandra calothyrsus L.), Guinea grass (Panicum maximum L.) and bean (Phaseolus vulgaris L.) by studying the changes in the concentration of P fractions at known distances from the root surface in an acidic (pH in water 4.5) Ultisol from Sri Lanka treated with a phosphate rock. Plants were grown in the top compartment of a two-compartment device, comprising two PVC cylinders physically separated by a 24-μm pore-diameter polyester mesh. A planar mat of roots was formed on the mesh in the top compartment, and the soil on the other side of the mesh in the lower compartment was cut into thin slices parallel to the rhizosphere and analysed for pH and P fractions.All plant species acidified the rhizosphere (pH [water] difference between bulk and rhizosphere soils was 0.17-0.26) and caused more rock to dissolve in the rhizosphere (10–18%) than in the bulk soil (8–11%). Guinea grass was most effective, though the rate of acidification per unit root surface area was least (0.02μmol H+ cm−2) among the four species. Tea produced the largest rate of acidification per unit root surface area (0.08μmol H+ cm+2). All species depleted P extracted by a cation–anion exchange resin and inorganic P extracted by 0.1 M NaOH. All except tea depleted organic P extracted by 0.1M NaOH in the rhizosphere. The external P efficiencies (mg total P uptake) of Guinea grass, bean, tea and calliandra in soil fertilized with phosphate rock were 4.82 ± 0.42, 4.02 ± 0.32, 1.06 ± 0.02 and 0.62 ± 0.02, respectively, and the corresponding internal P efficiencies (mg shoot dry matter production per mg plant P) were 960 ± 75, 1623 ± 79, 826 ± 33 and 861 ± 44. This study showed that the various crops cultivated in tea lands differ in their rates of acidification, phosphate rock dissolution and P transformation in the rhizosphere. This requires testing under field conditions.

Notizen: Prediction of compaction, tillage, root growth or other soil deformation events requires a description of the stress–strain properties of the soil such as the critical state model, but estimating the parameters is time consuming and expensive. I have developed a method of estimating critical state properties from a single shear box test, both saving much labour and providing more information than traditional analyses. The method is based on critical state analyses of the constant stress and constant volume shear box tests using the total stresses applied at the boundary. It derives the critical state property parameters from test data by minimizing the difference between test data and the simulated soil deformation (and hence the properties used in that simulation). The minimization is a form of regression analysis. The analyses resulted in good simulations of the history of states in space defined by τxyγxy and e space (constant stress test) or τxyγxy and σy space (constant volume test).For normally consolidated samples, the analysis of a single constant stress test provided estimates of the slope of the critical state line (M), the slope of the virgin compression line (λ), the slope of the rebound line (K), and the elastic modulus (E). The standard deviation of the estimate of kcould not be found. By contrast, the analysis of the constant volume test resulted in poor estimates, particularly of λ. This is because the test yields no information on changes of volume during deformation: hence volume change parameters are not successfully estimated. The constant volume test is therefore not suitable for back analysis.

Notizen: Microorganisms can clog pores in soils and decrease hydraulic conductivity and infiltration. We did three column experiments to clarify the effects. In all three columns, glucose solution of 50 μg cm−3 was percolated for 120 days, and both the saturated hydraulic conductivity, Ks, and the volume ratio of the gas phase, a, were measured continuously. The Ks decreased rapidly for the initial 10 days, and it slowly decreased for the following 110 days. By adding chloramphenicol to the second column as bactericide and cycloheximide to the third column as fungicide, we observed clogging by bacteria and fungi, respectively, bacterial clogging proceeding more rapidly than the fungal clogging. The volume of the gas phase increased and reached the maximum value of 30.6% after 103 days from the beginning of percolation. This large amount of gas was retained in the soil pores as bubbles and occluded the pathways of water, resulting in the decrease in Ks. When the percolating solution was changed to sodium azide (a strong biocide), after 120 days the volume of the gas phase decreased rapidly, and Ks increased simultaneously.

Notizen: Humic substances (HS) extracted from 14 Sphagnum peats of various geographical origin were submitted tocapillary electrophoresis (CE) in free solution and in entangled polymer solutions (25 gl-1 and 50 gl−1) of polyethylene glycol (PEG). Electrophoretic runs were made in uncoated capillaries (75 μm internal diameter) using a tris-hydroxymethylaminomethane (TRIS)-phosphate buffer (pH 8.3) eventually containing PEG and applying a voltage of 10 kV. The HS extract of a Lithuanian peat was fractionated by ultrafiltration into five fractions with a nominal mean relative molecular mass (M) of 3000, 7500, 20 000, 75 000 and 200 000 Da. Without PEG, migration times were not correlated with the logarithm of M, but linear relations were obtained with 25gl−1 and 50gl−1 PEG solutions. Both solutions separated the different fractions by size; the best regression and the largest interval of linearity, M from 3000 to 200 000 Da, was obtained with the 25gl−1 PEG solution. At 10kV and without PEG, migration times ranged from 6.5 to 8.1 min and did not differentiate the peats, whereas at 25gl−1 PEG, migration times ranged from 3.3 to 6.5 min and, when plotted as a function of either the r value or the von Post index (H), which are used to evaluate the degree of decomposition of horticultural peats, they separated samples on the basis of their geographical origin and probable type of mire complex. At 25gl−1 PEG, migration times also showed a well-defined linear decreasing trend with the increase of mean annual temperatures. These relations suggest the hypothesis that humification in mires goes along with an increase in the average size of humic molecules.

Notizen: Changes in land use can result in increased soil organic matter content, and decreases in Ca and pH which will affect the mobility of Cu in soil. We studied how the mobility and coagulation of dissolved organic matter and pH affected the mobility of Cu in contaminated sandy soil by batch and column experiments in the laboratory. The soil, with pH ranging from 3.8 to 5.7, had been polluted with Cu in the range 0.13–1.9 mmol kg−1 more than a decade ago. Calcium and Cu bound by dissolved organic matter (purified humic acid) was determined in the pH range 4–8; Cu2+ concentration ranged from 10−4 to 10−12M and Ca2+ concentration from 10−3 to 10−6M. Binding of Cu by dissolved organic matter as affected by Ca and pH could be predicted well with the non-ideal competitive adsorption (NICA) model. Coagulation of dissolved organic matter was affected by the amount of trivalent (Al3+) and divalent (Ca2+ and Cu2+) cations in solution. There was little effect of pH on coagulation between pH 4 and 6. The concentration of the divalent cations, Ca2+ and Cu2+, at which coagulation of dissolved organic matter appeared could be explained by differences in the binding of Ca and Cu by dissolved organic matter. Binding of Cu by dissolved organic matter as well as by solid organic matter, both affected by Ca and pH, could be described well with the NICA model. We investigated the coagulation and mobility of dissolved organic matter in column experiments and found that they enhanced Cu mobility. Three processes, Cu desorption by soil, dissolved organic matter coagulation and Cu complexation by dissolved organic matter, act simultaneously in the soil columns. All three with counteracting effects on Cu mobility are influenced by Ca and pH and could be adequately represented by the multicomponent NICA model.

Notizen: The plant availability of phosphate applied to calcareous soils is affected by precipitation and adsorption reactions, the relative significance of which is not well known. We used extended P-sorption curves obtained at phosphate addition rates up to 340 mmol P kg−1 soil to examine the relative contribution of precipitation and adsorption by 24 calcareous Spanish Vertisols and Inceptisols. Adsorption was dominant at 1 day and at small rates of addition (10–35 mmol P kg−1). With increasing clay and Fe and Al oxides contents of the soil, more phosphate was sorbed before the sorption curve bent upwards, as a result of Ca phosphate precipitation. Sorption curves showed a nearly vertical intermediate region, the length of which increased with time, suggesting that a Ca phosphate buffered the concentration of P in solution. The buffering concentration decreased with time, suggesting a progressive transformation of more to less soluble forms of Ca phosphate. A phase less soluble than octacalcium phosphate seemed to control the concentration of P in solution at 180 days in most soils. The apparent solubility of this phase decreased with increasing carbonate content in the soil. Precipitation of poorly soluble Ca phosphates apparently predominated up to a P addition dose ranging from about 30 mmol P kg−1 in some soils to more than 340 mmol P kg−1 in others. At larger doses, the way additional P was bound to the solid phase was different; phosphate was probably adsorbed, at least in part, to low-affinity sites on silicate clays and oxides.The proportion of sorbed phosphate that was isotopically exchangeable decreased with time, soil carbonate content and P addition dose for doses 〈100 mmol P kg−1. This is consistent with the idea that P in Ca phosphates is less isotopically exchangeable than P adsorbed on mineral surfaces. At larger additions of P, isotopic exchangeability was unrelated to the soil properties measured, probably because there was a variety of sorbed P forms influenced in turn by different soil components.

Notizen: The most widely used method for measuring the emission of a trace gas such as N2O from soil to the atmosphere involves the accumulation of the gas under closed chambers followed by sampling and analysis (by gas chromatography or infrared methods). These chambers can affect the gas exchange, and so improved designs have been proposed. We have tested their performance. One design includes a vent tube to allow ambient pressure fluctuations to occur also inside the chamber. We tested it against a sealed version on two different grassland sites during N2O peak emissions in spring 1997. On a welldrained soil with a fairly large air permeability vented chambers yielded fluxes as much as five times those of sealed chambers, depending on wind speed. By contrast, on a heavier and wetter soil with smaller air permeability vented chambers averaged only 88% of the fluxes observed with sealed chambers. The effects of venting cannot be explained solely on the basis of mean pressure differences inside and outside the chamber. It seems more likely that wind blowing over the vent depressurizes the chamber (Venturi effect), resulting in significant gas flow from the more permeable soil into the interior of the chamber. The opposite trend for the less permeable soil suggests that diffusion losses through the vent tube are greater than the increase in concentration due to soil gas flow. Venting can create larger errors than the ones it is supposed to overcome.

Notizen: Terre Rosse and Rendzinas occur on limestones close together under the same climatic conditions. Their differences in iron oxide mineralogy are believed to be due to differences in the pedoclimate. We monitored the soil moisture tension and the soil temperature over nearly 3 years in Terra Rossa-Rendzina pairs on hard limestone and soft chalk in Israel. The Terre Rosse dried out more rapidly than the Rendzinas mainly because of their smaller water-holding capacity. In summer, average soil temperatures in the Rendzinas were significantly lower than in the Terre Rosse.Haematite dominates the red Terre Rosse and goethite the yellower Rendzinas. This difference appears to be related to the soil climate, specifically the moisture regime of the two soils, and supports the hypothesis that release of Fe and formation of ferrihydrite in Terre Rosse during the wet winter is followed by transformation to haematite during marked desiccation in the dry summer. By contrast, wetter soil conditions in the Rendzinas direct the formation of Fe oxides more towards goethite. either directly or by transformation of ferrihydrite via solution.

Notizen: Frequent applications of chicken manure to a volcanic-ash soil resulted in an increased crop yield several years after the applications ceased. Improved nutrient cycling through the soil organic matter (SOM) was thought be the cause of this. An area that for several years had been under either unimproved fallow or continuous bean-maize intercropping (with chicken manure application) was planted with maize intercropped with the legume Arachis pintoi. Soil samples were fractionated into several sizes of aggregates and incubated for 6 weeks in intact form and after crushing the aggregates. Between 1.2 and 3.1% of the C in any aggregate size class exited in easily decomposable (i.e. not physically or chemically protected) form. Less than 0.8% of the macroaggregate C was physically protected by the aggregate structure. More than 97% of the C in any aggregate size class can be considered resistant. The large-or small-macroaggregate-protected SOM (i.e. in aggregates 〉 2000 μm and 250–2000 μm, respectively). once made available, was more easily decomposed than the unprotected SOM. The large SOM content (45.8–57.3 g C kg−1) but yet limited mineralizability indicates that mechanisms other than soil macroaggregation are important for protecting SOM in this soil. Binding of organic molecules onto allophane minerals is likely to be such a mechanism.The larger yield and nutrient uptake by the maize in the former bean-maize plots compared with the former fallow plots could not be explained by differences in SOM decomposition. We think that the frequent application of chicken manure to the former bean-maize plots increased the available phosphorus in these strongly P-sorbing soils by increasing the cycling of organic-P or by blocking some of the P-reactive sites. This, however, needs to be further investigated.

Notizen: The effects of a 3-year ley-arable rotation (2 years under grass, legume or a grass-legume mixture, followed by 1 year under cassava) on the organic C content of upland sandy soils in Northeast Thailand were evaluated using four field trials (Khon Kaen, Chaiyaphum, Mahasarakham and Udon Thani). At all sites under the existing management system of continuous cassava, soil organic C decreased by 9-20% during the 3-year experiment. The carbon model developed at Rothamsted (RCM-26) predicted that soil organic C would decrease consistently under continuous cassava until it reached very small amounts (0.2–0.3%). This was the case for all sites, except Chaiyaphum, where soil organic C had already declined to 0.1%. Evaluatin the rotations using RCM-26 showed that introducing a ley could increase soil organic C, except at Udon Thani where the organic C exceeded 0.47% before the start of the experiment. The data obtained with the rotations showed that RCM-26 could be used to predict the effects of changes in management on organic C content in the upland sandy soils of Norrtheast Thailand over the 3 years. To compensate for an underestimation of the effects of soil moisture deficit on the decomposition rates of organic matter, we propose that because of the prolonged dry season (from December to the following May) soil moisture deficit and the rate-modifying factor for moisture (Am) should be estimated independently of crop cover. Furthermore, to accommodate the very slow decomposition during this time, (Am) should be allowed to decrease to 0.1. Adopting this simple modification provides a more realistic estimate of the organic C inputs needed to simulate the content of soil organic C measured before trials began.

Notizen: Some minerals have large PO43− sorption capacities. However, we do not know how these mineral phases influence the speciation of organic P when organic matter decomposes. To characterize the interactions between mineral phases and organic P species, we incubated mixtures of beech leaf litter and Fe oxide, Al hydroxide, birnessite, and quartz sand. The samples were extracted with NaOH-NaF and analysed by 31P nuclear magnetic resonance (NMR) spectroscopy. Phosphate mono-and diesters gave the most prominent signls in the 31P NMR spectra. During incubation, the proportion of the monoester P decreased, whereas that of the diester P increased. Since NMR intensities assigned to teichoic acids increased, it seems that microbial P accumulated during incubation. The synthesis of microbial compounds was strongest in the presence of Fe oxide. All mineral phases investigated gave rise to a resonance in the 31P NMR spectra which was not present in the control treatment to which the mineral phases had not been added. The resonance was tentatively assigned to sugar diesters, which probably originated from organo-mineral interactions.

Notizen: Ilmenite-rich samples were obtained by chemical extraction methods from materials collected from a soil developing on an amphibolite and from its altered parent rock. The soil ilmenite of this mantle was found to be inherited from the rock, but its composition varied significantly from one soil fraction to another and according to its mineralogical association. Unit cell parameters are smaller than those of pure ilmenite: the a-dimension of the hexagonal structure varies from 0.5076 ± 0.0004 to 0.5083 ± 0.0007 nm. Mössbauer patterns at room temperature reveal that this mineral, which is most often associated with the iron-rich spinel phase, actually corresponds to a member of the haematite–ilmenite series having the general formula xFeTiO3.(1-x)Fe2O3, with 0.83 ≤x≤ 0.95. There is a correlation (r= 0.95) between x, the molar fraction of FeTiO3, and the a-dimension of the unit cell.

Notizen: The influence of clay content and silt–clay fabric on aggregate stability was investigated. Two silt—clay fabrics were produced in the laboratory by mixing silt particles with a clay phase: (i) a loose packing of the silt particles with clay aggregates, and (ii) a close packing of the silt particles with the dispersed clay phase, the latter coating and bridging the silt particles. Porosity and pore size distribution were measured, and the silt—clay fabric was described using scanning electron microscopy. The aggregate stability was measured under three treatments corresponding to different wetting conditions and energy levels: fast wetting, mechanical breakdown and slow wetting. Our results show that aggregate stability is related to both clay content and silt—clay fabric. Comparison of fragment size distributions and their mean weight diameter amongst the three treatments enabled identification of mechanisms responsible for the variation of aggregate breakdown. The compression of trapped air was the predominant breakdown mechanism for both fast and slow wetting and was related mainly to porosity characteristics. For the mechanical breakdown, the degree of disintegration depended on the cohesion of the silt–clay fabric, which is related to the continuity of the solid phase.

Notizen: Podzols tend to form on drift sands in The Netherlands given sufficient time. Differences in organic matter (OM) composition relate to vegetation succession on drift sand that evolves eventually into a micropodzol. We examined the relation between the water-soluble organic matter (WSOM) and the total OM composition in the Ah horizons of the first vegetation stages, under grass (Corynephorus canescens), moss (Polytrichum piliferum), heather (Calluna vulgaris) and pine (Pinus sylvestris), as determined by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and analysis of polysaccharides after acid hydrolysis. Polysacharides dominate the OM in the Ah horizons under grass and moss. Lignin and aliphatic compounds are minor compounds in these profiles, but are more important under heather and pine. The Py-GC traces of the WSOM under grass and moss contain abundant products derived from polysaccharides. The water-soluble fraction is enriched in phenolic and aliphatic compounds in comparison with their contents in pyrolysates of the total OM. In the WSOM fractions under heather and pine, phenols dominate the pyrolysates, whereas lignin-derived methoxyphenols are rare. Remarkably large amounts of alkenes and alkanes are present in the pyrolysates of these water-soluble fractions, most probably derived from aliphatic biopolymers. Their presence in water might be explained through the formation of colloids, which are stabilized by micelle-like arrangements.

Notizen: The impact on nitrate leaching of agronomic practices designed to immobilize nitrogen in autumn and winter was investigated over 4 years. Experimental treatments (reducing tillage depth, incorporating harvest residues, reducing fertilizer N by growing unfertilized grass or by spring-sown rather than autumn-sown crops) were compared with a control treatment in which autumn crops were sown after burning harvest residues, mouldboard ploughing and seedbed preparation. Winter cover cropping was also compared with winter fallowing. In the first year, incorporation of harvest residues or reducing tillage depth significantly decreased nitrate leaching compared with the control. Unfertilized grass did not affect leaching in the first winter but significantly decreased it in years 2 and 3. When winter cover crops were grown, nitrate leaching was never less than that under an autumn-sown cereal, and in the subsequent year leaching could be significantly greater. Winter fallowing caused the most nitrate leaching over the year. In the winter following a spring-sown crop, leaching under an autumn-sown crop greatly increased. Summed over 4 years, most leaching occurred with the winter fallow—spring cropping treatment; it was 18% more than where a winter cover crop preceded the spring crop. Reducing tillage depth or incorporating harvest residues did not significantly decrease leaching. Unfertilized grass ley followed by an autumn-sown cereal in the fourth year was the only treatment that significantly decrease leaching. Unfertilized grass ley followed by an autumn-sown cereal in the fourth year was the only treatment that significantly reduced leaching loss compared with the control. Incorporating harvest residues resulted in a balance between annual N inputs and outputs. All other treatments required substantial net annual N mineralization to balance annual inputs and outputs.

Notizen: Zinc (Zn) deficiency symptoms and sporadic responses to applied Zn are being observed frequently in the Nigerian savanna, and one cause is thought to be the growing use of phosphorus (P) fertilizers. This study was designed to test the hypothesis of P-induced Zn retention in the soils. Soil mixed eith P was incubated at field capacity for 3 weeks at 30 ± 2°C. P levels added to the soil were 0, 500, 1000 and 2000 mg per kg soil. After 3 weeks of incubation, water-soluble Zn in soil decreased by 92% and exchangeable Zn by 78% with 2000 mg kg−1 of applied P. Zn levels ranging from 0 to 200 mg kg−1 were added to the P-incubated soil to determine the Zn sorption isotherm and retention capacity. The P-treated soil retained 93 ± 2% of added Zn compared with 52 ± 2% of the control soil. P treatment changed the Zn sorption isotherm from an L-curve isotherm to an H-curve isotherm, indicating strong affinity of P-treated soil for Zn, probably as a result of the formation of Zn-phosphate complexes on the soil surface and precipitation at sufficiently large concentrations of P and Zn. At 2000 mg P kg−1, up to 90% of Zn retained by the soil was bound in solid form as ZnHPO4. Varying the soil pH from 3.5 to 9.0, Zn retention by the soil was related to Zn hydrolysis with maximum adsorption occurring at pH 7.3 ± 0.2. The dependence of sorbed Zn on Zn(OH)2° at pH 3.5–7.4 of P-treated soil indicated that significant van der Waals forces might be involved in Zn retention. The implication of the results of this study for the region is that fertilizer-P placement around a growing crop plant, commonly practised to maximize fertilizer-P efficiency, can potentially limit Zn solubility and availability.

Notizen: Permafrost desiccates and indurates soil horizons. During summer, the perennially frozen ground under the active thawed layer creates confined conditions, Whereas in winter the closed system between the permafrost and the freezing front migrating downwards leads to irreversible changes in the soil structure and to transformation and neoformation of minerals. Two examples were studied by field observation and laboratory analyses (optical microscopy, scanning electron microscopy, X-ray diffractometry, transmission electron microscopy and analytical electron microscopy). In Transbaikalia (southeastern Siberia) a Pleistocene cryogenic slope deposit on syenite contains detrital clays (chlorite, illite), but neoformed ferroan smectites dominate. In Patagonia, centimetre-sized silica concretions containing spongy and spheroidal opal occur in alluvium ascribed to cold Pleistocene periods. They seem to have formed from primary detrital smectite that was transformed to fibrous clay (sepiolite) then to acicular opal, and eventually to spheroidal opal. The neoformed opal contains 27% magnesium. These features occur systematically within fossil cryoturbations not related to present conditions. It appears that clay transformation and neoformation can happen at temperatures far lower than 0°C.