ALBERT

Notes: Abstract. This paper compares nitrate leaching losses from organic farms, which depended on legumes for their nitrogen inputs (66 site years) with those from conventional farms using fertilizers under similar cropping and climatic conditions (188 site years). The conventional farms were within Nitrate Sensitive Areas in England, but sites following special practices associated with that scheme were excluded. Nitrate losses during the organic ley phase (including the winter of ploughing out) were similar (45 kg N ha–1) to those from conventional long-term grass receiving fertilizer N inputs of less than 200 kg N ha–1 (44 kg N ha–1) and from the grass phase of conventional ley-arable rotations (50 kg N ha–1). Losses from conventional grass receiving higher N inputs were greater than from organic or less intensive grass. Nitrate losses following arable crops averaged 47 and 58 kg N ha–1 for the organic and conventional systems respectively, with part of the difference being due to the greater proportion of non-cereal break crops in the latter. Thus under similar cropping, losses from organic systems are similar to or slightly smaller than those from conventional farms following best practice.

Notes: Abstract. In the Sahel, promising technologies for agricultural intensification include millet stover mulching and ridging. A four year on-farm experiment was set-up in order to assess the effect of various combinations of these two technologies on crop development and yield in a millet (Pennisetum glaucum (L.) R. Br.) - cowpea (Vigna unguiculata (L.) Walp.) intercropping system. Treatments included bare surface, ridging, a surface applied banded millet stover mulch (2 t ha–1) and a banded millet stover mulch (2 t ha–1) buried in ridges. The latter three treatments were implemented exclusively in the cowpea rows, with an annual rotation between the millet and cowpea rows. On bare and ridged plots, millet yields fell below 100 kg grain ha–1 after the first year. This was ascribed mainly to soil acidification and loss of soil organic matter rather than to soil physical constraints or water availability despite extensive surface crusting and high soil penetration resistance and bulk density. Compared to the bare plots, ridging increased cowpea hay production by 330% over the four years which was attributed to lower soil penetration resistance and bulk density but also to a reduction of 0.15 cmol+ kg–1 exchangeable acidity in the ridges. Except during the severe drought year of 1997, millet grain yield in the banded mulch treatment remained fairly stable over time at 526 ± 9 kg ha–1. However, a detailed analysis revealed yield compensation mechanisms between various yield components depending on the timing of occurrence of the abiotic stresses. Cowpea productivity was always higher in buried banded mulch plots than in surface applied banded mulch plots but the former treatment appeared unable to sustain millet yields. This decline was attributed to a greater nutrient uptake by cowpea and more rapid acidification in the buried mulch treatment compared to the banded mulch treatment.

Notes: Abstract. Nutrient balance calculations have been advocated as indicators of the risk of nitrate loss from agricultural land. To explore this concept, a spatially distributed UK agricultural nitrogen balance was derived using annually updated statistics. The mean UK N surplus for 1995 was 115 kg N ha–1, made up of 51 kg ha–1for arable land, 140 kg ha–1 for agricultural grassland (excluding rough grazing) and an additional 14 kg N ha–1for agricultural land from pig and poultry units. Nitrogen surpluses were greater in lowland grassland (mainly in western, wetter areas) than in arable areas. However nitrate concentrations in rivers were generally greater in arable areas. The relationship between N balance and nitrate leaching was very different for grassland and arable systems, and was also sensitive to climate, level of inputs and management practices. Nitrogen surplus was therefore weakly or even negatively correlated with river nitrate concentrations or loads. A positive correlation was found only where the comparison was restricted to grassland-dominated catchments. Nitrogen surplus calculations identified areas of very high livestock densities, which would be associated with increased risk of pollution. However their use in isolation as indicators of N leaching, or of progress towards mitigation, could be misleading especially if comparing areas differing in land use, climate or soil type.

Notes: Abstract. Dynamic simulation models are increasingly used in environmental and agricultural science. Here we present a method that allows models to be used to determine optimum timing of sampling for field trials. The model is used to decide when to concentrate sampling effort before the field trial begins. The model chosen to design sampling strategy should include an appropriately sensitive description of all processes that influence measurements significantly. The simulation is run, using predicted weather data, to generate the full time series before the trial begins. Every point in the simulation is considered initially to be a potential sampling point. The potential error due to not including a measurement at each point is calculated using the ‘dot-to-dot’ method of b10Smith et al. (2002) by omitting simulated values consecutively. The calculated potential error provides a measure of the priority that should be given to sampling at each point. Where the error introduced by omitting the simulated value exceeds an acceptable error, the value at the last discernible time step should be measured so that all statistically significant changes in the system can be observed. The output from the calculation is a plan of sampling times needed to capture all statistically significant events that are likely to occur over the course of the trial.

Notes: Abstract. In grazed dairy pasture systems, a major source of NO3– leached and N2O emitted is the N returned in the urine from the grazing animal. The objective of this study was to use lysimeters to measure directly the effectiveness of a nitrification inhibitor, dicyandiamide (DCD), in decreasing NO3– leaching and N2O emissions from urine patches in a grazed dairy pasture under irrigation. The soil was a free-draining Lismore stony silt loam (Udic Haplustept loamy skeletal) and the pasture was a mixture of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). The use of DCD decreased NO3–-N leaching by 76% for the urine N applied in the autumn, and by 42% for urine N applied in the spring, giving an annual average reduction of 59%. This would reduce the NO3–-N leaching loss in a grazed paddock from 118 to 46 kg N ha–1 yr–1. The NO3–-N concentration in the drainage water would be reduced accordingly from 19.7 to 7.7 mg N L–1, with the latter being below the drinking water guideline of 11.3 mg N L–1. Total N2O emissions following two urine applications were reduced from 46 kg N2O-N ha–1 without DCD to 8.5 kg N2O-N with DCD, representing an 82% reduction. In addition to the environmental benefits, the use of DCD also increased herbage production by more than 30%, from 11 to 15 t ha–1 yr–1. The use of DCD therefore has the potential to make dairy farming more environmentally sustainable by reducing NO3– leaching and N2O emissions.

Notes: Abstract. This paper describes a study of 37 farms in the Batinah region of Oman where fodder crops and date palms are grown using saline irrigation water. Soil water salinities (εs) range from 2 to 50 dS m–1. Soil water salinity depends on irrigation water quality and management factors such as the amount and frequency of irrigation and the area of the irrigation basin relative to the vegetation canopy. An irrigation management model for soil salinity control IMAGE has been developed, based on the salt balance of the profile assuming that the εs is in equilibrium with the irrigation water. The input parameters required to run the model include the annual water application, irrigation interval, soil textural class, potential evaporation, the ratio of crop canopy to irrigation basin area and the salinity of irrigation water. Verification of the model using rather uncertain data from a survey of the farms showed that this simple approach predicted εs to within 2.5 dS m–1 in 82% of cases. The model showed that εs was highly sensitive to the size of irrigation basin and the amount and scheduling of irrigation, and so provides a tool for optimizing salinity management.

Notes: Abstract. There is increasing evidence that phosphorus (P) can be transferred to surface waters by leaching as well as by erosion and surface runoff. Recently it has been suggested that P soluble in 0.01 m CaCl2 may be a good indicator of the specific Olsen-P concentration (usually termed the ‘Change Point’) at which the rate of P leaching from soil suddenly increases and poses a greater threat of eutrophication to standing waters. We know that these ‘Change Points’ vary from soil to soil but, so far, we do not fully understand the mechanism(s) involved. Here, we combine methods for assessing isotopically exchangeable P and P sequential fractionation to gain an insight into the processes which cause this sudden increase in P solubilization. We suggest that Change-Points simply define the asymtote of rapid desorption isotherms relating to that P which is most readily isotopically exchangeable (i.e at 24 h –33P24) with the soil solution. This involves ligand exchange at hydroxyl sites associated with Fe and Al cations, which is kinetically governed by the concentration of surface complexes on soil minerals. Individual Change-Points reflect the mineralogy and surface chemistry of different soil types. Laboratory and field measurements of the Olsen-P Change-Point reflect these surface phenomena and are similar. Olsen-P extracts the portion of the exchangeable pool that most readily controls solution P, and the Olsen-P/33P24 ratio is linearly related to Olsen-P Change-Points. This may provide a method for estimating P Change-Points where gradients of soil P are not available.

Notes: Abstract. Soil removed on sugarbeet (Beta vulgaris L.) at harvest may be an important factor in soil degradation causing significant decline in soil productivity. This study evaluated soil losses on sugarbeet and estimated the cost of plant nutrients lost by this process. The losses were calculated using data from the agricultural reports published by the General Directorate of the Turkish Sugar Industry. Organic matter and plant available nutrient contents of soils removed from sugarbeet fields were determined. It was estimated that approximately 30 000 t of soil is lost annually in Erzurum, and 1.2 million t in the whole of Turkey. The cost of N, P and K losses is approximately 60 000 US$ annually for the study area.

Notes: Abstract. Inputs and outputs of sulphur (S) were quantified over a three year period using field lysimeters containing undisturbed 60 cm deep soil monoliths of a sandy loam. There were four treatments, including a control (no S) and three forms of sulphur fertilizers: ammonium sulphate (AS); micronized elemental sulphur (MS0); and bentonite clay and elemental sulphur mixture (BS0). Sulphur was applied at the beginning of the experiment in autumn at 50 kg ha–1. Atmospheric deposition varied between 6.7 and 7.8 kg S ha–1 yr–1. Leaching losses of S ranged from 35 kg ha–1 in the control to 83 kg ha–1 in the AS treatment over three years, with dissolved organic S accounting for 6–10% of the S leached. In the first year, 7, 26 and 72% of the applied S was lost to drainage water in the BS0, MS0 and AS treatments, respectively, and the percentages increased to 33, 75 and 96% by the end of year 3. No significant differences in sulphur uptake by herbage were found in any of the harvests except a significant increase in the BS0 treatment in the second cut of the second year. Over three years, total S outputs exceeded total S inputs in all treatments, with the control and the AS treatments showing a larger S deficit (34–35 kg ha–1) than the MS0 (23 kg ha–1) and BS0 (7 kg ha–1) treatments. The deficits indicate a depletion of soil S, probably through net mineralization of organic S. The results confirm that sulphate was highly mobile and prone to leaching under the experimental conditions, whereas the slow release characteristics of elemental S, particularly BS0, led to smaller leaching losses and larger residual values.

Notes: Nitrate and Man: Toxic, harmless or beneficial? By J. L ‘Hirondel and J-L L ‘Hirondel.

Notes: Abstract. In general, agricultural management has focused on differences between fields or on the gross differences within them. Recent developments in agricultural technology, yield mapping, Global Positioning Systems and variable rate applications, have made it possible to consider managing the considerable variation in soil and other properties within fields. This system is known as precision agriculture. More precise management of fields depends on a better understanding of the factors that affect crop input decisions. This paper examines the spatial variation in crop yield, soil nutrient status and soil pH within two agricultural fields using geostatistics. The observed properties vary considerably within each field. The relation between yield and the measured soil properties appears to be weak in general. However, the range of spatial correlation for yield, shown by the variogram, is similar to that of the soil chemical properties. In addition the latter changed little over two years. This suggests that information on the scale of variation of soil chemical properties can be derived from yield maps, which can also be used as a guide to a suitable sampling interval for soil properties.

Notes: Abstract. This study employed both natural and social sciences to examine the relationship between resources and economic development in the Red Soil Zone along the coast of South China. Based on the data collected by field investigation and laboratory analysis as well as from literature sources, the authors discuss the environmental problems and the main factors influencing them by using the case of Guangdong province. The results indicate that there are three important problems of Red Soil utilization: soil degradation and pollution, soil erosion and geological hazards. The main reasons for these problems involve the physical and chemical characteristics and mineral composition of the soil, climate and meteorological changes and human activities. The latter is currently the dominant factor influencing the change and deterioration of the Red Soils.

Notes: Abstract. The dual porosity soil water and contaminant transport model MACRO was tested for its suitability to represent water flows and leaching of phosphorus (P) through field drains following spreading of slurry. These flows are characterized by very high loadings of P, including a high proportion in colloidally attached form, for about one week following winter spreading of slurry, followed by quite a rapid decline to the low background level. Use was made of the option in MACRO for representing colloid facilitated contaminant transport. The model simulates transport through macropores and soil matrix pores (micropores) of contaminant carrying colloids, as well as trapping of colloids by straining and filtration using an adaptation of standard filtration equations. Calibration involved selecting soil hydraulic parameters, colloid filtration coefficients and P sorption characteristics for two soils from measured and literature values. Both P in solution and P attached to colloids were represented in simulated outputs. Reasonable agreement was found between simulated and measured water and leached P flows. Work with the model suggests that macropore flow through the soil to field drains of colloidally transported P is an important component of water pollution associated with slurry spreading

Notes: Abstract. Rising atmospheric CO2 concentrations and their association with global climate change have led to several major international initiatives to reduce net CO2 emissions, including the promotion of bioenergy crops such as short rotation coppice (SRC) willow. Although the above-ground harvested bio-fuel is likely to be the major contributor to the CO2 mitigation potential of bioenergy crops, additional carbon may be sequestered through crop inputs into plantation soils.  Here, we describe a process-based model specifically designed to evaluate the potential for soil carbon sequestration in SRC willow plantations in the UK. According to the model predictions, we conclude that the potential for soil carbon sequestration in these plantations is comparable to, or even greater than, that of naturally regenerating woodland. Our preliminary, site-specific model output suggests that soil carbon sequestration may constitute about 5% of the overall carbon mitigation benefit arising from SRC plantations. Sensitivity analyses identified the following factors as the principal controls on rates and amounts of soil carbon sequestration under SRC: carbon inputs (net primary production), decomposition rates of the major soil carbon pools, initial soil carbon content (an inverse relationship with rates of soil carbon sequestration), crop/plantation management, and depth of soil being influenced by the bioenergy crop. Our results suggest that carbon sequestration potential is greatest in soils whose carbon content has been depleted to relatively low levels due to agricultural land use practices such as annual deep ploughing of agricultural soils.

Notes: Abstract. Leaching of phosphorus (P) from agricultural land is the major cause of eutrophication of surface waters in Northern Ireland. However, soil testing using the Olsen method has shown that while soil P in some catchment areas of the Province is low, surface waters within these catchments are, nonetheless, every bit as eutrophic as other local catchments where soil P is high. Soil P measurements on over 6000 samples from Northern Ireland soils (A horizon only) have indicated that Olsen-P values of improved grassland on most parent materials are linearly related to animal intensification. Exceptions are soils derived from peat, marl and basalt. For each of the latter soils, the measured Olsen-P was shown to be around 10 mg L–1 lower than expected for farms with similar intensification on other parent materials. In particular, the mean Olsen-P values of samples from basaltic soils under grass with total Fe above 62 g kg–1 and total Mg above 16 g kg–1 were significantly lower than those from basaltic soils with low total Fe (〈37 g kg–1) and total Mg (〈8 g kg–1). As a result of the depressed Olsen-P value, excessive quantities of P may be applied to these soils to maintain a recommended soil P index thereby enhancing the potential for nutrient enrichment of adjacent surface waters. In such cases, coworkers have shown that acid ammonium oxalate may be a better extractant than bicarbonate as an indicator of plant-available P.

Notes: Abstract. This paper reviews current understanding of soil structure, the role of soil organic matter (SOM) in soil structure and evidence for or against better soil physical condition under organic farming. It also includes new data from farm case studies in the UK. Young SOM is especially important for soil structural development, improving ephemeral stability through fungal hyphae, extracellular polysaccharides, etc. Thus, to achieve aggregate stability and the advantages that this conveys, frequent input of fresh organic matter is required. Practices that add organic material are routinely a feature of organically farmed soils and the literature generally shows that, comparing like with like, organic farms had at least as good and sometimes better soil structure than conventionally managed farms. Our case studies confirmed this. In the reviewed papers, SOM was generally larger on the biodynamic/organic farms because of the organic additions and/or leys in the rotation. We can therefore hypothesize that, because it is especially the light fraction of SOM that is involved in soil structural development, soil structure will improve in a soil to which fresh organic residues are added regularly. Thus, we argue it is not the farming system per se that is important in promoting better physical condition, but the amount and quality of organic matter returned to a soil.

Notes: Abstract. Soil fertility is defined as the ability of a soil to provide the conditions required for plant growth. It is a result of the physical, chemical and biological processes that act together to provide nutrients, water, aeration and stability to the plant, as well as freedom from any substances that may inhibit growth. Within this definition, it is useful to distinguish between those components of fertility which change relatively slowly, perhaps over the course of a rotation, or in some cases, decades, and the more immediate contribution from materials such as fertilizers and manures. The term ‘inherent fertility’ is used to describe these more stable characteristics, while recognising that they are, to a large extent, products of soil management. We conclude that, although nutrient management in organically managed soils is fundamentally different to soils managed conventionally, the underlying processes supporting soil fertility are not. The same nutrient cycling processes operate in organically farmed soils as those that are farmed conventionally although their relative importance and rates may differ. Nutrient pools in organically farmed soils are also essentially the same as in conventionally managed soils but, in the absence of regular fertilizer inputs, nutrient reserves in less-available pools will be of greater significance.

Notes: Abstract. In an exploratory study land use in 27 catchments covering most of England and Wales was assessed (using the land use classification devised by the then Institute of Terrestrial Ecology, now a part of the Centre for Ecology and Hydrology) and related to loads and concentrations of total nitrogen, phosphorus (mainly as orthophosphate (Op)) and some pesticides in river flows reaching the surrounding seas in the years 1990–1993. There are good correlations between seven land use types and the concentrations of total nitrogen (r=0.83) and Op (r=0.73) entering the seas. The correlations for individual land use types are best for arable land: total nitrogen, r=0.77; Op, r=0.65; and are positive. However, except for the mixed arable and grassland, the relationships between the other five land use types (improved grassland, upland grassland, upland moorland, upland mixed, and afforested and upland) and contaminant concentrations are negative. If data from the Mersey catchment are discarded, on the grounds that contaminant concentrations in the river seem unduly high, correlations between land use and contaminant concentrations reaching the seas are improved for all land uses: total nitrogen, r=0.89; Op, r=0.83; and atrazine, r=0.78. Loads and concentrations of pollutants in rivers entering the sea could be used to validate models of losses from catchments. Models may need to take greater account of runoff and transport of soil particles than they do presently.

Notes: Abstract. Uptake in grass crops of ammonium acetate lactate extractable K (KAL) and reserve K (interlayer K + structural K) in soil was studied in 16 field experiments at different locations on a range of mineral soil types in Norway. The K uptake from soil, both from KAL and reserve K, was considerable, often even at the highest level of K fertilizer. During three years, only on the sandy soils with a low level of acid soluble K (KHNO3 minus KAL) was there a yield response to K fertilization. The KAL values declined rapidly and flattened off at a ‘minimum level’ which differed with soil type. This minimum level for KAL is a useful parameter in fertilizer planning, because the grass usually took up the K in excess of the minimum level over two years. The minimum value of KAL was significantly correlated with the content of clay + silt in soil. The decrease in KAL during the growing season was closely correlated to the KAL value in spring minus the minimum value and, therefore, the amount of K supplied to the grass from the KAL fraction can be calculated. Furthermore, the KAL value for the following spring may be estimated. The release from reserve K was partially related to acid soluble K.

Notes: Abstract. Soil organic carbon and total nitrogen stocks are presented for Central and Eastern Europe. The study uses the soil geographic and attribute data held in a 1:2 500 000 scale Soil and Terrain (SOTER) database, covering Belarus, Bulgaria, Czech Republic, Estonia, Hungary, Latvia, Lithuania, Moldova, Poland, Romania, the Russian Federation (west of the Urals), Slovakia, and Ukraine. Means and coefficients of variation for soil organic carbon and total nitrogen are presented for each major FAO soil grouping. The mean content of organic carbon, to a depth of 1 m, ranges from 3.9 kg C m–2 for coarse textured Arenosols to 72.9 kg C m–2 for poorly drained Histosols. Mean carbon content for the mineral soils, excluding Arenosols, is 15.8 kg C m–2. The top 1 m of soil holds 110 Pg C (Pg=1015 g), which corresponds to about 7% of the global stock of soil organic carbon. About 44% of this carbon pool is held in the top 0.3 m of the soil, the layer that is most prone to be changed by changes in soil use and management. About 166 million ha in Central and Eastern Europe have been degraded by compaction, erosion of topsoil, fertility decline and crusting. The achievable level of carbon sequestration for these soils, upon adoption of ‘best’ management practices or restorative measures, is estimated.

Notes: Abstract. There is a lack of information about the influence of tillage and time of sowing on N2O and NO emission in cereal production. Both factors influence crop growth and soil conditions and thereby can affect trace gas emissions from soils. We measured fluxes of NO and N2O in a tillage experiment where grassland on clay loam soil was converted to arable by either direct drilling or ploughing to 30 cm depth. We made measurements in spring for 20 days after fertilizer application to spring-sown and to winter-sown barley. Both were the second barley crop after grass. Direct drilling enhanced N2O emission primarily as a result of restricted gas diffusivity causing poor aeration after rainfall. Deep ploughing enhanced NO emission, because of the large air-filled porosity in the topsoil. NO and N2O emissions were smaller from winter sown crops than from spring sown crops.  The three rates of N fertilizer application (40, 80 or 120 kg N ha–1) did not produce the expected linear response in either soil available N concentrations or in NO and N2O fluxes. We attributed this to the lack of rainfall in the ten-day period after fertilizer application and therefore very slow incorporation and movement of fertilizer into and through the soil.

Notes: Abstract. Preferential flow may enhance phosphorus transport through the soil profile and thereby increase the risks for eutrophication of watercourses. Destruction of continuous macropores in topsoil by tillage provides the possibility for better contact between soil particles and P fertilizer. This is facilitated by incorporation rather than surface application of fertilizer, which should reduce the risk of rapid P transport from the soil surface through the unsaturated zone. To test this hypothesis, undisturbed soil monoliths (0.295 m in diameter and 1.2 m in length) were collected at a field site with a clay soil in which preferential flow is the dominant solute transport mechanism. After three years of observation, average total P loads reached 1.86, 1.59 and 1.25 kg ha–1for no-tillage, conventional tillage, and conventional tillage where the P fertilizer was incorporated, respectively. More than 80% of total losses were in the form of dissolved P. The tillage treatment had no significant effect on P leaching loads compared to no-tillage, but the improved contact between soil particles and P fertilizer resulting from fertilizer incorporation significantly reduced P loads during the first year after application of 100 kg P ha–1. However, after further application of 100 kg P ha–1 two years later, there were no significant differences between the treatments.

Notes: Abstract. The effect of land use on the water retention capacity of Umbric Andosols in south Ecuador was studied. The objective was to acquire a better insight into the hydrological processes of the ecosystem and the role of the soil, in order to assess the impact of changing soil properties due to land use change on the hydrology of the high Andes region. Field data on the water retention capacity at wilting point of Umbric Andosols were collected for both cultivated field conditions and original bush vegetation. The pH in water and in NaF, texture, organic matter content and dry bulk density were measured to show which physicochemical soil characteristics are responsible for the water retention of the Umbric Andosols and for the irreversible loss in water retention due to air drying. Organic matter content appears to be very important and certainly more important than allophane clay content. Water retention of the organic litter layer was calculated to be 16 mm, this would be lost when vegetation was cleared and the land cultivated.

Notes: Abstract. The effects of time and temperature on the changes in Olsen P after phosphate application were studied in 13 calcareous soils from Pakistan, an Oxisol from Colombia and an Inceptisol from England. The phosphate sorption reactions were monitored in two stages. The short-term reaction (30 min shaking with added phosphate in the presence of the Olsen bicarbonate solution) showed that over this time the nature of the sorbing material and number of available sites for P adsorption were important but temperature was not. The extent of the short-term sorption was not related to the amount of calcium carbonate. In the long-term reaction (incubating the soils with phosphate at 10, 25 and 45 °C for one year) the amount of Olsen P decreased with time following a power relationship. Increased temperature increased the rate of reaction, following the Arrhenius principle i.e. Q10⊃ 3 (activation energy 83 kJ mol–1). The effects of time and temperature were well described by a modified power equation Y=a (1 +fTt)-b, where Y is the amount of Olsen P extracted after time t, a is the Olsen P value after the short-term reaction (the initial value), fT is the ratio of the rate constants at any two temperatures and b is a coefficient which represents the loss in extractability with time. On the basis of the initial Olsen P values and subsequent Olsen P values at different times and temperatures a unified decay curve Y/a= (1 +t)–0.20 was developed where the initial Olsen P values are normalized to 1. The parameters of this equation allow, with limitations, the prediction of changes in Olsen P in these soils if the initial Olsen P value of the soil is known.

Notes: Abstract. This study investigated the effect of the same volume of leaching water applied consecutively in either equal amounts or increasing amounts or decreasing amounts on the hydraulic conductivity of a saline sodic soil in 30 cm plastic columns in the laboratory. Gypsum was mixed with the surface 2–3 cm of soil. After leaching, the hydraulic conductivity was measured in each 10 cm depth of soil. Hydraulic conductivity decreased strongly (P〈0.05) with depth and the most effective method of applying the water was in gradually increasing amounts.

Notes: Abstract. The field experiment tested the effects of three management systems on nitrate leaching losses from a five crop rotation on the Lincolnshire Limestone in Eastern England. The Standard system was similar to farming practice in the area. The Protective system integrated individual practices which were expected to decrease nitrate losses (e.g. cover crops, cultivation delay in autumn and reduced intensity, manipulation of drilling dates and, during the first few years of the first rotation, straw incorporation). The Intermediate system was a compromise between the two extremes. All crops were grown at full and half recommended nitrogen rates. This paper reports data from the second full rotation (years 6–10), thus enabling the medium-term effects of continued management practices to be investigated. Average annual nitrogen leaching losses at 49, 35 and 25 kg N ha–1 for Standard, Intermediate and Protective systems, respectively, were significantly different. The respective flow-weighted average NO3 concentrations were 167, 131 and 96 mg l–1. Thus, adopting nitrate retentive practices through the rotation was able to substantially decrease losses. The Protective system was as effective as in the first full rotation, demonstrating that 10 years of such practices had not failed in the medium-term. However, continued minimal cultivation caused serious problems of weed build-up. The cost of weed control and yield loss caused by grass weeds made cereal production uneconomic in some years. Thus, rules for nitrate leaching control need to be tempered with practical and agronomic considerations. Also, few (if any) management techniques tested guaranteed that nitrate losses would be small in all years, as the interaction with winter weather, particularly rainfall, was of vital importance.

Notes: Abstract. A field plot experiment was conducted to investigate P mobilization from fertilized rice fields during rainfall-flooding events. The experiment tested the effects of inorganic fertilizer P, at two rates, and P fertilizer plus manure, at one rate, on the amounts of P lost in drainage water when the plots were subjected to four artificially simulated storm-flooding/drainage events over an eight day period. During the first drainage event, two days after P application, the concentrations and loads of soluble reactive P (SRP) and particulate P (PP) in the drainage water were some three to five times lower than they had been just 24 hours earlier due to rapid sorption and sedimentation. At subsequent events, the concentrations and loads of SRP in drainage water were almost two orders of magnitude lower than at the first event, i.e. the equilibrium between P release from fertilizer and manure and P sorption/fixation by the soil mineral fraction had shifted strongly in favour of the latter processes. During the first drainage event, the concentrations and loads of SRP in drainage water from the low P fertilizer treatment were similar to those on the low P fertilizer plus manure treatment, whereas, 24 hours earlier they had been significantly greater. At subsequent events, though, the highest concentrations and loads of SRP occurred in drainage water from plots treated with equal amounts of P fertilizer and manure. It is suggested that extending the time period between P application and flooding events by applying fertilizer and manure outside the main rainy season should significantly reduce the risk of P loss from paddy rice fields.

Notes: Abstract. Natural secondary succession, forest planting and agricultural practices after deforestation affect soil properties in many ways. During the last 50 years, land uses have greatly changed in the mountainous areas in southwestern China as the result of deforestation and cultivation. A study was initiated in Wolong Nature Reserve, Sichuan province to elucidate the complex relationships in a humid mountainous region. Soil properties under six typical land use types (natural forest, grassland, shrub, secondary forest, cultivated land and reforested land) were compared. Significant differences between land uses were found for soil bulk density (BD), total nitrogen (TN), soil organic carbon (SOC), available phosphorus (AP) and available potassium (AK). Cultivated land had the lowest levels for most soil properties compared to other land uses and shrubland had a higher SOC, TN and available nitrogen (AN) than other land uses. Soils under grassland and shrub contained the greatest carbon mass (TC). Further studies on reforested land indicated that soil properties could be changed by length of reforestation. The SOC and TN in particular showed a linear relationship with years since reforestation. The results suggested that in an area of China where the climate favours secondary succession, ‘leave nature as it is’ is a better choice than the policy ‘change farmland to forest land ‘, especially for the mountainous regions where there is lack of labour and financial support.

Notes: Abstract. Soil erosion and sediment delivery cause many environmental problems posing a substantial financial burden upon society. Policy makers therefore look for a strategy to minimize their impact. The spatial nature of soil erosion and sediment delivery, as well as the variety of possible soil conservation and sediment control measures, requires an integrated approach to catchment management. To evaluate such management, a spatially distributed soil erosion and sediment delivery model is necessary. Such a model (WaTEM/SEDEM) was applied to three agricultural catchments in Flanders (Belgium). The model was first used to identify where the measures to control soil loss should be taken. Secondly, a scenario analysis was used to select the most effective set of techniques. The findings showed that soil conservation measures taken in fields are not only effective in reducing on-site soil loss, but also in drastically reducing sediment yield. Off-site sediment control measures appear to be much less effective in reducing sediment yield than previously thought. The results also suggest that data from field experiments cannot be extrapolated to a catchment scale.

Notes: Abstract. When over exploited and coupled with climatic conditions, tropical soils are subject to increased erosion and a loss of soil organic matter. Countermeasures include the incorporation of organic materials such as crop and animal residues. We studied the effect of adding crop residues and manure to soil, at five sites in Ethiopia, on carbohydrate properties, aggregate stability and the C and N distribution within water-stable aggregates. The effects of organic amendments varied between sites. The largest content of carbohydrates was obtained in the control treatment at Holeta, Ginchi (90 kg ha–1 mustard meal), Jimma (5 t ha–1 cow dung + 9 t ha–1 coffee husk), Awassa (forested soil), and Sirinka (soil alley-cropped with Leuceanae). The aggregate stability of these soils was highly correlated with the OM content but not with carbohydrates. The smaller aggregates (〈1.00 mm) accumulated more carbohydrates than the larger (〉1.00 mm), thereby suggesting a protecting effect within the finer soil fractions. A protecting role played by humified OM components was also indicated by the C and N distribution as well as the C:N ratios which showed preferential accumulation in small rather than in large aggregates. The isotopic 13C-OC values of carbohydrate extracts were generally low, suggesting that OM was from plants with C3 photosynthetic pathways. Soil treatments with maize alone or combined with coffee husks at Jimma decreased the δ13C‰ values slightly, revealing that maize contributed a share of the labile OM. Despite the improvement in the soil OM content, neither the carbohydrate content nor the aggregate stability were increased to the level of the forested sites, suggesting that the additions of crop residues and manure were not alone sufficient to restore the soil physical quality.

Notes: Abstract. This paper reviews information from the literature and case studies to investigate whether productivity in organic systems is restricted by the supply of available N during the major phases of crop growth. Organic systems have the potential to supply adequate amounts of available N to meet crop demand through the incorporation of leys, N rich cash crop residues and uncomposted manures. However, this is seldom achieved because leys are only incorporated once every few years and organically produced crop residues and manures tend to have low N contents and slow mineralization rates. N availability could be improved by delaying ley incorporation until spring, applying uncomposted manures at the start of spring growth, transferring some manure applications from the ley phase to arable crops, preventing cover crops from reaching a wide C:N ratio and better matching crop type with the dynamics of N availability.

Notes: Abstract. Previous studies of the microbial status of soils managed under ‘organic’ and ‘conventional’ regimes have produced conflicting evidence of whether there are distinct differences in the size, composition and activity of the soil microbial biomass which may be attributed to management practice. In the present study, we have compared the microbiology of organically- and conventionally-managed soils at (primarily) two farms in England, over a two year period. Differences in microbial communities in soils under different management practice were subtle rather than dramatic. Many of the parameters measured, including total C and microbial biomass C, often showed no consistently significant differences in soils under different management. In soils from one farm, concentrations of ATP in Ringers solution soil extracts were mostly found to be significantly greater in organically-managed than in comparable conventionally-managed soils. While indirect (plate) counts showed that there were similar numbers of cultivable microorganisms present in these soils, total counts of bacteria (via DAPI-staining) were found to parallel the trends found for readily-extractable ATP. Numbers of metabolically-active bacteria, determined by FISH analysis using a EUB338 probe to detect ribosome-rich cells, indicated that the percentage of metabolically-active bacteria present was not determined by management practice. Total and active fungi were also found to be more abundant in organically-managed soils. It was concluded that changes in soil microbiology may occur as a consequence of switching to organic land management, but these may not be detectable by methods used frequently to assess soil biomass. In particular, increased numbers of viable but non-culturable bacteria and fungi in organically-managed soils points to a greater physiological diversity of microorganisms in such situations.

Notes: Abstract. Under a UK Government consultation procedure announced in 2001, it was proposed that measures agreed within already designated Nitrate Vulnerable Zones (NVZ ‘s) would be extended to include a considerably increased area of England, Wales and Scotland. Since existing NVZ ‘s in the UK have included relatively little grassland, it is important to examine how nitrate losses from grassland areas, especially from animal manures, one of the major potential sources of nitrate loss, can be minimized. Experiments were carried out on freely draining grassland soils at four sites (Devon, Hampshire, Shropshire and N Yorkshire) representative of a wide range of climatic and farming conditions across lowland England, over a four year period, 1990/91 to 1993/94. Slurry was applied to experimental plots over a range of times (including June and then monthly, from September to January) at a target rate of 200 kg N ha–1. Nitrogen leaching over the four years ranged from 0 to 〉50% of applied slurry N, with the largest losses occurring following applications in the September to November period. The use of a nitrification inhibitor with slurry applied in November failed to provide consistent reduction in nitrate leaching.A strategy to reduce the risk of N leaching from manures applied to freely draining grassland soils must take account of the characteristics of the manure, in particular its N content, the application rate and the amount of excess rainfall following application. The experimental results suggest that slurry applications to freely draining grassland, in September, October and November should generally be avoided, the rationale for this being dependent on the amount of excess rainfall subsequent to application. Farmyard manure represents a lower risk and does not justify the restrictions on application timing that appear to be necessary with slurry.

Notes: Abstract. A numerical model that incorporates the spatial variability of infiltration, surface storage and resistance to overland flow was developed, calibrated and validated for olive orchards. The model reproduced accurately amounts of runoff used in validation, and predicted runoff in olive orchards managed in different ways, in line with published results. The model was used to analyse the runoff generation in a virtual, 180 m length, 5% steep, olive grove, using 54 different scenarios which combined three different soil types, two tree canopy sizes and nine soil management techniques (four tillage scenarios: freshly or degraded tillage with and without a compacted plough layer; no-till, and four cover crops in strips differing in width and plant density). The results of the numerical experiment showed that no-till had the highest runoff coefficient, while a dense cover crop had the lowest. Recently tilled soils also exhibited some of the lowest runoff coefficients. The effects of increasing soil cover due to a greater tree canopy on runoff were significant and caused by the greater area of high infiltration beneath the canopy. Effects of tree canopy size were less important than the impact of soil management practices on runoff.

Notes: Abstract. In the Sahel, promising technologies for agricultural intensification include millet stover mulching and ridging. A four year on-farm experiment was set-up in order to assess the effect of various combinations of these two technologies on soil chemical and physical quality in a millet (Pennisetum glaucum (L.) R. Br.) –- cowpea (Vigna unguiculata (L.) Walp.) relay intercropping system. Treatments included bare surface, ridging, a surface applied banded millet stover mulch (2 t ha–1) and a banded millet stover mulch (2 t ha–1) buried in ridges. The latter three treatments were implemented exclusively in the cowpea rows, with an annual rotation between the millet and cowpea rows. Both the bare and ridge plots experienced a rapid loss of organic carbon, acidification and the development of extensive surface crusts but no increase in bulk density or penetration resistance. In the year of application, mulching improved soil quality in the cowpea row with respect to pH, organic carbon and exchangeable K+ and Mg++ content, penetration resistance and bulk density, and it reduced the decline in exchangeable Ca++ and total N content. In the year following mulch application, a general decline in soil chemical quality was observed in the millet row, except for organic carbon content, and a positive residual effect was observed on penetration resistance and bulk density. As a rule, the effects of mulching in the year of application tended to be stronger in the ridged treatment with buried residue than in the banded surface mulch. In the year following application, this tendency was reversed. For the purpose of reducing soil degradation by nutrient mining and wind erosion, a banded surface mulch therefore appeared more effective than buried mulch.

Notes: Abstract. Slurry from farm animals may contaminate water supplies, rivers and bathing waters with faecal coliforms, such as Escherichia coli. Where animals harbour the O157 strain the hazard to human health is particularly high, but both the hazard level, and the low incidence and sporadic nature of the excretion of E. coli O157 make it difficult to study this strain under field conditions. The survival of total E. coli and of E. coli O157 were compared in the laboratory for two soils under controlled temperature and moisture. E. coli O157 die-off rate was the same as or quicker than for total E. coli. This result meant that field experiments studying the fate of total E. coli should give a satisfactory evaluation of the risk of water contamination by the O157 strain. In four field experiments at three sites, slurry containing total E. coli numbers of 2.2 × 104 to 5.7 × 105 colony forming units per mL (c.f.u. mL–1) was applied to drained field plots. Field die-off was faster than expected from laboratory experiments, especially in one experiment where two weeks dry weather followed application. In all but this experiment, the first drain flow events after slurry application led to very high E. coli concentrations in the drains (103 to 104 c.f.u. mL–1). E. coli O157 was present in the slurry used for two of the experiments (33 c.f.u. per 100 mL in each case). However the proportion of E.coli O157 was very low (about 1 in 105) and it was not detected in the drainage water. After the first week E. coli drainage water numbers decreased rapidly but they were 1–10 c.f.u. mL–1 for much of the sampling period after slurry application (1–3 months).

Notes: Abstract. Predictive, regional use of soil organic matter (SOM) models requires evaluation of the performance of models with datasets from long-term experiments relevant to the scenarios of interest to the regional scale study, and relevant to the climate of the study region. Datasets from six long-term experiments were used to evaluate the performance of RothC and CENTURY, two of the most widely used and tested SOM models. Three types of model run were completed for each site: (1) CENTURY model alone; (2) RothC model run to fit measured SOC values, by iteratively adjusting C inputs to soil; and (3) RothC model run using C inputs derived from CENTURY runs. In general, the performance of both models was good across all datasets. The runs using RothC (iteratively changing C inputs to fit measured SOC values) tended to have the best fit to model data, since this method involved direct fitting to observed data. Carbon inputs estimated by RothC were, in general, lower than those estimated by CENTURY, since SOC in CENTURY tends to turn over faster than SOC in RothC. The runs using RothC with CENTURY C inputs tended to have the poorest fit of all, since CENTURY predicted greater C inputs than were required by RothC to maintain the same SOC content. A plausible model fit to measured SOC data may be obtained with widely differing C input values, due to differences in predicted decomposition rates between models. It remains unclear which, if either, modelling approach most closely represents reality since both C inputs to soil and decomposition rates for bulk SOM are difficult to determine experimentally. Further progress in SOM modelling can only be the result of research leading to better process understanding, both of net C inputs to soil and of SOM decomposition rates.  The use of default methods for estimating initial SOC pools in RothC and CENTURY may not always be appropriate and may require adjustment for specific sites. The simulations presented here also suggest details of SOC dynamics not shown by available measured data, especially trends between sampling intervals, and this emphasizes the importance of archived soil samples in long-term experiments.

Notes: Abstract. Efforts to assess the role of soil structure in soil and water processes have been limited by data based on two dimensional geometry or disturbed samples. Computed tomography (CT) is a non-invasive technique that allows for the three dimensional, non-destructive examination of heterogeneous materials. X-ray CT scanning was used to acquire serial images of contrasting soil types that could be used to render, and hence, quantify important soil constituents in three dimensions. By repeating the scanning techniques after an infiltration period, it was also possible to examine the nature of water movement in real time. Macropore architecture between different soil types was highly variable and generally appeared as unconnected pore segments at the resolution examined. As expected, water flow characteristics were similar to macropore structure, with wetting patterns resembling both Darcian and preferential flow identified in different soils. From this, it was found that in the sandy clay soil c. 90% of macropore space was active following infiltration, compared with c. 50% for the sandy loam soil. In addition, it was possible to visualize the three dimensional distribution of stones and other mineral material. The results illustrated the benefits of computed tomography over more conventional analyses of soil structure, and its potential as a tool for examining dynamic soil processes. However, problems associated with accessibility, resolution and artefacts still provide limitations of the technique.

Notes: Abstract. Continuous cultivation of soils of the semiarid tropics has led to significant land degradation. Soil erosion and nutrient loss caused by high runoff volumes have reduced crop yields and contributed to offsite damage. We compared a number of soil management practices (tillage, mulch and perennial/annual rotational based systems) for their potential to improve crop production and land resource protection in an Alfisol of the semiarid tropics of India. Runoff and soil erosion were monitored and surface soil and sediment were analysed for nitrogen and carbon to determine enrichment ratios. Amelioration of soils with organic additions (farmyard manure, rice straw) or rotating perennial pasture with annual crops increased soil carbon and nitrogen contents and reduced runoff, soil erosion and nutrient loss. Soil erosion totalled less than 7 t ha–1, but enrichment ratios were often greater than 2 resulting in up to 27 kg N ha–1 and 178 kg C ha–1 being lost in sediment. Up to an extra 250 mm of water per year infiltrated the soil with organic additions and was available for crop water use or percolation to groundwater. The results show that there are good opportunities for reducing degradation and increasing productivity on farms.

Notes: Abstract. Native woodland restoration is a conservation priority within the UK and there is an increasing awareness that a long-term strategy is required to guide this process. A GIS-based modelling approach has been developed, which links site conditions as expressed in an integrated soil and land cover dataset with the site requirements for different woodland types. There are three important aspects to the model – the parameter weightings, the added value of the integrated dataset, and the woodland categories which are described and predicted. The initial quantitative and qualitative validation has been encouraging although more is required and planned. The results indicate that for broad strategic planning purposes, predictions of woodland potential are not improved significantly when climatic factors are incorporated. The concept that soil acts as an integrator of other environmental variables is discussed alongside the practical application of the model by a range of users.

Notes: Abstract. Spate irrigation is a system used for wetting land prior to planting. Use is made of seasonal rivers (wadis) producing flash floods in the uplands, which are directed by structures to irrigate fields in the lowlands. A land suitability system for spate irrigation schemes in Eritrea was studied in the Sheeb area of Eritrea with and without land improvements. The availability of floods and soil moisture were the major land use requirements for spate-irrigated sorghum and maize, while salinity hazard has only a minor effect in spate irrigation systems. The suitable land for spate irrigation in the Sheeb area is distributed as follows: 16% is highly to moderately suitable, 24% is moderately suitable and 17% is marginally suitable. About 40% of the study area was found to be currently unsuitable for spate irrigation mainly due to a lack of floodwater and poor soils. With improvements to the spate irrigation system, such as construction of permanent flood diversion structures, the area of land suitable for spate irrigation will expand. The land suitability system presented in this study could be applied in other spate irrigation schemes of Eritrea and perhaps in other countries also.

Notes: Abstract. Forest soil sustainability and future crop productivity is at risk if mechanised harvesting operations cause soil damage. In UK upland forestry, soil protection is usually provided by placing harvesting residues (brash) over areas where machinery traffic is required. In this study, various thicknesses of brash mat were tested for their ability to reduce compaction of a surface water gley soil at Kielder Forest, Northumberland. Changes in penetration resistance and dry soil bulk density were studied after passes by forest harvesting and timber extraction machinery running on the brash. The study shows that normal harvesting operations caused some soil compaction. However, the brash mat system was shown as important in protecting the soil. Soil under brash mats experienced some compaction to at least 45 cm depth. The thickest brash mat, composed of residues from 10 rows of trees, was unable to prevent compaction completely. Nevertheless, the protective role of the brash mat system was clearly confirmed when compared to timber extraction over bare soil. The point at which compaction has a detrimental effect on the establishment and stability of future tree rotations remains uncertain.

Notes: Abstract. Agricultural soils are important sources of the tropospheric ozone precursor NO and the greenhouse gas N2O. Emissions are controlled primarily by parameters that vary the soil mineral N supply, temperature and soil aeration. In this field experiment, the importance of soil physical properties on emissions of NO and N2O are identified. Fluxes were measured from 13 soils which belonged to 11 different soil series, ranging from poorly drained silty clay loams to freely drained sandy loams. All soils were under the same soil management regime and crop type (winter barley) and in the same maritime climate zone. Despite this, emissions of NO and N2O ranged over two orders of magnitude on all three measurement occasions, in spring before and after fertilizer application, and in autumn after harvest. NO emissions ranged from 0.3 to 215 μg NO-N m–2 h–1, with maximum emissions always from the most sandy, freely drained soil. Nitrous oxide emissions ranged from 0 to 193 μg N2O-N m–2 h–1. Seasonal shifts in soil aeration caused maximum N2O emissions to switch from freely drained sandy soils in spring to imperfectly drained soils with high clay contents in autumn. Although effects of soil type on emissions were not consistent, N2O emission was best related to a combination of bulk density and clay content and the NO/N2O ratio decreased logarithmically with increasing water filled pore space.

Notes: Abstract. Complex relationships exist between different components of the organic farm and the quantity and quality of the end products depend on the functioning of the whole system. As such, it is very difficult to isolate soil fertility from production and environmental aspects of the system. Crop rotation is the central tool that integrates the maintenance and development of soil fertility with different aspects of crop and livestock production in organic systems. Nutrient supply to crops depends on the use of legumes to add nitrogen to the system and limited inputs of supplementary nutrients, added in acceptable forms. Manures and crop residues are carefully managed to recycle nutrients around the farm. Management of soil organic matter, primarily through the use of short-term leys, helps ensure good soil structure and biological activity, important for nutrient supply, health and productivity of both crops and livestock. Carefully planned diverse rotations help reduce the incidence of pests and diseases and allow for cultural methods of weed control. As a result of the complex interactions between different system components, fertility management in organic farming relies on a long-term integrated approach rather than the more short-term very targeted solutions common in conventional agriculture.

Notes: Abstract. On organic farms, where the importation of materials to build/maintain soil fertility is restricted, it is important that a balance between inputs and outputs of nutrients is achieved to ensure both short-term productivity and long-term sustainability. This paper considers different approaches to nutrient budgeting on organic farms and evaluates the sources of bias in the measurements and/or estimates of the nutrient inputs and outputs. The paper collates 88 nutrient budgets compiled at the farm scale in nine temperate countries. All the nitrogen (N) budgets showed an N surplus (average 83.2 kg N ha–1 yr–1). The efficiency of N use, defined as outputs/inputs, was highest (0.9) and lowest (0.2) in arable and beef systems respectively. The phosphorus (P) and potassium (K) budgets showed both surpluses and deficits (average 3.6 kg P ha–1 yr–1, 14.2 kg K ha–1 yr–1) with horticultural systems showing large surpluses resulting from purchased manure. The estimation of N fixation and quantities of nutrients in purchased manures may introduce significant errors in nutrient budgets. Overall, the data illustrate the diversity of management systems in place on organic farms, and suggest that used together with soil analysis, nutrient budgets are a useful tool for improving the long-term sustainability of organic systems.

Notes: Abstract. Earthworms influence a wide range of soil properties. They are affected by practices that perturb the soil or change organic inputs. This study compared populations in UK organic and conventional rotations differing in such practices. Three farm pairs, ranging from stockless to arable-grassland systems, were sampled on three occasions in each of two crop years. Additional farm pairs were sampled on a single occasion. Nine common earthworm species were grouped into three classes based on the depth ranges from which they were recovered. Cast and soil samples were taken from leys to compare aggregate stability, organic and nutrient content, and microbial biomass.  For similar rotation stages, populations of surface and shallow species classes were often larger in organic systems. In some comparisons the reverse was the case, particularly as the proportion of ley within each pair increased. System differences in biomass, but not abundance, could be attributed to the proportion of leys in rotations; individual earthworm weights were larger in conventional systems. Casts from both systems had markedly higher organic contents, stability, available P and K concentrations, and microbial biomass than underlying soil. This trend was more pronounced in conventional sites for nutrients and microbial biomass. Differences in populations and cast properties may have implications for soil fertility and wider ecosystem function.

Notes: Abstract. Generally, traditional soil surveys do not adequately account for the spatial variability of soil properties. Maps that are derived using these cursory soil data are likely to contain errors and thus make interpretation and soil management difficult. On the other hand quantitative methods of soil inventory at the field scale involve the design and adoption of sampling regimes and laboratory analysis that are time consuming and costly. In the latter case new technologies are required to efficiently sample and observe the soil in the field. This is particularly the case where soil salinization is prevalent, and detailed quantitative information for determining its cause is required. In this paper, a Mobile Electromagnetic Sensing System (MESS) is described and its application in an irrigated-cotton field, located in the lower Namoi valley in New South Wales, Australia. Results from the EM38 instrument were found to be correlated with the effective cation exchange capacity (r2= 0.81). This was related to variability in soil mineralogy across the field. In addition, differences in soil chemical and textural variables, measured along a transect and adjacent to water storage, were used to identify seepage areas near a water reservoir where soil salinization was evident.

Notes: Abstract. Precision Agriculture seeks to match resource application and agronomic practice with soil and crop requirements as they vary in both space and time. Therefore, an understanding of both the temporal and the spatial components of variability is essential before decisions can be made about the feasibility of site-specific management. In the present study, the spatial and the temporal components of variability in certain key soil properties of a grassland field were evaluated to assess the likely feasibility of adopting a site-specific approach to grassland management. A 7.9 ha grassland field was selected for the study and soil samples were taken three times at regular 25 m intervals across the field over a two year period, and chemically analysed. Classical and geostatistical procedures were used to evaluate the spatial variability and the temporal stability of soil property distributions. Soil extractable P and K had the greatest within-field variability and soil pH the least. Soil K distributions were also highly unstable over time and it was concluded that the optimal risk aversion strategy would be to apply uniform dressings of this nutrient to the entire field. In contrast, soil pH, P, Mg and sulphate distributions were not only temporally stable, but were also spatially correlated over reasonably large ranges. It was concluded that these properties might be managed in a site-specific way based on the results of periodic soil testing in three clearly defined management sub-units within the field. Over the two year period, C and N accumulated in the soil at surprisingly high rates on certain parts of the field but not in others.

Notes: Abstract. The worldwide occurrence of saline sodic and sodic soils on more than half a billion hectares warrants attention for their efficient, inexpensive and environmentally acceptable management. These soils can be ameliorated by providing a source of calcium (Ca2+) to replace excess sodium (Na+) from the cation exchange sites. Although chemical amendments have long been used to ameliorate such soils, the chemical process has become costly during the last two decades in several developing countries. As a low-cost and environmentally acceptable strategy, the cultivation of certain salt tolerant forage species on calcareous sodic and saline sodic soils, i.e. phytoremediation, has gained interest among scientists and farmers in recent years. In a field study conducted at three calcareous saline sodic sites (pHs=8.1–8.8, ECe=7.8–12.5 dS m–1, SAR=30.6–76.1) in the Indus Plains of Pakistan, we compared chemical and phytoremediation methods. There were four treatments; two involved plants: Kallar grass (Leptochloa fusca (L.) Kunth), and sesbania (Sesbania bispinosa (Jacq.) W. Wight). The other two treatments were uncropped: soil application of gypsum and an untreated control. All treatments were irrigated with canal water (EC=0.22–0.28 dS m–1). The plant species were grown for one season (5–6 months). Sesbania produced more forage yield (34 t ha–1) than Kallar grass (23 t ha–1). Phytoremediation and chemical treatments resulted in similar decreases in soil salinity and sodicity, indicating that phytoremediation may replace or supplement the more costly chemical approach. The soil amelioration potential of sesbania was similar to that of the Kallar grass, which suggests that moderately saline sodic calcareous soils can be improved by growing a forage legume with market value.

Notes: Abstract. Nitrate leaching was measured for four years at the Royal Agricultural College ‘s Coates Farm in the Cotswolds, England. Coates is a typical Cotswold mixed farm with thin, well-drained calcareous soils especially prone to leaching. Over the duration of this study there were dairy, sheep and arable enterprises on the farm. A ‘Farm Gate’ nitrogen (N) budget was constructed. Small 120 m × 20 m ‘farmlets’ were sited in ten fields across the farm, covering all parts of the rotation, as the sites for detailed measurements. Each farmlet received the same management as the rest of the field in which they were situated. Using ceramic probes inserted to 60 cm, soil water was sampled every two weeks throughout the winter drainage season. The annual drainage varied from 135 mm under grassland in 1996/7 to 600 mm under cereals in 1998/9. Average N losses by leaching were determined mostly by rainfall and were 65 kg N ha–1 yr–1, accounting for 25% of the N inputs. Especially leaky parts of the rotation were the ploughing out of a lucerne ley and the grazing of stubble turnips with sheep, both typical Cotswold farm practices. The research highlights some of the difficulties in developing practicable, profitable management practices to decrease nitrate losses.

Notes: Abstract. Differences in land-use history within soil series, although not influencing soil classification, lead to variability of non-diagnostic soil properties in soil databases. Regional studies that use soil databases are confronted with this considerable variability. This has, for example, been reported in regional studies focused on nitrate leaching from agricultural land. Such findings have a direct impact on regional assessments of nitrate leaching from dairy farms on sandy soils, a major environmental issue in the Netherlands. There is thus a need to deal with this variability in soil properties.We were able to relate soil organic nitrogen, soil organic carbon and its dynamics to land use history for a Dutch sandy soil series. Within one soil series, three different land use histories were identified: old grassland, reseeded grassland and grassland converted from continuous cropping with silage maize. The addition of landscape characteristics significantly improved the regression models based on land-use only. Once established for any given soil series, such relationships can significantly improve soil survey input into dynamic models of soil behaviour such as regional nitrate leaching studies.

Notes: Abstract. Many former estimates of regional scale C sequestration potential have made use of linear regressions based on long-term experimental data, whilst some have used dynamic soil organic matter (SOM) models linked to spatial databases. Few studies have compared the two methods. We present a case study in which the potential of different land management practices to sequester carbon in soil in arable land is estimated by different methods. Two dynamic SOM models were chosen for this study, RothC (a soil process model) and CENTURY (a whole ecosystem model with a SOM module). RothC and CENTURY are the two most widely used and validated SOM models worldwide. A Geographic Information System (GIS) containing soil, land use and climate layers, was assembled for a case study in central Hungary. GIS interfaces were developed for the RothC and CENTURY models, thus linking them to the spatial datasets at the regional level. This allowed a comparison of estimates of the C sequestration potential of different land management practices obtained using the two models and using regression based approaches. Although estimates obtained by the different approaches were of the same order of magnitude, differences were observed. Some of the land management scenarios studied here showed sufficient C mitigation potential to meet Hungarian CO2 reduction commitments. For example, afforestation of 12% current arable land could sequester 0.042–0.092 Tg yr–1 in the soil alone, or 0.285–0.588 Tg C yr–1 in both soil and biomass; 1990 level CO2 emissions for the study area were 4.7 Tg C with a corresponding reduction commitment of 0.282 Tg C. It is not, however, suggested that this is the only, or the most favourable way, in which to meet the commitments.

Notes: Abstract. A revised set of physical and chemical parameter estimates is presented for the soil units of the world, as described by the two FAO soil legends (version 1974 and 1988). The study is based on 9607 soil profiles, which include profiles held in version 1.0 of the WISE database. Upon a screening of data integrity and comparability of analytical methods, derived statistics were generated for 28 soil chemical and physical attributes identified as being useful for assessment of land suitability, crop growth simulation datasets, and analyses of global environmental change.

Notes: Abstract. Drainage of peat soils for agriculture can lead to large carbon losses due to oxidation of peat. We estimated peat subsidence rates and total carbon losses, due to 40 years of dairy farming on a former peat bog, by measuring the thickness of peat and total carbon of farmland and of an adjacent unmodified peat bog above a marker tephra layer that was deposited about 200 AD. Subsidence rates averaged 3.4 cm yr–1 (95% confidence interval of 3.2 to 3.5 cm yr–1) and carbon loss averaged 3.7 t ha–1 yr–1 (95% confidence interval of 2.5 to 5.0 t ha–1 yr–1). On average, 63% of the subsidence was due to consolidation, with the remainder (37%) attributed to losses of organic matter due to peat mineralization.

Notes: Abstract. In organic agriculture, where K may be a limited resource, reliable tools are important in the assessment of K availability in the soil in order to avoid K deficiency. We investigated the effect of four organic farming systems on the exchangeable K in the plough layer of a six-course crop rotation from 1994 to 1997. The accumulated K balances over the four years varied between −49 and +120 kg K ha–1and the corresponding exchangeable K (0–20 cm) in autumn 1997 was 7.1 and 9.6 mg K 100 g soil–1, respectively, as an average of the crop rotation. The exchangeable K fraction responded to the K application in manure and to the crop in the rotation. In an additional experiment, no yield response to K was found, despite a low level of exchangeable K. The exchangeable K was a useful indicator of changes in the K status in the farming system with the largest positive K balance, but this K fraction was insufficient as an indicator in the other three farming systems. The considerable variation of exchangeable K through the crop rotation makes the soil test method most suitable at the crop rotation level where fluctuations caused by crop and management are smoothed out.

Notes: Abstract. Phosphorus (P) in overland flow is mediated by soil P, added P, erosion, and hydrological processes and their interaction as affected by landscape position and length of flow. We investigated the effect of flow path length (1 to 10 m long plots) on P transport in overland flow with and without a localized dairy manure application (75 kg P ha–1 added to the upslope end [0.5 m] of each plot) and simulated rainfall (7 cm h–1), at two sites within an agricultural watershed in Pennsylvania, USA. Particulate loss in overland flow was c. 20% greater from manured than unmanured plots due to the less dense nature of manure than soil. Increased soil moisture at Site 2 contributed to a greater loss of P compared to Site 1, both with and without manure; with most occurring as particulate P (60 to 90% of total P). Further, the selective erosion of fine particulates (24 to 34% clay) and P loss increased with plot length. From a management perspective our results demonstrate that the forms and amounts of P loss are greatly influenced by flow path length and interactions among antecedent moisture, soil P, and texture.

Notes: Abstract. Nitrous oxide (N2O) is involved in both ozone destruction and global warming. In agricultural soils it is produced by nitrification and denitrification mainly after fertilization. Nitrification inhibitors have been proposed as one of the management tools for the reduction of the potential hazards of fertilizer-derived N2O. Addition of nitrification inhibitors to fertilizers maintains soil N in ammonium form, thereby gaseous N losses by nitrification and denitrification are less likely to occur and there is increased N utilization by the sward. We present a study aimed to evaluate the effectiveness of the nitrification inhibitor dicyandiamide (DCD) and of the slurry additive Actilith F2 on N2O emissions following application of calcium ammonium nitrate or cattle slurry to a mixed clover/ryegrass sward in the Basque Country. The results indicate that large differences in N2O emission occur depending on fertilizer type and the presence or absence of a nitrification inhibitor. There is considerable scope for immediate reduction of emissions by applying DCD with calcium ammonium nitrate or cattle slurry. DCD, applied at 25 kg ha–1, reduced the amount of N lost as N2O by 60% and 42% when applied with cattle slurry and calcium ammonium nitrate, respectively. Actilith F2 did not reduce N2O emissions and it produced a long lasting mineralization of previously immobilized added N.

Notes: Abstract. We evaluated the effectiveness of capillary-wick samplers (PCAPS) for continuous monitoring of resident nitrate concentration in three ‘soil-crop-climate’ systems differing in soil type, land use and climate. These systems involved: (i) acid silty soils under a beech-oak forest affected by heavy N-NH4+ deposition in Belgium; (ii) silty soils under wheat cropping and a short rotation willow coppice plantation (SRC) in Belgium; and (iii) volcanic ash soils under plantain cultivation with and without urea fertilization in Colombia. The PCAPS continuously applied a suction of 0 to 5.4 kPa to the soil water below the effective rooting zone without the need for an auxiliary vacuum source. The nitrate concentrations showed large variations over time and ranged between 6–192 mg l–1 under forest, 19–143 mg l–1 under wheat, 11–47 mg l–1 under SRC and 3–138 mg l–1 under fertilized plantain. The analysis of the soil leachates collected with PCAPS confirms previous results dealing with leaching of nitrate and alkaline and alkaline-earth cations in similar ‘soil-crop-climate’ systems. It was concluded that PCAPS was a suitable tool to collect soil solutions and that it could help to assess nitrate leaching losses in various ecological or cropping conditions.

Notes: Abstract. The páramo is a high-altitude ecosystem of the northern Andes. The vegetation is continuous, with grasses as the dominant groundcover. Because of their high water retention, páramos play a fundamental role in water availability for all the population of the inter-Andean valleys. There are many studies of this specific ecosystem, but very few are focussed on overgrazing and its effect on vegetation and soil properties. Intensive grazing started less than 20 years ago and was studied in a representative area in the western Cordillera of central Ecuador covered by recent volcanic ash deposits. Intensive sheep grazing has led to a strong decline in the number of plant species, the replacement of the tussock grass vegetation by a short carpet grass vegetation, and an increase of bare land. In that area, the upper 50 cm of Andisols are deeply affected by a convergent decrease of Al and Fe oxalate and pyrophosphate in soil extracts, carbon contents decrease from 100 g kg–1 to less than 50 g kg–1 in the humid zone, from 70 to 40 g kg–1 in the dry zone and a reduction of water-retention capacity at −33 kPa matrix potential from 800 g kg–1 to 200 g kg–1 in humid zones, from 350 to less than 100 g kg–1 in drier areas. They showed also a decrease in the macrostructure and the development of a highly water repellent microstructure. All these important transformations favour the development of aeolian erosion in dry areas, runoff on bare surfaces, and gully erosion on slopes. The role of the páramo in water-regulation of this ecosystem seems to have been adversely affected for the future.

Notes: The coagulation of humic substances and its role in controlling the solubility of organic matter in soils are not well understood. We therefore studied the physico-chemical behaviour of purified humic acid from forest soil coagulated with Na, Ca, Cu, Al at pH 4 and 6, and then modelled the behaviour with the Non-Ideal Consistent Competitive Adsorption Donnan (NICA-Donnan) model. We found that the coagulation of humic acid occurs when the Donnan potential is less negative than −0.08 V. Based on this result, an empirical relation between the Donnan potential of humic acid and its concentration in solution was derived. In addition, the Donnan potential of the dissolved organic matter in the soil solution of six soil profiles from forests was calculated using the NICA-Donnan model under the assumption that all the dissolved organic matter behaves as humic acid. The measured concentration of dissolved organic matter also decreases in a soil profile, as the calculated potential becomes less negative. The results are in many cases in semi-quantitative agreement with the predicted concentration based on the humic acid coagulation experiment. Acid soils contain more dissolved organic matter, which may result from the presence of a fairly large fraction of more soluble organic molecules, such as fulvic acid.

Notes: Throughout the world there is a trend towards retaining crop residues rather than burning them. For this reason, changes in soil chemistry and aggregation in a Vertisol induced by 59 years of burning or green cane harvesting with or without annual fertilizer applications were investigated. Crop residues were either burnt prior to harvest with the harvest residues raked off (R1), burnt prior to harvest with the harvest residues left on the soil surface (R2), or left unburnt with all the trash left on the soil surface (R3). Concentrations of organic C in the surface 10 cm of soil increased with fertilizer applications and with increasing amounts of crop residue returned in the order R1 〈 R2 〈 R3. Fertilizer applications caused an accumulation of residual P in both inorganic (Pi) and organic (Po) forms. A sequential P fractionation showed that fertilizer P accumulated in both labile and recalcitrant Pi and Po forms, and trash retention caused an accumulation of recalcitrant Po. Concentrations of K decreased in the unfertilized R1 and R2 treatments because K reserves were depleted. By contrast, there was an increase in the concentrations of K in the fertilized R3 treatment. The soil became more acid on the fertilized and, to a lesser extent, trash retention plots. We attribute this to nitrification and subsequent nitrate leaching. Acidification resulted in a loss of exchangeable Ca and Mg, a decrease in ECEC, and an increase in the concentrations of total and monomeric Al in soil solution, in exchangeable Al3+ and in the buffering reserve of non-exchangeable Al associated with organic matter. Aggregate stability was increased by increasing crop residues but decreased by fertilizer applications. The decrease was attributed to an increase in the proportion of exchangeable cations present in monovalent form due to applications of fertilizer K and leaching of Ca and Mg. We conclude that trash retention and annual fertilizer applications have substantial long-term effects on both organic matter status and soil pH and therefore on other soil chemical and physical properties.

Notes: The intensive use for over 100 years of copper sulphate (Bordeaux mixture) to fight mildew in vineyards has led to a substantial accumulation of copper (Cu) in surface soils. To assess the effects of such large concentrations, the surface soils of 10 Burgundy vineyards were sampled and analysed for total organic matter (carbon and nitrogen) and metal (copper and iron) contents. Physical (i.e. size fractionation) and chemical (sequential extraction) methods were used to determine the distribution of these elements. The most Cu-contaminated plots showed the largest accumulation of organic carbon and Cu in the coarse sand and fine sand fractions. Copper was strongly correlated with organic carbon and organic nitrogen in the coarse sand fraction and with organic nitrogen in the fine sand fraction. Copper was also highly correlated with both Fe and organic nitrogen in the clay fraction but not significantly with organic carbon. The sequential extraction showed that Cu was bound mainly to the Fe oxides. However, in the most Cu-contaminated plots, a part of added Cu was bound to organic matter. This study suggests that Cu protected indirectly the organic matter present in the coarse fractions against biodegradation, and therefore modified the distribution of organic carbon among the particle-size fractions. Iron appeared as the main factor responsible for Cu accumulation in the clay fraction, mainly through inclusion of Cu in Fe oxyhydroxides and possibly in clay–humus complexes.

Notes: Gustafsson et al. in a recent paper in this Journal reported the effects of adding HCl, AlCl3 and Si(OH)4 on the pH and concentrations of Al and Si in 1:1 soil:solution systems at three different temperatures, using samples of soil from an allophanic Bs horizon. Contrary to their conclusions, their observations are compatible with Al in the soil solution being in equilibrium with a proto-imogolite allophane; it is neither necessary nor even plausible to postulate a hypothetical Al hydroxide. Concentrations of 0.2–0.4 mm Si in the equilibrated solutions at pH 5 could arise from an amorphous silica, probably phytoliths. They cannot come from the allophane.

Notes: How significant are estimates of surface areas of soils obtained by adsorption methods? To answer this we tested the applicability of an equation that relates monolayer coverage (N) of an adsorbent with the area (A) of adsorbate, NAz = k, for six soil samples using six adsorbates of different sizes. The data obtained confirm the validity of the equation with the z parameter ranging between 1.25 and 1.41. Hence each soil sample showed preferences towards small-sized adsorbates for which the product NA (calculated surface area) is inversely related to the size of adsorbate. We also demonstrated that the equation has roots in the Langmuir adsorption equation.

Notes: The quantification of the spatial heterogeneity of soil structure is one of the main difficulties to overcome for an adequate understanding of soil processes. There are different competing concepts for the type of heterogeneity, including macroscopic homogeneity, discrete hierarchy or fractal. With respect to these different concepts we investigate the structure of the pore space in one single sample (4 × 103 mm3) by analysing basic geometric quantities of the pores 〉 0.3 mm within gradually increasing subsamples. To demonstrate the relation between geometrical and functional properties we simulate gas diffusion within the three-dimensional pore space of the different subsamples. An efficient tool to determine the geometric quantities is presented. As a result, no representative elementary volume (REV) is found in terms of pore-volume density which increases with sample size. The same is true for the simulated gas diffusion coefficient. This effect is explained by two different types of pores, i.e. big root channels and smaller pores, having different levels of organization. We discuss the different concepts of structural organization which may be appropriate models for the structure investigated. We argue that the discrete hierarchical approach is the most profitable in practice.

Notes: Farmers want to minimize losses of nitrogen (N) by volatilization of ammonia when adding fertilizers and improve fertilizer recovery of N by plants. We aimed to quantify the losses of N through NH3 volatilization as affected by soil moisture content, type of fertilizer, and placement method in Vertisols in Kenya, and conducted three experiments for the purpose under controlled conditions in the laboratory. We found that NH3-N losses were greatest at 80% water holding capacity, which we ascribed to the ready availability of water to dissolve the fertilizer at that water content. The soil's cation exchange capacity (CEC) did not influence volatilization, whereas the soil's pH indicated the potential of the soil to volatilize ammonia. Ammonia losses from the fertilizers were in the order urea 〉 ammonium sulphate 〉 ammonium nitrate applied. Incorporating fertilizer within the 0–5 cm soil layer more than halved NH3 volatilization but did not prevent it completely. These results indicate that soil pH, rather than CEC, is the main inherent characteristic influencing ammonia volatilization from Vertisols. Ammonium-based fertilizers should be incorporated within the 0–5 cm soil layer, or preferably somewhat deeper, to avoid losses via NH3 volatilization, particularly in alkaline soils. Nitrate fertilizers are preferable to urea where the risks of NH3 volatilization are large, provided due consideration is given to denitrification risks.

Notes: The retention walls in a pond containing the residues from the pyrite mine of Aznalcóllar (southern Spain) broke open on 25 April 1998, spilling approximately 6 × 106 m3 of polluted water and toxic tailings, which affected some 55 km2. Drying and aeration of the tailings resulted in oxidation, forming an acidic solution with high pollutant contents, the effects of which were studied in a calcareous soil. The infiltration of this solution markedly affected only the first 12 mm of the soil, where strong acidification caused the weathering of the carbonates, and where the fine mineral particles were hydrolysed. The SO42− ions in the acidic solution precipitated almost entirely at this depth, forming gypsum, hydroxysulphates and complex sulphates. The Fe3+ ions also precipitated there, mainly in amorphous or poorly crystallized forms, adsorbing to As, Sb, Tl and Pb dissolved in the acidic solution. The Al3+ ions, though partly precipitating in the acidic layer, accumulated mostly where the soil pH exceeded 5.5 (12–14 mm in depth). They did so primarily as amorphous or poorly crystallized forms, adsorbing to Cu dissolved in the acidic solution. The Zn2+ and Cd2+ ions accumulated mainly at pH 〉 7.0 (19–21 mm in depth), being adsorbed chiefly by clay mineral. After 15 months, only the first 20 mm of the soil were acidified by the oxidation of the tailings and most of the pollutants did not penetrate deeper than 100 mm. Consequently, the speed of the cleanup of the toxic spill is not as important as a thorough removal of tailings together with the upper 10 cm of the soil.

Notes: Classical linear models are easy to understand and fit. However, when assumptions are not met, violence should not be used on the data to force them into the linear mould. Transformation of variables may allow successful linear modelling, but it affects several aspects of the model simultaneously. In particular, it can interfere with the scientific interpretation of the model. Generalized linear models are a wider class, and they retain the concept of additive explanatory effects. They provide generalizations of the distributional assumptions of the response variable, while at the same time allowing a transformed scale on which the explanatory effects combine. These models can be fitted reliably with standard software, and the analysis is readily interpreted in an analogous way to that of linear models. Many further generalizations to the generalized linear model have been proposed, extending them to deal with smooth effects, non-linear parameters, and extra components of variation. Though the extra complexity of generalized linear models gives rise to some additional difficulties in analysis, these difficulties are outweighed by the flexibility of the models and ease of interpretation. The generalizations allow the intuitively more appealing approach to analysis of adjusting the model rather than adjusting the data.

Notes: This paper describes the movement of anions and cations through soils at the regional scale using block-scale and regional simulations of one-dimensional ion transport through cultivated soils. The simulations were based on field experiments in a region of about 10 km2 in Lower Saxony, Germany. Transport was modelled with the convection–dispersion equation, and the cation exchange was described using the Gapon equation. We evaluated the spatial variation of cation exchange parameters, obtained estimates valid at the block scale, and simulated the one-dimensional transport of anions and cations. The movement of anions and cations was simulated over blocks using effective transport parameters calculated from local transport parameters. The approach led to a good agreement between measured and predicted concentrations of Br–, Na+, K+, Ca2+ and Mg2+ on four different 1 ha blocks. However, the mean concentrations of K+ in the soil solution in the uppermost horizons could not be described satisfactorily by the model. For the regional simulations, transport and exchange parameters were estimated by block kriging. All variograms of the exchange parameters were spatially structured with correlation lengths varying from 100 m to 300 m. Results of the regional simulations imply that Cl– and K+ were transported substantially deeper in the southern part than in the northern part of the area. The transport depth of the ions strongly depended on the pore water velocities. The simulation of solute transport to the water table showed the influence of the depth of water table on the estimated travel times, superimposing the influence of the transport parameters in the region. The results of the regional simulations also emphasize the importance of careful fertilization, especially in regions with shallow water tables such as in the north of the area.

Notes: Current concern for soil quality has stimulated research on soil biological and chemical properties. In contrast, the mechanical behaviour of soil is somewhat neglected. We have examined the effects on soil mechanical properties of more than 100 years of contrasting fertilization employing three treatments from the Askov long-term experiment: UNF (unfertilized), NPK (mineral fertilized) and AM (animal manured). We have measured tensile strength of aggregates when air-dry and when adjusted to −10, −30 and −100 kPa pressure potential. Four aggregate size classes were investigated (1–2, 2–4, 4–8 and 8–16 mm diameter). Soil fragmentation was characterized in the field using a drop-shatter test. Bulk soil strength was determined in the field using a shear vane and a torsional shear box. Soil texture, pH, cation exchange capacity and microbial biomass were measured. The unfertilized soil has little soil organic matter and microbial biomass and is dense. Its aggregates were strong when dry and weak when wet. In contrast, the manured soil had strong aggregates when wet and rather weak ones when dry. The NPK soil generally had intermediate properties. The differences between the soils when dry seem to be related to differences in dispersible clay content, whereas the differences when wet are related to differences in the amount of organic binding and bonding material. The optimal water content for tillage as well as the tolerable range in water content was largest in the manured soil and smallest in the unfertilized soil. Our results indicate that soil mechanical properties should be measured over a range of water regimes to determine the effects of various long-term fertilization treatments.

Notes: The pseudo cross-variogram can be used for cokriging two or more soil properties when few or none of the sampling locations have values recorded for all of them. The usual estimator of the pseudo cross-variogram is susceptible to the effects of extreme data (outliers). This will lead to overestimation of the error variance of predictions obtained by cokriging. A solution to this problem is to use robust estimators of the pseudo cross-variogram, and three such estimators are proposed in this paper.The robust estimators were demonstrated on simulated data in the presence of different numbers of outlying data drawn from different contaminating distributions. The robust estimators were less sensitive to the outliers than the non-robust one, but they had larger variances. Outliers tend to obscure the spatial structure of the cross-correlation of the simulated variables as described by the non-robust estimator.The several estimators of the pseudo cross-variogram were applied to a multitemporal data set on soil water content. Since these were obtained non-destructively, direct measurements of temporal change can be made. A prediction subset of the data was subsampled as if obtained by destructive analysis and the remainder used for validation. Estimators of the auto-variogram and pseudo cross-variogram were applied to the prediction data, then used to predict the change in water content at the validation sites by cokriging. The estimation variances of these predictions were best calculated with a robustly estimated model of coregionalization, although the validation set was too small to conclude that the non-robust estimators were unsuitable in this instance.

Notes: There is growing concern about the fate and toxicity of herbicides to non-target receptors and an increasing need to measure these analytes sensitively. The responses of cellular and immunological biosensors to four commonly used herbicides (atrazine, diuron, mecoprop and paraquat) were investigated. In combination, these sensors assess toxicity and quantify concentrations of herbicides present in extracts from soil. The bioluminescence response of the lux-marked bacterial biosensor Escherichia coli HB101 was determined in aqueous extracts from soil to indicate toxicity. Smaller concentrations caused a toxic response for all four herbicides recovered from the Insch series than for those recovered from spiked water samples, but this was not a result of biodegradation of herbicides in the soil. This suggests that intrinsic soil factors may be altering the bioavailable fraction of herbicides, making them more toxic than equivalent concentrations in water.Herbicide concentrations were determined using immunological biosensors consisting of stabilized recombinant single chain antibodies (stAbs) specific for the four different groups of herbicides. These stAb fragments retain functionality in organic solvents such as methanol commonly used in soil extraction. Anti-atrazine, mecoprop, diuron and paraquat stAbs were successfully used to identify and quantify herbicides present in aqueous and methanol extracts from soil. The amounts recovered from immunoassay analysis were compared with chemical analysis using high performance liquid chromatography, and the two methods correlated. These stAb fragments might provide a more rapid and sensitive means of quantifying trace amounts of herbicides and their metabolites in aqueous and methanol extracts from soil.

Notes: Rain falling on soil causes slaking, mechanical disruption of aggregates and compaction. Too few data exist to predict the changes likely to occur in particular soil, landscape and management conditions. Experiments with simulated rain were set up to study and to model mathematically the changes of the pore system within the surface layer of a soil when rain was applied on a field cropped with maize. Macroporosity, pore-size and pore-shape distributions, and the pore volume were measured by image analysis of thin sections and the fractal dimensions of the pore surface roughness were estimated. The general trends of changes in porosity indicated the presence of two different sets of processes at the surface (0–3 cm) and in the layer immediately underneath (3–6 cm). In both layers most of the variation in macroporosity was due to a loss of elongated porosity. A theoretical approach recently developed to link rain and erosion to sealing properties was extended to describing the effect of rain on the elongated porosity and the pore volume fractal dimension in these two layers. The resulting set of equations describe in detail the evolution of soil porosity near the soil surface. Our approach could be useful when modelling the effects of sealing processes in soil erosion.

Notes: A novel hybrid stubble turnip, Appin, bred by the Scottish Plant Breeding Station (Brassica campestris ssp. rapifera cv. Tigra ×B. campestris ssp. nipposinica cv. Mizuna) was compared in small-plot cutting trials with stubble turnip (B. campestris ssp. rapifera cv. Ponda), forage rape (B. napus ssp. biennis cv. Canard) and fodder radish (Raphinus sativus cv. Neris) for 3 years, 1975–77, samples being taken from October to December or January each year to cover the likely period of utilization by grazing lambs. Except for the first year, Appin proved to yield less DM than Ponda, and be inferior in digestibility and metabolizable energy (ME) content, though N contents were on occasion higher. Canard had the highest overall ME content. In dry conditions in autumn 1977, Ponda proved the more reliable crop, suffering less depression in yield than other species. Anti-metabolite contents were determined in freeze-dried samples taken in winter 1976-77 and showed Canard to have the most brassica anaemia factor (S-methyl cysteine sulphoxide): contents of thiocyanate were generally similar between crops.As the degree of utilization of such forages when grazed can outweigh differences in recorded above-ground DM yields from cutting trials, it was considered that claims of better root anchorage and hence better utilization for Appin warranted evaluation in a grazing trial.

Notes: Two grass silages made from perennial ryegrass, and with D-values of 0·216 and 0·255, were offered ad libitum to 18 Ayrshire cows in two feeding experiments. On the control treatment the silages were supplemented with soybean meal only, and on the other two treatments with equal weights of DM from either barley or dried molassed sugar-beet pulp plus the same weight of soya as on the control treatment. The daily intakes of silage DM were not significantly different on the barley and beet-pulp treatments, and, on average, the intake of silage DM was reduced by 0·24 and 0·20 kg by feeding 1 kg barley and beet pulp DM respectively.The daily milk yields were not significantly different on the barley and beet-pulp treatments with mean values of 19·2 and 19·2 kg per cow respectively compared with 17·2 kg on the control treatment. On the barley and beet-pulp treatments the fat, SNF, CP and lactose concentrations in the milk and the live weights of the cows were not significantly different. It is concluded that the barley and beet pulp had similar feeding values and replacement rates when used as supplements with grass silage, and that the two feeds were interchangeable on an equal DM basis.

Notes: An experiment examining the relationship of daily herbage disappearance (DHD) and daily herbage allowance (DHA) is described. Cows with calves were grazed at three stocking rates on Kleingrass and Coastal Bermudagrass pastures. DHD and DHA were monitored at 14-d intervals. A significant positive linear relationship was noted between DHD and DHA (P〈inlineGraphic alt="leqslant R: less-than-or-eq, slant" extraInfo="nonStandardEntity" href="urn:x-wiley:01425242:GFS9:les" location="les.gif"/〉0·25). Equations derived for Coastal Bermudagrass and Kleingrass were not significantly different and resulted in a combined equation Ŷ= 0·275X + 0·209 with an r2 vaiue of 0·27. As DHA exceeded 6–9 kg DM per 100 kg live weight, efficiency of defoliation by the cows and calves declined.

Notes: The effects of five herbicides on seed yield and viability of perennial ryegrass cv. S24 were tested at two sites. Benzoylprop-ethyl, chlorfenpropmethyl, difenzoquat, ethofumesate and flam-prop-isopropyl were safe to use at doses recommended for use in other crops. When applied at three times the recommended dose, only difenzoquat reduced the yield and germination of seed and benzoylprop-ethyl reduced seed germination. The recommended doses of difenzoquat and ethofumesate were safe when applied on cv. Barlenna at different growth stages. Difenzoquat reduced seed yield only after three times the recommended dose was applied to tillered plants. Ethofumesate, even at three times the recommended dose, did not affect seed yield but plant numbers were reduced by early treatment. The results suggest that the herbicides tested may be safe to use in perennial ryegrass seed crops at the recommended doses but more work is needed on the safety of difenzoquat in relation to crop growth stage.

Notes: Abstract A glasshouse study was undertaken to determine the physiological and morphological changes in cocksfoot (Dactylis glomerata L.) during regrowth after defoliation. Individual plants were arranged in a mini-sward in a randomized complete block design. Treatments involved harvesting each time one new leaf had expanded (one-leaf stage), up to the six-leaf stage, with the plants separated into leaf, stubble (tiller bases) and roots. Stubble and root water-soluble carbohydrate (WSC), stubble and leaf dry matter (DM), tiller number per plant and leaf quality (crude protein (CP), estimated metabolizable energy (ME) and mineral content) were measured to develop optimal defoliation management of cocksfoot-based pastures. WSC concentration in stubble and roots was highest at the five- and six-leaf stages. Mean WSC concentration (g kg−1 DM) was greater in stubble than roots (32·7 ± 5·9 vs. 9·4 ± 1·5 respectively). There was a strong positive linear relationship between plant WSC concentration and leaf DM, root DM and tillers per plant after defoliation (Adj R2 = 0·72, 0·88 and 0·95 respectively). Root DM plant−1 and tiller DM tiller−1 decreased immediately following defoliation and remained low until the three-leaf stage, then increased from the four-leaf stage. Tillers per plant remained stable until the four-leaf stage, after which they increased (from 9·9 ± 0·5 to 15·7 ± 1·0 tillers plant−1). Estimated metabolizable energy concentration (MJ kg−1 DM) was significantly lower at the six-leaf stage (11·01 ± 0·06) than at any previous leaf regrowth stage, whereas CP concentration (g kg−1 DM) decreased with regrowth to the six-leaf stage. Both the levels of ME and CP concentrations were indicative of a high quality forage throughout regrowth (11·37 ± 0·04 and 279 ± 8·0 for ME and CP respectively). Results from this study give a basis for determining appropriate criteria for grazing cocksfoot-based pastures. The optimal defoliation interval for cocksfoot appears to be between the four- and five-leaf stages of regrowth. Delaying defoliation to the four-leaf stage allows time for replenishment of WSC reserves, resumption of root growth and an increase in tillering, and is before herbage is lost and quality falls due to onset of leaf senescence.

Notes: Abstract Two experiments were carried out in consecutive years to examine the influence of cutting date and restricting fermentation by carboxylic acid treatment on the nutrient intake from grass silage by beef cattle. In year 1, four cutting dates during July and August after a primary growth harvest and, in year 2, five cutting dates of primary growth between mid-May and early July were examined. Herbage was ensiled either untreated or treated with high levels of acid additive (‘Maxgrass’, mean 8·6 l t−1). Ninety-six (year 1) or forty-eight (year 2) continental cross steers were used in partially balanced changeover design experiments with each silage type either unsupplemented or supplemented with 4·5 (year 1) or 5·5 (year 2) kg concentrates head−1 d−1. Silage digestibility declined significantly between initial and final harvest dates (P 〈 0·001), whereas silage dry-matter (DM) and digestible energy (DE) intakes were significantly higher in the initial compared with final harvest dates in both years of the study (P 〈 0·01). Similarly, silage DM and DE intakes, and total DM intakes, of acid-treated and unsupplemented silages were greater than those of untreated and concentrate supplemented silages, respectively (P 〈 0·001). The results indicate that earlier cutting dates, and addition of acid to herbage before ensiling, can increase silage DM intake by beef cattle.

Notes: Abstract To indicate possibilities for the use of forages from seminatural grasslands in ruminant production systems, a literature study to describe the nutritive value of those forages was carried out. In species-rich grasslands, the digestibility of forages is usually lower than the digestibility of forages produced by grasslands used for intensive production. There is also more variation within a species-rich sward, because of different stages of maturity of the individual species and because of likely variations in digestibility among forage species independent of stage of maturity. Moreover, the presence of dicotyledonous species may have a positive or negative effect on digestibility. In forages from seminatural grasslands, the relationship between chemical composition and digestibility differs from that of Lolium perenne, which is often used as a research standard. Therefore, predictions of the digestibility of species-rich forage can be inaccurate. The relationship between in vivo and in vitro digestibility may also be different from the relationship that is common for L. perenne. In some cases, the in vivo digestibility is higher than the in vitro value, as calibrations are based on L. perenne. Therefore, the quality of forages from seminatural grasslands might be higher than predicted, and this may increase the scope for practical use of this kind of forage in ruminant nutrition systems.

Notes: The effect of adding Lactobacillus buchneri 40788, a heterofermentative lactobacilli, to whole-plant maize and its effect on fermentation and aerobic stability of the resulting silage were evaluated. Whole-plant maize (380 g DM kg–1 fresh weight) was ensiled in laboratory silos after the following treatments: untreated, L. buchneri 40788 at 1 × 105, 2·5 × 105, 5 × 105, and 1 × 106 colony forming units g–1 of fresh forage or, a commercial inoculant containing homolactic acid bacteria, a single species of propionibacteria and enzymes. Addition of L. buchneri 40788 resulted in a decrease in lactic acid concentration but increased the concentration of acetic acid in silage and markedly decreased the numbers of yeasts present in the silage. All levels of L. buchneri 40788, increased the aerobic stability of silages but the effect was greatest for the two highest levels of inoculation. Treatment with the commercial inoculant had no effect on the fermentation or aerobic stability of silage. On-farm treatment of maize silage with L. buchneri 40788, stored in a bag silo, resulted in changes in fermentation that were similar to those observed in laboratory silos. Treatment decreased the numbers of yeast in silage and increased aerobic stability (+25 h) of the silage when exposed to air. Treatment had no effect on the dry-matter intake of silage fed to sheep. These results showed that treating silage with L. buchneri 40788 can increase the aerobic stability of maize silage in laboratory and farm silos.

Notes: Infestations of pastures by species, such as creeping bentgrass (Agrostis stolonifera), may compromise the white clover (Trifolium repens) content in perennial ryegrass (Lolium perenne) mixtures. However, the interactions between white clover and species other than perennial ryegrass are not well understood. Strategies to prevent creeping bentgrass infestations require an understanding of its interactions with white clover, as the exclusion of white clover from infested pastures could be the result of either direct interaction or niche-differentiation in response to management. A methodology is presented which enables the segregation of the effects of direct interaction and niche-differentiation, based on existing dry-weight-rank measurements of a number of experimental pastures, subjected to a range of management strategies.Only between the two management extremities, i.e. permanent cutting of silage and lax grazing for long periods, did niche-differentiation occur between white clover and creeping bentgrass. The white clover content was enhanced under the cutting regime, whereas lax grazing for long periods stimulated the content of creeping bentgrass. White clover was actively excluded from creeping-bentgrass-dominated patches by direct interaction, whereas it showed a high compatibility with perennial ryegrass. This direct interaction presents challenges to the prevention of creeping bentgrass by management, as creeping bentgrass and white clover showed nearly identical requirements in terms of environmental conditions and grassland management.

Notes: Six experiments were carried out in two climatically different regions in south-east Norway in order to compare different procedures for autumn management and use of regrowth in seed crops of timothy (Phleum pratense L.) cv. Grindstad. The experiments were laid out after seed harvest in mid-August in crops with a stubble height of 5 cm (two experiments) or 12–15 cm (four experiments). Cutting to 5 cm on 15 September or 15 October, with or without an application of 50 kg N ha−1 immediately after seed harvest, and with or without an additional application of 30 kg N ha−1 after cutting, were compared with an uncut and unfertilized control treatment. As a main effect,autumn cutting increased seed yield in the subsequent year in only one experiment; this was laid out in a 13 cm stubble on a fertile soil near the coast. In the remaining five experiments seed yields were unaffected byautumn management regardless of climate or stubble height. Autumn cutting and N application increased the number of seedheads in two experiments, but this was offset by a drop in other seed yield components.On average for two cutting dates and for plots receiving an application of 50 kg N ha−1 after seed harvest, the dry matter (DM) was 1430 kg ha−1 on an inland site with 12–15 cm stubble, 1400 kg ha−1 on a coastal site with 5 cm stubble and 2460 kg ha−1 for two coastal sites with 12–15 cm stubble. Whereas forage yield and quality were fairly stable from the first to the second cut at the inland site, the yield of DM increased, but the crude protein and energy concentrations decreased from 15 September to 15 October at the coastal sites. It is concluded that the stubble and regrowth in seed crops of timothy cv. Grindstad can be harvested for forage without any effect on seed yield in the next year.

Notes: Nutritive value and voluntary intake of legumes are generally considered to be higher than those of grasses when ensiled at similar digestibility, although high levels of soluble protein can result in low N utilization by animals and high losses to the environment. The objectives of this experiment were to describe the optimum combination of Westerwolds ryegrass (Lolium multiflorum Lam. cv. Aubade) and lucerne (Medicago sativa L. cv. AC Caribou) silages to maximize liveweight gain of steers fed silage, determine chemical components that are important and ascertain whether steers selected the optimum mixture when given a choice. Both silages contained similar concentrations of dry matter (DM), acid-detergent fibre (ADF) and organic acids, but lucerne silage had higher concentrations of N, soluble-N and ammonia-N. Westerwolds ryegrass silage contained more neutral-detergent fibre (NDF). In a 12-week experiment, voluntary intake by Hereford steers was not influenced when the proportion of the two silages was changed from 1 to 0 in 0·25 increments. However, liveweight gain and feed efficiency increased linearly (P 〈 0·001) as the proportion of ryegrass silage fed was increased. When preconditioned to either of the two silages, steers showed a significant preference for ryegrass over lucerne (P 〈 0·05). When conditioned to a mixture of both silages, no preference was elicited. It is suggested that extensive solubilization and deamination of protein in the lucerne silage may have caused the preference for Westerwolds ryegrass silage and the higher liveweight gains on diets containing higher proportions of Westerwolds ryegrass silage.

Notes: Three replicate paddocks, each of 0·235 ha, containing adjacent monocultures of perennial ryegrass or white clover [50:50 by ground area, 6 cm sward surface height (SSH) at start of experiment] were continuously stocked with three yearling and four mature non-lactating, non-pregnant Scottish halfbred ewes for 12 weeks. Herbage intake, grazing behaviour and dietary selection were measured on seven occasions. Clover SSH declined rapidly over the first 5 weeks then stabilized at 1·2–1·6 cm, whereas perennial ryegrass SSH rose slightly initially, then declined gradually. Animals initially included proportionately c. 0·6 white clover in their diet but, by the end of the experiment, this had fallen to 0·3. Total daily herbage intake declined over the 12 weeks from 1·8 kg dry matter (DM) day–1 at the start to 1·0 kg DM day–1. Total grazing time increased from 561 min day–1 to 649 min day–1 at the end of the experiment. The results suggest that, despite overall herbage depletion and a greater depletion of white clover than perennial ryegrass as a result of the initial partial preference for white clover, the animals traded-off a reduced total intake and an increased grazing time in an attempt to maintain their initial preferred dietary composition.

Notes: Abstract An experiment was carried out over 2 years to evaluate the effects of increasing the proportion of cereal-based concentrates in diets containing high-digestibility and conventional medium-digestibility grass silages on the dry-matter (DM) intake, liveweight gain and carcass composition of beef cattle, and to examine the effects of grazed grass and the ratio of grass silage:concentrates in the diet on the fatty acid composition of selected muscle tissues. Late-maturing steers (n = 231) were offered diets based on high-digestibility (HD) (0·743 digestible organic matter (DOM) in DM) or medium-digestibility (MD) (0·643 DOM in DM) grass silages supplemented with barley/soyabean meal-based concentrates. The concentrates constituted 0·20, 0·40, 0·60 and 0·80 of total DM of the diets, which were offered ad libitum (AL). The two diets, which contained 0·80 concentrates, were also offered at 0·80 of AL intake. A further group of fourteen animals were given the medium-digestibility silage only for 5 months and then grazed perennial ryegrass pastures for a further 5 months (silage/pasture treatment). For the diets containing HD silage and 0·20, 0·40, 0·60 and 0·80 concentrate, and 0·80 concentrate at 0·8 of AL intake, the DM intakes were 9·4, 10·2, 10·4, 10·2 and 8·1 (s.e. 0·16) kg d−1, respectively, and daily carcass gains were 0·67, 0·78, 0·77, 0·79 and 0·62 (s.e. 0·029) kg d−1, respectively; for those containing MD silage and 0·20, 0·40, 0·60 and 0·80 concentrate, and 0·80 concentrate at 0·8 of AL, the DM intakes were 8·2, 9·3, 10·1, 10·1 and 8·0 (s.e. 0·16) kg d−1, respectively, and daily carcass gains were 0·38, 0·48, 0·64, 0·77 and 0·56 (s.e. 0·029) kg d−1 respectively. Increasing the proportion of concentrates in silage-based diets decreased the concentration of omega-3 (ω-3) polyunsaturated fatty acids (PUFA) (P 〈 0·001) and increased the concentration of ω-6 PUFA (P 〈 0·001) in muscle. Cattle on the silage/pasture treatment had the highest concentration of ω-3 PUFA in muscle (51 g kg−1 lipid), this value being over three times that for animals given diets containing MD silage and 0·80 concentrate in the diet. These results demonstrate the potential of HD silage made from perennial ryegrass relative to high concentrate diets. The consumption of pasture-finished beef could make a significant contribution towards increasing the intake of ω-3 PUFA in the human diet.

Notes: Extensification (a reduction in fertilizer inputs and stocking rate of grassland) is seen as one way of increasing the conservation value and of reducing the environmental impact of upland sheep production in the UK, but little is known about the consequences of such a change. This study determines the changes in animal production over ten years following the introduction of four extensive grazing management strategies to perennial ryegrass/white clover pastures at two upland sites. Fertilizer-free treatments were maintained with sward heights of: 4 cm (treatment 4/4U) or 8 cm (8/8U) during the whole of the grazing year, 4 cm during summer and 8 cm during autumn (4/8U) and 8 cm during summer and 4 cm during autumn (8/4U). A control treatment that received 140 kg N ha−1 year−1 was also maintained with a sward surface height of 4 cm (4/4F). Scottish Blackface sheep grazed all treatments.The 4/4F treatment carried the greatest number of animals (3746 grazing days ha−1 year−1); the 4/4U and the 8/8U treatments carried 0·73 and 0·43 of this number respectively. The number on the 4/8U treatment was similar to that on the 4/4U while the 8/4U treatment carried 1·41 of that on the 8/8U treatment (0·61 of 4/4F). Mean individual animal performance was greatest on the 8 cm swards and tended to be lowest on the 4/4F treatment. However, the 4/4F treatment produced the greatest live weight of lamb (623 kg ha−1 year−1) with the 4/4U producing 0·77, and the 8/8U producing 0·55, of this amount. Although there was year-to-year variation in agricultural output, it was concluded that the lower levels of sheep production that result from a change to extensive systems of grazing management can be maintained for at least 10 years.

Notes: Two experiments were conducted in the UK to investigate preference by cattle for areas of pasture treated or untreated with dairy cow slurry. Experiment 1 examined the effects of method and rate of slurry applied to a grass pasture in March (Spring); Experiment 2 examined the effects of method and timing of slurry application after cutting for silage in June (Summer). In both experiments, beef steers grazed grassland plots that had been treated with slurry on one half only of the plots for 4 weeks. Slurry was applied by shallow injection (I), trailing shoe (T) or conventional surface broadcasting (S) techniques. In Experiment 1, slurry was applied at 40 m3 ha−1 (HI) or 20 m3 ha−1 (LO) 21 d before grazing commenced; in Experiment 2, slurry was applied at 20 m3 ha−1 either 32 d (E) or 10 d (L) before grazing commenced. Sward height was measured and animal behaviour was recorded during 8 × 24 h measurement periods in each experiment. Preference for slurry-treated or untreated swards was indicated by a comparison of post-grazing sward height on each sward and the proportion of total grazing time spent on the slurry-treated swards. In Experiment 1, a smaller proportion of grazing time was spent on slurry-treated areas of swards compared with untreated areas of swards on all treatments, but the proportion of time spent grazing the slurry-treated sward was greater on method T than on methods I or S (0·28, 0·31 and 0·39 for methods S, I and T, respectively, s.e.d. = 0·035, P 〈 0·05). Steers showed no preference between slurry-treated and untreated swards by 49, 45 and 44 d after slurry application for methods S, I and T respectively. Differences between HI and LO were not significant (P 〉 0·05). In Experiment 2, aversion to slurry-treated swards compared with untreated swards was less for treatment E than for L, with a greater proportion of both residence and grazing time spent on the slurry-treated sward of treatment E than L (0·43 and 0·28, respectively, for residence time, s.e.d. = 0·025, P 〈 0·001, and 0·47 and 0·30, respectively, for grazing time, s.e.d. = 0·021, P 〈 0·001). Significant differences were shown between the methods of slurry application for treatment E, with a greater proportion of grazing time spent on the slurry-treated swards of methods I and T than method S (0·40, 0·52 and 0·49 for S, I and T, respectively, s.e.d. = 0·032, P 〈 0·001), and a greater difference between post-grazing heights on slurry-treated and untreated swards for method S than for I or T (30, 12 and 15 mm, respectively, s.e.d. = 4·8, P 〈 0·001). For treatment L, differences in the proportion of time spent grazing on slurry-treated swards compared with untreated swards were not significant between treatments (0·26, 0·34 and 0·31 for methods S, I and T, respectively, s.e.d. = 0·040, P 〉 0·05) and indifference between slurry-treated and untreated swards was achieved 77, 60 and 58 d after slurry spreading for methods S, I and T respectively. These results show that, when slurry is applied to pasture in a grazing rotation, the adverse effects on grazing behaviour associated with conventional surface broadcasting may be overcome by the use of novel slurry application techniques.

Notes: The topsoils of Andisols in the wet high altitude grasslands (páramos) of Ecuador have shrunk after recent changes from permanent grassland to agriculture. The question arises as to whether all Andisols in the region behave in the same way. We have therefore studied the shrinkage on drying of topsoils from four representative types of Andisol in the páramos using a combination of drying kinetics and mercury porosimetry. We aimed to identify and quantify the pore volumes that participate in either drainage or shrinkage or both. The key concept of hierarchical dual porosity of soils used to interpret the shrinkage curves was partly validated, but we also identified more complex relations between drainage, shrinkage and structure. We found that the older was the soil, the more weathered it was, and, consequently, the greater its aggregation and porosity. In turn, the total volumetric shrinkage was controlled by the initial void ratio of the wet soil samples. Our results also show that the solid–pore interfaces of the volcanic soil aggregates were less accessible after shrinkage than before.

Notes: The concept of ferrolysis as defined in the 1970s by Brinkman and co-workers is mentioned in the recent literature as a dominant process to explain clay disintegration, interlayering of clay minerals, and strong texture contrast of duplex soils, in which bleaching and mottling are predominant features. Ferrolysis is based on biochemical reduction of free iron(III) oxides to Fe2+ and re-oxidation of Fe2+ during alternating reducing and oxidizing conditions in the soil. The acidity produced during the oxidation is assumed to release cations from silicates which results in the destruction of clay minerals. A detailed analysis of data from chemical analyses, laboratory experiments, and mineralogical and micromorphological investigations, which have been considered to sustain the ferrolysis theory, has been carried out. Some soils in Belgium and France, which have been considered to be formed mainly by ferrolysis, show strong textural contrast or albeluvic features. It has been shown that the development of these soils is due to clay translocation rather than to clay destruction by ferrolysis. Fine quartz and chlorite, assumed to be secondary minerals formed during ferrolysis, are more likely formed by disintegration of larger quartz and chlorite particles.

Notes: Preferential flow needs self-dependent fluid mechanical characterization and quantification. A theoretical and experimental approach is presented to describe preferential flow with the three variables volume of flowing water and its kinetic energy and momentum. Two soils were irrigated at rates of 50, 75 and 100 mm hour−1 at one site and three times at 100 mm hour−1 at a second site. The variations of soil water content caused by irrigation were measured at five depths with horizontally installed TDR wave guides at 300-s intervals. The volume flux densities were calculated from the water balances. The computation of momentum and kinetic energy of preferential flow was based on the velocities of the wetting fronts and the amplitudes of the variations of soil water. Kinetic energy per unit volume of flow in the soil exceeds the one of irrigation by factors between 100 and 1000, which indicates concentration of flow. However, kinetic energy per unit volume of flow in the soil is less by factors of 106 to 108 than the capillary potential of soil water. Kinetic energy per unit volume of flow seems a reasonable variable for discriminating between preferential and ordinary flow at a threshold of 2 × 10−6 Pa.