ALBERT

Notes: Abstract. Soils and land use in the Atlantic Zone of Costa Rica were mapped independently at a scale of 1: 100000. At this scale, mapping units are often composite, both in terms of soil type and land utilization type. Combinations of given soil and land utilization types were produced by overlaying the soil and land use maps, on which there was 63% coincidence of unit boundaries. Each combination of land unit and land use was evaluated in terms of bio-physical potentials. From expert judgement land use was shown to be (a) in balance with the use potential, (b) exceeding the use potential (‘over-use’) or (c) less than the use potential (‘under-use’). 18% of the area is over-used, in non-sustainable forms of land use, but 51% is under-used and could be put to more demanding types of land use.

Notes: Abstract. Regression equations successfully allowed the calculation of water retained at—0.3 × 105 Pa and–15 × 105 Pa matric potentials from single soil characteristics, such as bulk volume or clay content, in clayey horizons derived in similar ways from a single parent material. It is possible to use these regression equations on other soils with similar clay fabrics. The fabric is expressed numerically using the pore volume associated with clay particles.

Notes: Abstract. The impact of lead shot on soils and crops was examined at a clay pigeon shooting site in northern England. Topsoil cores were collected along a 300 m transect from the shooting range, and the numbers of lead shot pellets per soil core, total and ‘plant-available’(0.5m acetic acid extractable) lead concentrations, organic matter content, pH and cation exchange capacity were determined. The number of oilseed rape plants and their stem diameters were recorded in 1 m2 quadrats placed at the soil sampling locations. Total and ‘plant-available’ lead concentrations in the soil were most but plant numbers per m2 and mean stem diameters were least in the area of greatest lead shot deposition. Total lead concentrations in the soil commonly exceeded 5000 mg/kg; these are considerably greater than threshold ‘trigger’ concentrations proposed by the Department of the Environment, above which soils are considered to be contaminated and warrant further investigation. Concentrations of lead in the oilseed rape plants themselves were also largest in the area of most intense lead shot deposition; in root samples the lead concentration exceeded 400 mg/kg. The management and remediation of contaminated soils at the clay pigeon shooting site are discussed.

Notes: Abstract. Nepal is facing a serious problem of being unable to maintain soil fertility in agriculture and forestry. Land use practices initiated over the past 10–15 years have resulted in insufficient nutrient inputs, while biomass use and production have increased. Changes in forest soil fertility have resulted from intensive use of forest biomass for animal feed and collection of forest litter for use in agriculture. The agricultural fertility changes have resulted from intensifying annual crop rotations from 1.5 to 2.5 crops and insufficient inputs. The removal of biomass from the forest has curtailed the natural organic cycle by virtually eliminating nutrient inputs.The soils are very acidic and have little C, N, P and exchangeable bases, but have large amounts of active iron. Basic nutrients are not sustained in agriculture and differences in inputs and management between irrigated and rainfed agricultural systems are becoming visible. Irrigated fields show the largest cation content because of input from irrigation water. Rainfed agricultural sites, which receive the most nutrients (fertilizers and manure), have the highest pH values and C and N contents. All soil fertility conditions are marginal and put into question the long-term sustainability of current levels of production. Alterations in the cropping intensity are needed and the introduction of nitrogen fixing trees and crops seems to be the most viable option towards sustainability.

Notes: Abstract. Rooting depth, watertable depth and oxygen regime were measured in plots of Sitka spruce, lodgepole pine and a 50% mixture of each species planted on a deep unflushed blanket peat. The water-table was about 10 cm deeper and roots occurred about 2 cm deeper under the pine than under the spruce or the mixture. In addition the mean concentration of oxygen at 50 cm depth was significantly larger under the pine and the mixture than under the spruce, showing that the rapid early growth of the pine had started to dry the peat. There was no evidence of any improvement in the growth of the spruce in the mixture compared to the pure Sitka spruce, suggesting that the expected nursing benefit had not occurred.

Notes: Abstract. The effect of organic matter content and other soil properties on soil erosion in the Rogate area, West Sussex, UK, was assessed using a rainfall simulator. Thirty soil samples (Podzols, Brown sands, Brown earths, Alluvial gley and Podzolized brown sands) collected from eroded and uneroded fields were exposed to 50 mm/h and 70 mm/h simulated rainfall. The results show that organic matter content influences soil erosion, through its effect on the stability of aggregates.

Notes: Abstract. Soil hydraulic conductivities are frequently required for process-based modelling of the soil water regime. Field-saturated hydraulic conductivity was measured with the Guelph permeameter in 10 soil series with a range of structures and textures. The permeameter offers a range of options for calculating conductivities depending on soil conditions, particularly homogeneity of pore distribution within each horizon. However, even horizons described as massive or apedal were not sufficiently homogeneous to satisfy the boundary conditions entirely.Hydraulic conductivities were calculated by the one head, fixed α* procedure; α* is an index of capillarity. No direct correlations were found between hydraulic conductivity and land use. However, the average hydraulic conductivity of coarse textured topsoils which were mainly under arable agriculture was less than that of the finer textured topsoils largely under grassland. Even limited structural development increased the hydraulic conductivities of fine textured, compact subsurface horizons. It is important to match the adopted procedure to the soil conditions both during the determination of flow rates in the field and in the subsequent analyses.

Notes: Abstract. Analysis of agro-climatic conditions forms the first stage of physical land evaluation. Monthly rainfall, potential evapotranspiration and air temperature data are analysed by the agro-climatic module of the Jamaica Physical Land Evaluation System (JAMPLES). Dependable rainfall (R75), the minimum amount exceeded in a given time period in 75% of the years, ranges from 537 to 5332 mm/yr at the 141 recording stations under review, and mean potential evapotranspiration (PET) ranges from 1120 to 1580 mm/yr. Annual R75/PET ratios range from 0.3–5.0 island-wide and regional differences permit delineation of four ‘moisture availability’ zones. These are subdivided with respect to the length of the ‘dependable’ growing periods (DGP) and dry periods. The DGP is less than 2 months in the southern coastal plains and 12 months long in the north-eastern part of the island. Mean daily air temperature decreases from 26 to 13°C with elevation, permitting the delineation of five temperature classes. Suitable regions for growing particular crops can be determined with the Jamaica Geographical Information System (JAMGIS), which includes a digitized version of the 1:250000 map of agro-climatic zones. More specific land suitability assessments, taking soil conditions and feasible land management practices into account, are prepared with the physical land evaluation module of JAMPLES.

Notes: Abstract. Crop responses to applied potassium fertilizers are erratic in many arid and semi-arid soils. The potassium supplying potential of river-bed sediments and release of interlayer potassium from eleven alkaline soils were measured in two separate experiments. Sediments from the Chenab and Ravi Rivers in Pakistan were exhausted of potassium by successively growing wheat, maize, mungbean, and wheat in them for a total of 200 days, using Hoagland solution to supply optimum amounts of other nutrients. Cumulative plant dry matter yield was significantly greater on the Chenab sediments. The quantities of potassium supplied to plants from the sediments of the two rivers were also significantly different.Interlayer potassium was extracted for 1230 minutes from a Udic Haplustalf (Pindorian series) by twelve different solutions each with the same electrolyte content (100 cmol). The sodium adsorption ratios (SAR) of the solutions were adjusted to 5, 10, 25, and 50, each with Ca: Mg ratios of 25:75, 50: 50 or 75:25, using solutions of sodium, calcium and magnesium chloride. The potassium released from the soil was inversely related to solution SAR. Increasing proportions of magnesium relative to calcium in solution favoured the release of potassium, except in the SAR 50 solution. Significantly different quantities of potassium were extracted by various solutions. Maximum potassium (442 mg/kg) was extracted by SAR 5 solution with a Ca: Mg ratio of 25:75. Interlayer potassium subsequently removed by this solution from 11 alkaline soils ranged from 407 to 499 mg/kg. The potassium released from all but three of the soils was related to their clay content (r= 0.72; n= 8). The release of potassium from the soils followed the Elovich function. The intercept (X1) and slope (X2) estimated for the function was related to potassium released (y) by the equation: y=−1.13 + 2.74X1−0.014X2 (r= 0.998; n= 8)The results imply that river sediments treated with irrigation water containing magnesium and sodium ions can contribute substantial amounts of available potassium for plant growth.

Notes: Abstract. Dryland salinity in the Mt Lofty Ranges, South Australia has developed as a result of native vegetation being replaced with pastures that use less water. Groundwaters have risen and mobilized ions (sodium, chloride, sulphate and iron) stored within deeply weathered micaceous sandstones and schists. Salinity resulting from sodium chloride is common in agricultural catchments around Australia, but saline sulphidic soils (with sulphate and iron) have only been studied in South Australia. Salinity is also associated with waterlogging and secondary sodicity. The amelioration of dryland salinity and waterlogging involves management of whole catchments, not just the area that is currently saline. It is imperative that all processes operating in saline catchments and their interactions are clearly understood.Salinity, waterlogging, sodicity, sulphidization and water erosion were studied in four saline sub-catchments in the Mt Lofty Ranges. Grey (bleached) and yellow mottles (iron depletions) or black and red stains (iron concentrations) develop under certain conditions of water saturation, salinization, sulphidization, sodification and water erosion in surface and subsurface horizons. The amounts of these diagnostic features were used to develop a farm planning key for managing saline catchments in the Mt Lofty Ranges. Using soil diagnostic features, soil-water processes in saline catchments are easily identified by farmers and land managers. Management options (e.g. fencing, tree planting and drainage) are then targeted to specific soils and can be easily incorporated by agricultural advisers into farm management plans. We recommend that soil diagnostic features which help predict the onset of land degradation be used in the production of land capability maps for farm planning purposes.

Notes: Abstract. Studies have been made of the effects of 15 g N/m2 as urea in two dressings during April and June on annual nutrient fluxes in runoff from reseeded blanket bog also receiving annually 6 g P/m2 as granular superphosphate and 6 kg K/m2 as potassium chloride. Urea applications increased significantly (P 〈 0.05) the mean annual ammonium-N flux from 17 mg/m2 for the P + K plots to 245 mg/m2 for the N + P + K plots. Annual fluxes of total P, K and Ca were also increased (P 〈 0.05) by the addition of urea. This was attributed to the effects of increased acidity around grass roots following N uptake as ammonium-N. In contrast, nitrate-N was removed from rainwater throughout the year and concentrations in runoff were at the limit of detection (〈 0.01 mg/1) on many occasions. Concentrations of organic-N in runoff exceeded those of ammonium-N, but were not significantly changed by fertilization.

Notes: Abstract. Biophysical and economic data from numerous sources are integrated using the ALES expert system. A systematic approach to data collection and evaluation procedure is presented. The collection of management data is emphasized if management and crop yield data are to be adequately correlated. Different land utilization types are evaluated for numerous land mapping units. The results show that direct comparison of land mapping units is possible both within and between different land utilization types. Use of the model enabled objective relationships to be developed between biophysical criteria, crop productivity and management, allowing economic measures of performance to be routinely determined for large databases. The study shows that land mapping units with the most favourable physical suitability class may not necessarily have the largest net return and that the best lands are determined not only by their ability to produce high yields but also their ability to achieve them at the least cost.

Notes: Abstract. Little is known about the in situ hydrological properties of Zimbabwean soils. This paper describes the water retention and transmission properties of two agriculturally important Zimbabwean fersiallitic soils measured in situ by the instantaneous profile method. The first soil, typical of those used by small scale farmers, is a deep coarse grained granitic sand. The second is a silty clay loam derived from mafic rocks, typical of the red clays associated with Zimbabwe's commercial farming areas. The K-θ functions for each layer of the sand were very similar and the profile could be described by a single function, with permeability increasing with depth. In contrast, the silty clay loam could not be described by a single function, as permeability decreased with depth. However, in both soils water movement became negligible below a matric potential of—0.01 MPa; this is thought to be a more appropriate field approximation of the upper limit of plant available water than—0.033 MPa which is often used for tropical soils.

Notes: Abstract. The effect of Medicago arborea on erosion on a burnt area was studied in experimental plots near Valencia, Spain, between 1989 and 1992. Its growth and development was studied, and its effect was compared with the natural vegetation (matorral) and bare soil. Medicago decreased soil loss by 41.7% and runoff by 25.7% compared with bare soil. However, under natural vegetation soil loss was 27.5% less than under Medicago.

Notes: Abstract. Microbial transformations and chemical distribution of N were compared in two upland stagnohumic gley soils at the same site. In 1981 one soil was improved for more intensive agriculture by lime and fertilizer applications and reseeding with a grass/clover mixture. The other soil (referred to here as unimproved) was also reseeded in 1981, but no lime was added and the sward has subsequently reverted to rough grazing land. Improvement resulted in greater soil microbial activity. The improved soil showed greater rates of denitrification, net N immobilization and N fixation (acetylene reduction) and contained more microbial biomass N than the unimproved soil. However, no major differences in the distribution of organic N fractions were detected. This indicates that a large amount of the soil N present before improvement did not undergo mineralization and remained unavailable to plants.

Notes: Abstract. Sisal production in Tanzania has declined sharply in the past two decades because of a decrease in the area grown and a decrease in yields. As sisal is cultivated without manuring, depletion of soil fertility is considered one of the main causes of the declining yields. This paper presents a balance of the macronutrients N, P, K, Ca and Mg for sisal grown in a plantation in NE Tanzania on deep, red clay soils (Ferralsols). Annual fibre yields declined from 2.5 t/ha in the 1960s to about 1 t/ha in the 1980s. Hybrid sisal is a demanding crop and in ten years, with a total fibre yield of 11 t/ha, about 260 kg of N, 40 kg of P, 385 kg of K, 890 kg of Ca and 330 kg of Mg are removed in the harvested leaves. A comparison of soils after two and three 10-yr cycles of sisal production showed that in the third cycle the pH decreased by 0.5 units and that exchangeable bases were decreased by fifty per cent or more. The amounts of K, Ca and Mg removed from the soil were similar to those in leaves. However, soil analyses could not detect changes in total N and available P, possibly because of the large amount of total N in the soil and the lack of precision in the N and P analyses. In the Ferralsols, potassium is likely to become deficient first, followed by magnesium and calcium. The soil has little available P, and an increase in soil acidity may decrease it further and also create aluminium and manganese toxicities. In order to maintain sisal production, fertilization with P, K, Ca and Mg is necessary, and to improve yields N must also be applied.

Notes: Abstract. Analyses of soil and hay samples collected from the Park Grass Experiment at Rothamsted during the last 137 years indicate slow but significant increases in KCl- and EDTA-extractable aluminium in soil and a sudden and very large recent increase in the concentration of aluminium in the herbage. The latter is associated with a sudden increase in the rate of acidification of the soil over the last 10–15 years and the mobilization of aluminium as the soil enters the aluminium buffer range -a Chemical Time Bomb. Such severe acidification from atmospheric inputs on a well-buffered soil illustrates how quickly an apparently stable situation can change as a result of acid deposition. It highlights the need to protect soils and plants from the effects of acidification by decreasing acid inputs or by liming.

Notes: Abstract. The aggregate stabilities of a soil restored after opencast mining and an undisturbed soil were measured over a complete cropping year from the time of ploughing a grass ley in autumn. This was to examine the effects of various post-restoration cropping regimes on soil aggregate stability and soil porosity. A wet sieving technique and a mild dispersion method were used to determine indices of soil macro- and micro-aggregate stability, respectively. Air filled porosity at field capacity and crumb porosity were also determined. Removal, storage and restoration decreased macro- and micro-aggregate stability. After restoration, the different grass managements i.e. cutting for silage and grazing, had similar effects on soil aggregate stability and maintained greater aggregate stability than the arable regimes. The pattern of fluctuation in soil macro-aggregate stability over the year was similar under all crops at both sites, but at the restored site there was a decline in stability, and differences in the air filled porosity at field capacity developed between cropping regimes. Micro-aggregate stability was less at the restored than at the undisturbed site and showed no seasonal variation or difference between cropping regimes. However, a difference in crumb porosity between cropping regimes did develop.

Notes: Book reviews in this article: Soil organic matter dynamics and sustainability of tropical agriculture. Edited by K. Mulongoy & R. Merckx. World soil erosion and conservation Edited by D. Pimental. Fundamentals of soil behaviour (2nd edition) By James K. Mitchell.

Notes: Abstract. The effect of ploughing on the vertical and horizontal distribution of 137Cs was investigated at two fields in Bavaria from 1987 to 1991. Soil samples from four layers in eight plots along a transect were taken in each field after each ploughing and harrowing. Total activities and activity concentrations were evaluated separately for 137Cs derived from Chernobyl and from global fallout of weapon testing. In 1987 137Cs from global fallout was already well mixed in both fields because of the long residence time in the soil. 137Cs derived from Chernobyl, however, was distributed rather inhomogeneously in vertical as well as in horizontal directions. The coefficient of variation of the vertical activity concentrations within the Ap horizon decreased continuously from the first to the fourth ploughing, in one field by a factor of five. The number of ploughings necessary to attain a uniform vertical distribution of Chernobyl-derived caesium was three and four in the two fields. Along the transects inhomogeneities caused by the spatial variability of the deposition of radiocaesium during the Chernobyl fallout were not removed by ploughing.

Notes: Abstract. The influence of conventional and soil-specific management on leaching and runoff losses of soil-applied alachlor (2-chloro-2′,6′-diethyl-N-(methoxymethyl) acetanilide) was studied across a soil catena (landscape) with varied slope and drainage characteristics. The catena consisted of: a well-drained Ves (fine-loamy, mixed, mesic Udic Haplustoll) soil on the backslope (1–4%), a Ves soil on the sideslope (6–12%), and a poorly drained Webster (fine-loamy, mixed, mesic Typic Haplaquoll) soil on the toeslope (0–3%). In general, the concentration of alachlor in runoff water was greater in the Ves soil than in the Webster. In 1992 alachlor concentrations in runoff (water, sediment + water) were less for soil-specific rates (2.20 or 2.80 kg/ha) than for a uniform rate (3.36 kg/ha) in both Ves soils. There was no significant difference in alachlor concentration related to application rates (soil-specific rate 3.66 kg/ha) in the runoff from the Webster soil. Averaged across soils and events, the concentrations of alachlor in runoff (water, sediments + water) were less for soil-specific rates than for the uniform rate. Alachlor was not detected in soil samples obtained from depths greater than 15 cm in any soil or treatment after the first sampling. At the first sampling in 1992 (7 days after application) alachlor was detected down to 45 and 90 cm in the Ves and Webster soils, respectively. Detectable amounts (≥0.1 μg/1) of alachlor were observed in soil water samples extracted from all three soils during some sampling dates. No particular trends were observed with soils or application rates.

Notes: Abstract. Each year since 1986 information has been collected about the farming systems at intersections of a nationwide 7 km square grid in Denmark. These management data and corresponding soil analyses were used in the model DAISY to simulate water and nitrogen dynamics. The model was validated with respect to harvested dry matter yield and nitrogen content in the soil. Simulated nitrate leaching from farmland areas from 1 April 1989 to 31 March 1993 was related to precipitation zones, soil type, fertilizer strategies and cropping systems. The mean simulated nitrate leaching for the whole of Denmark was 74 kg N/ha/yr, with a large yearly variation in the period considered. The simulated nitrate leached from soils with a sandy subsoil corresponded to 51% of the applied fertilizer, twice that leached from soils with a loamy subsoil. The application of pig manure resulted in average leaching losses of 105 kg N/ha/yr. The simulated nitrate leaching losses at sites where only artificial fertilizer was applied were in the following order: cereal with undersown grass 〈 crop followed by winter cereal or winter rape 〈 cereal or rape without a catch crop 〈 root crops without a catch crop. Where only artificial fertilizers were applied, the simulated mean annual leaching was 59 kg N/ha from spring barley and 40 kg N/ha from winter wheat. A map of simulated nitrate leaching in Denmark was produced using a Geographical Information System.

Notes: Abstract. Physical and chemical properties were compared during 1992 in adjacent bio-dynamic and conventionally managed Haploxeralfs under improved, summer-irrigated pastures in the Goulburn Valley of N.E. Victoria. Intensive dairy production has been practised on both the farms since the early 1950s, and aspects of the bio-dynamic method have been practised on one farm for the past 18 years. Particle-size analysis showed that the soil profiles of each field are derived from similar parent materials. The bio-dynamic soil had greater macro-porosity to a depth of at least 420 mm, lesser soil strength at 60, 120 and 200 mm, smaller dry bulk density values between 120 and 200 mm and larger organic matter content in the upper 50 mm. Volumetric soil water content measured along three transects to a depth of 1.4 m in the summer showed that the bio-dynamic field was drier at depths greater than 200 mm. After heavy rains during the winter, the conventionally managed soil had an air-filled porosity unfavourable for plant roots (2%) at 200 mm depth, whereas the bio-dynamic soil was marginal for root growth (7%). The more favourable physical and chemical properties in the bio-dynamic soil may be attributed to less grazing pressure, longer intervals between irrigations, use of the bio-dynamic horn-manure preparation, intermittent compost applications, less tractor traffic and the encouragement of taller pasture growth.

Notes: Abstract. The effects of deep tillage, straw mulching and farmyard manure on maize growth in loamy sand and sandy loam soils were studied in experiments lasting three years. Treatments included all combinations of conventional tillage (10 cm deep) and deep tillage (35–40 cm deep), two farmyard manure rates (0 and 15 t/ha) and two mulch rates (0 and 6 t/ha), replicated three times in a randomixed block design.Deep tillage decreased soil strength and caused deeper and denser rooting. Mulching decreased maximum soil temperature and kept the surface layers wetter resulting in better root growth. Farmyard manure also improved root growth, and the crop then extracted soil water more efficiently. All three treatments increased grain yield in the loamy sand, but in the sandy loam only tillage and farmyard manure increased yields significantly. Deep tillage and straw mulch effects varied with soil type and amount of rainfall in the growing season. In the loamy sand the mean responses to deep tillage and mulching were largest in a dry year. A tillage-mulch interaction was significant in the loamy sand.

Notes: Abstract. The long-term effects of land clearing methods (manual, shear blade, tree-pusher/root-rake combination, traditional), tillage systems (disc ploughing, mechanized no-tillage, traditional) and cropping systems (annual cropping, alley cropping, graxed pasture) on surface soil physical and chemical properties were evaluated on an Alfisol in south-western Nigeria ten years after land clearing. Long-term soil physical degradation was greatest after mechanized land clearing or tillage systems. The erosion resulting from soil compaction with mechanized land management systems resulted in exposure of subsoil. Cropping system had no significant effect on soil physical properties. Alley cropping decreased exchangeable calcium and pH, and increased total acidity mainly through the greater demand for calcium by the hedgerow species. Grazed pasture depleted exchangeable potassium because it was taken up by the grass and exported from the site by the cattle following consumption of the grass.

Notes: Abstract. The laboratory, spatial and temporal components of variation associated with sampling soil for the measurement of pH, organic matter and extractable P, K, Mg, S, Cu, and Co were studied over two years using soil samples from 15 farms in S.E. Scotland. On each farm a selected field was divided into 4–8 sectors, and sampled three times each year, in June, August and October, by bulking 25 cores taken in a ‘W’ pattern. Analysis of variance showed that inter-field variation was greater than that between sampling dates for most of the properties measured. Restricted Maximum Likelihood Estimation showed that for all elements except K and S the variation between fields was greater than that within a field. Temporal variation was usually smaller than spatial, but K and Co showed similarly small temporal and spatial variations. Variation associated with laboratory procedures was much less than either spatial or temporal variation except for S, most of the total observed variation of which resulted from laboratory error. It is suggested that the most cost effective field sampling technique is to split a field into sectors, sample each individually and analyse a bulked sample made up from the sectors.

Notes: Abstract. Leaching losses of solutes can be calculated if two variables, the amount of water passing through the soil and the concentration of solute in that water (a flux concentration), are known. Two simple approaches, soil extraction and suction cup sampling, were used to estimate the concentration of solutes in the water moving through a silt loam soil. The results were compared with actual concentrations measured in the drainage water from a sub-surface (mole-pipe) drained soil.Seasonal leaching losses were calculated as the sum of the products of estimated monthly drainage and the estimated average monthly solute concentration in the soil solution. These results were compared with the leaching losses measured in drainage water from the mole-pipe system. For non-reactive solutes such as bromide (an applied solute) and chloride (a resident solute), the suction cup data provided better estimates of the leaching losses than did the soil extraction data. The leaching losses calculated using volume-averaged soil solution concentrations (obtained by soil extraction) overestimated the loss for the resident solute, but under-estimated the loss for the surface-applied solute. On the other hand, the data for non-reactive solutes suggest that measurements on suction cup samples may be representative of the flux concentration of a solute during leaching. For nitrate, a biologically reactive solute, there was no clear pattern in the differences between the estimated and measured leaching losses. The flux-averaged concentration in the drainage water was about midway between those measured in the suction cup samples and in the soil solution.

Notes: Abstract. The variability of five soil series developed in sedimentary formations in southeastern Nigeria and mapped from aerial photographs was investigated in relation to texture, soil reaction, organic carbon, total nitrogen, exchangeable bases, exchangeable acidity, cation exchange capacity and available phosphorus. Air photo delineation of the five soil series was based on terrain physiography alone. Most of the soil series were very variable in available phosphorus, but the coefficients of variation for other soil properties were less than the 33%) threshold adopted for within-series homogeneity critical for land use management. Soil series mapping at 1:50000 scale based on aerial photographs is therefore a cheap, rapid technique, which gives a satisfactory basis for land management to improve productivity and decrease soil degradation in Nigeria.

Notes: Abstract. The presence of spring barley plants increased the numbers of nematodes, particularly of plant-feeders, compared with fallow plots in a Scottish organic farming system. The addition of farmyard manure (FYM) had no detectable effect on nematode populations but poultry manure (PM) caused a considerable increase. The application of PM also altered the types of nematode present and favoured bacterial-feeders and rhabditids in particular. These changes suggest that PM causes shortterm (within a growing season) increases in microbiological activity and nutrient cycling, whereas FYM is more likely to bring about long-term changes.

Notes: Abstract. Topsoil (0–20 cm) and subsoil (60–100 cm) properties are compared at agricultural and nearby natural vegetation sites in São Paulo State. Differences are related to land use and climate, in order to estimate soil carbon storage under various ecosystems and also to study the effects of high-input agriculture on the chemical composition of soils with low activity clays. Within each land use, organic carbon in the topsoil is most strongly related to clay + silt content. This relationship is stronger for cropped, short savannah (cerrado) and tall savannah (cerradão) sites than for semi-deciduous and evergreen forest sites. Losses of topsoil carbon with cropping can be predicted if the initial carbon and the clay+silt contents are known. The greatest carbon losses after long term cultivation occurred in forest mineral topsoils, ranging from 6% for perudic clayey soils to 37% for ustic sandy soils. No significant difference in carbon content was found between the paired savannah-cultivated sites. In most of the originally less fertile soils cation exchange capacity was greater in the cultivated topsoil (Ap) than in the topsoil under savannah or forest (A1), probably because of liming and phosphate fertilization. Most subsoils at agricultural sites show increases in exchangeable bases (mainly Ca) and base saturation, but no significant change in pH.

Notes: Abstract. Bulk and undisturbed block samples of soil were collected from beneath five cricket tables and outfields managed by a local authority and used by local league cricketers. Thin sections made from the undisturbed blocks revealed considerable differences in soil structure and composition between the cricket tables. Topdressings of varying textures have been added to all the tables over the years. Texturally-layered profiles have built up beneath three of the tables because the topdressings have not been mixed. Horizontal organic mats often occur within and between the associated platy aggregates. Rooting is shallow under these tables, and the lower compacted layers often contain evidence for restricted drainage at certain times during the year. At one site, and to a lesser extent at another, greater mixing of the topdressings has been achieved by earthworms, but these seem to have been eradicated at the other sites. Although they create a better plant-growing medium, the earthworms seem to have had a detrimental effect on the playing quality of the cricket table.

Notes: Abstract. Nitrate leaching in lysimeters containing a tropical sandy agricultural soil was studied over two summers with maize (Zea mays L.) and one winter season with wheat (Triticum aestivum L.). The treatments included two moisture regimes and two nitrogen sources, cattle manure and inorganic fertilizer-N (either ammonium nitrate or ammonium sulphate) applied at 100 kg N/ha in the summers. Neither manure nor fertilizer-N was applied in the intervening winter. Leachate volume from the manured lysimeters was mostly larger than from fertilized ones because of poor growth and less evapotranspiration. The largest seasonal nitrate loads (17–39 kg N/ha) were obtained in the wet summer immediately after installation of the lysimeters. Nitrate loads in winter (3.7–18.6 kg N/ha) were larger than those obtained in fertilized (0.6 and 9.3 kg N/ha) and manured (0.3 and 3.0 kg N/ha) lysimeters for the two moisture regimes in the second summer. The drier conditions in the second summer decreased N-mineralization and leaching of manure.

Notes: Abstract. Field studies at five locations on farmer's fields irrigated with residual sodium carbonate water (RSC) indicated that gypsum applications at the rate of 100% of the gypsum requirement of soil plus the quantity of gypsum required to neutralize RSC in excess of 4 mEq/1 decreased SAR values, and improved infiltration rate, crop emergence and wheat grain yields. The soil pH decreased by 0.3–0.4 units. Once soils have been ameliorated by this treatment, further small applications of gypsum are needed to decrease the RSC in irrigation water and avoid further soil deterioration.

Notes: Abstract. At Woburn Experimental Farm (SE central England) sulphur (S) deficiency symptoms occurred in a winter oilseed rape crop grown in Lansome field on soil of the Cottenham series, but not on the Blithe series soil in the adjacent Mill Dam Close field. At maturity, the two crops produced a similar amount of dry matter but seed yield and harvest index were significantly less in Lansome. Total S uptake of the crop in Lansome was less than half of that in Mill Dam Close, which was similar to the amount normally found in a S sufficient crop. Both soils are of light texture (loamy sand and sandy clay loam for the Cottenham and Blithe series, respectively), and there was little difference in the extractable S concentration in the topsoils between the two fields. However, more extractable S was found in the subsoil of Blithe series, because it contains more free Fe and Al oxides and has a lower pH. These results show that any evaluation of the soil S supply needs to take into account the pool of available S in the subsoil.

Notes: A slightly modified critical-state model was formulated in order to account for the volume-change behaviour at yield and failure observed in triaxial tests on unsaturated soils. Model parameters were specified for two soils (a sandy loam and a loam), each at three different soil-moisture contents. Maximum shear strain was integrated numerically for 36 cylindrical load paths with constant confining pressure (type I) or constant mean normal stress (type II). Predicted stress-strain relationships for load paths bringing soils from a normally-consolidated to a critical state were compared with stress-strain relationships observed for identical load paths in triaxial tests of the lubricated ends variety.The agreement between predicted and observed maximum shear strain depended on type of load path and soil-moisture content. The model failed to predict maximum shear strain at stress states close to critical. The absolute difference between observed and predicted strain was on average ≤0.05 for deviatoric stresses smaller than 90% of the critical-state values. The comparable maximum differences were 0.11 and 0.07 for load-path types I and II, respectively. The largest differences were found for the largest soil-moisture contents. The type of load path had a considerable effect on sample distortion, type I giving rise to larger (predicted and observed) maximum shear strain at common stress states.

Notes: The Green & Ampt infiltration analysis is applied to the problem of the water uptake by aggregates when they are surrounded by water. Two situations are analysed, namely, when there is free escape of the displaced air and when there is no escape of the air. These extreme situations provide bounds for estimating the water uptake for the practical case when some air escapes through the aggregate's surface in the form of bubbles as the aggregate wets up. It is shown that the rate of water uptake is directly proportional to the square of the sorptivity of the aggregate material and inversely proportional to the square of the final water uptake. Experiments on spherical stabilized clay aggregates of different radii were in agreement with the theoretical analysis that predicted the observed very rapid wetting up. The analysis also showed that when there was free escape of air, the rate of advance of the wetting front into cylindrical and spherical aggregates decreased from an initially infinite value to a minimum value and then increased to an infinitely large value when the front reached the centre of the aggregate, in contrast to the continually decreasing rate into plate-like aggregates. This was demonstrated in experiments on the radial water movement into a fine sand contained in a cone.The analysis and experimental results indicate that preferential macropore flow in aggregated soils can be initiated very rapidly when air entrapment occurs within the aggregates.

Notes: A simple model was employed to interpret the results of a series of measurements of gas diffusion in soil cores. The model divides air-filled porosity into three functional categories: arterial, marginal and remote. Diffusion along the axis of the core occurs through arterial pores; marginal pores do not contribute to axial diffusion; remote pores are isolated from gas transport. Simulations based on the model closely resembled data acquired from real cores. Optimizing the fit between real and simulated data gave estimates of the three functional pore fractions which generally made sense (compaction or wetting of cores resulted in reduced arterial and increased marginal porosities, for example). Dividing the pores into the different classes specified by the model was functionally equivalent (i.e. observable results were identical) to the introduction of a tortuosity factor to represent pore convolution. In order to account for observed diffusion rates in terms of pore convolution alone it is sometimes necessary to invoke implausibly high tortuosities; the introduction of marginal porosity renders this unnecessary without in any way compromising the ability of the model to simulate real diffusion data.

Notes: Assessment of gas diffusivity in situ gives a direct measure of the ability of soils to exchange gas with minimal soil disturbance. A versatile, readily portable probe for measuring the diffusion of a tracer gas through soil in situ is described. The radioactive tracer 85Kr is injected into a cell located at the end of the probe. The change in activity within the cell as the gas diffuses out is measured by a Geiger-Muller tube in the cell. The probe can be used by insertion either directly into an auger hole (buried-probe mode) or into a chamber pushed into the soil surface. A method to simulate diffusion numerically using Fick's equation for both methods of insertion is presented. In the tests reported, diffusivity was estimated by expanding or contracting the time axis of the simulation until it matched the observed count rates. A goodness-of-fit was attached to each diffusivity estimate. The probe was generally effective, giving diffusivities comparable to those measured in the laboratory on cores taken near the cell (buried-probe mode) or linked to the surface chamber. Poor fits were found for some diffusivities measured in the buried-probe mode on coarsely structured soils. These were attributed to non-uniform distribution of porosity and possible upward leakage of tracer when used at shallow depths in the buried-probe mode. However, thein situ diffusivities may be more representative than those measured in cores in the laboratory because of the greater sample volume. We show how the probe can be used to detect soil layers that restrict gas diffusivity and differences in aeration status between tillage treatments.

Notes: The surface structure of many Australian red and red-brown earths frequently collapses (slakes) when dry, disturbed aggregates are wetted by rain or irrigation. The resulting fine matrix sets, on drying, to a strong, cohesive layer of up to 200 mm thick (hard setting). We investigated the mechanism of collapse and the extent to which the structure of aggregate beds Iron hard setting and non-hard setting soils collapsed when wetted by quick flooding or slowly with water at a suction of 200 mm, then drained in sequential steps of increasing suction and finally dried at 40°C. After flood wetting, but before draining, no collapse was observed due to the small effective stress prevalent in the flooded beds.After suction wetting, some collapse was measured owing to the effective stress (approximately 1.4 kPa) from the applied suction. On draining, flood-wetted beds collapsed extensively (volume strain 〉0.20), largely due to the disappearance of large pores (〉75 μm diameter). Suction-wetted beds collapsed less (volume strain 〈0.16) and retained more large pores. Hard setting soils collapsed more following both flood and suction wetting (volume strain 〉0.20 and 0.10, respectively), while non-hard setting soils did not collapse as extensively (volume strain 〈0.16 and 0.09, respectively). Results indicate that the mechanism causing collapse was independent of wetting method and involved two steps: (i) slaking of aggregates on wetting, and (ii) collapse of the aggregate bed on draining as a result of development of effective stress within the beds.

Notes: At the groundwater–surface-water interface the last modification of discharging groundwater takes place. In this study the redox potential was measured in situ in four groundwater discharge areas with a size of 3–4 m2. Three of them were the upper reaches of streams in coniferous forests and one was an alder fen. Measurements were made at different seasons, with 50 and 100 platinum micro-electrodes respectively, in each area. Readings were taken in the upper 30 cm of the soil, at two depths.A method study showed that the electrodes needed a longer equilibrium time than is usually reported. The main finding of this study was the large spatial variation within soils in the discharge zone; regions as small as 10 cm in diameter could have redox potentials covering several hundred mV. It was not possible to identify a seasonal variation due to the large spatial variation. Differences in the distribution of the redox potential with depth may be explained by the structure of the peat affecting flow patterns and the residence time of water.

Notes: The strength of soils is related to structural stability. Aggregate structure which collapses on wetting may set to a hard, consolidated layer on drying (hard setting). This process may be moderated by suction wetting and possibly by application of calcium, but the mechanism of moderation is not clear. We investigated the collapse-strength relationship and the mechanism by which wetting method and calcium act to reduce strength in hard setting and non-hard setting soils. Indirect tensile strength of aggregate beds that had been wetted with water or 10mM CaCI2 by rapid flooding or at a suction of 200 mm, was measured after draining to various suctions and drying at 40°C.The greater the volume strain during wetting and draining, the greater the tensile strength. Beds that were suction wetted, either with water or calcium solution, showed minimal collapse and did not develop high strength on drying. Water-flooded beds had the greatest dry strength while beds flooded with calcium solution developed significantly lower strength. The critical factor determining tensile strength of the beds appeared to be the presence of large (〉75 μm diameter) pores. The greater the volume strain on wetting, the smaller the proportion of larger pores and the greater the tensile strength on drying. Flood wetting caused more loss of large pores and closer packing of particles. Wetting with calcium solution did not affect the degree of collapse compared with that of water alone but did produce beds with larger pores than when wetted with water. Consequently the strength of the calcium-wetted beds was lower.

Notes: We wished to determine whether soil-test P was affected by storing air-dry soil samples at room temperature. The soil samples had been collected from field experiments and air-dried (〈40°C) before measuring soil-test P (bicarbonate-extractable P). The samples were from field plots that had been treated with different applications of fertilizer P (superphosphate, rock phosphate) one or more years previously. Soil-test P was measured on two different sub samples of the same sample: either A, in the year the sample was collected; or B, after the sample had been stored at fluctuating room temperatures either from 2 to 8 years (four field experiments) or 17 years (59 field experiments). The room temperature ranged from 10 to 30°C, and averaged 17°C. The aim was to test whether soil-test P was systematically and consistently different between sub samples A and B.Differences between A and B were mostly small, and there were no consistent or systematic differences. For the Colwell soil test, applied to a range of south-western Australian soils, possible decreases in soil-test P due to continued reaction with the soil could not be detected using bicarbonate-extractable soil P, and storage of air-dry samples at room temperature did not significantly affect soil-test P measured up to 17 years later. We conclude that, provided fertilizer P has had time to react with soil in the field, no further changes in Colwell soil-test P occur during air-dry storage for up to 17 years at room temperature.

Notes: A method for the measurement of Pb and Cd in equilibrium soil solutions involving soil equilibration with a dilute Ca electrolyte, centrifugation and filtration to 〈0.2 μm was evaluated. The procedure was subsequently used for the analysis of 100 Pb- and 30 Cd-contaminated soils. Solutions were analysed for Pb- and Cd using graphite-furnace AAS and the concentrations of Pb2+ and Cd2+ were estimated using standard speciation calculations.The concentrations of Pb and Cd found in the soil solutions were in the range 3.5–3600 μg dmp −3 and 2.7–1278 μg dm −3 respectively; both ranges represented less than 0.1% of the total metal concentration in the soils. Depending on solution pH, Pb +2 accounted for between 42–78% of Pb in solution while about 65% of Cd in solution was present as Cd+2. The concentrations of Pb2+ and Cd2+ in solution suggested that the soil solutions were undersaturated with respect to the solid phases PbC03 and CdC03 but supersaturated with respect to Pb5(P04)3Cl and, for some samples, Cd3(P04)2 respectively. However, for both metals, a good empirical relationship was obtained between the total metal concentration in soil (mol kg−1), free metal concentration in solution (mol dm−3) and solution pH. The relationships took the general form of a pH-dependent Freundlich adsorption equation:〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:13510754:EJSS59:EJSS_59_mu1"/〉For both lead and cadmium relationships, the values ofn and K1 were close to unity, so that the distribution coefficient could be estimated from pH and a single metal-dependent constant, K2. The algorithms appeared to be valid over a metal concentration range of four logarithmic units and pH range of 3.5–7.5.

Notes: The effect of the presence of alpechín, wastewater from the olive-oil industry, on the reaction of three soils with Cd, Cu and Zn is studied. Adsorption of Cu and Zn by all the soils studied, and Cd by one of the soils, is markedly decreased by the presence of high doses of alpechín, while Cd adsorption by the other two soils increases in the presence of the residue. Adsorption of Cu and Zn in the absence of alpechín releases considerably more Ca than the exchangeable contents at a rate of about 0.5-1 moles of Ca for each mole of metal adsorbed, and this rate is decreased in most cases when alpechín is present. The behaviour of Cd with respect to Ca release is less definite. The relationships between solution concentrations and pH show that alpechín increases the mobility of Cd and Cu in the presence of some soils, while in the case of Zn no effect is evident.It is concluded that soil carbonate is the most relevant component involved in Cu or Zn retention, and, in the presence of alpechín, part of the carbonate surface is blocked and becomes unavailable for retention. Formation of soluble Cu complexes is suggested to occur in some cases.

Notes: Perennial legume varieties and ecotypes belonging to the species sainfoin (Onobrychis viciifolia Scop.) and French honeysuckle (Hedysarum coronarium L.) were investigated under different management treatments (two regimes of irrigation, cutting and seeding densities) at the Forage Crops Institute in Foggia, Italy (which has a typical Mediterranean environment) for two seasons, 1990 and 1991. Dry-matter production, seed production and seed yield components were affected more by harvest year and irrigation than by seeding density. Mean increases due to irrigation were 2·8% and 60·6% respectively for dry-matter and seed yield in sainfoin and 35·3% and 32·5% respectively in French honeysuckle. Under both cutting regimes, the higher seeding density was more suitable for sainfoin, increasing stems m−2 with irrigation and seed yield without irrigation. In French honeysuckle the lower seeding density was more suitable for production of inflorescences per tiller and for seed weight without irrigation. Higher seeding density positively influenced seed yield under irrigation. The seed yield components most influenced by irrigation were: 1000-seed weight, seeds per inflorescence and inflorescence per stem. French honeysuckle genotypes were potentially more productive in dry matter and seed yield under both irrigation regimes than the sainfoin, which was more productive in seed yield when cut. The ecotypes of both legumes represent a genetic resource, particularly for seed yield after forage cutting, to be utilized in breeding programmes for developing varieties well adapted to Mediterranean environments.

Notes: The effect of growth regulators on mineral composition of red clover (Trifolium pratense L.) was assessed in two growing seasons, daminozide {butanedioic acid [mono(2,2-dimethylhydrazide)]} or mefluidide [N-(2,4-dimethyl-5{[(trifluoro-methyl)sulphonyl]amino} phenyl) acetamide]] was applied early (mid-May) or late (late May) at low rate [daminozide, 4 kg active ingredient (a.i.) ha−1; or mefluidide, 0·13 kg a.i. ha−1] or twice the low rate (high rate) to an early-flowering cultivar, Florex, and a late-flowering cultivar, Altaswede; the controls were the untreated cultivars. Red clover was deficient in S, but all other minerals were present in sufficient amounts for productive cattle. The first cutting showed increases in P and Zn contents after an early application of daminozide, Cu was increased when the high rate of daminozide was applied early, and Ca, Cu, K and Mg were increased when mefluidide was applied early or at the high rate. There were no interactions between daminozide and cultivar in terms of minerals, but mefluidide treatment increased Mg in Altaswede only. Altaswede showed a narrower N/S ratio in the first cutting, and contained more P, K and Mg in both cuttings than did Florex. This study indicated that growth regulator application, particularly the early application of daininozide at the high rate, improved the mineral profile in red clover.

Notes: The productivity and persistence of prairie grass (Bromus willdenowii Kunth) cv. Grasslands Matua were compared with a similarly managed endophyte-free tall fescue × perennial ryegrass hybrid (Festuca arundinacea Schreb. ×Lolium perenne L.) cv. Johnstone. A field study was conducted on the Appalachian Plateau of southern West Virginia, USA (81°W, longitude; 38°N, latitude; 850m above sea level) for three consecutive years. Nitrogen totalling 0, 168, and 336 kg N ha−1 year−1 was applied to stands managed as hay. Annual herbage yields were similar for both species in year 1 (1989), but by year 3 (1991) Matua sown-grass yield was about 35% of first-year yields. Total herbage yield for Matua plots in the third year was similar to first-year yields owing to encroachment by non-seeded grasses and white clover (Trifolium repens L.). Matua was susceptible to powdery mildew [Blumeria graminis (DC) E. O. Speer] in this environment, and was similar in productivity (first year only) and nutritive quality to tall fescue × perennial ryegrass hybrid. Matua use may be limited to areas where low-temperature stress and resultant winter damage is unlikely to occur.

Notes: In two changeover design experiments, fifteen early- and sixteen late-lactation cows were used to investigate the effects of offering food beet with ad libitum grass silage and concentrates with different CP content on milk yield and quality. In Experiment 1 (early lactation) cows were offered no fodder beet (0) or 4 kg DM d−1 (4) in conjunction with one of three concentrates containing 159, 191 or 244g CP kg−1 DM (L.M.H.). Treatments were therefore 1L/0, 1L/4, 1M/0, 1M/4, 1H/0 and 1H/4. In Experiment 2 (late lactation) cows were offered the same level of fodder beet in conjunction with two concentrates containing 129 and 229 (L,H) g CP kg−1 DM. Treatments were therefore 2L/0, 2L/4, 2H/0 and 2H/4.In both experiments feeding fodder beet reduced silage DM intakes (P 〈 0·001) and increased total DM intake (P 〈 0·05 to P 〈 0·001). The substitution rate (r) ranged from 0·46 to 0·59kg of silage DM (kg−1 fodder beet DM).In Experiment 1, fodder beet tended to increase milk yield, composition and yield of constituents, but the effect was statistically significant for milk protein content only (P 〈 0·01). In Experiment 2, milk yields for 2L/0, 2L/4, 2H/0 and 2H/4 were 11·3, 12·1, 11·7 and 12·5 kg d−1 respectively (s.e.d. 0·43, non-significant), fat contents were 44·4, 47·3, 44·3 and 46·8g fat kg−1 respectively (s.e.d. 0·73, P 〈 0·001), protein contents were 34·3, 35·6, 35·3 and 36·2 g protein kg−1 respectively (s.e.d. 0·28, P 〈 0·001), fat yields were 494, 574, 512 and 579 g fat d−1 respectively (s.e.d. 20, P 〈 0·001) and protein yields were 385, 426, 407 and 442 g protein d−1 (s.e.d. 13, P 〈 0·01) respectively.Increasing CP in the concentrate significantly increased milk yield in Experiment 1 (23·9, 22·5, 23·5, 23·8, 26·2, 26·5kg d−1 for 1L/0, 1L/4, 1M/0, 1M/4, 1H/0 and 1H/4 respectively, P 〈 0·05). Higher CP in concentrate also resulted in significantly increased milk protein yield in early-lactation (P 〈 0·001) and milk protein content in late-lactation (P 〈 0·01) cows. There was a significant interaction between fodder beet and concentrate CP content for milk protein yield (P 〈 0·001) in Experiment 1.

Notes: First-harvest direct-cut, double-chopped grass (190 and 164g DMkg−1 in Experiments 1 and 2 resptectively) was ensiled without an additive or, in Experiment 1, with 30 kg t−1 grass of an absorbent additive based on sugar beet pulp (Sweet ‘n’ Dry) or with 3·441 t−1 grass of formic acid and, in Experiment 2, with 30, 50 and 70 kg t−1 grass of Sweet ‘n’ Dry or with 50kg t−1 grass of unmolassed sugar beet pulp. The preservation and nutritive value of the silage, in-silo losses (including silage effluent production), silage intake and animal performance of adult and growing cattle were examined.In Experiment 1 all three silages were well preserved, although the formic acid-treated silage displayed significantly lower pH, ammonia nitrogen (NH3N) [g kg−1 total nitrogen (TN)] and volatile fatty acids (VFAs) than the other two silages. In Experiment 2 absorbent-treated silages displayed significantly lower pH, buffer capacity (Bc), NH3N (gkg−1 TN), CP, modified acid detergent fibre (MADF) and VFAs than untreated silage.Treatment of grass with the absorbent additives at ensiling resulted in reduced effluent production. In Experiment 1 each kilogram of Sweet ‘n’ Dry retained approximately 11 effluent, and in Experiment 2 silages made with Sweet ‘n’ Dry applied at 70kgt−1 and sugar beet pulp applied at 50 kg t−1 produced similar volumes of effluent and each kilogram of absorbent retained 1·0 and 1·31 of effluent respectively.In Experiment 1 sixty beef cattle [mean initial live weight (LW) 460 kg] were grouped according to LW and allocated to treatment at random. For untreated silage (unsupplemented or with 1 or 2 kg supplement head−1 day−1), absorbent-treated silage (unsupplemented or with 1 or 2 kg supplement head−1 day−1) and formic acid-treated silage (1 kg supplement head−1 day−1) the daily silage DM intakes were 6·12, 6·21, 6·40, 7·65, 7·45, 7·11 and 7·85 (s.e. 0·280) kg respectively, the daily liveweight gains were 0·22, 0·56, 0·81, 0·59, 0·74, 0·81 and 0·75 (s.e. 0·071) kg respectively and daily carcass gains were 0·31, 0·47, 0·67, 0·47, 0·61, 0·70 and 0·57 (s.e. 0·043) kg respectively throughout a 75-day feeding period.In Experiment 2, fifty-six growing cattle (mean initial weight 312 kg) were grouped according to LW and allocated to treatment at random. For untreated silage (unsupplemented or with 1·5 kg Sweet ‘n’ Dry or 1·5 kg commercial concentrates head−1 day−1), silage treated with Sweet ‘n’ Dry at 30, 50 and 70 kg t−1 grass and silage treated with 50kg sugar beet pulp t−1 grass the daily silage DM intakes were 5·46, 5·28, 5·33, 6·21, 6·27, 6·60 and 6·62 (s.e. 0·154) kg respectively and daily liveweight gains were 0·39, 0·75, 0·81, 0·63, 0·76, 0·94 and 1·75 (s.e. 0·052) kg respectively throughout a 122-day feeding period. In this experiment 360g kg−1 more absorbent was required when it was included at ensiling rather than offered as a supplement to untreated silage to achieve the same individual animal performance.

Notes: When grazed sward surface height was controlled within the range 3·75-5·25 cm during spring and summer, the effects of two annual stocking rates of twenty (SR20) and twelve (SR12) Cheviot ewes per hectare with their lambs and two rates of nitrogen fertilizer, 100(N100) and 200(N200)kg Nha−1 per year on animal performance and yield of silage from areas of pasture surplus to grazing requirements were measured. Decision rules for management of sward height resulted in good control of swards and consistent and satisfactory individual animal performance across treatments. Total output of lamb was greater for SR20 than for SR12 (699 vs 424kg live weight ha−1; P 〈 0·001). Yield of silage was less for SR20 than for SR12 [27 vs 184 kg dry matter (DM) per ewe; P 〈 0·001] and less for N100 than for N200 (65 VS 146 kg DM per ewe; P 〈 0·01). Around the mating period, when sward height fell below 3·5cm, supplementary feed was offered. More concentrates were offered to the SR20 than to the SR12 ewes (12·3 vs 1·2kg DM per ewe; P 〈 0·001) and to the N100 than to the N200 ewes (8·3 vs 5·2kg DM per ewe; P 〈 0·01); trends in the amounts of hay offered during that period were similar.

Notes: This study sought to define the optimum defoliation interval for Lolium perenne, with the maximum interval being determined by the onset of senescence, as reflected by the number of fully expanded leaves, and the minimum interval set by the replenishment of water-soluble carbohydrates (WSCs).In a glasshouse set at 13°C/23°C night/day temperature and at a plant spacing of 94 m−2 (3290 tillers m−2), the accumulation of dry matter against leaf number and days was exponential to the four-leaf stage of the regrowth cycle. Senescence commenced at the 3·5-leaf stage.WSCs in roots, stubble and leaf showed a very significant linear relationship with leaf number. Levels of WSCs in leaves were restored to predefoliation values by the one-leaf stage, after which WSCs accumulated preferentially in the stubble, rising to 22% at the four-leaf stage.Regrowth after 6 d was significantly greater for plants defoliated at the three-leaf stage than at the one-leaf stage, but this difference disappeared at the end of the regrowth cycle. This questions the importance of WSCs in determining the yield of ryegrass under normal rotational grazing management.Regrowth at 6 d was related positively to stubble WSCs (r2= 0·66) and to stubble DM per tiller(r2=0·71)

Notes: A large, and often neglected, component of grazing intake is behavioural. Grazing animals may employ two strategies to increase their intake rates during grazing: increasing bite mass and decreasing handling time. These strategies are discussed in the context of fasted and non-fasted sheep grazing white clover (Trifolium repens L. cv. Kent wild white) and perennial ryegrass (Lolium perenne L. cv. Parcour). It is concluded that within a forage species sheep have little flexibility for increasing their intake rates by altering their handling times but have some latitude for altering bite masses. Between forage species, differences in intake rates may be more strongly affected by the ‘species-specific’ requirement for mastication than by differences in bite masses per se. Comparisons are also made with grazing strategies of cattle.

Notes: Calcium-rich pyromorphite [Pb5(PO4)3Cl] has been positively identified as the major lead-bearing phase in mine-waste soils from the South Pennine Orefield, UK, by a combination of EXAFS spectroscopy, ATEM and XRD. Evidence for a pyromorphite-like structure was provided by electron diffraction of individual Ca-rich, lead chlorophosphate grains in the soil using ATEM. Approximate unit-cell parameters derived from electron diffraction were used to identify peaks on the powder XRD trace obtained from the soil sample, allowing the cell parameters to be refined. The unit-cell parameters derived for the Ca-rich pyromorphite [a= 0.9789(7), c= 0.726(1) nm] are smaller than those reported for pure end-member pyromorphite (a= 0.998, c= 0.733 nm; Baker, 1966) and are sufficiently different to prevent positive identification by conventional XRD analysis. Lead absorption spectra and interatomic distances obtained from EXAFS performed on bulk soils confirmed the predominance of pyromorphite-like structure. EXAFS is shown to be a useful tool in the identification of soil minerals. It gives information about the local environment of one specific element in solids, be they crystalline or amorphous, and is unaffected by the limited chemical substitution of Ca for Pb.The identification of impure Pb minerals in soil by techniques other than XRD suggests that previous studies, based on XRD, may have underestimated the amount of soil Pb present as discrete Pb compounds.

Notes: The mineral forms of phosphorus in three urban sewage sludges were characterized using high-resolution solid-state phosphorus-31 nuclear magnetic resonance (NMR) coupled to a sequential extraction. The sludges studied were an anaerobically-digested and heat-treated sludge (Paris-Achères), an activated sludge (Briare) and an anaerobically-digested sludge (Nancy). NMR observations were conducted using both single-pulse and cross-polarization sequences in order to distinguish between 31P nuclei far from 1H nuclei, and 31P located within a fraction of a nanometre of 1H. This approach showed that a complex mixture of P species was present in these sludges. A mixture of hydrogenated octocalcium phosphates and apatites was observed in the three samples. Monetite was present in the anaerobically-digested sludge and brushite in the activated sludge. Dehydrogenated condensed calcium phosphates (compounds with a Ca:P ratio higher than 1.0 such as fluorapatite or tricalcium phosphate) and dehydrogenated pyrophosphates were also probably present in the anaerobically-digested sludge. A poorly-ordered wavellite was observed in the three sludges after the HCl extraction. However, results were inconclusive as to whether this mineral was present in the three sludges, or had been precipitated during the sequential extraction.

Notes: The adsorption of a radioisotope of caesium, 137Cs, has been interpretation and ratio and solution measured on four soils with differing clay mineralogies. All measurements have been made using unwashed soils in suspensions shaken for 2 h at 20°C. The effects of concentration in potassium and caesium, the nature of the background electrolyte and the soil:solution ratio have been investigated. The results are expressed either as the distribution coefficient, KD or as Freundlich isotherms.The distribution coefficient of each of the soils decreases markedly as the concentration of caesium increases. The adsorption properties of the soils are not determined by the dominant clay mineralogy alone. Adsorption is always lower in 0.01 m CaCl2 solution than in water. The addition of potassium has relatively little effect on adsorption of trace amounts of caesium; however, KD decreases with increasing concentrations of stable caesium. The major reason for the dependence of KD on the soil: solution ratio is found to be the non-linear adsorption isotherm; the influence of the varying compositions of the solution and exchange complex is minor.The validity of the use of a single KD value as an indicator of adsorption capacity and the meaning of the relative values of the Freundlich parameters are considered. The implications of these findings for the use of radiotracers and the usefulness of KD as an indicator of bioavailability are discussed.

Notes: The paper examines the ability of a critical-state model to predict stresses and deformations of agricultural soil in a variety of laboratory shear and compression tests. The critical-state model used is a simple extension to the well-known Modified Cam Clay model. The extension provides a smoother transition from elastic to plastic behaviour and, amongst other things, introduces a capacity to model cyclic loading. The model is incorporated into a finite-element program.The model predictions are compared with: experimental observations of simple and direct shear tests with both constant normal stress and constant volume conditions; cyclic uniaxial compression tests; compaction tests in U-shaped and V-shaped boxes; and observations of some gross structural features caused by shear in direct-shear boxes. Predictions are made for both the compressing, strain-hardening and the expanding, strain-softening regimes of behaviour. In all cases the material properties for the model were obtained from tests other than those being used for the comparisons.The model predictions generally compare well with the various experimental results, although some numerical problems were encountered in strain-softening conditions. This demonstrates the versatility of the critical-state model for predicting fairly general stress and, deformation conditions in unsaturated soils using only five material-property constants. It also demonstrates that common laboratory strength and compression tests are adequate to measure the material properties.

Notes: Critical state parameters were determined in constant cell volume triaxial tests on three remoulded agricultural topsoils, a sandy loam, a clay loam and a clay. Tests were made at a range of water contents. The normal consolidation lines tended to be linear on a semi-logarithmic plot up to a degree of saturation of c. 0.85, above which the soil was incompressible but highly deformable. The slopes of the projected critical state lines were slightly greater than the slopes of the normal consolidation lines for all three soils. For each soil, both lines pivoted about a point as water content increased and, for the two lighter-textured soils, the increases in compactibility tended to be greatest near the plastic limit. For all three soils, strength remained fairly constant with increasing water content until the soil was at around 70-85% of the cone penetrometer plastic limit. Strength then decreased with increasing water content, with the smallest decrease in the sandy loam.

Notes: A device that infiltrated water over a small circular surface area having a radius ranging between 1.45 mm and 2.5 mm was used to measure the sorptivity of initially air-dry aggregates of size greater than 20 mm. The small infiltration area caused the water uptake to be dominated by capillarity that allowed the use of a simple formula to obtain the sorptivity from the steady-state flow rate that occurred very early after the start of imbibition. The results of measurements of sorptivity made on a fine sand agreed with those obtained from measurements on one-dimensional water infiltration into columns of the sand. Sorptivity measurements on stabilized aggregates of a clay soil and on air-dried field aggregates of a clay soil were easily made. The simplicity and rapidity of the method allowed measurements to be conveniently replicated.

Notes: Ninety years after the start of the Askov long-term fertilization experiment on sandy loam, bulk soil was taken from the 0–20 cm and 30–35 cm depths of unfertilized (UNF), animal-manure (FYM) treated and mineral-fertilized (NPK) plots and analysed for textural composition, carbon content, pH, CEC, particle density and plasticity limits. Undisturbed soil cores (100 cm3) from the 8–12 cm layer were brought to six different matric potentials and subjected to confined uniaxial compression, drop-cone penetration and annulus shear tests. Water-retention curves based on seven matric potentials were produced for undisturbed cores from the 8–12 and 30–35 cm layers. In the field, in situ shear strength of plough-layer soil was determined by a vane shear tester and a torsional shear box.FYM and NPK treatments increased the soil organic carbon content by 23 and 11% of the amount in UNF, respectively. Corresponding increases observed in CEC were 17 and 11%. The water content at the lower and upper plastic limits both decreased from FYM to NPK to UNF. Soil bulk density in the 0-20 cm layer was reduced in FYM and NPK treatments relative to UNF, whereas the volume of soil pores larger than 30 μm was unaffected by past fertilization.Soil receiving animal manure showed the greatest soil strength when exposed to annulus shear, drop-cone penetration and confined uniaxial compression tests, Shear strength measurements indicated that the UNF sandy loam soil reacted like a sand, the increase in soil strength upon drying primarily being due to increased internal friction. In contrast, soil from FYM and NPK treatments showed reactions typical of a loamy soil, the increase in soil strength during drying being caused by increased cohesion in the soil matrix. The field tests employed were unable to detect the management-induced differences in soil physical parameters found in the laboratory tests.This study shows that physical soil properties related to conditions for tillage and traffic, to crop development and erosion are significantly influenced by differences in soil organic matter levels resulting from contrasting methods of fertilizer management. Exhausting a loamy soil by long-term lack of fertilizer application severely affects the physical properties of the soil.

Notes: Aggregates (9.5–12.7 mm) from ten soils were equilibrated at a range of matric suctions (Ψa) between 1 kPa and 100 MPa before immersion in water or wetting on a porous plate at zero suction. The soils were from cultivated and grassland sites and included hardsetting and non-hardsetting Australian and British soils as well as a Vertisol. The initial rate of wetting of each aggregate, and the composition and size distribution of the slaked fragments were measured. There was a significant inverse linear relation between the amount of slaking produced by plate wetting air-dry soil (Ψa=100 MPa) and its organic carbon content (r= 0.82***). The three cultivated hardsetting soils shared several common features. Their slaking was the most pronounced after plate wetting and occurred at the smallest Ψa(10 kPa). Their slaking also increased linearly with rate of wetting and the particle-size distribution of their slaked fragments varied significantly and considerably with Ψa. This last observation demonstrates that it is not always helpful to call the fragments produced by slaking, microaggregates.Possible explanations for our results and their agricultural implications are discussed.

Notes: Silages were made from the first cut of a predominantly perennial ryegrass sward. The silages were either untreated (W) or treated with formic acid (31 t−1, F) or with 106 lactic acid bacteria (LAB) g−1 grass of each of three strains alone (A. Lactobacillus plantarum MTD1; B, Pediococcus species 6A2; C, L. plantarum 6A6) or in combination (AB. AC) to give seven treatments. The silage fermentation in 10-kg silos was followed chemically and microbiologically and the nutritive value of selected treatments evaluated using 2-t silos.The control silage (W) fermented well. Addition of formic acid restricted fermentation and produced a silage with a high ethanol concentration. After day 4, all inoculated silages had lower pH values and higher lactic acid concentrations and a higher ratio of lactic acid to acetic acid than the control silage. Chemically there was little difference between the inoculated silages in terms of final composition. Microbiologically the LAB applied in treatments B and C dominated the LAB populations in those silages when applied alone; however, they were suppressed when applied in combination with inoculant A.When fed to sheep, the intake of the formic acid-treated silage was significantly (P 〈 0·01) lower than that of the other silages and the intake of silage treated with inoculant A significantly (P 〈 0·001) higher than that of silages treated with inoculants B and C. The apparent organic matter (P 〈 0·001) and nitrogen (P 〈 0·01) digestibilities of the formic acid-treated silage were also significantly lower than those of the other silages.

Notes: The effect of a reduced level of nitrogen fertilizer application upon the herbage consumption of a continuously grazed sward of tall fescue has been investigated during two successive years. Two contrasting cultivars were used and two levels of leaf area index were maintained on the swards in order to obtain a wide range of sward structure. The herbage growth, herbage senescence and herbage consumption were measured directly on labelled tillers. It was possible to estimate the different components of the defoliation process (frequency and intensity) at the level of individual tillers of each leaf category. The results show that the effect of reduction in N fertilizer on herbage consumption rate is proportionally more important than that on herbage growth rate. In consequence, the efficiency of herbage utilization in continuously grazed conditions is reduced when nitrogen nutrition becomes limiting for herbage growth. The data suggest that this phenomenon is not directly attributable to nitrogen deficiency but is an indirect effect owing to the reduction of the stocking density at the low N level, which leads to a lower frequency of defoliation of individual tillers.

Notes: Plots of a 2-year-old sward of Merlinda perennial ryegrass received a routine dressing of 100 kg N ha−1 as compound fertilizer in March 1991, followed by further dressings of 100 kg N ha−1 after cuts 1, 2 and 3 in a simulated four-cut silage system, either the same day as cutting or with a delay of 3, 7, 10 or 14 d. Partial irrigation ensured that fertilizer could be taken up immediately. Annual total dry matter yield, the dry matter yield for the experimental cuts 2–4 and their apparent response to N showed no effect of delays of 0–10 d in reapplication of fertilizer, but a significant (P 〈 0·01) reduction for 14 d delay. Significantly (P= 0·001) higher apparent recovery of N in the cut herbage was recorded where reapplication of fertilizer had been delayed by 7 or 10 d (93% and 91% respectively) in comparison with either smaller (0 delay, 78%; 3 d delay, 87%) or greater delay (14 d, 86%). It is suggested that lower recoveries at 0 and 3 d result from the sward's reduced NO3 uptake following defoliation and that, while in practical situations the conditions may not be as rigorous as those imposed in this experiment, further experiments to determine the fate of N not recovered in the herbage are warranted, so defining management circumstances in which immediate reapplication of N might not be advisable.

Notes: The productivity and response to fertilizer nitrogen (N) was measured in herb-rich wetland hay meadows within a Site of Special Scientific Interest (SSSI) in Somerset, UK. Output from hay cut after 1 July each year and from beef production at aftermath grazing was measured over a total of 4 years.Total utilized metabolizable energy (UME) output averaged from 40·6 GJ ha−1 year−1 without fertilizers to 61·7GJha−1 at 200kgNha−1 (N-200), the highest rate used, with about two-thirds of this output from hay. N response was markedly curvilinear above about 50kgN ha−1, but data from a concurrent experiment suggested that the comparatively low replacement rates of P and K applied were limiting at higher N rates. When hay cutting was delayed until early August in a wet year, yield response to N was lost because fertilized swards had passed a peak in yield several weeks before harvest.Compared with other published data, the results suggest that output and response to N is not constrained by the diversity of the flora or the damp conditions. The data will help to estimate the financial implications for farmers of restricted or zero fertilizer use within SSSIs and the wider Environmentally Sensitive Areas.

Notes: Supernatants derived from desiccated plant material gathered from Agrostis/Festuca vegetation had an inhibitory effect on the germination and early development of seedlings of Trifolium repens cv. S184. Two compounds, o-hydroxyphenylpropionic acid and benzoic acid, were identified chromatographically and their structures confirmed by mass spectrometry. Commercial preparations of the two compounds were effective inhibitors at a concentration of 10−2 and 10−3m respectively when T. repens was used as the phytometer species. Benzoic acid lost its inhibitory effect when the pH of the two solutions was adjusted to pH 5·5. The roots of seedlings of white clover were severely distorted by o-hydroxyphenylpropionic add at 10−3m. It is likely that phenolic acids, produced from the surface trash created by slot seeding procedures, interfere with the establishment of white clover in upland pastures.

Notes: Cattle slurry was applied to grassland on two contrasting soils in autumn and spring between 1987 and 1990. Slurry was applied with or without the addition of acid, to lower the pH to 5·5, and, in autumn only, with or without a nitrification inhibitor. Ammonia volatilization, denitrification and apparent recovery of N by the cut herbage accounted for 61–86% of the ammonium nitrogen (NH4+-N) applied in slurry. Estimates from lysimeter experiments indicated that nitrate leaching from autumn application may have accounted for an additional 1–2% only. Acidifying slurry reduced volatilization losses to 1–12% of the NH4+-N applied, and the nitrification inhibitor halved denitrification losses from autumn applications. Reductions in nitrogen losses were reflected in significant increases in first-cut herbage yields which, for slurry applied in the autumn with acid and the nitrification inhibitor, were generally greater than those from 120 kg ha−1 N as ammonium nitrate applied in the spring. There were no significant differences between treatments at subsequent cuts in each season but, owing to the large increases at first cut, total yields were significantly higher for autumn-applied slurry with acid and nitrification inhibitor.

Notes: The drop-disc method of estimating herbage dry-matter production was evaluated for ryegrass from growth commencement to the silage stage; the latter typically corresponded to a maximum dry matter (DM) mass of almost 7 t ha−1. A close linear relationship (r2= 0·829) was found between disc settlement height and DM mass up to 4–5 t ha−1 for the period when growth was mainly vegetative rather than reproductive. During the latter stage, the presence of stems and the occurrence of lodging had a detrimental effect on the quality of disc calibration data. The technique was demonstrably useful in experiments as a cheap, rapid and trouble-free method for monitoring the initiation of grass production and rate of production during the vegetative stage.

Notes: A simple and accurate remote sensing technique for the fine-scale mapping of grassland protein densities was developed during a study of sward quality and antelope dispersion in Kenya, East Africa. Using measures of spectral reflectance and a vehicular navigation system, estimates of protein densities were recorded at rates exceeding 1000 samples per hour. Nitrogen analyses confirmed that reflectance measures were accurate predictors of protein density for a variety of grass swards but not for two species of sedge. Because the regression coefficients linking reflectance to protein density differed significantly between sward types, good estimates using this method will require a separate calibration for each type of grassland. By monitoring and correcting for variations in ambient light levels, the method can be used under a wide range of lighting conditions and for long periods. This facilitates sampling sufficiently systematically and intensively that contour plots of protein density can be constructed and then correlated with distributions of underlying abiotic factors, foraging activity of sympatric herbivores, or prior maps to characterize successional and historical change.

Notes: The effects of feeding herbages fertilized with 0 (nil), 32 (low), 66 (medium) or 96 (high) kg of sodium per hectare per year to sheep on herbage digestibility and mineral availability were examined. Modified acid detergent fibre (MADF), ash, magnesium (Mg) and phosphorus (P) contents were increased by the application of sodium (Na) treatments, while potassium (K), sulphur (S) and true protein (TP) contents were reduced. Dry matter (DM) and MADF intakes were increased in the low and medium treatments and DM and MADF digestibility increased in all Na-treated herbages. The medium- and high-sodium treatments increased salivary Na content and Na/K ratio and decreased K content. Blood K content was not affected by treatment. Intake, faecal output, apparent availability, urinary output and balance of Na were increased by the application of Na treatments. Potassium intake, balance, apparent retention and urinary output were increased by the low, unaffected by the medium and reduced by the high sodium treatment. The low and medium Na treatments increased the intake and apparent availability of Mg; Mg balance and apparent retention were increased by all Na treatments. Feeding the Na-treated herbages increased intakes, apparent availability, balance and apparent retention of Ca, P and total cations.The low and medium Na treatments increased S intake, faecal output and apparent retention. It is suggested that through increasing the balance and apparent retention of minerals, the application of sodium fertilizer to pasture will improve the mineral status of sheep, particularly at the low and medium application rates employed in this experiment.

Notes: Five experiments were carried out to measure the effects of seed rate and fertilizers on the establishment and early growth of reseeded grass mixtures in the Falkland Islands.Experiments 1 and 2 compared seed rates within the range 7·5-35kg ha−1. Experiment 3 assessed the effects of three levels of each of nitrogen (N), P2O5, K2O and CaCO3 applied as seedbed fertilizers. Experiments 4 and 5 were similar in intent to Experiment 3, but treatments consisted of either nil or a very heavy application of the same fertilizer elements. In all experiments, the grass seed mixtures were sown in late summer after rotavation and burning of Cortaderia pilosa dominant indigenous vegetation on peaty soils. Percentage ground cover was estimated in the following spring and dry matter production through the first year was determined by sample harvests.Initially, heavier seed rates resulted in higher percentage ground cover of sown species, but dry matter production over the season following sowing showed a significant increase only between the 25 and 35 kg ha−1 rates in Experiment 2. The modest levels of seedbed fertilizers applied in Experiment 3 had no significant effect on either percentage ground cover of sown species or dry matter production. Even at the higher levels used in Experiments 4 and 5, only N consistently increased dry matter yields, although a significant positive response was also obtained from CaCO3 in the final harvests.The implications of the results to farmers in the Falkland Islands who may be contemplating reseeding are discussed.

Notes: A comparison was made of the effect of season and maturity on the in situ ruminal breakdown and intestinal protein digestion in dairy cows between intensively N-fertilized grass (whole sward) and moderately N-fertilized ryegrass and clover from a mixed sward. From May to September 1990, eight consecutive cuts were made, representing alternate harvests of late and early swards. Limited effects of fertilizer-N on chemical and ruminal degradation characteristics and intestinal digestion of grasses were observed. Clover had higher ash, crude protein (CP) and lignin and lower hemicellulose, cellulose and sugar contents than grass. Moreover, soluble fractions of organic matter (OM) and CP were higher, and rumen-undegradable OM and CP fractions were lower. Soluble fractions of grasses and clover decreased and undegradable fractions increased during the season. More mature swards showed increased undegradable fractions. Degradation rates of OM and CP in clover were, respectively, higher than or similar to those of grass. Seasonal effects on degradation rates differed between grass and clover. Effectively rumendegradable (g kg−1 DM) carbohydrates and CP, escaped protein and intestinal digestion of escaped protein were higher in clover than in grasses. Inclusion of clover in swards may result in higher post-rumen protein supply. Supplementation of clover-based diets is suggested to compensate for an increased loss of N in the rumen.

Notes: Lucerne (Medicago sativa L.) sown at 2·8-11·2 kg ha−1 in spring was thinned in the autumn by digging plants from alternate 15- or 30-cm lengths of row. Both thinning treatments decreased the subsequent year stand density by 34%. Yields the following year were reduced by 24 and 17% for the 15- and 30-cm treatments respectively, and the next year by 10% for both treatments. Thinning effects were similar at all sowing rates. During the year following thinning, plants did not grow larger in response to the thinning. Thus, development of compensatory growth by lucerne plants following sudden stand thinning is slow.

Notes: Results from a series of five small-scale plot experiments which simulated different strategies for lowering ammonia volatilization following slurry application to grassland are reported. Strategies studied were band spreading, shallow-channel application, spike injection, rate of surface application and dilution. Volatilization was measured over the first 4 h following application with ventilated enclosures. Band spread slurry resulted in 0·4 of the volatilization that occurred from surface application of the same rate of slurry. The benefit of band spreading was shown to arise from higher application rates in the bands when compared with the same quantity of slurry spread over the surface. When surface-spread slurry was applied to the same depth of slurry as in bands, the volatilization per unit volume of slurry was the same. Shallow-channel application was more effective than band spreading and lowered volatilization per unit volume of slurry to 〈0·1 of that from surface-spread slurry. Spike injection was equally effective as shallow-channel application but, owing to perceived difficulties in machine design, construction and operation, was deemed impractical. Shallow-channel application has potential, though further work is required to optimize centre-to-centre spacing of the channels. As the application rate of surface-applied raw slurry increased, ammonia volatilization per unit volume of slurry applied decreased. Application at 50 m3 ha−1 resulted in 0·4 of the specific volatilization per unit volume of slurry that occurred at 6·3 m3 ha−1. Within the dilution treatments, the amount of water added to the slurry was linearly and inversely related to volatilization. At a dilution of 0·9-1·2:1 water: slurry the specific volatilization per unit volume of slurry was 0·5 of that from undiluted slurry.

Notes: Frequency data from different-sized plots are generally accepted as being incomparable. However, how basal frequency data are influenced by plant basal diameter is not well known. Computer simulations were used to determine the influences of grass plant basal diameter on basal frequency data. Basal frequency, basal area and density were estimated with simulated 5 × 10 cm and 20 × 50 cm rectangular plots. Simulated plants had basal diameters ranging from 1.9 to 12.7 cm.Basal diameter had a significant effect on the relationship between frequency and both basal area and density. As differences in plant size increase, the effect on basal frequency becomes larger and the likelihood of an ecologically important influence also increases. Thus, frequency data should not be used to compare relative abundance of species, unless corrections are made for differences in plant basal diameter among species. Additionally, frequency data should not be used to monitor change in abundance of a species through time, unless mean plant basal diameter can be assumed to remain relatively constant.Basal frequency data could be used to ‘signal’ when change has occurred. Then, other sampling methods must be used to determine the nature and direction of change or relative species abundance. For frequency data, the simplicity of collection may be offset by difficulty in interpretation.

Notes: In two experiments (1990 and 1991) perennial ryegrass (cv. Talbot) pasture was subjected to six different management treatments by adjusting stock numbers to achieve set sward heights for set periods between turn-out in early April and weaning in early July. The main objective of the experiments was to measure the effect of differences in sward management up to July on subsequent sward type, and the effect of sward type on the performance of weaned lambs between mid-July and early October when all swards were grazed at a sward height of 7 cm. In Experiment 1 swards were grazed at 7 cm initially and then reduced to 3 cm at various dates and maintained at 3 cm until early July. In Experiment 2 swards were grazed initially at 7 cm, and this was reduced to 3 cm and then allowed to return to 7 cm at various dates up to early July.Grazing at a sward height of 7 cm up to weaning, in early July, gave mean twin lamb growth rates of 310 g d−1, while at a tower sward surface height of 3 cm lamb growth rate was reduced to 206 g d−1 The density of seed heads produced from July was strongly influenced by earlier management. Grazing at 7 cm up to July gave a high density of seed heads (213m−2), and this reduced (126 m−2) by grazing to 3 cm. Seed heads were almost eliminated (17 m−2) by grazing at 7 cm until late June followed by grazing down to 3 cm in early July. Reducing sward surface height from 7 cm to 3 cm at an earlier date tended to increase the development of seed heads from early July. Where swards were grazed from 7 cm to 3 cm and then allowed to return to 7 cm, the later in the pre-weaning period this took place the greater the reduction in seed head development. Greater seed head density was associated with a significant decrease in the nitrogen content of the herbage on offer in Experiment 2, but an increase in modified acid detergent (MAD) fibre content was not significant.Despite the differences in the sward type on offer, the effect on weaned lamb growth rate was small. Lamb liveweight gain during autumn was significantly reduced in Experiment 2 following earlier grazing at 7 cm compared with 3 cm, but liveweight gain differences in Experiment 1 were not significant.

Notes: Leaf blades of perennial ryegrass (Lolium perenne) at five developmental stages, from unemerged to dead, were collected from cut swards grown under field conditions. Similarly, leaflets of white clover (Trifolium repens) at four developmental stages, from tightly folded to proximal to the youngest fully developed leaf, were collected. The leaves were analysed for N, P, K, Ca, Mg and Na.In perennial ryegrass, the concentration of N declined by about half and those of P and K declined by about two-thirds, as leaves aged. By contrast, the concentration of Ca increased more than fivefold and that of Mg about twofold as leaves aged. The concentration of Na initially increased more than twofold but then declined as leaves died. In white clover the concentration of N declined by about 20% as leaves aged, while the concentrations of P and K declined by about 50%; the concentration of Ca increased about fivefold, that of Mg declined by about 15% and that of Na increased by about 15%.The application of N increased the concentrations of N and K in ryegrass leaf blades at all stages of development. The application of P increased the concentrations of P and Na in the leaves of both species.

Notes: An experiment was conducted to examine the relationships between sward surface height and the intake and liveweight gain of lactating female goats and their single kids and of 12-month-old castrated male goats continuously grazing grass pasture. Herbage intake was measured using the n-alkane marker technique. Goats grazed the experimental area from May to August at nominal sward heights of 3–4, 5–6, 7–8 and 9–10 cm. Sward heights achieved were variable but were consistently ranked in treatment order.The herbage intake of females [57-140 g DM (kg LW0.75)−1 d−1] and castrates [26-88 g DM (kg LW0.75)−1 d−1] increased linearly with sward height over the range 3.2-11.0 cm. The liveweight change of females and castrates reflected the pattern of change in sward height.The herbage intake of kids [17-41 g DM (kg LW0·75)−1 d−1] was not related to sward height, but there was a consistent increase in liveweight gain with sward height from 98 to 129 g d−1. The herbage intake of kids did not increase with age with means of 25–29 g DM (kg LW0·75 d−1 for kids aged 9–17 weeks.There was evidence that all classes of goat selected green leafy material of high digestibility.

Notes: A mathematical model of the aerobic stability of grass silage is presented. The model is shown to predict as well as more complex models previously published. Sensitivity analysis performed on model parameters suggests that current understanding of the temperature dependence of yeast growth needs to be advanced in order to produce more accurate models of deterioration. Inhibition of yeast growth by organic acids is identified as a critical process worthy of further investigation. We discuss how model validation experiments must identify different yeast species and track their growth separately. Such experiments should also attempt to minimize or measure heat losses.

Notes: The growth of grass and clover components in mixed swards on a site restored after opencast coal mining and an undisturbed control site were compared. Soil nitrogen supply was reduced at the restored site. This inhibited grass growth but was beneficial for the clover component.Growth at the restored site was also inhibited by a compacted subsoil, which reduced available soil water content and impeded access to available soil water. This inhibited crop production from the middle of the second silage crop onwards. In 1989 this was associated with the soil at the restored site reaching permanent wilting point at 40cm. In 1990 this effect was associated with the restored site soil reaching permanent wilting point at 70cm. These drought effects reduced clover growing point population and stolon mass. Grass tiller populations were unaffected.

Notes: An experiment was carried out to examine the effect of supplementation on the performance of spring-calving dairy cows grazing swards of differing perennial ryegrass and white clover content. Seventeen heifers and sixty-four Friesian cows in their third to ninth week of lactation were turned out onto one of three pastures with different proportions of perennial ryegrass and white clover. Nine animals on each pasture received either 0, 2 or 4 kg d−1 of a concentrate with a crude protein concentration of 180 g kg−1 dry matter (DM). Prior to grazing, swards contained proportionately 0·01 (L), 0·15 (M) and 0·20 (H) of total DM as clover. During the experiment, grazing pressures were adjusted by movement of buffer fences to maintain compressed sward heights at 6 cm. Samples taken 26 and 68 d after the start of grazing showed little change in the proportion of clover in sward L (〈 0·01 and 0·02 respectively), but convergence in the proportion of clover in swards M and L (0·08-0·16 and 0·10-0·15 respectively). Mean daily yields of milk, fat, protein and lactose increased significantly with increased clover content and, even without supplementation, daily yields were 25·4, 0·98, 0·73 and 1·09 kg respectively on sward H. Of the milk components, only protein was significantly increased by increasing sward clover content. The response in milk yield to supplementation was greater on sward L than on swards M and H.

Notes: A 10-week grazing experiment was conducted on a perennial ryegrass sward with lactating ewes and their twin lambs. Three paddocks were rotationally grazed with rest periods of from 4 to 5 weeks. Sward surface heights at the start of each grazing were 145, 259 and 250mni for treatments RG1, RG2 and RG3. A further four paddocks were maintained by continuous variable stocking (CS) at sward surface heights (SSHs) of about 30, 60, 90 and 120mm. Sward and animal measurements were made on the two different grazing managements as the RG swards were grazed down, giving measurements at similar sward heights for treatments RG and CS.There was less green leaf and the total herbage mass present under RG was less than on CS swards at the same sward heights, demonstrating the differences in structure between rotationally and continuously grazed swards.Regression analysis of animal factors on sward factors showed that grazing behaviour was more highly correlated with green leaf mass than SSH or any of the other sward measurements. On the RG swards, maximum intake per animal was reached at about 1500 kg green leaf mass ha−1. A SSH of 60mm allowed the CS ewes to achieve the highest intake rate, but at this height the ewes on treatments RG2 and RG3 were restricted to approximately half this rate. The results suggest that green leaf mass or leaf area index, rather than sward surface height, could be used as a rational basis to relate intake of herbage to sward state for swards changing rapidly in leaf to stem ratio.

Notes: Management treatments were applied to an established ryegrass/white clover sward with the aim of producing differences in clover content. The treatments were: mowing (M) with no fertilizer N (intended to give high clover), grazing by cattle (C) with no fertilizer N (medium clover) and grazing by sheep (S) with 300 kg N ha−1 applied (low clover). Following treatments significant differences (P 〈 0.001) were observed, with M, C and S containing respectively. 237, 81 and 3 kg DM ha−1 of live clover. Treatment M swards had fewer ryegrass tillers but greater numbers of clover growing points than did treatment S, with values being intermediate on treatment C. Following overwintering most of the differences in the clover component between treatments C and M were lost, but those on treatment S still persisted. Management can be used to manipulate the botanical composition of ryegrass/white clover swards, but these changes may be only transient.

Notes: In a range of perennial ryegrass/white clover swards, variation in the surface heights of the grass and clover components, the rates of increase of these surface heights and the specific leaf areas (SLAs) of ryegrass and white clover were described for 1 year. The swards were of an early- or late-flowering (Aurora or Melle respectively) perennial ryegrass variety growing with either a small- or a medium-leaved (Kent or Milkanova) white clover and were either continuously stocked by sheep or continuously stocked apart from a rest period in April-May (Aurora) or May-June (Melle).The surface heights of grass and clover were not affected by the variety of their companion species, and the surface heights of the two clover varieties were similar. The grass was always taller than the clover, although the magnitude of the difference between the species varied with time of year and the timing of the rest period.Before the summer solstice the rate of increase in height of grass was greater than that of clover except at cool temperatures (5°C) and warm temperatures (16°C), and in the unrested Melle sward. After the solstice the rates of increase in height, particularly of clover, were lower than the rates seen at similar temperatures before the solstice.Overall, the SLAs of both clover varieties were greater than those of ryegrass when grown with Aurora but not when grown with Melle, and the SLAs of both species increased during the year. By October the SLAs of both grass varieties were less than those of their companion clovers.The results are discussed in relation to their implications for the species composition of the swards.

Notes: Book reviewed in this article: Sward Measurement Hand Book, 2nd edn Edited by Alison Davies, R. D. Baker, Sheila A. Grant and A. S. Laidlaw Organic Grassland John Newton Improved Grassland Management John Frame Agrométéorologie des Cultures Multiples en Régions Chaudes (in French) C. Baldy and C. J. Stigter Grassland Invertebrates—Ecology, Influence on Soil Fertility and Effects on Plant Growth J.P. Curry

Notes: Plants of a white clover population, Ac 3785, were grown in binary mixtures with perennial ryegrass cv. Talbot and the ‘coexisting’ population, Ba 10281, in boxes. Treatments imposed were ‘no root competition’ and ‘full competition’, which prevented or allowed the root systems of the competing species to intermingle respectively. Shoot competition was permitted in both treatments. Measurements of dry-matter yield and leaf area of the clover and grasses were made on three occasions following sowing.The dry-matter yield of both grasses was higher than that of clover at all three harvests and under both treatments, and this yield advantage tended to increase with time. Both grasses yielded more under full competition than where root competition was prevented. Talbot was higher yielding than the coexisting population under both treatments. Clover dry weight and leaf area index (LAI) were considerably higher under the ‘no root competition’ treatment. There was no effect of companion grass on clover dry weight, but clover LAI was significantly higher with its coexisting population than with Talbot in the ‘no root competition’ treatment.The LAI and dry weight data indicate that clover leaf morphology changed in response to the companion grass where root competition was prevented. Thus, the superior aerial compatibility of Ac 3785 with its coexisting grass was limited by below-ground factors. Possible ecological reasons for this effect are discussed.

Notes: Fresh ryegrass and lucerne were macerated and compressed into thin mats over a 4-week period at two yield levels. The mats were left lo dry outside during the day. and inside overnight, and compared with unconditioned crops. Under a low swath yield of 4 t DM ha−1, mats required 0·7-1·4 mm pan evaporation lo reach 70% moisture, suitable for wilted silage, compared with 1·8-3·8 mm pan evaporation for unconditioned crops. On an average non-rainy day. mats were ready to harvest as wilted silage after 2–5 h, whereas the unconditioned crop required between 6 h and 36 h of wilting. With a high swath yield of 8 t DM ha−1, mats required 1·4-3·0 mm pan evaporation to reach 70% moisture compared with 2·4-5·1 mm for unconditioned windrows. Low-yield mats reached 20% moisture, suitable for hay, in 2 d of drying, after 4·5-5·3 mm of pan evaporation. The thickness and cohesion of the mats were measured to assess their sensitivity to mechanical handling. The effect of controlled rainfall on mats was also investigated. Since mat making was most effective in low-yield crops, it could become a useful complement to low-input, extensive forage production. Mat making could eliminate most silage effluent losses; it could re introduce haymaking of ryegrass as a viable system under certain circumstances.

Notes: Plants of three cultivars of lucerne (Medicago sativa L.) and of red clover (Trifolium pratense L.) were grown at four levels each of water availability and temperature in all combinations to evaluate these factors as determinants of plant growth. Plants grew in conventional plant growth chambers from age 2 to 4 weeks with the roots held between layers of polyester cloths that held a volume of nutrient solution which was adjusted at 24-h intervals by flushing and blotting the cloths. The experimental design consisted of two growth chamber runs at each of four temperatures. Within each run, water treatments and the species-cultivar combination were arranged In four replicates of a split-plot design with water treatment as whole plot and species-cultivars as subplots.Plant response variables over all treatments were significant (P 〈 0·05) for temperature and water for shoot weights, root weights, shoot/root ratios and number of roots. Cultivars within species had no significant difference in response lo the treatments, but species differences were significant for alt response variables except shoot/root ratio.

Notes: Forty per cent of while clover nodes had roots when a pasture was rotationally grazed by sheep compared with 29% when grazed continuously by set stocking. Nodal roots were most frequent during spring and least frequent during summer. About 5% of nodes had a root primordium which had not developed but was still viable. A high proportion of nodal roots (66%) occurred within 10 nodes of the apex. Root presence was highly correlated with the establishment and survival of branches but was less closely related to branch initiation or the viability of axillary buds. It is suggested that the association between nodal roots and branches is strongest when resources are limited, and that root survival at a node is enhanced by the presence of a branch originating at the same node.

Notes: Grass was treated with six different cell wall-degrading enzymes and ensiled under different conditions [dry matter (DM) content, stage of maturity]. Silage samples were dried, ground and incubated with buffered rumen fluid. Gas production was monitored over 48 h and gas production curves were fitted to a modified Gompertz equation.In general, enzyme-treated silages showed a shorter initial lag phase and lower maximum gas production rate, indicating that the enzymes degraded cell wall material to more rapidly fermentable components, leaving a more slowly fermentable fraction. The total amount of gas produced was not altered by enzyme treatment, but a shift towards more rapidly fermentable material was observed. These changes in gas production kinetics went hand in hand with a change in chemical composition (more degradation of neutral detergent fibre and higher production of lactic acid in the enzyme-treated silages than in the control silages). Silages treated with enzyme preparations that did not contain cellulase did not differ from the control silages either in gas production kinetics or in chemical composition.Wilting up to 300 g DM kg−1 had no influence on gas production kinetics, whereas wilting up to 488 g DM kg−1 resulted in a longer initial lag phase, a lower maximum rate and lower total gas production. With increased maturity, lower total amounts of gas and lower maximum rates were observed. The measurement of changes in gas production kinetics of enzyme-treated silages compared with control silages is a useful and rapid technique for prescreening the effects of enzyme addition.

Notes: The aim of this study was to improve the quantitative determination of the plant opal content (i.e. phytoliths) in soils.The proposed method is based on: (i) the separation of plant opal from the silt and sand fractions of the soil, using heavy liquid flotation (aqueous solution of ZnBr2, density = 1.92 g cm−3); (ii) the subsequent determination of alkali-soluble silicon by atomic absorption spectrometry. Extraction and analytical procedures were tested on a broad sample of temperate and tropical soils with very different phytolith contents.Our investigations lead to the following conclusions: (i) a selective dissolution of opal in alkaline solutions (e.g. hot 0.5 m NaOH as proposed by Jones, 1969) is inaccurate so that a sink-float method must be used before any dissolution procedure; (ii) to dissolve opal completely, a 0.5 M NaOH dissolution treatment at 150°C can be easily and successfully carried out in steel PTFE-lined pressure vessels; (iii) the reproducibility of the determination is satisfactory for a step-by-step procedure (mean coefficient of variation = 13.4%).The comparison of this new method of quantitative assessment of soil opal with two other methods (gravimetric and phytolith-counting methods), shows very highly significant correlations (P〈0.001). Therefore, this procedure is a useful tool in studies connected with pedological and environmental history.

Notes: Two Oxisols (Mena and Malanda), a Xeralf and a Xerert from Australia and an Andept (Patua) and a Fragiaqualf (Tokomaru) from New Zealand were used to examine the effect of pH and ionic strength on the surface charge of soil and sorption of cadmium. Adsorption of Cd was measured using water, 0.01 mol dmp−3 Ca(NO3)2, and various concentrations of NaNO3 (0.01–1.5 mol dm−3) as background solutions at a range of pH values (3–8).In all soils, the net surface charge decreased with an increase in pH. The pH at which the net surface charge was zero (point of net zero charge, PZC) differed between the soils. The PZC was higher for soils dominated by variable-charge components (Oxisols and Andept) than soils dominated by permanent charge (Xeralf, Xerert and Fragiaqualf). For all soils, the adsorption of Cd increased with an increase in pH and most of the variation in adsorption with pH was explained by the variation in negative surface charge. The effect of ionic strength on Cd adsorption varied between the soils and with the pH. In Oxisols, which are dominated by variable-charge components, there was a characteristic pH below which increasing ionic strength of NaNO3 increased Cd adsorption and above which the reverse occurred. In all the soils in the normal pH range (i.e. pH〉PZC), the adsorption of Cd always decreased with an increase in ionic strength irrespective of pH. If increasing ionic strength decreases cation adsorption, then the potential in the plane of adsorption is negative. Also, if increasing ionic strength increases adsorption below the PZC, then the potential in the plane of adsorption must be positive. These observations suggest that, depending upon the pH and PZC, Cd is adsorbed when potential in the plane of adsorption is either positive or negative providing evidence for both specific and non-specific adsorption of Cd. Adsorption of Cd was approximately doubled when Na rather than Ca was used as the index cation.

Notes: The fate of 15N-labelled synthetic urine (50 g N m−2) applied to an irrigated pasture soil was studied using large undisturbed monolith lysimeters (800 mm diameter × 1200 mm deep). Over a period of 1 year, the pasture plants recovered the largest fraction of the applied 15N (43%) and approximately 20% of the applied 15N still remained in the soil, the majority of which was found in the topsoil (0–20 cm). Although the experiment was conducted under relatively intense rainfall and irrigation conditions, only 8% of the applied 15N was found to have leached below 1200 mm after 1 year. During this time, the average peak concentration of nitrate in the leachate reached 42 mg NO3−-N dm−3. The amount of nitrogen (N) lost by the process of denitrification was calculated as 28% of the applied 15N. This large loss of N to the atmosphere was attributed to the wet soil conditions which prevailed.

Notes: Soil solution was obtained from potted rhizosphere or non-rhizosphere soils by water displacement or soil centrifugation. The pH of the displaced solutions was lower than that of bulk soils when solutions were obtained from non-rhizosphere soil, although it increased as plants grew. This increase probably reflected true changes in rhizosphere pH, generated by the uptake by plants of N03-N. In contrast, the pH of soil centrifugates was usually close to that of the bulk soils, implying that buffering by colloids had occurred during sampling. Concentrations of elements in solutions from non-rhizosphere soil were similar for both methods when soils were incubated at ambient pCO2. However, when non-rhizosphere soils were incubated at elevated pCO2, displacement solutions had lower pH values, and much larger concentrations of elements, compared to soil centrifugates.Comparison of mass flow of elements versus actual plant uptake showed that Ca and Mg accumulated, while K, Zn and Cd were depleted from the rhizosphere. Displacement solutions showed this accumulation or depletion of the elements more clearly than soil centrifugates. These differences were attributed to the fact that, at constant soil moisture, the rhizosphere developed mainly in larger pores, which were sampled by displacement. With centrifugation, a mixture of pore sizes was sampled, so that rhizosphere solution was only obtained when all of the soil had become rhizosphere.Soil centrifugates obtained after 22 days of growth also contained higher concentrations of organic carbon than displacement solutions, indicating contamination due to the disruption of roots and/or micro-organisms. We conclude that water displacement is suitable for sampling solution from light to medium textured rhizosphere or non-rhizosphere soils and that soil centrifugation is only of limited suitability.

Notes: Soil from Eutrochrept A horizons under long-term spruce forest (Sf), mixed deciduous forest (Df), permanent grassland (Gp) and arable rotation (Ar) was fractionated according to particle size and analysed for contents of C, N, lignin-derived phenols and carbohydrates.Whole soil from Sf, Df, Gp and Ar contained 84, 59, 73 and 25 g C kg−1 soil, respectively. For all sites, the C content declined and C/N ratio increased in the order: clay (〈2 μm), silt (2–20 μm), sand (20–2000 μm). Clay and silt were significantly lower in C in Ar than in Sf, Df and Gp, C associated with sand being substantially lower under arable rotation.The yield of lignin-derived phenols decreased and carboxyl functionality and methoxyl demethylation of lignin derivatives increased with decreasing particle size, indicating a progressive lignin alteration. Whole soil from Sf and Gp was substantially higher in vanillyl (V), syringyl (S) and cinnamyl (C) units (VSC) than soil from Df and Ar. Compared to whole soil, clay was depleted and sand enriched in VSC. Only sand appeared to be affected significantly by land use. Sand from Ar and Df was more enriched in VSC than sand from Gp and Sf.Whole soil carbohydrates decreased in the order: Gp〉Ar〉Df〉Sf. Sand- and clay-sized separates were enriched in carbohydrates compared to silt. Carbohydrates in sand were mainly of plant origin whereas microbially-derived sugars accounted for a larger proportion in the clay. Compared to Sf, Df and Gp, clay from Ar was enriched and sand depleted in microbial sugars.Lignin and carbohydrate distribution patterns indicate that organic matter was in a more advanced stage of decomposition in the sand separates from forest than from agricultural A horizons. The forest soils also show a higher degree of oxidative changes in lignin associated with clay. In contrast, differences between silt from the four A horizons were small.

Notes: The effects of geometry upon diffusion from instantaneous sources is considered. Although surface area is important initially, it is the square of the volume of the source which determines flux from the source at large times. This asymptotic shape independence is demonstrated for spherical and cuboidal sources.