ALBERT

Notes: Abstract. In organic farming, potassium (K) deficiency may become a significant problem due to nutrient import restrictions. Knowledge about potential K leaching in systems with different K budgets is therefore important for effective agricultural management. We investigated the effect of four organic farming systems (two livestock densities in combination with two types of organic manure) on crop yields, K leaching and K balances in a six course crop rotation from 1993/94 to 1997/98. Average K concentrations in soil water extracted by means of ceramic suction cups at 1 m depth were 0.6 mg K l−1 corresponding to a K leaching loss of 1.5 kg ha−1 yr−1 which was less than expected from values reported in the literature. Variation in K budgets from −12 to +30 kg ha−1 yr−1 did not affect K leaching. In an additional experiment with application of 988 kg K ha−1 as KCl, K leaching accounted for only 0.2% of the applied K although 40% of the accompanying Cl was leached. The main part of the applied K was retained in the topsoil. It was concluded that K leaching was a result of the fertilizer history rather than of the current K budget.

Notes: Abstract. Nitrate nitrogen (NO3-N) leaching from animal production systems in the northeast USA is a major non-point source of pollution in the Chesapeake Bay. We conducted a study to measure NO3-N leaching from dairy slurry applied to orchardgrass (Dactylis glomerata L., cv. Pennlate) using large drainage lysimeters to measure the direct impact of four rates of slurry (urine and faeces) N application (0, 168, 336, 672 kg N ha−1 yr−1) on NO3-N leaching on three soil types. We then used experimentally-based relationships developed earlier between stocking density and NO3-N leaching loss and leachate NO3-N concentration to estimate the added impact of animal grazing. Nitrate N leaching losses from only dairy slurry applied at the 0, 158, 336, and 672 kg N ha−1 yr−1 rates were 5.85, 8.26, 8.83, and 12.1 kg N ha−1 yr−1, respectively with corresponding NO3-N concentrations of 1.60, 2.30, 2.46, and 3.48 mg l−1. These NO3-N concentrations met the 10 mg l−1 US EPA drinking water standard. However, when a scenario was constructed to include the effect of NO3-N leaching caused by animal grazing, the NO3-N drinking water standard was calculated to be exceeded.

Notes: Abstract. The African oil palm (Elaeis guineensis) is relatively well adapted to the pedoclimatic conditions of central Amazonia. The clayey upland soils of the region are well supplied with nitrogen, although they are deficient in most other nutrients. Under these conditions, oil palm does not respond to N fertilization with yield increases. In this research, the N status of a central Amazonian upland soil was evaluated after having supported a productive oil palm plantation for 15 years without N fertilization. Mineral N in the upper 2 m of soil showed pronounced spatial patterns, with very low concentrations close to the palms, indicative of efficient N uptake by the palms, and evidence for nitrate leaching into the subsoil in the inter-tree spaces despite the near-absence of a leguminous cover crop during the previous ten years. The pronounced increases of mineral N with increasing tree distance were explained by increases in N mineralization and a strong decrease in fine root length density of the palms, especially in the subsoil. Failure of the palms to fully occupy the available soil volume with their roots was apparently related to fertilizer placement close to the stem base, which over the years had led to steep fertility gradients between the soil under the trees and the inter-tree spaces. Broadcast fertilization would have presumably favoured a more extensive lateral root development of the palms, and consequently improved nutrient and water uptake from the inter-tree spaces. The incomplete soil occupation by the palm roots also suggests that young oil palms can be associated with shade tolerant crops without much risk of root competition. These conclusions may be valid also for other tree crops and may help to reduce nitrate leaching and consequently the need for N fertilization in Amazonian tree crop agriculture.

Notes: Abstract. Four experiments studying ground preparation for the restoration of disturbed land to a woodland cover are described. They provide consistent evidence to suggest that methods of soil replacement which minimize compaction are preferable to conventional methods followed by deep ripping to relieve compaction induced in the placement operation. In addition, soil loosening using an excavator is more effective than that achieved by ripping. The research supports modern guidance which advocates ‘loose tipping’ as the best method of ground preparation for a woodland or forestry after-use on sites reclaimed after dereliction or mineral extraction.

Notes: Abstract. Denitrifying enzyme activity (DEA) declined to a greater extent and was more variable in soils stored air-dried for 6 months than after storage at 4 °C. DEA was greatest in fertilized soils. The relative differences in DEA between soils were maintained after storage at 4 °C. We suggest that storage at 4 °C is more appropriate than air-drying.

Notes: Book reviewed in this articles: Agriculture, Fertilizers and the Environment. Edited by M. Lægreid, O. C. Bøckman and O. Kaarstad. Ramiran 98. Proceedings of the 8th International Conference of the FAO European System of Co-operative Research Networks in Agriculture (ESCORNENA) on Management Strategies for Organic Waste Use in Agriculture. Edited by J. Martinéz & M.-N. Maudet.

Notes: Abstract. The incidence of soil water erosion was monitored in 12 erosion-susceptible arable catchments (c. 80 fields) in England and Wales between 1990 and 1994. Factors associated with the initiation of erosion were recorded, and the extent of rills and gullies measured. Approximately 80% of the erosion events were on land cropped to winter cereals. In 30% of cases, the initiation of erosion was linked to valley floor features, which concentrated runoff. Poor crop cover, wheelings and tramlines were also assessed as contributory factors in 22%, 19% and 14% of cases, respectively. In c. 95% of cases rainfall events causing erosion were ≥10 mm day−1 and c. 80% were 〉15 mm day−1. Erosion was also associated with maximum rainfall intensities of 〉4 mm h−1 for c. 90% of cases and 〉10 mm h−1 for c. 20%. Mean net soil erosion rates were approximately 4 t ha−1 per annum (median value 0.41 t ha−1 per annum) and associated mean P losses 3.4 kg ha−1.

Notes: Abstract. A study of the leaching losses of nitrate under urine patches in irrigated and non-irrigated dairy pastures in the South East of South Australia was undertaken with repacked and monolith lysimeters 1 m deep, and with monolith lysimeters 150, 300 and 450 mm deep. The aim was to quantify differences in measurements of drainage and nitrogen fluxes for these different lysimeters. Drainage of water and N flux were found to vary significantly between types and depths of lysimeters. Drainage volumes in repacked lysimeters were 78% and 33% more than in monolith lysimeters in irrigated and non-irrigated paddocks, and N fluxes were 5 and 3 times higher in repacked lysimeters respectively. The results indicate that lysimeter estimates of recharge rates and N fluxes to water tables are best determined by leaching studies which are longer term, and use deep monolith lysimeters. Shorter term studies and the use of shallow or repacked lysimeters have potential to distort conclusions.

Notes: Abstract. Under the Kyoto Protocol, the European Union is committed to an 8% reduction in CO2 emissions, compared to baseline (1990) levels, during the first commitment period (2008–2012). However, within the overall EU agreement, the UK is committed to a 12.5% reduction. In this paper, we estimate the carbon mitigation potential of various agricultural land-management strategies (Kyoto Article 3.4) and examine the consequences of UK and European policy options on the potential for carbon mitigation.We show that integrated agricultural land management strategies have considerable potential for carbon mitigation. Our figures suggest the following potentials (Tg yr−1) for each scenario: animal manure, 3.7; sewage sludge, 0.3; cereal straw incorporation, 1.9; no-till farming, 3.5; agricultural extensification, 3.3; natural woodland regeneration, 3.2 and bioenergy crop production, 4.1. A realistic land-use scenario combining a number of these individual management options has a mitigation potential of 10.4 Tg C yr−1 (equivalent to about 6.6% of 1990 UK CO2-carbon emissions). An important resource for carbon mitigation in agriculture is the surplus arable land, but in order to fully exploit it, policies governing the use of surplus arable land would need to be changed. Of all options examined, bioenergy crops show the greatest potential. Bioenergy crop production also shows an indefinite mitigation potential compared to other options where the potential is infinite.The UK will not attempt to meet its climate change commitments solely through changes in agricultural land-use, but since all sources of carbon mitigation will be important in meeting these commitments, agricultural options should be taken very seriously.

Notes: Abstract. A method to predict field-saturated hydraulic conductivity (Kfs) from soil structure, as described in soil profile descriptions, was developed using 627 Kfs measurements. As the soil structure classes used are very similar to an international classification (FAO, 1990), the derived relationships (class pedotransfer functions) could be widely applicable. A total of 49 unique combinations of primary and secondary structures were identified but the relationship between these structures and Kfs was poor. However, this relationship became clearer when the structures were grouped according to both the ped size and ped orientation. It improved further with the removal of data from horizons with significant amounts of vertically orientated angular stones or very coarse roots. Soils with vertically orientated peds larger than 50 mm had a geometric mean conductivity of 0.33 cm day−1 while those with fractures in both the horizontal and vertical planes had a geometric mean conductivity of 4.1 cm day−1. Soils with peds between 20 and 50 mm had a geometric mean conductivity of 17.9 cm day−1 and those with peds 〈20 mm had a geometric mean conductivity of 53.0 cm day−1. Those soils with only horizontally orientated structures proved to be anomalous in that the conductivity increased as ped size increased.

Notes: Abstract. Bacterial contamination of water is a problem worldwide and is often acute in developing countries where human and animal waste is disposed of on land for use as fertilizer or because of poorly developed sanitation systems. Studying leaching risk through soils is difficult when no suitable microbiological laboratory is available. A method using the movement of ZnO particles through soils as a surrogate for studying bacteria directly was tested. ZnO particles with a similar size to bacteria can readily be detected by chemical analysis. For a range of nine different soil textures, leaching rates of ZnO particles under near saturated conditions were significantly correlated with leaching rates of Escherichia coli cells (P=0.013). For both ZnO and E. coli, leaching was generally greatest through fine textured soils.

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

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

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

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

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

Notes: Book reviewed in this articles: Soil Microbiology. Second edition 2000. By Robert L. Tate

Notes: Abstract. The effect of drought between summer 1995 and 1997 on stream and river nitrate concentrations was investigated using sites close to the long-running meteorological station in Oxford, UK. Nitrate concentrations in the River Windrush were relatively low during the drought, but after it had ended reached the highest level since records began in 1973. The low concentrations during the drought probably reflect a reduced contribution from agricultural runoff. High nitrate concentrations were found in a field drain at Wytham Environmental Change Network site during and after the drought, but discharge was greatly reduced. A woodland stream at Wytham had much lower nitrate concentrations than the field drain but these similarly increased during and after the drought. There was evidence that both a concentrating effect of low water volumes and enhanced soil nitrogen mineralization and nitrification rates were causing concentrations to rise. The effects of mineralization and nitrification were more important in woodland than agricultural land. Nitrate load over the course of a year was determined largely by discharge, but steeper gradients for the relationship between cumulative load and cumulative discharge were seen during and after the drought than before, reflecting the higher concentrations.

Notes: Abstract. A survey was undertaken in 1996, by postal questionnaire sent to a stratified sample of 1500 pig producers in England and Wales; 576 (37%) responded. The survey provided data on manure production, manure storage and application strategies (timing, techniques and nutrient recycling to crops).Total pig manure production, in England and Wales is estimated to be at about 10.03 m t per year, with about 45% as slurry and 55% as FYM, according to this survey, where calculations have been based on undiluted outputs of excreta. About 45% of slurry is stored in above-ground tanks or earth-banked lagoons. Above-ground tanks most commonly held an amount of slurry equivalent to 3–6 months production, but earth-banked lagoons were more variable in capacity and over 20% could hold more than 9 months production of slurry.Annual statistics on fertilizer use indicate that farmers make little allowance for the nutrient content of manures. However, the results of this survey suggest that farmers generally make a genuine effort to allow for the nutrients applied, but that they currently fail to be assured by the advice available to them or their confidence is lacking for other technical reasons. Autumn represents the peak period for spreading, with 30% of slurry and 50% of FYM applied at that time.

Notes: Book reviewed in this articles: Pollution by heavy metals in the soil - plant system. By Chen Huaiman et al.

Notes: Book reviewed in this articles: Managing Risks of Nitrates to Humans and the Environment Edited by W.S. Wilson, A.S. Ball and R.H. Hinton

Notes: Abstract. Land disposal of sewage sludge in the UK is set to increase markedly in the next few years and much of this will be applied to grassland. Here we applied high rates of digested sludge cake (1–1.5×103 kg total N ha−1) to grassland and incorporated it prior to reseeding. Using automated chambers, nitrous oxide (N2O) and carbon dioxide (CO2) fluxes from the soil were monitored 2–4 times per day, for 6 months after sludge incorporation. Peaks of N2O emission were up to 1.4 kg N ha−1 d−1 soon after incorporation, and thereafter were regularly detected following significant rainfalls. Gas emissions reflected diurnal temperature variations, though N2O emissions were also strongly affected by rainfall. Although emissions decreased in the winter, temperatures below 4 °C stimulated short, sharp fluxes of both CO2 and N2O as temperature increased. The aggregate loss of nitrogen and carbon over the measurement period was up to 23 kg N ha−1 and 5.1 t C ha−1. Losses of N2O in the sludge-amended soil were associated with good microbial conditions for N mineralization, and with high carbon and water contents. Since grassland is an important source of greenhouse gases, application of sewage sludge can be at least as significant as fertilizer in enhancing these emissions.

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

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

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

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

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

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

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

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

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

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

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

Notes: Abstract. Research conducted in the MAFF Nitrate Programme has been used to formulate new and improved guidelines on the efficient use of manure nitrogen (N). In order to reduce nitrate leaching losses, manures containing large amounts of available N (i.e. slurries and poultry manures) should not be applied to free-draining soils in the period from autumn to early winter. Also, for efficient nutrient utilization manure application rates should be consistent with agronomic requirements (up to 250 kg total N ha−1 yr−1). Existing farm machinery was shown to be capable of applying manures evenly to grassland and arable stubbles, but required an accurate estimate of application rate and the careful matching of spreading widths. To provide growers with detailed guidance on the fertilizer N replacement value of manures the computer-based decision support system MANNER (MANure Nitrogen Evaluation Routine) has been developed. The much improved understanding of manure N losses and availability has been summarized in a series of ‘Managing Livestock Manures’ booklets, the MAFF Fertilizer Recommendation booklet and the Codes of Good Agricultural Practice.

Notes: Abstract. The large input of research effort on aspects of nitrate leaching over the last two decades has produced many innovative scientific and practical results. The MAFF Nitrate Programme has enabled considerable progress to be made in unravelling much of the complexity of the grassland nitrogen (N) cycle, and identifying gaps as essential first stages in providing improved managements for N in grassland systems. From a practical standpoint, there have been key outputs which have allowed the identification of options for policy, and which should allow grassland farmers to increase the efficiency of N use throughout their farming system and thereby improve the sustainability of their enterprises. As well as quantifying N transformations, transfers and losses, other important outcomes have been the development of user-friendly models of N cycling (NCYCLE and variants) and an easy to use field kit to determine mineral N in pasture soils. The use of modelling to produce fertilizer recommendations with a Decision Support System and of new approaches developed within the Programme, in particular system synthesis desk studies, and ‘farmlet’ investigations to determine the consequences of modifying N flows and losses, have allowed us to produce solutions to satisfy the dual aims of meeting environmental and economic production targets.

Notes: Abstract. The MAFF Nitrate Programme has provided policy makers and the agricultural industry with a much improved understanding of soil nitrogen cycling, and the cost-effectiveness of a range of nitrate reduction strategies. This understanding has been disseminated as improved economically-based advice on fertilizer N inputs to arable and grass crops, and information on the N value of livestock manures as affected by timing and method of application. In addition, strategies for reducing nitrate losses have been developed, including the use of over-winter cover crops, the management of cultivations and crop residues, and the conversion of arable land to low-input grassland.A wide variety of information dissemination methods have been used, including face-to-face discussions, demonstrations, articles in the farming press, booklets aimed at farmers, technical information for advisers and consultants, recommendation reference books and computer-based fertilizer recommendation systems.

Notes: Abstract. A number of changes in agricultural land-management show some potential as carbon mitigation options. However, research has focused on CO2-carbon mitigation and has largely ignored potential effects of land management change on trace gas fluxes. In this paper, we attempt for the first time, to assess the impact of these changes on fluxes of the important agricultural greenhouse gases, methane and nitrous oxide, in the UK.The estimates presented here are based on limited evidence and have a great (unquantifiable) uncertainty associated with them, but they show that the relative importance of trace gas fluxes varies enormously among the scenarlos. In some, such as the application of sewage sludge, woodland regeneration and bioenergy production scenarios, the inclusion of estimates for trace gas fluxes makes only a small (〈10%) difference to the CO2-C mitigation potential. In the animal manure and agricultural extensification scenarios, including estimates of trace gas fluxes has a large impact, increasing the CO2-C mitigation potential by up to 50%. In the no-till scenario, the carbon mitigation potential decreases significantly due to a sharp increase in N2O emissions under no-till.When these land-management options are combined for the whole agricultural land area of the UK, including trace gases has an impact on estimated mitigation potentials, and depending upon assumptions for the animal manure scenario, the total mitigation potential either decreases by about 10% or increases by about 30%, potentially shifting the mitigation potential of the scenario closer to the EU's 8% Kyoto target for reduction of CO2-carbon emissions (12.52 Tg C yr−1 for the UK).

Notes: Book reviewed in this articles: Review of Soil Research and Management in Papua New Guinea. Special issue of Papua New Guinea Journal of Agriculture, Forestry and Fisheries, 1998.

Notes: Abstract. In cracking clay soils the movement of water and solutes is greatly influenced by the arrangement of cracks and aggregates in the soil profile. It is essential that a model to simulate leaching from clay soils takes into account the routes of water movement and the interaction between water in the macropores and the soil aggregates. This paper describes modification of the CRACK model, which includes an explicit description of the structure of an aggregated clay soil and can simulate the movement of water and solutes, to create CRACK-NP, which incorporates nitrogen transformations and pesticide sorption and degradation. The application of the model to data from the Brimstone Farm experimental site in Oxfordshire, UK, is described. Results show that the model provides good simulations of both nitrate and pesticide leaching at the site but further testing is required to evaluate its performance over a wider range of hydrological conditions at this and other sites.

Notes: Abstract. A number of mathematical models to predict soil water evaporation are available in the literature which generally require complex input data. In the present study, a simple parametric model has been developed by coupling existing and newly developed equations to assess soil water evaporation and drainage under field conditions in relation to potential evaporation rate, soil texture, time and depth of tillage and crop residue management. The model has moderate input data requirements and predicts well the effects of tillage and crop residue management practices on soil water loss (evaporation+drainage) with multi-drying and -wetting cycles prevailing under natural conditions. The root mean squares of deviations between observed and predicted cumulative water loss at different periods of study were 0.82, 2.04, 2.31 and 1.74 cm for untreated, residue-mulch, tillage and residue-incorporated treatments, respectively. Simulation analysis on cumulative evaporation and evaporation rate has shown that the evaporation reduction with different combinations of tillage and crop residue followed the order of residue-undercut〉residue-mulch〉residue-incorporated〉tillage. Thus, the magnitude of beneficial effects of crop residues and tillage on soil water evaporation reduction are associated with amount of residues, mode of residue management (mulched or incorporated in the soil) and time and depth of tillage.

Notes: Abstract. A pilot-scale test confirmed that malodorous air containing 600 mg l−1 ammonia can be passed through a soil filter with 98.5% removal efficiency. Furthermore, the concentrations of methyl mercaptan, dimethyl sulfide, dimethyl disulfide, actaldehyde, and trimethyl amine were also significantly reduced using soil as a filter. The tests provide technical information for planning of industrial-scale soil filters: linear velocity, bed depth, properties of soil, reliability, and effects of soil deodorization on various types of odorous substances. It is concluded that the soil can be an effective filter to remove noxious and malodorous gases derived from industrial processes.

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

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

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

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

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

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

Notes: Abstract. An equation is developed to permit temperature correction (to some chosen reference temperature) for field-based soil columns that measure the depletion of nitrate in the water column above a soil layer where denitrification occurs. The derivation is based on the assumption that the overall nitrate depletion is diffusion controlled by the nitrate flux from the water column into the soil and the soil denitrification obeys Michaelis-Menten kinetics. The expression is tested on results from a large soil column maintained in a greenhouse where natural temperature cycling occurred.

Notes: Abstract. Nitrate leaching was measured over the eight drainage seasons spanning the nine years from 1990–1998 on the 157-year old Broadbalk Experiment at Rothamsted, UK. The weather pattern of two dry, three wet and three dry years was the dominant factor controlling nitrogen (N) loss. Both the concentration of nitrate in the drainage waters and the amount of N leached increased with the amount of N applied, mostly because of long-term, differential increases in soil organic matter and mineralization. On average, losses of N by leaching were 30 kg ha−1yr−1 when no more than the optimum N application was applied and were typical of amounts leached from arable land in the UK. Losses increased significantly in both amounts and as the percentage of N applied for supra-optimal applications of N and from autumn-applied farmyard manure (FYM). Extra spring-applied fertilizer was very effective at increasing yields on plots given FYM in the autumn but at the expense of leaching losses three times those from optimum fertilizer N applications. Losses increased after potatoes because they left significant amounts of mineral N in the soil, and decreased after forage maize because it used applied N more effectively. Losses measured 120 years ago from identical treatments were 74% greater than current losses because of today's larger yields and more efficient varieties and management practices. Average concentrations of nitrate in drainage waters did not exceed the EU limit of 11.3 mg NO3-N l−1 until supra-optimal amounts of N fertilizer (〉150–200 kg ha−1yr−1) were applied in spring or FYM was applied in autumn. However some drainage waters from all plots, even those that have not received fertilizer for 〉150 years, exceeded the limit when rain followed a dry summer and autumn. Nitrate leaching into waters will remain a problem for profitable arable farming in the drier parts of Eastern England and Europe despite increased N use efficiency.

Notes: Book reviewed in this articles: Modelling Soil-Biosphere Interactions. By C. Müller

Notes: Abstract. The soil sequestration components of recent estimates of the carbon mitigation potential of UK agricultural land were calculated on the basis of a percentage change to the soil carbon stock present in the soil. Recent data suggest that the carbon stock of soil in UK arable land has been overestimated, meaning that potential soil carbon sequestration rates were also overestimated. Here, we present a new estimate of the carbon stock in UK arable land, and present revised estimates for the carbon mitigation potential of UK agricultural land. The stock of soil organic carbon in UK arable land (0–30 cm) is estimated to be 562 Tg, about half of the previous estimate. Consequently, the soil carbon sequestration component of each mitigation option is reduced by about half of previously published values. Since above-ground carbon accumulation and fossil fuel carbon savings remain unchanged by these new soil carbon data, options with a significant non-soil carbon mitigation component are reduced by less than those resulting from soil carbon sequestration alone. The best single mitigation option (bioenergy crop production on surplus arable land) accounts for 3.5 Tg C yr−1, (2.2% of the UK's 1990 CO2-carbon emissions), whilst an optimal combined land-use mitigation option accounts for 6.1 Tg C yr−1 (3.9% of the UK's 1990 CO2-carbon emissions). These revised figures suggest that through manipulation of arable land, the UK could, at best, meet 49% of its contribution to the EU's overall Kyoto CO2-carbon emission reduction target (8% of 1990 emissions), and 31% of the greater target accepted by the UK (12.5%). Even these reduced estimates show a significant carbon mitigation potential for UK arable land.

Notes: Abstract. Nitrogen losses via nitrate leaching, ammonia volatilization and nitrous oxide emissions were measured from contrasting outdoor pig farming systems in a two year field study. Four 1-ha paddocks representing three outdoor pig management systems and an arable control were established on a sandy loam soil in Berkshire, UK. The pig management systems represented: (i) current commercial practice (CCP) - 25 dry sows ha−1 on arable stubble; (ii) ‘improved’ management practice (IMP) - 18 dry sows ha−1 on stubble undersown with grass, and (iii) ‘best’ management practice (BMP) 12 dry sows ha−1 on established grass. Nitrogen (N) inputs in the feed were measured and N offtakes in the pig meat estimated to calculate a nitrogen balance for each system. In the first winter, mean nitrate-N concentrations in drainage water from the CCP, IMP, BMP and arable paddocks were 28, 25, 8 and 10 mg NO3 l−1, respectively. On the BMP system, leaching losses were limited by the grass cover, but this was destroyed by the pigs before the start of the second drainage season. In the second winter, mean concentrations increased to 111, 106 and 105 mg NO3-N l−1 from the CCP, IMP and BMP systems, respectively, compared to only 32 mg NO3-N l−1 on the arable paddock. Ammonia (NH3) volatilization measurements indicated that losses from outdoor dry sows were in the region of 11 g NH3-N sow−1 day−1. Urine patches were identified as the major source of nitrous oxide (N2O) emissions, with N2O-N losses estimated at less than 1% of the total N excreted. The nitrogen balance calculations indicated that N inputs to all the outdoor pig systems greatly exceeded N offtakes plus N losses, with estimated N surpluses on the CCP, IMP and BMP systems after 2 years of stocking at 576, 398 and 264 kg N ha−1, respectively, compared with 27 kg N ha−1 on the arable control. These large N surpluses are likely to exacerbate nitrate leaching losses in following seasons and make a contribution to the N requirement of future crops.

Notes: Book reviewed in this articles: Cycles of Soils - Carbon, Nitrogen, Phosphorus, Sulfur, Micronutrients. By F.J. Stevenson & M.A. Cole.

Notes: Abstract. A large soil block was constructed to determine the importance of preferential flow routes compared with matric flow pathways at a pasture site in mid-Devon. The sandy loam soil was well structured and uniform. The soil block measured 5 m×3 m×1 m and was instrumented with an array of 54 tensiometers, TDR wave guides and suction samplers connected to an in situ chloride analysis system. Four steady state irrigation experiments were conducted with a range of rainfall intensities. During each experiment chloride and nitrate tracers were applied and the patterns of movement were observed. Although the application of tracer was uniform and the soil was relatively homogeneous, there was large variability across the block in terms of time taken to reach the peak concentration (TPC) and the peak concentration itself. About 44 samplers operated at the greatest intensities (10–2 mm h−1) and only 35 at the smallest (1 mm h−1). No relationship was found between TPC and depth. The fastest TPC and largest concentrations were associated with the greatest rainfall intensities. Relative importance of the individual water pathways was a function of soil heterogeneity: parts of the soil block were highly active with several pathways having short TPCs and conductivities in excess of 4 m day−1 whereas other areas had longer TPCs and conductivities of 1–2 m day−1. The pattern was also dynamic, with conductivities of the pathways changing through time, though most of the faster pathways maintained their greater conductivities for more than one year.

Notes: Abstract. There is a need to develop sustainable nitrogen (N) management systems that minimize environmental losses by maximizing the use efficiency of applied fertilizers, particularly with wide-row annual crops that are often poor at utilizing N. A key approach is to match nitrogen supply with crop demand using improved methods of fertilizer application and timing. One technique is to target liquid ‘starter’ fertilizers close to the seed, or around the roots of transplants, and to omit or reduce conventional broadcast applications. This paper examines the effects of starter fertilizer combined with various rates of seedbed and/or top-dressed N on the growth and yield of bulb onion (Allium cepa L.), crisp lettuce (Lactuca sativa L.), forage maize (Zea mays Bonaf.) and sugarbeet (Beta vulgaris L.). Starter fertilizer improved early growth and, in combination with reduced rates of supplementary N, gave yields comparable with higher rates of base N with each crop, except sugarbeet. The use of top-dressed N was as effective as base N in supplementing starter fertilizer and had the benefit that it allowed a top-dressing requirement to be estimated accurately using a simple nitrogen balance equation. These results, taken with earlier work, show that starter fertilizers offer clear opportunities for reducing N inputs, while maintaining yield and quality of these crops.

Notes: Abstract. This paper describes the results of laboratory-based research which investigated the losses of the herbicide, isoproturon, and a non-adsorbing solute, bromide, from topsoil aggregates under high (7 mm h−1 and low 2.7 mm h−1) intensity simulated rainfall. The structures of the micro- and macro-aggregates from a clay soil of the Denchworth Series (from Wytham, Oxfordshire, UK) were observed using a scanning electron microscope, and the slaking of the topsoil aggregates was also investigated in order to provide a context for interpreting the experimental results. The topsoil at Wytham was found to have a bimodal structure with small microaggregates of 0.71 to 1 mm diameter clustered together to form larger macroaggregates of up to several centimetres diameter. Selected aggregates were air dried and then repacked in Buchner funnels to several centimetres depth in order to remove variability in the experimental results due to the effects of surface microrelief. Under saturated surface conditions high intensity simulated rainfall was less efficient at removing both non-adsorbing and adsorbing solutes from the repacked topsoil aggregates than low intensity rainfall. The observed decrease in the concentration of isoproturon and bromide in the leachate with time could be explained by a transport non-equilibrium effect.

Notes: Abstract. There is increasing evidence that phosphorus has been accumulating in the surface horizons of agricultural soils to the extent that some soils represent a potential diffuse source of pollution to surface waters. The relationships between equilibrium phosphorus concentration at zero sorption (EPC 0) of soil and a number of soil physicochemical variables were investigated in the surface layers of arable and grassland agricultural soils sampled from the Thame catchment, England. Soil EPC0 could be predicted from an equation including soil test (Olsen) P, soil phosphate sorption index (PSI) and organic matter content (OM) (R2=0.88; P〈0.001) across a range of soil types and land use. The simple index Olsen P/PSI was found to be a good predictor of EPC0 (R2=0.77; P〈0.001) and readily desorbable (0.02 m KCl extractable) P (R2=0.73; P〈0.001) across a range of soil types under arable having soil organic matter contents of 〈10%.

Notes: Abstract. Emissions of N2O were measured from different agricultural systems in SE Scotland. N2O emissions increased temporarily after fertilization of arable crops, cultivation of bare soil, ploughing up of grassland and incorporation of arable and horticultural crop residues, but the effect was short-lived. Most of the emission occurred during the first two weeks, returning to ‘background’ levels after 30–40 days. The highest flux was from N-rich lettuce residues, 1100 g N2O-N ha−1 being emitted over the first 14 days after incorporation by rotary tillage. The magnitude and pattern of emissions was strongly influenced by rainfall, soil mineral N, cultivation technique and C∶N ratio of the residue. Comparatively large emissions were measured after incorporation of material with low C∶N ratios. Management practices are recommended that would increase N-use efficiency and reduce N2O emissions from agricultural soils.

Notes: Book reviewed in this articles: Nutrient Disequilibria in Agroecosystems Edited by E.M. Smaling, O. Oenema & L.A. Fresco

Notes: Abstract. The effects of pig slurry applications to a hydrologically isolated field treatment plant (at Solepur) were studied over a period of eight years. Thirty repeated doses, averaging 160 m3 ha−1 were applied from April to October of each year (1991–1995), to reach a total application of 4930 m3 ha−1. All slurry samples were analysed for their total solids (TS), macronutrient (C, N, P, K, Ca) and micronutrient (Cu, Zn) content. In total, 284 tonnes of total solids (57 t TS ha−1 yr−1), 115 tonnes of carbon (23 t C ha−1yr−1), 24.5 tonnes of nitrogen (4900 kg N ha−1 yr−1), 7964 kg of phosphorus (1593 kg P ha−1 yr−1), 16 518 kg of potassium (3304 kg K ha−1 yr−1), 183 kg copper (37 kg Cu ha−1 yr−1) and 266 kg zinc (53 kg Zn ha−1 yr−1) were applied to the soil. Thus, this site provides an opportunity to assess the balance and to examine the long-term behaviour of nutrients under conditions of intensive land application of pig slurries or similar effluents.The main nutrient fluxes through the soil-water system were determined for each element. Over 40% of the total carbon applied was retained by the soil. About 25% of the slurry nitrogen applied remained in the soil profile and 12.5% was leached through the drainage water as nitrate. Most of the slurry phosphorus applied was retained in the soil profile either as P-Dyer extractable (83%), or as total soil phosphorus (112%); 〈0.01% was found in the drainage water. Forty-three per cent of the potassium applied in the slurry was recovered from the soil profile and 15% was recovered in the drainage water. Most of the copper (62%) and zinc (74%) applied in the slurry remained in the soil as EDTA extractractable forms; very low percentages (0.05% and 0.6% respectively) were found in the drainage water.

Notes: Abstract. Volcanic ash soils are generally recognized as soils with excellent and stable physical properties. Here we characterized the porosity and water properties of volcanic ash Andosols and Nitisols from Guadeloupe in contrasting banana systems: (1) perennial crop without mechanization, (2) mechanized and regularly replanted crop. Desiccation from 1 kPa to 1550 kPa moisture tension leads to significant shrinkage in the Andosol, representing a 50% reduction of the void space. The clayey Nitisol exhibited limited shrinkage. Soil clods from the mechanized plots had a significantly smaller macroporosity than that from perennial plots. The soil hydraulic conductivity was also drastically reduced in the compacted layers of the mechanized plots. However, Nitisols appeared to be less affected than Andosols. Laboratory compression tests showed that both soils were susceptible to compaction at soil moisture close to field capacity. The shrinkage properties of the Andosol were due to microaggregation of non-crystalline components upon drying. The relative stability of the macroporosity in the Nitisol was probably related to the presence of stable microaggregates made of halloysite and iron oxide. Two major processes promote soil structure degradation in the Andosol under mechanized banana cropping, surface desiccation and soil compaction. They are both induced by repeated tillage after clearing.

Notes: Abstract. This paper describes a soil classification system developed for agronomists in Cambodia that has proved useful in improving soil fertility management. The classification system relies on soil characteristics that are easily identifiable in the field and have agronomic relevance. The system was used in the on-farm trial programme of the Cambodia-IRRI-Australia Project (CIAP) in 1996 and 1997 to determine whether it could adequately discriminate between soil types and improve fertility management.  Using diagnostic criteria that could be identified in the field, 11 soil groups were defined and subdivided into a further 20 phases. Soil groups were defined as units of morphologically similar soils, which occurred at the same position in the landscape. Classification of soil phases within a soil group was primarily based on soil properties that had significance for crop production, this included information gained from local experience and expertise. A modified version of the Fertility Capability Classification (Sanchez et al., 1982) was added as a third level to allow a more quantitative classification in cases where soil analytical data was available, and to facilitate the transfer of agronomically important soil information from outside Cambodia.  The soil groups adequately predicted differences in grain yields of rice grown on the different soils in on-farm trials and provided the basis for soil-specific management recommendations. Local agronomists have welcomed the system and have incorporated it into their research and extension operations.

Notes: Book reviewed in this articles: Impact of land-use change on nutrient loads fromdiffuse sources. Edited by Louise Heathwaite

Notes: Abstract. A novel agronomic system of soil classification for managing rice soils in Cambodia (CASC) was developed recently. It integrates local knowledge about the soil with its conceptual and taxonomic understanding by soil scientists. Using quantitative soil survey data we evaluated the agronomic efficacy of the classification system. Although the CASC is based on simple field criteria it explained 25 to 44% of the variation in soil prop-erties relevant for agronomic decision making. It failed, however, to differentiate soil types based on pH (6% of variances explained). Despite its simplicity it performed as well or better than the most widely used soil map in Cambodia (Crocker, 1962), and unlike this small-scale soil map it allows classification on a field-specific basis. The average values of soil properties were often significantly different between groups. Organic carbon, clay content and plant available magnesium and calcium contributed most to the discrimination of CASC soil groups. The predictive accuracy when allocating new samples on the basis of quantitative survey data to soil groups of the CASC was 50% to 100%, except for soil groups Kein Svay (0%) and Kampong Siem (20%). The CASC is valuable for managing Cambodian rice soils and may also be used for up-scaling and mapping of soil information.

Notes: Abstract. Broadcast granular fertilizers are inefficient at supplying nitrogen (N) to wide-spaced row crops. Substantial nitrate residues can remain in the soil post-harvest, even when recommended fertilizer practices are followed. This paper explores the benefits of an alternative strategy based on targeting small amounts of liquid nitrogen starter fertilizer close to the seed at drilling to increase N use efficiency and reduce potential pollution. Bulb onion (Allium cepa) and crisp lettuce (Lactuca sativa) were grown with various rates and combinations of ammonium phosphate (AP) and urea ammonium nitrate (UAN) as ‘starters’, in comparison with seedbed incorporated ammonium nitrate. AP consistently improved early growth and final yield of both crops compared to broadcast ammonium nitrate, but UAN showed no additional benefits. AP in combination with broadcast N, or injected UAN, generally increased N recovery, and produced yields of marketable quality produce matched only by much higher rates of broadcast N. A reduced N input system based on starter fertilizers is likely to be acceptable to the industry, but would rely on a method to predict how much N is required to supplement that provided by the starter.

Notes: Abstract. Daily measurements of precipitation and temperature at 82 locations in Denmark for periods of 10 to 43 years, were used for calculation of the impact energy and intensity of rain, climatic erosivity (hereafter called erosivity). The computed erosivity values were analysed for trends and variations in time and space. Analysis of 43 years of data from 6 locations showed a change in the annual distribution of intense (erosive) precipitation, with a tendency to bi-modality, increasing erosivity in September, and decreasing erosivity in August. Amounts of precipitation in autumn have generally increased, but the erosive power of rain has increased even more. The geographic location of high erosivity varied considerably from year to year. Using a simple crop model, the interaction between crop cover and erosivity was investigated. This suggested that changes in climate in combination with changes in cropping and management practice have increased risk of serious erosion over the period 1954 to 1996. We recommend that present and future cropping and management practices be evaluated for risk of adverse interaction with high erosivity events.

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

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

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

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

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

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

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

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

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

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

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

Notes: Abstract. Arable crops in the UK make a large contribution to nitrate leaching by virtue of the land area they cover (〉4.5 million ha). By contrast horticultural crops occupy only a small area (〈 0.2 million ha) but can leach very large amounts of nitrogen. The application of nitrogen fertilizer to arable and horticultural crops is very cost-effective, stimulating its use. MAFF's Nitrate Research Programme for arable and horticultural crops aims to reduce nitrate leaching and maintain productive farming through Best Management Practice. The Programme has led to the development and testing of methods to measure nitrate leaching, the identification of ‘leaky’ crops, soils and practices, and strategies to optimize the use of fertilizer nitrogen. Data have been used to construct and test models of nitrate leaching, which in turn have been used to evaluate the leakiness of potential rotations. Current best practice to minimize nitrate leaching requires measures to improve the efficiency of nitrogen use by crops, combined with measures to protect soil nitrogen from leaching during the late autumn to spring drainage period. This involves consideration of many factors: an appropriate crop variety must be chosen; a green cover must be maintained for as much of the year as is practicable; crops should be drilled early; fertilizer requirements should be calculated using a recommendation system and allowing for soil mineral nitrogen and any manures applied; fertilizers should be spread evenly with a properly calibrated spreader, perhaps using split applications; starter fertilizers and banding of fertilizers should be used where appropriate to reduce losses from vegetables; pest and disease infestation must be minimized; any irrigation must be applied carefully with scheduling. Research is now moving on to study whole farm systems and the interactions between losses of nitrogen and other pollutants to the environment with the aim of minimizing total environmental impact.

Notes: Abstract. A national agri-environmental database and nitrate modelling system has been developed to support the UK government's nitrate policy development. The framework, ‘MAGPIE’, consists of a database and models linked within a Geographical Information System and provides a user interface which allows detailed spatial and statistical investigation of the current state (data and model output) and the impact of changes in conditions or agricultural practice. Data on crops and livestock numbers taken from the annual agricultural census were modified in relation to land cover data derived from remote sensing, and other sources. These data and data on climate, soils and altitude were interpolated to a 1 km grid. The models of nitrate loss were adapted to work with this data set while retaining as far as possible the salient features of the more detailed models and data from which they were derived. The resulting Policy Decision Support System was found to give estimates of mean annual flow and nitrate load for agricultural catchments which matched measured data closely. The system has contributed to work on a number of policy issues both within the UK and in the UK's contribution to international policy development on pollution derived from agriculture.

Notes: Book reviewed in this articles: SOILpak for dryland farmers on the red soil of Central Western NSW 1999. Edited by A.N. Anderson, D.C. McKenzie & J.J. Friend.

Notes: Abstract. A methodology is presented that explores soil survey information at the national level (1:1 M), generating sustainability indicators for wheat cultivation in Uruguay. Potential yields were calculated for simplified crop production situations under several constraints, such as limitation of water availability calculated from soil physical properties and climatic conditions, and limitation of nutrient availability calculated from soil fertility and climatic conditions. Land quality sufficiency was examined by comparing these yields with the constraint-free yield conditioned only by solar radiation, temperature and the crop's photosynthetic properties. Crop growth was simulated only for areas suitable for the defined agricultural use. Model runs were repeated with inclusion of a topsoil loss scenario over 20 years as defined from an erosion risk analysis. Comparison between crop growth simulations for the two situations, gives an indication of the changes in land quality status, which supplies an indicator for agroecological sustainability.On the basis of crop growth simulation it is concluded that wheat production constraints in Uruguay appear to be mainly related to water availability limitations, while nutrient availability is near optimal for the suitable soils. The simulated loss of topsoil impacts most on soil physical properties, expressed in reduced water-limited yields. Soil fertility status, evaluated by change in nutrient-limited yields, was little affected by the scenario.

Notes: Book reviewed in this articles: The Carbon Cycle. Edited by T.M.L. Wigley & D.S. Schimel

Notes: Abstract. After six years of bush-fallow, residual effects on soil productivity of tillage practices prior to the fallow were investigated on an Alfisol in south western Nigeria. In 1996 fallow was followed by maize intercropped with cover crops of Pueraria phaseoloides, Mucuna pruriens or cowpea (Vigna unguiculata) and no intercrop. Parameters measured included soil properties, ground cover, crop growth and yield, rainfall erosivity, runoff and soil loss.In spite of six-years of bush-fallow and establishment of cover crops, soil erosion was significantly greater on plots that had been conventionally cultivated previously using disc ploughs, harrows and mechanical rotovators (1.78 t ha−1season−1) compared to previously no-till plots (1.34 t ha−1season−1). Crop growth and yields were least and soil loss greatest (2.83 t ha−1season−1) on the previous bare plot.Maize grain yield was highest using Pueraria phaseoloides as an intercrop (2.15 t ha−1) followed by a cowpea intercrop (1.92 t ha−1), maize without intercrop (1.87 t ha−1) and Mucuna pruriens intercrop (1.71 t ha−1). The maize grain yields reflected levels of competition from the cover crops. Cowpea–maize intercrop may be most suitable for farmers because maize yields were satisfactory and cowpea grain serves as additional subsistence. Cowpea yields were 390 kg ha−1. Soil erosion was also moderate using cowpea as an intercrop (1.71 t ha−1season−1). However, Pueraria phaseoloides gave the best erosion control with a soil loss of 1.34 t ha−1season−1.

Notes: Abstract. Composted domestic waste was applied either as a mulch or was incorporated into the topsoil. Mulching reduced the seasonal midday soil temperature ranges from between 14 °C and 27.5 °C to between 14 °C and 26 °C, averaging a 0.6 °C fall. However, at sub-optimal temperatures for maize production under the temperate conditions of South East England, the difference may be critical. Compost mulch also improved soil-water conservation in an average year, but not in a very dry year. Compost application increased soil-available N, but increased K uptake was considered to be more important for crop yield than either N additions or the effect on retained soil water. Overall, compost applied as a surface mulch, or incorporated into medium-textured soils in the south and east of England increased crop yield.

Notes: Abstract. A five year field experiment was conducted to assess the influence of crop rotation and field pea residue incorporation into the soil on maize yield. The data indicated a 30% increase in maize yield grown in rotation with field pea compared to when it was grown after wheat and a further increase of 35% when field pea residues were incorporated into the soil. The effect of field pea and residue incorporation was greater in the presence of fertilizer nitrogen indicating the enhanced capacity of the crop to utilize N from the residue. Legume residue management in sub-tropical regions of the world, having coarse textured soils low in organic matter, could help to increase the yield of cereals besides saving some of the expensive fertilizer input.

Notes: Abstract. Land requirements for Pinus halepensis Mill. growth were studied in thirty plots of a 40 year-old plantation in the semiarid Lower Ebro valley, northeast Spain, by comparing site index values to land characteristics. Site index at 40 years ranges from 4.1 m to 12.3 m. Moisture availability is the basic requirement for growth while nutrient availability has only a minor influence. Changes in moisture availability in the area are controlled by changes in soil rootable depth, with a minor effect of aspect. Soils developed on Tertiary gypsum rock are not suitable for afforestation with this species. Geomorphic and soil information may be combined, at various degrees of detail, to provide reliable estimates of Aleppo pine growth.

Notes: Book reviewed in this articles: Urban soils—Applications and Practices. By P. J. Craul

Notes: Book reviewed in this articles: Managing Soil Fertility for Intensive Vegetable Production Systems in Asia By Morris, R. A. (ed.).

Notes: Abstract. Diffuse soluble reactive P (SRP) & total P (TP) loads from over 50 major river catchments in Northern Ireland were predicted using an export coefficient modelling approach. Phosphorus export coefficients for each CORINE land cover class, derived from satellite imagery, allowed the prediction of P loads from a breakdown of the CORINE land cover classes by catchment using a GIS. This approach was validated using observed P loads calculated from flow and concentration data. Mean measured Olsen-P concentrations in the soil A-horizon were also determined on a catchment basis. Plots of P loads to the watercourse versus Olsen-P concentrations in the soil showed a breakpoint around 22 mg Olsen- P l−1 for both SRP & TP data. Below Olsen-P concentrations of 22 mg l−1, SRP & TP losses were essentially independent of Olsen-P at 0.28 and 0.63 kg P ha−1 yr−1, respectively. Above Olsen-P concentrations of 22 mg l−1, there was considerable spread in the P loss data. Nevertheless, significant upward trends in SRP and TP losses to watercourses were detected with increasing Olsen-P at a rate of approximately 0.5 and 1.0 kg P ha−1 yr−1, for SRP and TP respectively, for each 10 mg l−1 increase in Olsen-P.

Notes: Abstract. The paper highlights the advantages of modelling to simulate dynamic processes and to couple environmental data more closely with effects on crops. The CERES-Maize crop model and the DSSAT software package were selected for the work and the region of the Triângulo Mineiro in the state of Minas Gerais was selected as the study area. The results showed that there are differences in the potential production of the Latosols of the Triângulo Mineiro and this should be taken into account when extrapolating or transferring technology for other regions within the same cerrado ecosystem of central-west Brazil. It is essential to improve the number of points with weather data collection since, as demonstrated for Frutal, the climate of the Triângulo can determine differences in potential agricultural production as well as risk for production. The study showed that the use of crop models can improve land suitability evaluations, for land use planning, or establishing strategies for rural funding.

Notes: Abstract. The catchment simulated comprises 57 hectares of heavy clay soil managed as six arable fields. Mole and pipe drains carry surplus water into two ditches, one feeding into the other. Their combined flow was passed through a flume with an automatic water sampler, samples from which were analysed for nitrate. Measurements of nitrate concentration made during periods of water flow from 1990 to 1993 were simulated using a model comprising sub-models for leaching, mineralization, nitrogen uptake by crops and subsoil denitrification. The simulations were plotted against the measurements. For statistical evaluation, the correlation coefficient was used to assess the degree of association between the measurements and the simulations and the mean difference to assess the agreement. The correlation between the simulations and the measurements was significant in two of the three seasons, but the mean difference was significant in all three. However, taking all three seasons together gave a very highly significant correlation and a non-significant mean difference.

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

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

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

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

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