ALBERT

Notes: Book reviewed in this article: SOILpak for Cotton Growers. Third edition 1998. Edited by David C. McKenzie.

Notes: Abstract. Preferential flow has been increasingly recognised as a major component of water movement in many soils, particularly clays. This paper reviews problems in the measurement of solute fluxes in these soils, and discusses the solutions that have been adopted in UK studies of cracking clay soils. The estimation of solute fluxes is subject to many sources of error, which are best reduced by replicated measurements, such as those available in multi-plot experiments.

Notes: Abstract. Soil cores from river marginal wetlands from three sites in the UK (Torridge and Severn catchments), sampled and restrained in PVC piping, were flooded with dilute aqueous potassium nitrate. Half of the cores were sterilized prior to flooding to destroy the denitrifying bacteria. The change in nitrate concentration in the flood-water was measured over time. It is argued that the observed nitrate depletion rates (from 1.2 to 4.7 kg ha−1 d−1) is the result of microbially-mediated denitrification. The results show the method to be a simple and direct procedure for the assessment of spatial variation in nitrate-sink capacity. The depth of the denitrifying layer at the soil–water interface was confirmed to be of the order of a few mm only. A one-dimensional model for the diffusive flux in the flooded soil was developed which, on differentiation, gave a predictive expression for denitrification rate in terms of the effective soil diffusion coefficient for nitrate, the flood-water depth and concentration, and the thickness of the microbially active zone.

Notes: Book reviewed in this article: The Soils and Land Use Potential of the Southern and Eastern Slopes of Kilimanjaro, Tanzania.

Notes: Abstract. A database of 1065 fields in all parts of Finland, two soil profiles (augerhole borings) per field, was screened for acid sulfate (a.s.) soils. Each field represented 2100 14;ha of cultivated land. Soil pH and redox potential were determined in the field, at intervals of 10 14;cm, to a depth of 200 14;cm. Of the maximum of 124 profiles considered as a.s. soils according to the Soil Taxonomy and ILRI (International Institute of Land Reclamation and Improvement) systems, 46 profiles exhibited pH 〈3.5. These represented 48 14;000 14;ha of land. More than half of these severely acidic soils were associated with reduced subsoils and probably contained actively oxidizing sulfidic materials within 150 14;cm of the soil surface, while the remaining profiles were oxidized at least down to 150 14;cm. Using Soil Taxonomy criteria, the total area of cultivated a.s. soils was 67 14;000–130 14;000 14;ha. The minimum estimates exclude soils that may be leached or too low in sulfide to meet the criteria of a.s. soils. Application of the ILRI system produced an estimate of 61 14;000–130 14;000 14;ha. In the maximum estimate, 27% of the profiles were raw, 61% ripe and 12% potential a.s. soils. According to the FAO/UNESCO system, the area of cultivated a.s. soils (pH 〈3.5 or assumed sulfidic materials) is considerably less: 43 14;000–78 14;000 14;ha. All these estimates are only a fraction of the area considered to be covered by a.s. soils by established Finnish criteria. The choice of estimate has important economic implications for liming subsidies and planning regulations for the drainage of a.s. soils.

Notes: Abstract. The effect of increasing rates of nitrogen (N) fertilizer on the yield response of 3 or 4 consecutive winter cereal crops after ploughing out grass was investigated at six field sites on commercial farms in England and Wales. Amounts of N required for an economically optimum yield (〉3 kg of grain for each kg of fertilizer N applied) ranged from 0 to 265 kg ha−1 and were dependent on soil N supply, but not on crop yield. Optimum N rates were large (mean 197 kg N ha−1) at three sites: two sites where cereals followed 2-year grass leys receiving low N inputs (〈200 kg N ha−1), and at one site where a cut and grazed 4-year ley had received c. 315 kg N ha−1 of fertilizer N annually. At the other three sites where 4 and 5-year grass leys had received large regular amounts of organic manures (20–30 t or m3 ha−1) plus fertilizer N (c. 300 kg ha−1 each year), optimum N rates were low (mean 93 kg N ha−1) and consistently over-estimated by the farmer by an average of 107 kg N ha−1. Optimum N rates generally increased in successive years after ploughing as the N supply from the soil declined. Determination of soil C:N ratio and mineral N (NO3N+NH4N) to 90 cm depth in autumn were helpful in assessing fertilizer N need. The results suggest there is scope to improve current fertilizer recommendations for cereals after grass by removing crop yield as a determinant and including an assessment of soil mineralizable N during the growing season.

Notes: Abstract. Soils, of clay texture, were taken from two crop rotations in a long term trial, (i) maize - spring oats - maize, (ii) maize - spring oats - autumn oats - red clover, and from an adjacent uncropped fenceline. Wet sieving was preceded by wetting under vacuum, wetting under tension or by direct immersion. The undisturbed soil was the most stable; the inclusion of clover in the rotation improved aggregate stability. Direct immersion was most disruptive in disintegrating aggregates followed by vacuum and pre-wetting under tension.

Notes: Abstract. A decision support system to predict the plant availability of nitrogen (N) following organic manure applications to land has been developed, drawing together the latest UK research information on factors affecting manure N availability and losses. The ADAS MANure Nitrogen Evaluation Routine (MANNER) accounts for manure N analysis, ammonia volatilization, nitrate leaching and mineralization of manure organic N. Only a few easily available inputs are required to predict the amount of N volatilized or leached, and the fertilizer N value for the next crop grown. Predictions from MANNER have been evaluated by comparison with independently collected data from a range of experimental studies where pig, cattle and poultry manures were applied to arable crops. Good agreement was found (r2 60–79%, P〈0.001), confirming that MANNER can provide a reliable estimate of the fertilizer N value of farm manures spread to arable land under a range of conditions.

Notes: Abstract. A lysimeter study from April 1993 to June 1997 assessed the effects of winter cover crops and unfertilized grass on both the volume of water draining over winter and the amounts of nitrate leached. There were three to five replicates of each treatment in a fully randomized design. The lysimeters were undisturbed monoliths of loamy medium sand, 1.2 m deep and 0.8 m diameter.There were six treatments: sown cover before spring-sown crops (SC), natural regeneration (‘tumbledown’) before spring-sown crops (T), unfertilized grass (UG), bare soil permanent fallow, (PF), winter barley (WB) and conventional overwinter fallow before spring-sown crops (WF). Sugarbeet replaced cereals in 1996 as a disease break, and in consequence no cover was established in SC and T in autumn 1996. Of the four years of the study, two were above-average rainfall, while two were of less than average rainfall. Results are only quoted if statistically significantly different from WB (P=0.10).Over the first winter, NO3―N losses were similar under UG (26 kg ha−1) and PF (29 kg ha−1), due to the slow establishment and growth of the grass. In the following three winters NO3―N losses under UG were small (c. 6 kg ha−1), giving an overall mean of c. 11 kg ha−1. Sown cover crops and T gave means of c. 16 and 22 kg ha−1 respectively, compared with c. 27–31 kg ha−1 under PF, WB and WF.Mean NO3―N concentrations were smallest under UG (4.4 mg l−1) and SC (10.6 mg l−1), although both T (13.7 mg l−1) and PF (12.4 mg l−1) were less than under WB and WF (15.8–18.7 mg l−1). Overwinter drainage was greatest from UG and PF, at 239 and 247 mm respectively. In the three winters that cover crops were grown, drainage was decreased by, on average, 30 mm year−1 compared with WF. However, there were large differences in effects between years, with significant decreases in only one year.We conclude that the widespread adoption of cover crops before spring-sown crops will reduce overwinter drainage in UK Nitrate Vulnerable Zones by no more than c. 2%, compared with no cover before spring-sown crops.

Notes: Abstract. Gross N mineralization and nitrification rates were measured in soils treated with dairy shed effluent (DSE) (i.e. effluent from the dairy milking shed, comprising dung, urine and water) or ammonium fertilizer (NH4Cl) under field conditions, by injecting 15N-solution into intact soil cores. The relationships between gross mineralization rate, microbial biomass C and N and extracellular enzyme activities (protease, deaminase and urease) as affected by the application of DSE and NH4Cl were also determined. During the first 16 days, gross mineralization rate in the DSE treated soil (4.3–6.1 μg N g−1 soil day−1) were significantly (P 14;〈 14;0.05) higher than those in the NH4Cl treated soil (2.6–3.4 μg N g−1 soil day−1). The higher mineralization rate was probably due to the presence of readily mineralizable organic substrates in the DSE, accompanied by stimulated microbial and extracellular enzyme activities. The stable organic N compounds in the DSE were slow to mineralize and contributed little to the mineral N pool during the period of the experiment. Nitrification rates during the first 16 days were higher in the NH4Cl treated soil (1.7–1.2 μg N g−1 soil day−1) compared to the DSE treated soil (0.97–1.5 μg N g−1 soil day−1). Soil microbial biomass C and N and extracellular enzyme activities (protease, deaminase and urease) increased after the application of the DSE due to the organic substrates and nutrients applied, but declined with time, probably because of the exhaustion of the readily available substrates. The NH4Cl application did not result in any significant increases in microbial biomass C, protease or urease activities due to the lack of carbonaceous materials in the ammonium fertilizer. However, it did increase microbial biomass N and deaminase activity. Significant positive correlations were found between gross N mineralization rate and soil microbial biomass, protease, deaminase and urease activities. Nitrification rate was significantly correlated to biomass N but not to the microbial biomass C or the enzyme activities. Stepwise regression analysis showed that the variations of gross N mineralization rate was best described by the microbial biomass C and N.

Notes: Abstract. The efficient use of biologically fixed N in agriculture is important in organic farming and when N fertilizers are either expensive or unavailable. The aim of the study was to determine the effects of cultivation and sowing dates on the efficiency of use of biologically fixed N built up during a period of grass/clover ley by subsequently sown ryegrass. Dates of cultivation in two field experiments conducted in consecutive years (1994/95 and 1995/96) ranged from August to October and sowing was carried out either immediately after cultivation or after a delay of one month. Nitrate-N losses through leaching, herbage yields and N offtake by ryegrass were measured from 1994 to 1996. A laboratory experiment was carried out to assess net N mineralization and nitrification in the soil of the field experiment under different conditions.The utilization of mineralized N ranged from 30 to 100 kg ha−1 in both field experiments. Herbage yield and recovery of mineralized N by ryegrass was greater when sowing was carried out immediately after cultivation than when it was delayed for one month. Cultivation in late October was inferior to cultivation in August or September but the optimum date (August to September) differed between the two years (1994/95 and 1995/96) due to differences in weather, especially rainfall, affecting N leaching during the germination and early growth phases. Indeed the main differences in the efficiency of utilization of mineralized N between treatments could be attributed to differences in NO3–N leaching losses during the autumn establishment period. Decreases in soil temperature during autumn resulted in a modest decrease in net N mineralization but a much more substantial decrease in the rate of nitrification, which has implications for NO3–N leaching. The optimum time for cultivation cannot be refined to a particular calendar date but reasonably accurate long-term rainfall forecasts in conjunction with data on soil moisture deficit would provide the means to set an optimum cultivation date.

Notes: Abstract. Deterministic leaching models are used to estimate regional losses of nitrate from agricultural land to the environment. The estimated leaching losses are associated with uncertainty arising from uncertainty in the input data used. In the present case study we have assessed this uncertainty by use of Monte Carlo analysis, using the Latin hypercube sampling technique. Input data have preferably been adopted from publicly available data. Data which could not be retrieved from the databases was assessed by guided estimates or based on local data. The estimated annual leaching loss from the study region was around 106 kg N ha−1, which is in agreement with previous findings. The uncertainty in the leaching expressed in terms of coefficients of variation (CV) depended on the agricultural practices. CV's for arable farm rotations, cattle farm rotations, and pig farm rotations were around 20, 30 and 40%, respectively. Breakdown of the total uncertainty into contributions of different error sources did not isolate one single all important source.

Notes: Abstract. The nitrogen (N) conserving effects of Italian ryegrass (Lolium multiflorum L.) undersown as a nitrate catch crop in spring barley (Hordeum vulgare L.) were evaluated over a ten-year period in outdoor lysimeters (1.5 m deep, diam. 1 m) with sandy loam soil. Spring barley grown every year received 11.0 or 16.5 g N m−2 before planting or was kept unfertilized. The N was given either as calcium ammonium nitrate or as ammoniacal N in pig slurry. From 1985 to 1989, ryegrass was undersown in the barley in half of the lysimeters while barley was grown alone in the remaining lysimeters. The grass sward was left uncut after barley harvest and incorporated in late winter/early spring. From 1990 to 1994 all lysimeters were in barley only.Barley dry matter yields and crop N offtakes were not affected by the presence of undersown ryegrass, although grain yields appeared to be slightly reduced. After termination of ryegrass growing, N offtake in barley (grain+straw) was higher in lysimeters in which catch crops had been grown previously.The loss of nitrate by leaching increased with N addition rate. Regardless of N dressing, ryegrass catch crops halved the total nitrate loss during 1985–1989, corresponding to a mean annual reduction in nitrate leaching of 2.0–3.5 g N m−2. From 1990 to 1994, lysimeters previously undersown with ryegrass lost more nitrate than lysimeters with no history of ryegrass. The extra loss of nitrate accounted for 30% of the N retained by ryegrass catch crops during 1985–1989.It is concluded that a substantial proportion of the N saved from leaching by ryegrass catch crops is readily mineralized and available for crop offtake as well as leaching as nitrate. To maximize benefits from ryegrass catch crops, the cropping system must be adjusted to exploit the extra N mineralization derived from the turnover of N incorporated in ryegrass biomass.

Notes: Abstract. Escherichia coli serotype O157 is a virulent human pathogen the global incidence of which has increased. It has been demonstrated that cattle are the primary reservoir of this pathogen. This has serious implications for the land-based disposal of organic wastes such as cattle manure, cattle slurry and abattoir waste. Further, it also has serious ramifications for the protection of surface and groundwater drinking supplies and public access to pasture land. However, while soil and vegetation can be expected to directly influence the survival of this pathogen, there is a paucity of information concerning the behaviour and survival of E. coli O157 in agricultural environments. It appears that E. coli O157 presently contaminates between 1 to 15% of UK cattle herds, depending on region, and that faecal excretion of the bacterium shows a distinct seasonality which also reflects the incidence of human infections. E. coli O157 can remain viable in soil for greater than 4 months and appears to be a highly resilient pathogen possessing the capability to adapt easily to environmental stresses. While most human cases of E. coli O157 related food poisoning have been associated with the consumption of contaminated meat and dairy products, there is also evidence that human infection has occurred through the ingestion of contaminated soil, fruit and vegetables and drinking water. In this review the potential threat to human health posed by the application of contaminated organic wastes to soil and possible strategies for reducing the amount of pathogen entering the food chain are highlighted.

Notes: Book reviewed in this article: Gaseous Nitrogen Emissions from Grasslands Edited by S.C. Jarvis & B.F. Pain.

Notes: Abstract. Growing cover crops during the winter before spring-planted crops is often suggested as an effective method to decrease nitrate leaching. A four-course crop rotation (potatoes-cereal-sugarbeet-cereal) was followed through two rotations on a sandy soil in the English Midlands. Three management systems were imposed on the rotation to test their effects on nitrate loss. The effects of cover crops on nitrate leaching and crop yields were compared with the more conventional practice of over-winter bare fallow before potatoes and sugarbeet.Cover crop N uptake was variable between years, averaging 25 kg ha−1, which is typical of their performance on sandy soils in the UK. The cover crops usually decreased nitrate leaching but their effectiveness depended on good establishment before the start of drainage. Over 7 years, cover crops decreased the average N concentration in the drainage from 24 to 11 mg l−1. Potato yield and tuber N offtake increased after cover crops. Ware tuber yield increased by an average of c. 8%; this was unlikely to be due to additional N mineralization from the cover crop because the potatoes received 220–250 kg fertilizer N ha−1, and non-N effects are therefore implicated. Sugar yield was not increased following a cover crop.After 8 years of nitrate-retentive practices, there were no measurable differences in soil organic matter. However, plots that had received only half of the N fertilizer each year contained, on average, 0.14% less organic matter at the end of the experiment.

Notes: Abstract. The Pilot Nitrate Sensitive Areas Scheme was set up in England in 1990 to test measures aimed at reducing nitrate losses from agricultural land. Ten groundwater catchments were chosen to typify the geology and farming of areas where nitrate concentrations in abstracted water were high. Voluntary and compensated controls on farming, based on recent research, were introduced. Scheme membership was for 5 years from 1990 or 1991, and 86% of the agricultural land entered the Scheme. On all farms entering the Scheme, manure and fertilizer use were restricted and green cover crops were required over winter (Basic Scheme). Additional payments were available for conversion of arable land to zero or low-input grassland (Premium Scheme). Intensive pig and poultry farmers were assisted with the costs of transporting manure for spreading over a wider area. The most effective changes were improved management of livestock manures, especially of the very large local quantities from housed pig or poultry units; conversion of arable land to low-input grassland; and use of cover crops. There were no indications of reduced crop yields but some requirements increased costs and management complexities. Estimates based on both model calculations and measurements indicated that nitrate losses from agricultural land decreased by about 30%, with considerable variation between areas.

Notes: Abstract. The structure of soils in areas of rain forest cleared for pasture is often compacted due to trampling by animals. When pasture is abandoned, regeneration of forest cover may be achieved from natural seed sources nearby.However, the regeneration of soil structure is also important for local hydrology and successful establishment of some plant species. In this study we investigated changes in soil structure and hydraulic properties in a series of plots on volcanic soils in the San Luis Valley, Costa Rica. The plots were current pasture, 15- and 20-year-old regenerating forest, and primary rain forest.Infiltration rate increased with increasing forest age and the water release characteristic reverted gradually from one with greater water retention at all matric potentials in the pasture plot towards that found in the primary forest. Compaction and low porosity were features of both the current pasture and 15-year-old regenerating forest in comparison to the primary forest.

Notes: Abstract. Over 170 countries have ratified the UN Framework Convention on Climate Change (UNFCCC) which aims at ‘the stabilisation of greenhouse gases in the atmosphere at a level that will prevent dangerous anthropogenic interference with the climate system’. The Kyoto Protocol, signed in 1997, commits the developed (‘Annex 1′) countries to a reduction in gaseous emissions. The global increase in atmospheric CO2, the main greenhouse gas, comes mainly from fossil fuels (6.5 Gt C yr−1), together with about 1.6 Gt C yr−1 from deforestation. The atmospheric increase is only 3.4 Gt C yr−1, however, due to a net sink in terrestrial ecosystems of about 2 Gt C yr−1, and another in the oceans. Increasing net carbon sequestration by afforestation of previously non-forested land is one way of reducing net national emissions of CO2 that is permitted under the Kyoto Protocol. Future modifications may also allow the inclusion of carbon sequestration brought about by other forestry and agricultural land management practices. However, associated changes in net fluxes of two other greenhouse gases identified in the Protocol — nitrous oxide (N2O) and methane (CH4) — will have to be taken into account. Growth of biomass crops can increase N2O emissions, and drainage of wetlands for forestry or agriculture also increases them, as well as emissions of CO2, while decreasing those of CH4. The problems of how to quantify these soil sources and sinks, to maximize soil C sequestration, and to minimize soil emissions of CH4 and N2O, will present a major scientific challenge over the next few years — one in which the soil science community will have a significant part to play.

Notes: Abstract. The effectiveness of Festuca ovina and Poa pratensis as contour grass strips for erosion control was examined in a laboratory experiment for an crodible sandy loam soil on 21, 25 and 29% slopes. No significant differences P〈0.05 were observed in runoff between the plots with grass strips and bare soil but significant differences in soil loss were recorded. Both grasses reduced crosion in the early part of the simulated storms by ponding water behind the barrier, filtering sediment and causing deposition within the ponded area. The P. pratensis barrier was less rigid and became flattened under submergence in the later part of the storms. Runoff flowed over the grass strip forming rills on the slope below, which then cut back and undermined the barrier. These barriers resulted in as much soil loss as bare soil towards the end of the storms on all three slopes. The F. ovina was effective in controlling erosion on the 21% and 25% slopes but not on the 29% slope.

Notes: Abstract. The recommended method of reducing the emission of NH3 while spreading manure is to plough or harrow the manure into the soil. This in turn increases the possibility of N2O emission. At two sites in southern Sweden emissions of NH3 and N2O were measured after spreading pig slurry by broadcasting and band spreading. The band spreading technique can be used in growing crops i.e. when nitrogen is most needed, and it is thought that the NH3 emission is smaller with this technique compared to broadcasting. The average NH3 loss was 50% of applied NH4+ during warm/dry conditions and 10% during cold/wet conditions. The N2O emission was always less than 1% of applied NH4+. When the NH3 emission decreased, the direct N2O emission increased. However, when taking into account the indirect N2O emission due to deposition of NH3 outside the field, the spreading techniques all produced similar total N2O emissions. The ammonia emission was not much lower for the band spreading technique compared to broadcasting, when compared on seven occasions.

Notes: Book reviewed in this article: Soil Erosion at Multiple Scales: Principles and Methods for Assessing Causes and Impacts Edited by F. W. T. Penning de Yries, F. Agus & J. Kerr

Notes: Abstract. Solutions collected from lysimeters of acid soils can show pH values close to or even above neutral. Laboratory experiments on an acid soil from Burundi were planned to test if denitrification or CO2 degassing might explain such a paradox. In the first experiment, soil profiles were reconstituted in columns and leached with 55 μm Ca(NO3)2 solutions at 30 °C and 4 °C. Two drainage regimes were applied: intermittent suction or no suction at the bottom of the columns. In the second experiment, pH values were measured in solutions drained from different horizons at 30 °C, before and after equilibration with ambient air. Sterilized soil was also tested in the same way. Results from experiment 1 showed that despite the accumulation of water in the bottom of soil profiles when no suction was applied, aeration still existed so that reduction reactions, namely denitrification, are not expected to affect greatly the percolate composition. Indeed nitrate concentration was similar in both drainage regimes and was close to the input value. The pH values in percolates were close to 7 at 30 °C and they dropped to about 5.5 when the columns were at 4 °C. In experiment 2, equilibration of percolates with ambient air resulted in pH increase which was greater for the top horizon (C-rich) but negligible when the soil was first sterilized. These convergent results illustrate the very important effect of CO2 degassing on pH of drained solutions when microbial activity is stimulated at high temperatures, in C-rich soil. This is of prime importance when interpreting results from lysimeter experiments. By chance, this study also showed that large quantities of nitrate can be produced in soil at low temperatures.

Notes: Abstract. As leaching of nutrients and agrochemicals can occur readily in cracking clay soils, which are important to UK agriculture, it is essential to identify management systems for them that can minimize the risk of contaminants reaching surface waters. The long-term Brimstone Farm study has provided considerable evidence on the movement of water and solutes through such soils and offers a unique opportunity to determine the factors influencing these processes. Management procedures, such as subsurface drainage and tillage, which are widely used for the production of cereals in these soil types, greatly influence the risk of contamination. At Brimstone Farm, tillage has been shown to change the hydrology in terms of both water table control and the route of water movement, and to increase the mineralization of nitrogen and the consequent risk of nitrate leaching. Drainage, essential in these soils, also creates a risk of solute losses, especially pesticides. Ways to retain effective drainage yet decrease losses to surface waters are discussed.

Notes: Abstract. Sustaining soil fertility under agricultural intensification and expansion onto marginal lands is a significant challenge in the Nepalese Middle Mountains. In a detailed watershed study it was shown that the overall soil fertility is poor, forest soils display the poorest conditions as a result of biomass removal, and sustaining agriculture is questionable due to the transformation from traditional to multiple cropping systems. Parent material is a significant factor influencing low phosphorus status while insufficient inputs create deficiencies in total carbon, nitrogen and bases. A nutrient budget model was developed to assess inputs, redistribution and losses relative to soil fertility. Yield, input and management data obtained from farm interviews, and soil analysis data were used in the calculation of nutrient budgets. Results from modelling indicate declining soil fertility under rainfed agriculture, forest and rangelands, and marginal conditions under irrigated agriculture subject to intensive cultivation. Nutrient deficits were relatively low for irrigated rice-wheat systems, which benefit from nutrient inputs via sediments and irrigation waters, but the introduction of triple cropping showed greater deficits. Nutrient balances were most critical under rainfed maize production where 94% of the farms were in deficit. Current shortages of organic matter make elimination of nutrient deficits problematic but improvement of composting, biological N-fixation and fertilizer efficiency and reducing erosion were found to be potential options.

Notes: Abstract. During three consecutive years (1993–1995) a split-plot design with three replications was used to study the biological and physical role of mulch in the improvement of crusted soil water balance and its productivity in the north of Burkina Faso. The main treatment was the use of an insecticide, to obtain plots with and without soil fauna (SF and NSF). The subsidiary treatment consisted of four mulch types randomly applied on subplots. These were straw of Pennisetum pedicellatum applied at 3 t ha−1, woody material of Pterocarpus lucens applied at 6 t ha−1 and composite (woody material and straw) treatments applied at 4 t ha−1. In addition there was a control, with no mulch (bare plot). Data on soil faunal activity, runoff, sediment accumulation from wind blown soil, vegetation cover and vegetation dry matter yield were collected on all plots.The biological activity (mainly termites) in mulched plots was the key element in the efficacy of mulching to rehabilitate crusted soil. Water infiltration and dry matter yield were statistically lower on NSF plots than on SF plots and runoff and dry matter yield were not different from the values obtained on bare plots. A significant correlation was found between runoff, all vegetation data and termite-voids. Sediment accumulation due to the physical barrier of the mulch was not found to be a significant factor in the improvement of vegetation performance and the reduction of runoff.

Notes: Abstract. Ammonia volatilization with and without gypsum incorporation was measured in Gujranwala soil (Udic Haplustalf) in an incubation study using different nitrogen fertilizers e.g. urea, ammonium sulphate (AS), calcium ammonium nitrate (CAN), and urea nitrophos (UNP). Nitrogen from different fertilizers was applied at the rate of 200 mg N kg−1 to two sets of soils in plastic bags (1.0 kg soil) and plastic jars (0.5 kg soil). Soil moisture was maintained at field capacity. Application of urea increased soil pH to 9, three hours after its addition. Ammonium sulphate and calcium ammonium nitrate had little effect on soil pH. Ammonium volatilization losses from fertilizers were related to the increase in soil pH caused by the fertilizers. Consequently maximum losses were recorded due to application of urea. Losses through ammonia volatilization were significantly lower with AS, CAN and UNP in descending order. Gypsum incorporation significantly reduced the losses. Therefore, application of gypsum to soil before urea may substantially improve N use efficiency for crop production by reducing N losses.

Notes: Abstract. Precision farming is the process of adjusting husbandry practices within a field according to measured spatial variability. In this review, we explore the prospects for precision farming using the principles that underly conventional soil management and agronomy.The cost-effectiveness of precision farming is determined by the cost of defining zones within fields, the stability of zones through time, the difference in treatment between zones in terms of cost, and the responsiveness of the crop in terms of yield and quality to changes in treatment. Cost-effective precision farming is most likely where prior knowledge indicates large heterogeneity and where treatment zones can be predicted, for example from soil type or field history.Soil related factors are likely to provide the main basis for precision farming because they tend to be stable through time and influence crop performance. In particular, soil mapping may usefully indicate the moisture available for crop growth, organic matter maps may be utilized for precision application of fertilizers and soil acting herbicides, and variation in soil pH can be mapped and used as a basis for variable lime application. However, comprehensive nutrient mapping is less likely to be economic with existing techniques of chemical analysis. The value of yield mapping lies in identifying zones which are sufficiently stable to be of use in determining future practices. Maps of grain quality and nutrient content would significantly augment the value of yield maps in guiding marketing decisions and future agronomy. Interactions between soil differences and seasonal weather are large, so yield maps show considerable differences from season to season. Interpretation of such maps needs to follow a careful, informed, analytical process.Extensive and thorough field experimentation by crop scientists over many years has shown that yield variation arises as a result of a large and complex range of factors. It is highly improbable that simple explanations will be appropriate for much in-field yield variation. However, the capacity to sense yield variability within fields as opposed to between fields, where there are many confounding differences, provides an opportunity for the industry to improve its understanding of soil-based effects on crop performance. This should support its decision taking, whether through precision farming or through field-by-field agronomy.The main obstacle to the adoption of precision farming is the lack of appropriate sensors. Optimal sensor configurations that will measure the specific needs identified by end-users need to be developed.The conclusions reached in this paper probably apply to farming throughout northern Europe.

Notes: Abstract. A lysimeter experiment showed a decrease in maximum concentrations and total losses of the herbicide isoproturon leached from a heavy clay soil where the topsoil had a finer, deeper tilth than with a standard agricultural tilth. Volumes of leachate for the first flow event of the season were also smaller and leaching of bromide was slower. The isoproturon was radiolabelled so that its movement could be assessed using a novel radio-scanning technique. Bypass flow began close to the surface as a scan at 8 cm depth showed that only 0.5% of the total soil area had an activity more than four times the nominal background level. At depths of 10–20 cm, isoproturon was preferentially retained within areas of very fine aggregates. No radioactivity was detected in the scans below 20 cm depth, suggesting little or no retention of isoproturon during transport through the subsoil to the bottom of the lysimeter. Rhodamine-B dye injected to the base of the topsoil (approximately 20 cm depth) was also used to assess flow pathways through the subsoil. The dye spread laterally across the interface between topsoil and subsoil and then penetrated the subsoil through cracks and fissures. Even within cracks, transport of dye frequently occurred through only a very small proportion of the total crack area. The macropore flow model MACRO 4.0 was used to simulate results from the lysimeter experiment. The fourfold decrease in maximum concentrations of herbicide from the finer tilth lysimeter could be predicted by varying only a parameter describing aggregate sizes at depths of 6–24 cm, suggesting that transfer of herbicide between macropore and micropore regions was faster in the finer tilth. Differences in concentrations of bromide could be simulated only by adjusting the soil hydraulic parameters for the fine tilth to reflect a slight decrease in the predominance of bypass flow relative to matrix flow.

Notes: Abstract. Degradation of isoproturon in a heavy clay soil followed first-order reaction kinetics with half-lives at 15 °C of 27 and 208 days in the topsoil and subsoil, respectively. Adsorption when shaken with 3 mm sieved samples of the soil fitted the empirical Freundlich relationship with k values of 3.25 in the topsoil and 1.06 in the subsoil. Adsorption in a static system with different sized aggregates of soil did not reach equilibrium, even after 24 hours contact, and the rate of adsorption was slower with larger aggregates. Following an adsorption period of 24 hours, desorption equilibrium was reached more rapidly with larger (6–10 mm) than with smaller (〈3 mm) aggregates. Adsorption isotherms measured in a static system with a soil:water ratio typical of field conditions in winter also indicated less adsorption than that measured in shaken, laboratory systems with low soil:water ratios. The rate of change in water extractable residues of the herbicide was more rapid than that of total extract-able residues following application of isoproturon to the heavy clay soil in the field. The implications of the results for isoproturon leaching under field conditions are discussed.

Notes: Book reviewed in this article: Land Resources: Now and for the future By A. Young.

Notes: Abstract. In order to optimize the management of the N-fertilizer inputs with drip fertigation on sandy-silt soil under apple tree orchard cultivation, we observed in situ: (i) the N and water soil transfers, (ii) the N levels in all leaves, fruits and annual shoots, and (iii) the root distribution. Then we used a mechanistic one-dimensional model (WAVE, Vanclooster et al., 1994) to quantify the annual parameters of the water and nitrogen balance on a daily basis. The horizontal heterogeneity along the row of the tree-soil-dripper system has been treated with two adjacent compartments: one under the dripper and receiving fertigation and the other outside this zone. N transfers in the tree make it impossible to estimate directly N uptake by roots over time.The simulated N losses were due to equal amounts of N leaching below 0.9 m deep (9 g N tree−1year−1 and denitrification (7 g N tree−1year−1. The simulated losses of gaseous N were localized predominantly in the compartment under the dripper and showed a higher rate of leaching during the period of N input when the wet conditions and the high NO3− concentrations were favourable to denitrification. The N-leaching at 0.9 m depth was greatest outside the growing season and was caused by the extension of the N-inputs after the harvest date. This practice, based on the objective to store nitrogen before the period of dormancy does not seem to be justified.

Notes: Abstract. People in the Southern Highlands of Papua New Guinea cultivate some land semi-continuously within a regime of shifting cultivation; the staple crop is sweet potato (Ipomoea batatas). The fertility of Tropepts, variably affected by falls of volcanic ash, was investigated to give further understanding of how subsistence farmers avoid the soil constraints that commonly prompt abandonment. While organic matter, N and K all decrease significantly with time under cultivation, they do not reach critical levels. Phosphorus also decreases significantly over time, although contents are small throughout. Other nutrients show no significant variation with period of use or abandonment. These findings comply with the diversity of crops cultivated early in the life of ‘gardens’, followed by sweet potato, cultivated as a virtual monocrop in long established ‘gardens’. It continues yielding adequately regardless of decrease in nutrient availabilities, notably because nutrient ratios remain favourable for tuberisation and because of sweet potato's tolerance of small phosphorus concentrations. It appears that burning of vegetation significantly increases available minerals and helps maintain a supply which is adequate for longterm sweet potato monoculture. Similar situations are postulated for other areas of less-weathered soils within the tropics.

Notes: Abstract. The mean extractable sulphur (S) concentration in 315 upland topsoil samples collected in 1988/89 from beneath pasture in NE Scotland was 13 μg S g−1 (range 2–77 μg S g−1). More than two thirds of the samples had S concentrations less than that acceptable for productive soils. Continued decreases in atmospheric S inputs may have increased this proportion subsequently. The analysis of herbage S also indicated that two-thirds of the samples were below 0.2% S. A ‘respirometric index’, namely CO2 produced during cellulose decomposition without added S as a percentage of that produced with added S, was significantly less than 100% in a quarter of the soils. Results of three different extraction procedures suggested that sulphate in the soils was present mainly as free plus adsorbed rather than precipitated forms. Soil extraction identified a significant non-sulphate S fraction, presumably organic S. The variability in extractable S stemmed from a combination of geographical, depositional and local site and soil factors. Extractable S was significantly correlated with soil organic matter content and inversely with soil pH and together these factors explained 37% of the variability. While significant differences in mean concentrations between geographical area, soil association and drainage status were evident, no trends could be observed between the major soil subgroups or with altitude.

Notes: Abstract. We investigated whether a polyacrylate polymer could be used to remediate a soil which had been contaminated with copper for many years. Perennial ryegrass was grown in a loamy sand containing 230 mg ammonium-acetate-EDTA extractable Cu kg−1 and amended with 0, 0.1 and 0.2% of polymer. Growth of perennial ryegrass was stimulated in the polymer-amended soil, especially in the soil with 0.1% of polymer. After plant growth for 177 days, the amount of water extractable copper present in the unamended soil was 17 times that of the original soil. In the soil amended with 0.1% of polymer the level of copper after plant growth was only 0.11 times the amount present in the unamended soil. When the soil was incubated with polymer in the absence of plants, the level of water extractable copper was not reduced. The polymer seems to compete with plants for copper, and to prevent the increase of copper in soil solution brought about by root exudates.

Notes: Abstract. Soils developed on volcanic parent materials have many intrinsic qualities favourable to cropping. However, fertility decreases dramatically when they are badly managed. A short review and case studies from Réunion and Guadeloupe highlight the special characteristics of these soils, and their response to management.The interplay of cropping systems and physical characteristics of Andisols is first considered through the example of Pelargonium and food crop systems in Réunion. Progressive decrease in production and cropping potential shows in falling yields as well as in the overall decline of the system. The example of banana production in Guadeloupe highlights the increase in inputs needed to realise the land's potential and to maintain yields, in particular more tillage and pest treatment.In both cases, these trends are connected to the co-evolution of soil characteristics and cropping systems. They lead to an increase of risks with less security and less scope in the choice of cropping systems. Technical solutions in the form of erosion-control measures, rotation and planting techniques have been developed and prove to be relevant and consistent in their benefit.

Notes: Abstract. Soil classification is a tool for stratifying and generalizing information on soil resources but most systems are tailored to handle only slightly disturbed soil. We tested the applicability of the legend of the FAO-Unesco Soil Map of the World and the new World Reference Base for Soil Resources by classifying at the highest order 831 profiles from a nationwide 7 km grid survey in Denmark, where soils are developed in Quaternary glacial and marine sediments and intensively farmed. Comparison of the variability of pH and % clay +% silt of the master horizons (A, E, B, and C) within and between the major well-drained soil groupings shows that liming, fertilizing and ploughing have produced significantly deeper A-horizons with higher pH, lower % humus and C:N ratios on the two-thirds of the country that is cultivated. ‘Anthropogenic’ mollic and umbric horizons are a common result but the liming causes a random final classification of these surface horizons and, hence, random allocation of the soils in both systems. It separates cultivated soils and their undisturbed equivalents, and results in considerable within-group variation in soil texture. Grouping of cultivated and undisturbed soils, on the other hand, results in wide within-horizon pH ranges for most groups, again compromising the advantage of making useful general statements on the basis of classification.We propose that anthropogenic mollic and umbric horizons should be allowed in any soil group and that ‘anthric properties’ should be used to distinguish between profoundly changed cultivated soils and largely undisturbed soils, hereby constructing a two-tier system within each highest-order soil group. We classified the soils according to this proposal. The results show generally narrower ranges for both pH and % clay +% silt. We evaluated the within-group homogeneity by multivariate analysis of variance of pH, % clay +% silt, % clay, % humus, C:N ratio, exchangeable cations, and CEC. The results (Wilks's Lamda) show a higher degree of group compactness compared to the original FAO and World Reference Base systems.

Notes: Abstract. In dairy farming systems the risk of nitrate leaching is increased by mixed rotations (pasture/arable) and the use of organic manure. We investigated the effect of four organic farming systems with different livestock densities and different types of organic manure on crop yields, nitrate leaching and N balance in an organic dairy/crop rotation (barley–grass-clover–grass-clover–barley/pea–winter wheat–fodder beet) from 1994 to 1998. Nitrate concentrations in soil water extracted by ceramic suction cups ranged from below 1 mg NO3-N l−1 in 1st year grass-clover to 20–50 mg NO3-N l−1 in the winter following barley/pea and winter wheat. Peaks of high nitrate concentrations were observed in 2nd year grass-clover, probably due to urination by grazing cattle. Nitrate leaching was affected by climatic conditions (drainage volume), livestock density and time since ploughing in of grass-clover. No difference in nitrate leaching was observed between the use of slurry alone and farmyard manure from deep litter housing in combination with slurry. Increasing the total-N input to the rotation by 40 kg N ha−1 year−1 (from 0.9 to 1.4 livestock units ha−1) only increased leaching by 6 kg NO3-N ha−1. Nitrate leaching was highest in the second winter (after winter wheat) following ploughing in of the grass-clover (61 kg NO3-N ha−1). Leaching losses were lowest in 1st year grass-clover (20 kg NO3-N ha−1). Averaged over the four years, nitrate concentration in drainage water was 57 mg l−1. Minimizing leaching losses requires improved utilization of organic N accumulated in grazed grass-clover pastures. The N balance for the crop rotation as a whole indicated that accumulation of N in soil organic matter in the fields of these systems was small.

Notes: Abstract. Eight lysimeters, each with a surface area of 0.5 m2 and a length of 60 cm, were taken over mole drains from a Denchworth soil and divided into two groups with either a standard agricultural tilth or a finer, deeper topsoil tilth. They were variously instrumented to measure soil moisture content at three depths and losses of nitrate, a bromide tracer and radiolabelled isoproturon, all of which were followed over a year. Leaching of isoproturon was initiated by artificial irrigation either 1 or 39 days after application. The finer tilth seemed to increase the water-holding capacity of the topsoil, and this resulted in slower wetting of the subsoil, decreased flow volumes from the first events of the season and a delay of approximately four weeks in the time to the maximum concentration of the bromide tracer in leachate. The finer topsoil tilth also decreased maximum concentrations of isoproturon from 29 to 15 μg l−1 following irrigation 1 day after treatment and from 43 to 9 μg l−1 following irrigation 39 days after treatment. Total losses of isoproturon were three times larger with the standard agricultural tilth. Differences were attributed to a decrease in bypass flow through the topsoil with the finer tilth, particularly during events early in the season. There was a small decrease in total losses of nitrate in leachate from the finer tilth compared to that from the standard tilth.

Notes: Abstract. The effects of afforestation on potential nitrification, nitrification and ammonification rates were studied at an experimental site in NE Scotland 4½ years after afforestation of former arable land. The site had been planted with three tree species (Sitka spruce, sycamore and hybrid larch) at three different planting densities, with half the plots treated with inorganic NPK fertilizer. Laboratory measurements of potential nitrification, nitrification and ammonification rates, measured using a perfusion system, were compared between the unforested control and combinations of the various treatments. Differences in soil pH and soil moisture content were also investigated.Potential nitrification rates measured in plantation soils were significantly lower than in the unplanted control soil. Nitrification and ammonification rates were also consistently lower, although these differences were only significant in a few of the treatments. Soils planted with a normal tree density had a tendency to show higher nitrification rates compared to soils planted with a high tree density.The results suggest that afforestation of former agricultural soils may cause changes in important parts of the soil N cycle soon after planting. At this early stage in the life of the plantation this appears to be unrelated to changes in soil pH or moisture content, even though soils beneath the trees are drier. The apparent change may be the result of differences in the soil microbial community associated with the type of organic matter substrate present in the unplanted and planted soils.

Notes: Abstract. Increasing concerns for the financial and environmental impact of the use of broadcast fertilizer by the UK horticultural industry is leading to the development of alternative application techniques, which aim to reduce inputs through improved efficiency. One such technique, ‘starter’ fertilizer, was investigated with drilled and transplanted crisp lettuce (Lactuca sativa) on two fertile peaty soils. Starter fertilizers injected below the seed of the drilled crop, or as spot applications around the planting module, were tested alone and in various combinations with different rates of broadcast fertilizer. The work extended previous findings, based largely on mineral soils, and demonstrated that high yields of iceberg quality lettuce can be achieved with reduced inputs of broadcast fertilizer, and that there can be additional benefits of earlier maturity and improved quality. It is concluded that starter fertilizer can contribute to the development of environmentally beneficial farming practices whilst maintaining the productivity and competitiveness of the horticultural industry.

Notes: Abstract. Ancient forests which have never been under agriculture often have larger ecological and pedological value than later established forests. We made a reconstruction of the land use history of the Meerdaal forest complex in central Belgium since 1759. Soil profiles of 33 recent forest sites and of contiguous forest parcels were examined morphologically by augering to 120 cm depth. pHKC1 was determined on samples from every horizon. The data were analysed by Principal Component Analysis, and the axes were used as a basis for derivation of horizon parameters. Former agricultural land use since 1759 can still be recognized in three soil morphological characteristics: colour of the eluviation horizon, intactness of the horizon containing illuviated clay and thickness of the organic layer. These parameters were combined into a ‘naturalness index’, which differs significantly between ancient and recent forest and can be easily and cost-effectively obtained to assess the degree of man-made disturbance of forests on loess-derived soils.

Notes: Abstract. A long-term lysimeter experiment with undisturbed monoliths studied leaching behaviour and balances of phosphorus (P), potassium (K) and nitrogen (N) during a seven year crop rotation on four types of soil receiving inorganic fertilizers, manure and grass compost respectively. It was shown that application of manure did not lead to any direct change in nutrient leaching, unlike the application of fertilizers to soils of normal fertility. However, soil type considerably affected the nutrient concentrations in the drainage water.Manure applied in amounts equal to the maximum animal density allowed by Swedish legislation slightly oversupplied P and N (0.5–3.5 and 18–38 kg ha−1 y−1 respectively) compared to the crop requirement and leaching losses for most of the soils. The relationship between lactate-soluble P in the topsoil and the concentrations of dissolved P in the drainage water was very strong. However the strength of this relationship was dependent on just one or two soils. P losses from a fertile sandy soil were large (1–11 kg ha−1 y−1) throughout the crop rotation and average crop removal (13 kg ha−1 y−1) plus the leaching losses were not balanced (average deficit 3–6 kg ha−1 y−1) by the addition of fertilizer, manure or grass compost. No decreasing trend was found in the P losses during seven years. However, the K deficit (average 26 kg ha−1 y−1) led to a significant reduction in the leaching trend from this soil. The other soils that had a smaller K deficit showed no significant reduction in the leaching of K.

Notes: Abstract. Guizhou province has one of the most severe soil erosion problems in China, with 44% of its total area affected. Within the province, Bijie prefecture is the most severely eroded with 63% of the total area affected. In recent decades this erosion is mainly caused by man's agricultural and industrial development. Not only is erosion restricting crop production, it is the cause of disastrous floods which recur with a frequency far greater than in the past. Reduced infiltration of rain has led to a third of the wells and a fifth of the streams running dry, depriving people and livestock of drinking water.This unsustainable use of land can only be corrected by a combination of population control, prevention of slash and burn cultivation and return of steeply sloping land to forest and grassland. Greater appreciation of the need for soil and water conservation is an essential part of this process.

Notes: Dissolved organic nitrogen and carbon (DOC) are significant in the C and N cycle in terrestrial ecosystems. Little is known about their dynamics in the field and the factors regulating their concentrations and fluxes. We followed the fluxes and concentrations of the two in a Norway spruce (Picea abies (L.) Karst.) forest ecosystem in Germany from 1995 to 1997 by sampling at fortnightly intervals. Bulk precipitation, throughfall, forest floor percolates from different horizons and soil solutions from different depths were analysed for major ions, dissolved organic N and DOC. The largest fluxes and concentrations were observed in percolates of the Oi layer, which contain amino N and amino sugar N as the major components. The average ratio of dissolved organic C to N in forest floor percolates corresponded to the C/N ratio of the solid phase. Concentrations and fluxes were highly dynamic with time and decreased with depth. The largest fluxes in forest floor percolates occurred when the snow melted. The concentrations and fluxes of dissolved organic N were significantly correlated with DOC, but the correlation was weak, indicating different mechanisms of release and consumption. The dynamics of dissolved organic N and DOC in forest floor percolates were not explained by pH and ionic strength of the soil solution nor by the water flux, despite large variations in these. Furthermore, the release of these fractions from the forest floor was not related to the quality and amount of throughfall. Concentrations of dissolved organic N in forest floor percolates increased with soil temperature, while temperature effects on DOC were less pronounced, but their fluxes from the forest floor were not correlated with temperature. In the growing season concentrations of both dissolved organic N and C in forest floor percolates decreased with increasing intensity of throughfall. Thus, the average throughfall intensity was more important than the amount of percolate in regulating their concentrations in forest floor percolates. Our data emphasize the role of dissolved organic N and DOC in the N and C cycle of forest ecosystems.

Notes: The migration of colloidal particles in the unsaturated zone may enhance leaching of sorbing contaminants to surface waters and groundwaters. This paper describes a simple model of particle leaching and translocation based on the dual-porosity model MACRO. The model includes descriptions of processes such as ‘source-limited’ particle detachment due to the kinetic energy of rain, replenishment of the depleted store of particles up to a maximum value determined by the amount of dispersible clay in the soil, and convective transport of particles in macropores subject to a filter sink term varying as a function of pore water velocity. Estimates of model parameter values are obtained by comparing simulations with measurements of particle concentrations in the discharge from tile drains made in a silty clay soil in southwest Sweden. Calibrated in this way, the model is shown to reproduce satisfactorily the observations. A sensitivity analysis suggests that the critical parameters in the model are those related to particle filtering during vertical transport in soil macropores.

Notes: The stabilization of organic matter in soil by interaction with aluminium (Al) or allophane is important in maintaining soil quality, and in retarding the decomposition of soil organic matter. Complexation of Al by soil organic matter may also ameliorate Al toxicity. Here we use 13C-NMR spectroscopy to assess the interaction of soil organic matter with both Al and allophane in two poorly drained podzols containing only trace amounts of iron. The 13C-NMR spectrum of the subsoil of the allophane-rich One Tree Point podzol shows an intense peak at 179 p.p.m., assigned to carbon in carboxylic acids. This peak shifts to 177 p.p.m. after removal of allophane (11% of the soil mass) by treatment with HF. We infer that the carboxyl groups in the organic matter are bonded to structural Al on the surface of allophane spherules. In the non-allophanic Te Kopuru podzol, on the other hand, the organic matter apparently interacts with Al ions in the soil solution. This soil also has more aromatic carbon and fewer carbons in carboxyl and carbohydrate structures than the allophanic sample. There is an indication that allophane stabilizes carbohydrate groups as well as carboxyl groups.

Notes: Soil profiles under beech, spruce and a grassland have been analysed to study the evolution of natural n-alkanes in pollution-free ecosystems. The soils had all developed on granitic bedrock, at an altitude of 1300–1500 m in the region of Mont-Lozère (southern Massif-Central, France). In contrast to the grassland soil, the two forest soils both possessed a well-developed acidic moder humus-type horizon. This could be subdivided as follows: fresh litter (OL), fragmentation (OF) and humification (OH) layers; two litters, one fresh (OL1) and one old (OL2) could actually be distinguished in the beech forest soil. The n-alkane signature of the parent plants was preserved in the top litter. Immediately underneath, in the OF layer(s) the original n-alkane signatures were progressively but rapidly replaced by a common signature composed of n-C27 and n-C25 with larger proportions of the former than of the latter. These two hydrocarbons were most probably produced in situ by fungi. These results appear to illustrate the action of soil microorganisms which metabolize the inherited n-alkanes and produce new compounds of the same family. Unlike the alkanes and the low molecular weight fatty acids ≤ C20 (which increase greatly in the OL2 layer under beech as a result of intense microbial activity), the heavy fatty acids (〉 C20) show no significant change in the organic horizon.

Notes: This paper reports a procedure for determining the content of strongly fixed NH4+ in soil. The procedure consists of a Kjeldahl digestion followed by an acid attack of the residue with a 5 m HF:1 m HCl solution. Distillations after each of the two treatments recover different forms of NH4+. The procedure was tested on fine earth (〈 2 mm) and skeleton (〉 2 mm) fractions of two forest soils developed on sandstone parent material. In both soil fractions we evaluated three different forms of NH4+-N: (i) Kjeldahl, (ii) non-exchangeable and (iii) micaceous. The last is located in the interlayer of mica flakes larger than 50 μm that resist the Kjeldahl digestion and is considered strongly fixed. The total NH4+-N content of a soil is obtained by the summation of the Kjeldahl and the micaceous NH4+-N. In the soils under consideration, the micaceous form prevails in the skeleton because this fraction is richer in micas of sand size (〉 50 μm). Following the proposed procedure, we found that micas (muscovite and biotite) contain about 3000 mg kg–1 of NH4+-N in the interlayer. The presence of micaceous NH4+-N in soil is generally ignored because the skeleton is usually excluded from analyses, and the micas larger than 50 μm cannot be dissolved by the Kjeldahl treatments. The micaceous NH4+ is the least extractable form of NH4+-N, and we infer that it is the least available to plants.

Notes: Hardsetting of soil comprises two contrasting, unfavourable physical conditions at different water contents, namely extreme hardness when dry and complete slaking when wet. This behaviour was changed by adding small amounts of ferrihydrite and aluminium hydroxide to the soil. The aggregation and its stability in the wet state increased, whereas the tensile strength of the dry soils decreased. Both resulted mainly by making the fine particles less mobile by aggregation. In some cases adding large amounts of Al hydroxide caused a resuspension of soil particles by reversing the charge, resulting in instability when wet and high stability when dry. We postulate that aggregation results from the interaction between negatively charged siliceous surfaces and positively charged oxides. In addition we think that newly formed Si–O–Fe bonds play a role in binding particles together as a result of a positive relation between the amount of ferrihydrite added and the oxalate-soluble Si. We conclude that hardsetting resulting from weak structure is caused by lack of aggregating agents such as metal hydroxides.

Notes: Simple models describing nitrogen processes are required both to estimate nitrogen mineralization in field conditions and to predict nitrate leaching at large scales. We have evaluated such a model called LIXIM, which allows calculation of nitrogen mineralization and leaching from bare soils, assuming that these are the dominant processes affecting N in bare soil. LIXIM is a layered, functional model, with a 1-day time step. Input data consist of frequent measurements of water and mineral N contents in soil cores, standard meteorological data and simple soil characteristics. The nitrate transport is simulated using the ‘mixing-cells’ approach. The variations in N mineralization with temperature and moisture are accounted for, providing calculation of the ‘normalized time’. An optimization routine is used to estimate the actual evaporation and the N mineralization rates that provide the best fit between observed and simulated values of water and nitrate contents in all measured soil layers.The model was evaluated in two field experiments (on loamy and chalky soils) including treatments, lasting 9–20 months. The water and nitrate contents in soil were satisfactorily simulated in both sites, and all treatments, including a 15N tracer experiment performed in the loamy soil. In the chalky soil, the calculated water balance agreed well with drainage results obtained in lysimeters and independent estimates of evaporation. At both sites, N mineralization was reduced by the incorporation of crop residues (wheat or oilseed rape straw); the amounts of nitrogen immobilized varied between 20 and 35 kg N ha−1. In the treatments without crop residues, the mineralization rate followed first-order kinetics (against normalized time) in the loamy soil, and zero-order kinetics in the chalky soil. In the latter soil, the mineralization kinetics calculated in situ were close to the kinetics measured in laboratory conditions when both were expressed against normalized time.

Notes: Predictions of changes in soil solution chemistry and exchangeable cations which occur on ash deposition after slash burning are complex and may be facilitated by the use of chemical models. Multi-ion sorption in the topsoil of an Amazonian Acrisol was studied by sequentially adding small amounts of electrolytes to soil and mixtures of soil and ash in batch experiments. A chemical equilibrium model that included inorganic complexation, multiple cation exchange and sparingly soluble salts (aluminium hydroxide and magnesian calcites) was used to interpret the results. The model predicted well the pH and sorption values in all experiments in which there was no addition of ash. The model suggested that cation exchange was the main process determining concentrations of soil solutions in all cases where neutral salt solutions were added, and that proton buffering was achieved by the dissolution of Al(OH)3 which was followed by Al3+ adsorption. Calculation of ion activity products in solutions from various batch experiments in soil + ash mixtures suggested that magnesian calcites of differing solubility may be in equilibrium with the activities of Mg2+ and Ca2+ in solution. An incongruent dissolution of Mg resulted in less soluble magnesian calcites in the ash. The model estimated satisfactorily the pH and the sorption of ions for all experiments with differing ash additions to the soil. Most of the Ca and significant amounts of Mg added in the ash are expected to remain for a long time in the soil and may determine the Ca and Mg status of the soil solution, primarily controlled by principles of solubility products.

Notes: To understand the process and the kinetics of potassium release from the clay interlayer in natural and arable soils in more detail, I tested the hypotheses that large, monovalent cations, especially NH4+ and Cs+, can reduce the release rates of K+ which is exchanged by Ca2+, even if these monovalent cations are present in concentrations of only a few μm. Percolation experiments were carried out with different illitic soil materials, some containing vermiculite, with 5 m m CaCl2 at pH 5.8 and 20°C, in some cases for over 7000 h. NH4+ and Cs+ both caused a large decrease in the rate at which K+ was released, Cs+ especially. Suppression began at 5 μm NH4+ Blocking by 20 μm NH4+ was easily reversible: the release rates readily increased when NH4+ was omitted from the exchange solution. Blocking by 2 μm Cs+ was equal to approximately 90% of that at 10 μm Cs+. Larger concentrations of Cs+ than 10 μm did not further reduce release but rather caused a slight increase, probably because of enhanced exchange of K+ by Cs+ without exfoliation of the interlayer space. Blocking by Cs+ was not reversible within 〉 7000 h of percolation by 5 m m CaCl2. The blocking effect was reproduced in several different soil materials using 10 μm Cs+ but was most pronounced in vermiculite-rich samples. As NH4+ is present in most arable soils, at least in concentrations of a few μm, I conclude that the observed effects are of significance in the K dynamics processes in soils, for example near the roots of plants. Further, very small concentrations of Cs+ in exchange solutions containing a large background of Ca2+ appear to be useful for suppressing K+ release from the interlayer in laboratory studies, probably without significantly altering the exchange at outer mineral surfaces.

Notes: Burning vegetation produces partly charred plant material which subsequently could contribute to the highly refractory proportion of soil organic matter. The presence of charred organic carbon (COC) was investigated in 17 horizons originating from nine soils from Germany and the Netherlands using a suite of complementary methods (high-energy ultraviolet photo-oxidation, scanning electron microscopy, solid-state 13C nuclear magnetic resonance, lignin analysis by CuO oxidation). Charred organic carbon could not be detected in the A horizons of an Alisol and a Gleysol, but it contributed up to 45% of the organic carbon and up to about 8 g kg–1 of the soil in a range of grey to black soils (Cambisol, Luvisol, Phaeozem, Chernozem and Greyzem). All these soils have chernozemic soil properties (dark colour, A–C profile, high base saturation, bioturbation). A 10-km colour sequence of four chernozemic soils, which were very similar in chemical and physical properties, showed a strong relation between colour and the content of COC. This suggests that the COC affects mainly soil colour in the sequence studied. Finely divided COC seems to be a major constituent of many chernozemic soils in Germany. These results suggest that besides climate, vegetation and bioturbation, fire has played an important role in the pedogenesis of chernozemic soils.

Notes: Accessibility of adsorbates to internal active sites of soils depends mainly on the porous structure of the material. We aimed to determine the distribution of pore sizes in soils with varied physico-chemical properties, by combining adsorption of gases and mercury porosimetry. Microporosity was studied by physical adsorption of N2 at 77 K and CO2 at 273 K; mercury intrusion porosimetry allowed us to evaluate the macroporosity; and mesoporosity was determined by capillary condensation of N2 and mercury porosimetry. The soils investigated were essentially macroporous, with volumes between 0.33 and 0.73 cm3 g–1; the maxima in the differential pore-size distribution were in the range 1500–4000 nm. Volumes of meso- or micropores were always less than 10% of macropore volumes. Calculations based on the theory of Dubinin and the αs-method (for N2 at 77 K) provided, generally, coincident results. In a soil containing much organic matter, N2 adsorption was only one-ninth that of CO2 adsorption, showing that N2 adsorption into the narrow micropores of organic matter was kinetically restricted. When accessibility to micropores was not restricted, the total volume of micropores could be deduced from N2 adsorption, whereas CO2 measured exclusively the narrowest microporosity.

Notes: A study was conducted to determine the influence of switchgrass roots on the mobility, adsorption–desorption and mineralization of atrazine in Cullen clay loam and Emporia loamy sand soils. Bromide and atrazine distribution profiles in the leachates indicated greater preferential movement in columns with roots than in columns without roots. Larger concentrations of atrazine were detected at lower depths of Emporia soil with switchgrass roots than without. Adsorption of atrazine was greater in Cullen than in Emporia soil and conformed to Freundlich isotherms. In both Cullen and Emporia soils, adsorption and desorption were not different between soil with or without switchgrass roots. After 84 days of incubation, less than 6% of the applied atrazine was mineralized in the Cullen soil and 2% in Emporia soil. Mineralization was greater in the Cullen soil than in the Emporia soil at 42, 56, 70 and 84 days of sampling. The presence of switchgrass roots did not affect the mineralization of atrazine in Emporia soil. The presence of switchgrass roots caused preferential movement of atrazine, but did not affect its adsorption and mineralization in either soil type.

Notes: Infiltration and sheet flow depend mainly on hydraulic conductivity under nearly saturated conditions which can vary in space and time. We have studied the variation in relation to the topography at different stages of a cultivation year to understand the origin of sheet flow over the land where maize is grown. The sampling was done to a complete factorial design with two landscape positions, upslope and downslope, two sites in relation to wheeling, no and under wheeling, and three dates in relation to soil surface changes and agricultural operations, June and October 1995 and April 1996. Four measurements were randomly distributed on each of the four sites and each of the three dates. The hydraulic conductivity was measured with a tension disc infiltrometer controlling tension at the soil surface. Steady-state infiltration rates were measured at four soil water tensions: 0.1, 0.3, 0.6 and 1.5 kPa. We also measured bulk density and soil moisture content. Hydraulic conductivity decreased during the year at all tensions by a factor of 2–3 where there was no wheeling, and a factor of 4–6 under wheeling. This decrease was greater downslope than upslope, particularly under traffic. The topographic effect was less than that of time but significant. Whereas the hydraulic conductivity was similar over the field at the beginning of the crop cycle (June), it differed according to the landscape position at the end (April), especially under traffic. These topographic variations of the hydraulic conductivity may be due to slight variations of soil components and hydric conditions in the particular case studied. They are important in relation to the characteristics of rainfall and runoff and help explain the spatial and temporal distributions of sheet flow and erosional processes that themselves may contribute to a redistribution of soil particles and induce feedback effects on sheet flow and infiltration.〈section xml:id="abs1-2"〉〈title type="main"〉Variations topographiques et saisonnières de la conductivité hydraulique en condition non saturée mesurée à l’échelle parcellaire par infiltrométrie Résumé La répartition des pluies entre infiltration et ruissellement dépend principalement de la conductivité hydraulique proche de la saturation qui varie à la fois dans l’espace et le temps. Les variations de la conductivité hydraulique selon la topographie sont analysées dans l’objectif de mieux comprendre la distribution spatiale du ruissellement dans le versant. Ces variations spatiales ont été quantifiées durant une année culturale sur une parcelle de maïs, en relation avec la topographie de la parcelle et la succession des opérations culturales. Le plan d’échantillonnage est un plan factoriel complet prenant en compte la position topographique, amont et aval, la localisation relative aux traces de roue, avec et sans trace de roue, et trois dates relatives à la dynamique des états de surface et aux opérations culturales, juin et octobre 1995 et avril 1996. Quatre mesures de la conductivité hydraulique ont été réalisées sur chaque site avec un infiltromètre à succion appliquéà la surface du sol. Les flux infiltrés ont été mesurés à l’équilibre et à quatre potentiels: –0.1, –0.3, –0.6 et –1.5 kPa. Ces mesures ont été complétées par un suivides teneurs en eau et des densités apparentes sur l’ensemble du versant et de la période d’étude. La conductivité hydraulique décroît au cours de l’année quel que soit le potentiel. Elle est divisée par un facteur deux à trois durant toute la période d’étude sans trace de roue, par un facteur quatre à six avec trace de roue. Cette diminution de la conductivité hydraulique dépend de la position topographique: elle est plus forte en aval qu’en amont, en particulier sur passage de roue. Tandis que la conductivité hydraulique apparaît relativement homogène sur le champ en début de cycle cultural, elle varie fortement de l’amont à l’aval en fin de cycle cultural, en particulier sur trace de roue. Ces variations spatiales de la conductivité hydraulique semblent liées à de faibles variations des constituants du sol qui interagissent avec des conditions hydriques très différentes. Ces variations de la conductivité hydraulique sont importantes au regard des caractéristiques des pluies et du ruissellement sur ce site. Elles expliquent pour partie la distribution spatiale et temporelle du ruissellement et des processus d’érosion qui eux-même peuvent contribuer à la redistribution des constituants dans le versant et induire des effets retour sur les processus de ruissellement et d’infiltration.

Notes: Heavy density fractions of soil contain organic matter tightly bound to the surface of soil minerals. The chemical composition and ecological meaning of non-metabolic decomposition products and microbial metabolites in organic–mineral bonds is poorly understood. Therefore, we investigated the heavy fraction (density 〉 2 g cm–3) from the topsoil of a Gleysol (Bainsville, Ottawa, Canada). It accounted for 952 g kg–1 of soil and contained 19 g kg–1 of organic C. Pyrolysis-field ionization mass spectra showed intensive signals of carbohydrates, and phenols and lignin monomers, alkylaromatics (mostly aromatic) N-containing compounds, and peptides. These classes of compound have been proposed as structural building blocks of soil organic matter. In comparison, the light fraction (density 〉 2 g cm–3) was richer in lignin dimers, lipids, sterols, suberin and fatty acids which clearly indicate residues of plants and biota. To confirm the composition and stability of mineral-bound organic matter, we also investigated the heavy fraction (density 〉 2.2 g cm–3) from clay-, silt- and sand-sized separates of the topsoil of a Chernozem (Bad Lauchstädt, Germany). These heavy size separates differed in their mass spectra but were generally characterized by volatilization maxima of alkylaromatics, lipids and sterols at about 500°C. We think that the observed high-temperature volatilization of these structural building blocks of soil organic matter is indicative of the organic–mineral bonds. Some unexpected low-temperature volatilization of carbohydrates, N-containing compounds, peptides, and phenols and lignin monomers was assigned to hot-water-extractable organic matter which accounted for 7–27% of the carbon and nitrogen in the heavy fractions. As this material is known to be mineralizable, our study indicates that these constituents of the heavy density fractions are degradable by micro-organisms and involved in the turnover of soil organic matter.

Notes: A wavelet is a compact analysing kernel that can be moved over a sequence of data to measure variation locally. There are several families of wavelet, and within any one family wavelets of different lengths and therefore smoothness and their corresponding scaling functions can be assembled into a collection of orthogonal functions. Such an assemblage can then be applied to filter spatial data into a series of independent components at varying scales in a single coherent analysis. The application requires no assumptions other than that of finite variance. The methods have been developed for processing signals and remote imagery in which data are abundant, and they need modification for data from field sampling. The paper describes the theory of wavelets. It introduces the pyramid algorithm for multiresolution analysis and shows how it can be adapted for fairly small sets of transect data such as one might obtain in soil survey. It then illustrates the application using Daubechies’s wavelets to two soil transects, one of gilgai on plain land in Australia and the other across a sedimentary sequence in England. In both examples the technique revealed strongly contrasting local features of the variation that had been lost by averaging in previous analyses and expressed them quantitatively in combinations of both scale and magnitude. Further, the results could be explained as the spatial effects of change in topography or geology underlying the variation in the soil.〈section xml:id="abs1-2"〉〈title type="main"〉Analyse et éclairissement sur la variation du sol en utilisant les ondelettes RésuméUne ondelette est un noyau compact d’analyse qu’on peut passer sur une séquence de données pour quantifier la variation localement. Plusieurs familles d’ondelettes existent. Chaque famille est caractérisée par des fonctions d’échelle de longueurs d’ondes et de degrés de lissage différents, le tout constituant un ensemble de fonctions orthogonales. L’application de ces fonctions sur des données spatiales est une méthode d’analyse unique et cohérente qui permet de filtrer des données spatiales en identifiant des composantes indépendentes à différentes échelles. L’application n’éxige que l’hypothése d’une variance bornée. Ces méthodes ont été developpées pour le traitement de signaux qui contiennent énormement de données comme des images de télédétection. Elles necessitent des modifications avant de les appliquer sur des données d’échantillonage provenant du terrain. Cet article décrit la théorie d’ondelettes. Il introduit l’algorithme pyramidal pour une analyse à quelques résolutions. Il montre ensuite comment on peut adapter l’algorithme pour un ensemble de données peu nombreuses comme celles qu’on peut obtenir lors d’une prospection du sol sur des transects.Les resultats montrent l’application des ondelettes de Daubechies à deux transects pédologiques, lepremier situé sur une plaine marquée de gilgaï en Australie, et le second à travers une séquence de sediments jurassiques en Angleterre. Dans les deux exemples, la technique a révélé des contrastes bien marqués de certain traits locaux qui ont été totalement occultés dans des analyses antérieures basées sur le calcul des moyennes. La technique des ondelettes permet aussi une quantification de ces traits locaux, en fonction de l’échelle d’observation et de la magnitude. De plus, ces résultats peuvent être interprétés par les effets d’une variation spatiale de la topographie ou de la géologie qui sont à l’origine de la variation du sol.

Notes: Data from two Podzol O and E horizons, sampled in 1-cm layers at 13 points within 2 m × 2 m plots, were used to test the hypothesis that the composition of hydrogen ions (H) and aluminium (Al) adsorbed to the solid-phase soil organic matter (SOM) determines pH and Al solubility in organic-rich acidic forest soils. Organically adsorbed Al was extracted sequentially with 0.5 m CuCl2 and organically adsorbed H was determined as the difference between total acidity titrated to pH 8.2 and Al extracted in 0.5 m CuCl2. The quotient between fractions of SOM sites binding Al and H (NAl/NH) is shown to determine the variation in pH and Al solubility. It is furthermore shown that models in which pH and Al solubility are linked via a pH-dependent solubility of an Al hydroxide and in which cation exchange between Al3+ and Ca2+, rather than cation exchange between Al3+ and H+, is the main pH-buffering process cannot be used to simulate pH or Al solubility in O and E horizons. The fraction of SOM sites adsorbing Al increased by depth in the lower O and throughout the E horizon at the same magnitude as sites adsorbing H decreased. The fraction of sites binding the cations Ca2+ + Mg2+ + K+ + Na+ remained constant. It is suggested that a net reaction between Al silicates (proton acceptors) and protonated functional groups in SOM (proton donors) is the long-term chemical process determining the composition of organically adsorbed H and Al in the lower part of the O and in the E horizon of Podzols. Thus, in the long term, pH and Al solubility are determined by the interaction between organic acidity and Al alkalinity.

Notes: In a field experiment with Italian ryegrass residual effects of N applied in late April at four rates, 28, 84, 140 and 196 kg ha−1, and of different dates of first harvest ranging from 1 to 14 weeks after N application, were studied. The harvests after the first added about 10 kg dry matter yield and about 0.16 kg N yield for each extra kg N applied in April. Residual response was similar for each increment of applied N. A positive residual response to N was obtained in May of the year following N application despite high winter rainfall. N content of herbage during part of the summer was reduced by extra N applied in April although N yield was increased. The reduction in N content was accompanied by a reduction in P and K content, these latter elements having been applied only once and at a uniform rate on all plots. Loss of N, P and K from the crop, when a period of more than about 9 weeks regrowth was allowed prior to the first harvest, was not recouped at subsequent harvests. Residual marginal recovery of N in Aberystwyth was no higher than in comparable experiments in Cambridge although marginal recovery of N at the first harvest had been appreciably lower in Aberystwyth than in Cambridge.

Notes: A mathematical model which simulates a single-cut forage conservation system is described. It was designed to investigate the effect of machine performance on the nutrient content of conserved forage but its scope is much wider, so that the effects of such aspects as crop growth characteristics, climatic differences and management policy can be assessed. An example of the use of the model to determine the value of chemical additives to high moisture content hay is described in detail. Various uses of the model are discussed and some of its limitations are shown to be caused by a lack of data on factors determining dry matter losses.

Notes: Inoculation in the glasshouse revealed marked differences in resistance to both ryegrass mosaic virus (RMV) and crown rust (Puccinia coronata Corda) among eight unselected populations of Italian ryegrass (Lolium multiflorum Lam.). Two generations of selection for crown rust resistance led to a significant improvement in all eight populations, while one generation of selection for RMV gave a more variable response. Frequency distributions of individual genotype scores suggested that much of the resistance to crown rust was under the control of one or two genes with major effects, while resistance to RMV appeared to be controlled by a large number of genes each having a small effect.In the field, resistance to RMV meeisured after 20 months was strongly correlated with that obtained in the glasshouse. Natural infection by crown rust in the field was too low to reveal any differences between populations, although three populations from the Po Valley region of Northern Italy became heavily infected with Puccinia recondita.Selection for disease resistance significantly reduced the persistency of three populations, but that of four others was unaffected and one showed a significant improvement. Selection reduced water-soluble carbohydrate (WSC) levels in spring slightly but significantly from 27.6 to 25.8% WSC overall. These results emphasize that agronomic performance must be monitored during selection for disease resistance.

Notes: A field investigation was carried out over 3 years to determine if there was a synergistic effect on total or seasonal yield when cultivars of perennial ryegrass were grown in combination.The three cultivars used were Stormont Zephyr, Hora and Perma, representing respectively early, medium late and late maturing groups. Each cultivar was grown as a pure stand and also as a 50:50 mixture with each of the other two cultivars. Each of these swards was maintained under two rates of nitrogen fertilization (300 and 600 kg per ha per annum) and under two harvesting treatments (4 and 8 harvests per annum).Mixture yield did not exceed significantly the pure sward yieid of the highest yielding component. Occasional yield improvements were detected for the mixtures averaged as a group over monocultures averaged as a group. There was a tendency, especially under frequent cutting, for the yield response to nitrogen to be greater from mixed than from pure swards.

Notes: Persistence assessments on eight mid-season and ten late cultivars of perennial ryegrass were made at the end of the second, third and fourth years after sowing. Botanical analyses were carried out on the herbage from plots cut in the fourth year and these results related lo the different persistence assessments. It was found that persistence assessments carried out at the end of the second year enabled predictions to be made about botanical composition of cuitivars in the fourth year. Little extra precision was gained by delaying assessment until the third or fourth years as the ranking order of cultivars with respect to persistence remained largely unchanged. All persistence assessments were positively correlated with yields of sown cultivars and negatively correlated with yields of unsown herbage species in the fourth year. However, only low correlation coefficients were obtained between persistence assessments and the total yield of sown cultivar and unsown species in the fourth year, due to yield substitution between these two components.In swards sown as monocultures low persistence in a cultivar is considered to be a lack of perenniality and tiller regeneration rather than poor competitive ability against volunteer species though in mixed swards competitive ability per se will have considerable influence upon the changes in botanical composition under different managements. Persistence and yield capacity are seen, however, as distinct characteristics of a cuitivar and long-term yield potential is a joint function of these characteristics.

Notes: The effects of applying nitrogen at different growth stages to S24 and S23 perennial ryegrass grown for seed were investigated in a series of field experiments from 1971 to 1976. These varieties of ryegrass were found to be insensitive to timing of nitrogen application from apex initiation to the stage when ears first emerged. However, if nitrogen application was delayed until about 30% or more of the ears had emerged, yields were lower compared with earlier applications, this effect being significant when nitrogen was delayed until 70–80% ear emergence because of a decrease in both numbers of fertile tillers and number of seeds per unit area. No advantages were found for splitting nitrogen applications between apex initiation and ear emergence.

Notes: Oven- and freeze-dried samples of the separated green material of Trichophorum caespitosum, Molinia caerulea, Eriophorum vaginatum, Erio-phorum angustifolium, Juncus acutiflorus and J. squarrosus collected in May, July and September were analysed for dry matter digestibility (DMD) using an in vitro procedure and for structural carbohydrate content.Results were affected by method of drying, oven-dried (45°C) samples in general giving lower estimates of quality than freeze-dried samples. Low DMD values were obtained for J. squarrosus for all sampling dates. The remaining species had DMD values above 60 in May; some maintained these levels until July but all had low values by September.A comparison was made between in vitro DMD and predicted DMD using the data from the structural carbohydrate analyses and the summative equation of Van Soest (1965a). Two species, J. acutiflorus and J. squarrosus, showed poor agreement between values obtained by the two methods. The other species showed good agreement between values in May and July but poor agreement in September.The data are discussed in relation to the quality and seasonal patterns of growth of species of hill vegetation.

Notes: In two 4 × 4 Latin Square experiments, one with dry cows and one with sheep, animals were given ad libitum early-cut ryegrass silages prepared using formic acid (2.31 t−1) as an additive. The silages were offered either untreated or partially neutralized with either a low (8 g kg−1 fresh weight) or high (16 g kg−1) level of sodium bicarbonate or with sodium bicarbonate solution (50 g kg−1) given as an intraruminal infusion at a rate sufficient to provide bicarbonate at a rate similar to that provided by the high level of dietary addition.In cows the bicarbonate treatments were associated with a depression in the intake of organic matter which at the high level of addition of bicarbonate was statistically significant (P 〈 0.05). In sheep the bicarbonate treatments were associated with a slight increase in the intake of organic matter but the efFects were non-significant (P 〉 0.05). In both species water intake increased directly with the quantity of bicarbonate ingested.In both experiments the bicarbonate treatments increased rumen pH but there were no significant treatment effects on the concentration of ammonia or of total or individual short-chain fatty acids in the rumen fluid. In sheep, bicarbonate addition or infusion had no effect on the digestibility of organic matter but at the high levels of bicarbonate supplementation there was a tendency for the digestibility of nitrogen to be depressed.In two further experiments each with two dry cows determinations were made of the effects on food intake of (a) the insertion of water-filled bags into the rumen and (b) the removal of digesta from the rumen. Treatment (a) produced consistent and significant (P 〈 0.05) depressions in dry matter intake and treatment (b) increased (P 〈 0.05) dry matter intake in one cow but not in the other.The lack of significant improvement in silage intake through the addition of sodium bicarbonate to the diet indicated that the acidity of the silage was not a major factor limiting appetite. On the other hand, the effects of the insertion of water-filled bags into the rumen and of the removal of digesta from the rumen on feed intake were consistent with appetite being controlled through a rumen-fill mechanism.

Notes: Moisture and mineral concentrations and calorific values of cattle dung pats were studied under field conditions. The rate of moisture loss from dung pats varied according to the season but the dung was rarely re-wetted by rainfall. Soluble mineral ions were only leached from pats by prolonged rainfall. Magnesium was particularly resistant to leaching. In the summer months about 15% of the organic matter in the dung was lost over 2 months. The calorific value of the dung decreased by 18% in the same period. The loss of organic matter resulted in a concentration effect in calcium, iron, magnesium and nitrogen.

Notes: The regrowth of Italian ryegrass was studied at weekly intervals from 2 to 14 weeks after a cut in late April when 140 kg ha-1 N was applied. Reduction in digestibility with delay in date of harvest was due to both an increase in the proportion of cell wall and a reduction in the digestibility of the cell wall, particularly the former from week 2 to about week 5 and particularly the latter after week 5. The reduction in the digestibility of the cell wall was about equally attributable to reduction in digestibility of cellulose and to reduction in digestibility of hemicellulose. The proportion of lignin in cell wall was highly correlated with both digestibility of cellulose and digestibility of hemicellulose. The proportion of digestible cell wall in dry matter was not as constant as has sometimes been noted, increasing by about 5 percentage units from week 2 to week 5 and decreasing by about 10 percentage units from week 5 to week 13. During the latter period the decline in digestible cell wall in dry matter accounted for nearly half the decline in true digestibility of dry matter. The ratio of cellulose:hemicellulose averaged 1:0.89 and hemicellulose was more digestible than cellulose. Rate of increase in yield of cell contents appeared to diminish from about the third week of regrowth onwards, whereas the rate of increase in yield of dry matter did not begin to diminish until about the seventh week. In vitro dry matter digestibility was not increased by adding extra N to the digestion tubes, even with samples containing only 1% N in dry matter.

Notes: A reproducible method of causing tiller death on individual ryegrass (Lolium perenne L., cv. S23) plants is described. This was achieved by subjecting whole plants grown previously for 7 weeks in full light (100%) and full nutrient (100%) to either light stress (17.5% or 2.5%) or nutrient stress (10% or 0%) or various combinations of light and nutrient stress. Detailed records were made of tiller appearance, position and weight, and the probability of tiller death was calculated. Analysis of each plant indicated that the smallest tiller, which was often, but not always the youngest, was the most vulnerable when the whole plant was stressed. Tiller position was relatively unimportant in determining survival. The results are discussed in relation to tiller mortality in natural populations and crop communities.

Notes: Book reviewed in This Article: Protein and Non-protein Nitrogen for Ruminants By various authors Green Crop Fractionation Occasional Symposium No. 9, British Grassland Society Edited by R. J. Wilkins Soil Organisms as Components of Ecosystems Proceedings of the Sixth International Soil Zoology Colloquium, Uppsala, 21–25 June 1976 Ecological Bulletins No. 25 Edited by U. Lohm and T. Persson

Notes: The causes of tiller death in a 2-year-old perennial ryegrass sward were examined between April and August 1977. Physiological causes accounted for most tiller deaths and grazing by slugs and rodents was more important than the damage caused by stem-boring larvae. Tillers which died were mainly small and vegetative, although some flowering tillers died prematurely. Low nutrient status delayed but did not prevent tiller death.Using 14CO2 it was shown that small tillers fixed relatively less radiocarbon than did larger tillers and they did not receive much support for their carbon economy. Selective defoliation showed that in April defoliated tillers imported radiocarbon from undefoliated tillers but that in July at anthesis an undefoliated reproductive tiller retained most of the carbon it fixed, despite its vascular association with defoliated tillers. It appears that much of the tiller death during the period April-August is due to the failure of the more favourably placed tillers to support other tillers which are heavily shaded.

Notes: Five experiments were conducted to determine the effect of pre-harvest treatment with steam or formic acid on the moisture concentration (MC) in crops of lucerne, two varieties of perennial ryegrass, tall fescue and Italian ryegrass. In each experiment, plots were treated with a mixture of hot gases and steam (S) or sprayed with an aqueous solution of formic acid (F). In the tall fescue experiment the F treatment was applied to the cut swath but in all other instances the F and S treatments were applied to the swards before cutting and the MC changes after treatment compared with those in untreated cut swaths (W 1). Twenty-four hours after initial treatment all S plots, and those F plots other than tall fescue, were cut and the subsequent water loss compared with that from (i) untreated material cut at the same time (W 2) and (ii) the W 1 plots cut the previous day.In all five experiments the change in the MC of the S plots was similar to that of the W 1 plots both before and after cutting. The reduction in the MC of the F plots before cutting was less than that of the S and W 1 plots, and in three of the five experiments water loss from cut F plots was apparently restricted in comparison with that from untreated cut material (W2).Neither desiccant treatment showed great promise as a pre-treatment to cutting for hay making although formic acid may have limited value when a crop is to be harvested directly for silage or artificial dehydration.In an appendix, the efficacy of using accumulated vapour pressure deficit as a basis for comparing the water loss from the untreated cut crops drying under different conditions is demonstrated.

Notes: Storage losses in moist hay treated with propionic acid were compared with those occurring in untreated moist hay in two experiments and with field-cured hay in three experiments. Dry matter losses in treated hays ranged from 41 to 8.6% and from 1.7 to 12.6% in untreated hays. Digestible organic matter losses in both treated and untreated hays were generally greater than dry matter losses. Only in one experiment did propionic acid application significantly reduce nutrient losses in moist hays.Nutrient losses, and water-soluble carbohydrate losses in particular, were shown to be correlated with maximum and cumulative bale temperatures during storage in two of the experiments. The rise in hale temperatures during storage was reduced in all three experiments, to a greater or lesser extent, by application of the additive.Loss of propionic acid from the hay during and after application was very large. In the three experiments 86.2, 85.3 and 85.6% of the acid applied was lost by the end of the storage period. Acid distribution studies indicated that variation in acid concentration within bales was as great as between bales. It was concluded that more research is needed into applicator design and position on the baler and into alternative application methods if the benefits of propionic acid as a moist hay preservative are to be fully exploited.

Notes: The resistance often early, ten medium late and ten late flowering ryegrass populations to two rates of dalapon (2.8 and 5.6 kg ha-1 acid equivalent) was measured in a box experiment. There was no difference in the mean effect of dalapon on the maturity groups at the time of greatest yield reduction, but the recovery of the late flowering population was, on average, better than that of the medium late group. There was a range of reaction to herbicide within all three maturity groups and, in general, the high yielding populations without dalapon were the most resistant, but there were exceptions. Assessment at 2.8 kg ha-1 acid equivalent gave a similar ranking order to that using twice the amount of dalapon. The results of the current box experiment with seedlings were consistent with those obtained in the field at another location (Faulkner, 1974) for the eleven cultivars common to both trials. The resistance of a permanent pasture population was much lower than that of some cuttivars.

Notes: Two contrasting Gremie perennial ryegrass and Blanca white clover seeds mixtures were established. Each sward type was either continuously or rotationally (four paddocks) grazed at two stocking rates by lambs of 26–28 kg initial mean live weight in two 12-week experiments. Dry matter production, assessed by the cage method, was lower on the high-clover sward during the first experiment but overall was similar between seeds mixtures. Clover content, and differences between sward types, declined with time and was lowered by continuous grazing in both experiments and by the higher stocking rate in the first experiment.Animal performance was related to intake and both were increased by lowering stocking rate, increasing clover content and adopting a continuous grazing system. The results are discussed in relation to the experimental methods used and to other published findings.

Notes: Four Italian ryegrass varieties of different origins and winter hardiness were grown as spaced plants at a lowland and an upland site and subjected to ten managements comprising two nitrogen levels and five autumn cutting treatments. Tiller mortality after the winter of 1971–72 was measured in March and subsequent spring recovery from winter damage in April.Although the winter was not severe, there was considerable winter kill, particularly at the upland site where the most severe treatment combinations killed up to 90% of the plants of the more susceptible varieties. In general, winter kill was increased by raising the level of nitrogen fertilizer and by late or frequent autumn defoliations, and significant interactions between locations and the two treatment factors emphasized the importance of the siting of the experiment.The varieties difFered in their overall winter hardiness, with Bb 1430 and RvP suffering less tiller mortality than S22 and Grasslands Paroa in all the treatment combinations, but significant interactions of varieties with locations and cutting treatments revealed that the magnitude of the difference between varieties varied with location and cutting management. Regression analysis of these interactions, however, showed that the tiller mortality of all four varieties increased linearly with the increasing stresses applied by the location × management combinations. There was no differential variety recovery from winter kill, the spring yields being entirely related to the level of tiller mortality experienced.These results are discussed in relation to the breeding of winter hardy varieties, the choice of variety and autumn management practice.

Notes: Two experiments were conducted with sheep to investigate the effect of silage chop length on voluntary intake and eating and ruminating behaviour. The silages, made from Italian rye-grass, either received no additive or formic acid at a rate of 4 g kg−1 and were chopped to lengths of 5.3 cm (long), 1.8 cm (short) before ensiling or 1.8 cm (long/short) before feeding. The addition of the additive and short chopping improved the fermentation characteristics of the silage. Voluntary intake of silage dry matter and organic matter was higher with the short than with the long silage. Differences in silage digestibilities and cellulolytic activity did not explain the increase in silage intake. Sheep on the long silage had a lower rate of intake and a shorter ruminating time than on short silage, and thus the effective breakdown of the silage in the rumen was delayed, i.e. an increased latency time. Pseudo-rumination was significantly higher on the long than on the short silage.

Notes: In two experiments conducted with Ayrshire dairy cows in 1974 and 1975 on swards of S23 perennial ryegrass, four systems of continuous grazing were investigated. The leys received 345 and 370 kg ha-1 fertilizer nitrogen in 1974 and 1975 respectively and were stocked at the rate of five cows per ha. In 1974, a comparison was made between two systems which either integrated silage making with, or separated it from, the continuous grazing. The provision of a silage aftermath in late July increased milk yield after that time, but had no significant effect on milk yield over the 19-week experimental period. In 1975, a comparison between weekly and monthly applications of fertilizer N showed no significant differences between milk yields in a 20-week period. The feeding of supplementary concentrates from late July onwards significantly increased milk yield. The treatments in both years had only small and mainly non-significant effects on milk composition. On average, excluding the concentrate treatment, the annual output of milk was 10,800 kg ha-1 using spring-calved cows.

Notes: Book reviewed in This Article: Green Crop Fractionation: an Economic Analysis by R. J. Wilkins, S. B. Heath, W. P. Roberts, P. R. Foxell and A. Windram.

Notes: Maize silages made in October were fed to forty-three autumn-calving cows during a 20-week winter feeding trial. The control silage received no additive whereas a non-protein nitrogen (NPN) additive was applied to the other silage at harvest time. The four experimental feeding treatments were: A, maize silage + 6 kg d−1 barley; B, maize silage with NPN + 6 kg d−1 barley; C, maize silage + 5 kg d−1’barley + 1 kg d−1 extracted decorticated groundnut cake; D, maize silage with NPN. The mean daily milk yields of cows on the treatments were 14.7, 15.1, 15.3 and 15.0 kg respectively. All cows received maize silage ad libitum. There were no significant differences in milk yield but the milk produced by the cows on treatment D had significantly lower concentrations of milk fat, protein and solids-not-fat when compared to the other three treatments. The cows on treatment D had a negative liveweight change which was significantly different (P 〈 0.05) from those of the cows on treatments B and C.

Notes: The aim of this study was to investigate whether bovine faeces could replace rumen liquor collected from fistulated sheep in the determination of organic matter digestibility (OMD) of forages in vitro. The first experiment compared two inocula that had been prepared by mixing 83 and 333 g of cattle faeces with 1 litre of artificial saliva according to the first stage of the in vitro technique of Tilley and Terry (Journal of the British Grassland Society,18, 104–111, 1963). Inocula made from 333 g of faeces gave higher values of OMD than that prepared from 83 g of faeces and was used in subsequent studies. When a 48-h acid pepsin digestion, the second stage of the Tilley and Terry (1963) technique, was included, the OMD values and the ease of filtering of undigested residues were increased. The second experiment compared digestibility determined with inocula produced from faeces with that produced from rumen liquor. The OMD of a ryegrass hay determined with an inoculum prepared from faeces was 0·468 compared with 0·528 when using an inoculum prepared from rumen liquor. The third experiment investigated the accuracy of estimating the OMD of eight contrasting forages determined using rumen liquor from three sheep (y) and faeces from two cows (x). All regressions were significant (P 〈 0·001) and had residual standard deviations (r.s.d.) of between ±0·019 and ±0·022. The final study compared faeces collected from cattle fed with either hay or concentrates. The OMD of forage was higher from the hay-fed animals, but the r.s.d. values of the regressions were similar. It was concluded that cattle faeces shows potential as an alternative to rumen liquor collected from rumen-fistulated sheep for use in the in vitro digestibility assay of forages.

Notes: The effect of botanical composition and nutrient availability on the relative allocation of biomass to stems and leaves in a permanent upland pasture in the central Pyrenees was assessed. Six short-term and medium-term fertilizer treatments (nitrogen and phosphorus) were applied to a meadow to create large differences in the proportions of the different species and a wide range of herbage nutrient status. The above-ground herbage dry-matter components (green leaves, sheaths and stems for grasses and dicotyledons, and senescent material) were measured for the first growth cycle.The leaf mass depended mainly on the herbage N status, whereas the stem mass depended both on the botanical composition and on the herbage N and P status. During spring growth, the proportion of leaves in the above-ground dry matter decreased faster in plots that had the highest nutrient status or that were composed of species characteristic of nutrient-rich (Festuca-poor) habitats. Application of fertilizer decreased the proportion of leaves both for grasses and dicotyledons, but to a larger extent for grasses. There was a single relationship between the proportion of leaves in the above-ground dry matter and the total mass of above-ground dry matter, irrespective of the sampling date, the botanical composition or the herbage nutrient status. This statistical relationship resulted from (i) a faster increase in stem mass than leaf mass for a given botanical composition when the herbage nutritional status increased, (ii) a greater stem mass when the sward was composed of species usually found in nutrient-rich habitats.

Notes: The objective of this study was to investigate the relationship between level of sward height reduction (SHR) and short-term intake of herbage by lactating dairy cows offered swards differing in initial bulk density (BD). Three experiments were carried out in which cows were presented with swards representing different levels of SHR (nominally described as ungrazed, low, moderate and high). Experiments 1 and 2 differed with respect to initial sward BD [ungrazed sward 1·7 vs. 2·5 kg dry matter (DM) m−3 respectively]. Experiment 3 investigated the interaction between BD and SHR.In each experiment, sixteen Holstein/Friesian cows (fitted with excreta collection bags) grazed for a 1-h period in 200-m2 plots that had been grazed on the previous day to predetermined sward surface heights (SSH) (= levels of SHR). Herbage intake rates were assessed from changes in live weight, with a correction for insensible weight loss (IWL). Biting rates were recorded from visual observation. High levels of SHR were associated with a significant reduction in SSH, herbage mass and leaf fraction, and a significant increase in sward BD, stem and dead fraction, and DM concentration.Herbage intake, expressed either as DM intake per bite or DM intake per hour, declined as level of SHR increased from low to high. The level of SHR generally had no effect on biting rate. Intake rates varied from 1·9 to 4·4 kg DM h−1, whereas DM intake bite−1 ranged from 0·5 to 1·3 g. Pooled regression analysis identified SSH (P 〈 0·001; r2 = 0·94) as the principal determinant of DM intake bite−1. The regression equation was not significantly improved by the addition of terms for leaf fraction, BD, or herbage mass. In Experiment 3, a significant interaction between level of SHR and sward BD was observed. It is concluded that the principal factor controlling intake (g DM bite−1 or kg DM h−1), as swards are progressively grazed down, is SSH, but at a high level of SHR, sward BD also influences intake bite−1.

Notes: The severity of damage by certain invertebrate species to white clover (Trifolium repens) leaves on the main stolons of plants grown in mixed perennial ryegrass/white clover swards was examined in a field experiment in the Netherlands in which two cutting frequencies (high and low) and three white clover cultivars (Retor, Alice and Gwenda) were used. The damage to the leaves was described in terms of the numbers of damaged leaves and the extent of that damage (slight 〈20%, moderate 20–50% and heavy 〉50%). The relationships between leaf damage and sward characteristics (white clover content, above-ground biomass and sward height) were evaluated throughout the growing season.Over the whole experimental period, 23·7% and 27·4% of the total number of leaves produced per stolon were damaged by slugs and weevils in the low- and high-frequency cutting treatments respectively. High-frequency cutting increased the number of leaves in the total leaf damage and moderate leaf damage categories by 21·4% and 34·8%, respectively, compared with the low-frequency cutting. The cv. Retor (medium-leaved) experienced the most severe damage by invertebrates. It had much higher leaf damage than cvs Alice (large-leaved) and Gwenda (small-leaved) at either cutting frequency, both in the total number of damaged leaves and in the different damage categories. Differences among cultivars in the number of damaged leaves and relative leaf damage occurred primarily in spring, late summer and autumn, but did not differ during the early- and mid-summer months.This study indicates that variations in leaf damage among clover cultivars were associated with differences in measured sward characteristics. Both the number of damaged leaves and the relative leaf damage were strongly negatively correlated with white clover content and biomass in spring, late summer and autumn under each cutting treatment. White clover content and biomass explained 65%, 59% and 50% of the variation in the number of damaged leaves in spring, late summer and autumn, respectively, and 58%, 57% and 45% of the variation in relative leaf damage in these three periods. Thus, sward characteristics may play a role in regulating the severity of invertebrate damage to clover leaves in addition to the primary effects of HCN.

Notes: In a field experiment carried out over 3 years, the nitrate content of herbage from perennial ryegrass (Lolium perenne) swards increased exponentially with nitrogen application rate, but herbage nitrate content appeared to reach potentially dangerous concentrations only when nitrogen application rates were greater than those needed to stimulate dry-matter production. Thus, on average over all the harvests, maximum yield could be obtained with annual application rates of 400 kg N ha–1 (six applications of 67 kg N ha–1) for perennial ryegrass and 300 kg N ha–1 (six applications of 50 kg N ha–1) for perennial ryegrass/white clover (Trifolium repens) swards, whereas the mean nitrate concentrations were 3340 and 2929 mg NO3 kg–1 dry matter (DM) respectively. Nitrate content, however, varied considerably from harvest to harvest, reaching maxima of 9345 mg NO3 kg–1 DM at 400 kg N ha–1 for perennial ryegrass and 6255 mg NO3 kg–1 DM at 300 kg N ha–1 for perennial ryegrass/white clover. The nitrate content of herbage from perennial ryegrass/white clover swards was always greater than that of perennial ryegrass swards receiving the same rate of nitrogen application, even though in the herbage from the mixed sward the nitrate content of white clover was usually less than half that of the perennial ryegrass component. The physical environment did not have a clearly interpretable effect on nitrate content, although herbage harvested in May had a much lower nitrate content than that harvested at any other time of the season. It was not possible to find a single multiple regression equation relating herbage nitrate content to nitrogen application and to other environmental variables that explained more than 60% of the variance in herbage nitrate, but it is suggested that, by reducing the later-season nitrogen applications from 67 to 50 and finally to 33 kg N ha–1 for perennial ryegrass and from 50 to 33 kg N ha–1 for perennial ryegrass/white clover, it would be possible to achieve over 90% of the maximum yield while reducing average nitrate content to 〈40% of that at maximum yield, with no samples containing more than 2300 mg NO3 kg –1 DM.

Notes: The effect of management of maize residues on the population of insects inimical to the establishment of alfalfa, Medicago sativa L., was examined 1 month after sowing. Alfalfa was sown in early and late April, and late May for 3 consecutive years in Centre County, Pennsylvania, USA. The sowings were made by conservation tillage (direct drilled into maize residue with minimal disturbance of soil) into three different maize residues after (1) silage, (2) silage-plus-winter rye cover and (3) grain. A fourth sowing was by conventional tillage (spring ploughing and harrowing maize residue) after grain. A pesticide, carbofuran (granular formulation) was applied at sowing to half of the plots. Methiocarb bait, a molluscicide, was applied as a split application to the same plots, one-half at sowing and the remainder 2 weeks later. Alfalfa plots in the silage-plus-rye maize residues were colonized with fewer insects than the other residue treatments. Excessive growth of rye in early spring that was not successfully suppressed by herbicide treatment produced vigorous rye plants and fewer alfalfa seedlings. Consequently, silage plus rye had the lowest yield of alfalfa in early April sowings in 2 out of 3 years. Insects known to feed on alfalfa, such as tarnished plant bugs, Lygus lineolaris (Palsot de Beauvois), the plant bug, Plagiognathus politus Uhler, pea aphids, Acyrthosiphon pisum (Harris), and meadow spittlebugs, Philaenus leucophthalmus spumarius (L.), were collected by sweep net 1 month after sowing and less often in the silage-plus-rye treatment. These species were present in greater numbers in the other maize residues that had significantly more alfalfa forage.The insidious flower bug, Orius insidious (Say), and a damsel bug, Nabis americoferus Carayon, were collected in significantly greater numbers in the early April sowings, which corresponded with the peak populations of pea aphid. The potato leafhopper, Empoasca fabae (Harris), was most abundant in plots sowed in late April or late May.Pesticide treatment applied at the time of sowing had very little effect on numbers of insects collected by sweep net 1 month later in 1986 and 1988. However, pesticide treatment significantly increased yield by 280 kg ha−1 in 1987, even though sweep net collections of insects were not reduced by the pesticide treatment. Therefore, the beneficial effect of the pesticide could not be explained on the basis of the insects collected.The highest yields of alfalfa were obtained from the early April sowing into maize residues. This coincided with the time when the majority of alfalfa pests were less abundant than in later sowings; fewer pests were found on the sowings into silage-plus-rye residue. Also, when the rye forage yield was combined with the alfalfa yield, this became the most productive system.

Notes: Quantitative traits and allozymes were used in two experiments to clarify the ecotypic differentiation of natural cocksfoot (Dactylis glomerata) populations from north-west Spain. Thirty-nine populations belonging to the four main ecotypes in Galicia were cultivated in two field experiments. In the first experiment, there were significant differences between ecotypes for heading date, flag leaf length, growth habit and vigour. Coastal populations were the least infected by rust. In the second experiment, allozyme markers presumed to be diagnostic for ssp. glomerata vs. izcoi (TO1 1·00, TO1 1·03) were found in all populations studied (ten tetraploids and one diploid izcoi). This suggests that gene flow occurs between coastal and interior populations. Culm and panicle lengths of tetraploids (without application of fertilizer) were inside the izcoi range in 1997, but some plants from all populations exceeded it in 1998. It is concluded that ssp. izcoi also occurs on the coast. Populations with a high level of complementary seasonal growth were detected.

Notes: The trace gas ethylene affects plant growth and atmospheric chemistry and it interferes with soil restoration. In soil ethylene is simultaneously produced and consumed by different microorganisms. The effects of land use and soil moisture conditions on processes leading to an accumulation of ethylene are still unclear. We measured the rates at which montane and lowland soils from Austria produced and consumed ethylene over a range of water tensions and oxygen supply. Complete anaerobiosis (waterlogging, zero tension) favoured ethylene production, whereas ethylene degradation rates were greatest in soils at 30 kPa water tension. Soils from the lowland region of eastern Austria produced ethylene at rates of up to 12 pmol C2H4 g–1 h–1 under anaerobic conditions, and they consumed ethylene at rates reaching 231 pmol C2H4 g–1 h–1, after addition of 20 μl l–1 ethylene. Deciduous forest soils consumed ethylene fastest. Ethylene formed rapidly and was also consumed rapidly in soils rich in humus and total nitrogen. Soils taken from the mountains both produced and consumed ethylene more rapidly than lowland soils did. Production rates reached 146 pmol C2H4 g–1 h–1 under anaerobic conditions. Spruce forest soils produced significantly more ethylene than pastures. Ethylene formation was negatively correlated with soil pH. In montane soils ethylene production was related to the availability of simple carbon sources, expressed by the amount of extractable glucose equivalents. Maximum ethylene degradation amounted to 895 pmol g–1 h–1. Most of the soils were net sinks for ethylene at a water tension of 30 kPa and drier.

Notes: Transport of gas in soil depends on the paths available through the porous system. We determined the rate of diffusion of air through a core of silty-clay soil experimentally. After the experiment, the core was impregnated with resin and sectioned at 100 μm. From the images of the sections, the porous structure was reconstructed in three dimensions with a 100-μm resolution and gas diffusion was simulated in it. We computed the self-diffusion to describe gas diffusion. The experiment and simulation were compared using tortuosity, which is the ratio between the self-diffusion coefficient calculated in air and the coefficient calculated in the reconstructed sample. The results showed that the experimentally measured tortuosity (2.3) and the numerically calculated tortuosity (1.75) were similar. This suggests that the self-diffusion propagator is useful for simulating self-diffusion in a numerical three-dimensional reconstructed sample and that the scale chosen for the reconstruction of the sample (100 μm) was suitable for this particular soil. Résumé Les propriétés de transfert en phase gazeuse des sols ont étéétudiées sur un sol limono-argileux. A l’issue de l’expérience, l’échantillon a été imprégné avec une résine polyester puis sectionné en coupes sériées. A l’aide des images numérisées des coupes, l’échantillon a été reconstruit en trois dimensions. Nous avons ensuite simulé le processus de diffusion gazeuse dans l’échantillon reconstruit à l’aide du propagateur de diffusion. Expérience et simulation ont été comparées à l’aide de la tortuosité, rapport entre le coefficient de diffusion gazeuse dans l’air et celui dans le sol. Les résultats montrent que la tortuosité mesurée expérimentalement (2,3) et la tortuosité calculée numériquement (1,75) sont proches. Ceci prouve que l’utilisation du propagateur de diffusion est justifiée pour la simulation du processus de self-diffusion dans un échantillon tridimensionnel reconstruit et que l’échelle choisie pour la reconstruction (100 μm) s’avère pertinente pour l’étude de la diffusion gazeuse dans ce sol.

Notes: It is common practice to fit mathematical models to radionuclide activity–depth profiles in soils in order to quantify rates of vertical migration through the soil profile. We have fitted six such models to 21 different activity–depth profiles of radiocaesium (137Cs) derived from Chernobyl and determined relations between the models and the values of their parameters. The advection and dispersion parameters obtained using four solutions to the advection–dispersion equation (each based on different initial and boundary conditions or different simplifications) are in good agreement. We further develop a relation between parameter values obtained using the advection–dispersion models and those determined by a simpler exponential function of the form Aexp(–Bt) where t is the time and A and B are parameters to be estimated. One of the advection–dispersion models proved to be significantly better than the others in terms of goodness-of-fit, versatility and ease of use. A simple model, using calculations based on measured characteristics of the activity–depth profile, was shown to accord well with parameters derived from more complex models based on statistical curve fitting. We have also evaluated the ‘residence time’ or ‘compartmental’ model approach to characterizing radionuclide activity–depth profiles. We relate such models to a numerical solution of a simple advection equation, and we show that apparent dispersion in compartmental models is an artefact of numerical dispersion, which can be quantified by the Courant condition. For activity profiles that have a significant advection component, using solutions to the advection–dispersion equation, we have observed a strong positive correlation between advection and dispersion in the profile.

Notes: Immobilization of nitrogen (N) in decomposing straw varies between soils, and the objective of this study was to identify the mechanisms responsible. Internode segments of wheat straw were incubated in Denmark and in Scotland in arable soils fertilized with NH4NO3, labelled with 15N, for periods up to 1 year. Straw was recovered from the soils periodically and analysed for microbial biomass and different forms of N using chemical methods and CPMAS 15N NMR spectroscopy.The total N content of the straw increased, as long as the soil was not too wet, such that there was overall immobilization. This was accompanied by a rapid increase in the content of amino acid N and to a lesser extent of glucosamine N and a concomitant decrease in the carbohydrate content of the straw. Using direct and plate counts for bacterial and ergosterol content for fungal estimation, we found that fungal biomass was much greater than that of bacteria. This correlated with the forms of N in the straw as determined by CPMAS 15N NMR, which showed spectra that were more typical of fungi than of bacteria. It seems that immobilization of N is primarily caused by fungi as they decompose the straw.

Notes: Collecting soil data is time-consuming and costly, often exceeding practical possibilities. A methodology for the delineation of soil mapping units in an alluvial plain of Western Peloponnese, Greece, was investigated. A detailed soil survey of an area of 300 ha was used to obtain the basic soil data for evaluating the performance of the proposed methodology. The methodology consists of the following steps: (a) data collection from borings and representative soil profiles, (b) definition of the soil mapping units in the study area, (c) determination of the range of the diagnostic variables for each mapping unit from field observations and statistical analysis of the analytical data from representative soil profiles, (d) determination of the class of each diagnostic variable by observation at a network of boring points, (e) subjective assignment of numerical values to soil variables at the bore points, (f) estimation of the values of each soil variable at the points of a regular grid using the interpolation methods kriging and inverse squared distance, (g) application of the fuzzy set theory to the interpolated data and the production of thematic fuzzy maps, and (h) validation of the results through a number of independent test borings. The results obtained show that the proposed methodology can produce soil maps of recent alluvial plains with acceptable accuracy and cost.