ALBERT

Notes: Abstract. Crops grown on virgin upland Vertisols of Zambia, are reported to perform rather poorly. However, subsoiling followed by repeated cultivation over two years apparently improves crop growth. Highest yields were recorded under long-term cultivation (12 years). To evaluate the reasons for these differences in crop response to Vertisol management, physical and hydrodynamic characteristics of soil profiles were studied in three soil management systems. The management systems were: uncultivated or virgin land; land cultivated for two years; and land cultivated for 12 years. The mean soil aggregate size decreased with increased time of cultivation, mostly due to the decrease of the largest sized aggregates. The surface horizon dried more slowly on the long-term cultivation plot. A comparison of the hydraulic conductivities indicated that water intake in the deeper layers improved with increased period in cultivation. Oxygen diffusion measurements showed good aeration at field capacity, to a depth of 0.32m on the long-term cultivation plots, but only to 0.17 m and 0.25 m for 2 years cultivation and virgin plots respectively. Repeated cultivation was beneficial in improving surface soil tilth and in improving subsurface drainage, thus removing the problem of a perched water table which occurred close to the soil surface under natural conditions.

Notes: Abstract. The chemical extractability of heavy metals introduced into the soil during 7 years application of sewage sludge, composted municipal solid waste and sheep manure, and their availability to citrus plants were studied. The total content of metals in the soil (0-20 cm)was increased by the use of sludges and compost, but only the Ni content in the saturation extracts of soil was significantly increased. Total Cd, Cr, Cu, Ni, Pb, and Zn were sequentially fractionated into water-soluble plus exchangeable, organically bound, carbonate-associated, and residual fractions. Most of the heavy metals were present in carbonate and residual fractions, although substantial amounts of water-soluble plus exchangeable Cd, and organically bound Cu and Ni were found. No significant increases in the metal contents in leaves and orange fruits were observed, with the exception of Pb in leaves. Several statistically significant correlations between metal content in plants, metal content in soil fractions, and chemical characteristics of soil were also found.

Notes: Book reviewed in this article: Human impact on Erosion and Sedimentation By D. E. Walling & J.-L. Probst (editors).

Notes: Book reviewed in this article: Soil erosion by water in Africa: Principles, Prediction and Protection By D. Nill, U. Schwertmann, U. Sabel-Koscella, M. Bernhard & J. Breuer.

Notes: Abstract. To provide a practical aid to improving fertilizer practice a mechanistic model was developed that can be readily calibrated for widely different crops. Most of the inputs are easy to obtain and the others, the amounts of fixed soil-K and the velocity constants for fixation and release of soil-K, can be readily measured by a novel procedure which is described.The model calculates for each day the potential increase in plant weight and the increment in root length, from the current plant mass, its %K and pan evaporation. It calculates the maximum amount of K that could be transported through soil to the root surfaces. It modifies this potential uptake by taking account of the ‘feedback’ of plant K on root absorption to give the actual uptake and a new %K in the plant. It calculates the radii of the depletion zones around each root increment and the interchange between the solution, exchangeable and fixed-K in these zones and also in the undepleted regions of soil. Routines are included for the effects of weather on the various processes. Differences between species are accommodated by selecting one of three algorithms for root growth and by adjusting the values of two crop-K parameters that define the decline in a critical and a maximum possible %K with increase in plant mass per unit area.A simplified version of the model runs interactively on the Internet at:

Notes: Abstract. The effect of rate and timing of autumn/winter straw incorporation on the immobilization of spring-applied N-fertilizer are studied. The immobilization of 15N-labelled fertilizer by straw was determined in pot trials with a sandy loam soil (Wick series) collected from two field experiments. In experiment 1, straw was incorporated at four different rates in the autumn; experiment 2 had a fixed rate of straw (7.5 t/ha) incorporated at monthly intervals from September to March. Immobilization in spring was not enhanced when only stubble was incorporated in autumn. However, autumn incorporation of 7.5 t/ha straw resulted in a significant increase in the immobilization of spring-applied N, equivalent to 10 kg/ha; when 15 t/ha straw was incorporated, immobilization increased to 18 kg/ha. The enhancement of immobilization, immediately following fertilizer application, was dependent on the extent of straw decomposition prior to N application. Thus immobilization was related to cumulative thermal time (day °C above 0°C; Tsum between the date of straw incorporation and fertilizer application). Straw which had been incorporated for Tsum 〉 1200 no longer caused appreciable immobilization of spring fertilizer.

Notes: Book reviewed in this article: Erosion and sediment yield: global and regional perspectives Edited by D. E. Walling and B. W. Webb.

Notes: Abstract. The restorative ability of herbaceous (Psophocarpus palustris, Pueraria phaseoloides) and woody (Leucaena leucocephala, Senna siamea, Acacia leptocarpa, Acacia auriculiformis) legume species and of natural regrowth was studied on an eroded and compacted Oxic Paleustalf in southwestern Nigeria. Compared to the control treatment that was continuously cropped for 15 years, four years of fallowing significantly improved test crop yields. However, fallowing with the above species did not substantially improve soil properties, particularly soil bulk density. A longer fallow period may be needed to amend soil physical conditions of this degraded Alfisol. Soil chemical properties were greatly improved following land clearing and plant biomass burning in 1993. However, the residual effect of burning on soil fertility was insignificant in the second cropping year. Among the fallow species, P. palustris and natural fallow showed the best residual effect on test crop performance. Despite the high biomass and nutrient yields of S. siamea and A. auriculiformis, test crop yields on these plots were low due to the border effects from the uncleared and fallowed subplots.

Notes: Abstract. To study the influence of different vegetation species and plant properties on the generation of surface runoff and soil erosion in south east Spain, a series of rainfall simulation experiments was conducted on small (c. 1.5 m2) plots. These were carried out in October 1993 and May 1994 on two sites close to Murcia. Six vegetation types were studied, with some at different stages of maturity, giving a total of nine vegetation treatments and two bare soil treatments. Four replicates of each treatment were exposed to a rainstorm of 120 mm/h for 15 minutes. The results of the experiments show that there are few significant differences in the ability of the vegetation types studied to control runoff or soil erosion. Of the plant properties considered, only plant canopy cover showed a significant relationship with soil loss and runoff with the greatest reduction in soil loss taking place at canopy covers greater than 30%. The implications of this research are that future efforts should be directed at developing ecological successions and revegetation methods which promote a substantial and sustainable canopy cover.

Notes: Abstract. The effect of superficial liming of acidic forest soils on CO2 and N2O emissions and CH4 uptake was investigated with closed chambers in two deciduous and two spruce forests, by weekly to biweekly measurements over at least one year. The flux rates of untreated areas varied between 1.94 and 4.38 t CO2-C/ha per y, 0.28 and 2.15 kg/N2O-N/ha per y and between 0.15 and 1.06 kg CH4-C/ha per y. Liming had no clear effect on CO2 emissions which may change in the long-term with decreasing root turnover and increasing C-mineralization. Apart from one exception, liming resulted in a reduction of N2O emissions by 9 to 62% and in an increase of CH4 uptake by 26 to 580%. The variability in N2O emissions between the forest sites could not be explained. In contrast, the variability of annual CH4 uptake rates could be explained by N content (r2= 0.82), C content (r2= 0.77), bulk density (r2= 60), pore space (r2= 0.59) and pH (r2= 0.40) of mineral soil at a depth of 0 to 10 cm, and by the quantity of material in the organic layer (r2= 0.66). Experiments with undisturbed columns of the same soils showed that between 1 and 73% of the total N2O emissions came from the organic layer. However, atmospheric CH4 was not oxidized in this layer, which represents a diffusion barrier for atmospheric CH4. When this barrier was removed, CH4 uptake by the mineral soil increased by 25 to 171%. These results suggest that liming of acidic forest soils causes a reduction of the greenhouse gases N2O and CH4 in the atmosphere, due to changes in the chemical, biological, and physical condition of the soils.

Notes: Abstract. Agricultural soils, having been depleted of much of their native carbon stocks, have a significant CO2 sink capacity. Global estimates of this sink capacity are in the order of 20-30 Pg C over the next 50-100 years. Management practices to build up soil C must increase the input of organic matter to soil and/or decrease soil organic matter decomposition rates. The most appropriate management practices to increase soil C vary regionally, dependent on both environmental and socioeconomic factors.In temperate regions, key strategies involve increasing cropping frequency and reducing bare fallow, increasing the use of perennial forages (including N-fixing species) in crop rotations, retaining crop residues and reducing or eliminating tillage (i.e. no-till). In North America and Europe, conversion of marginal arable land to permanent perennial vegetation, to protect fragile soils and landscapes and/or reduce agricultural surpluses, provides additional opportunities for C sequestration.In the tropics, increasing C inputs to soil through improving the fertility and productivity of cropland and pastures is essential. In extensive systems with vegetated fallow periods (e.g. shifting cultivation), planted fallows and cover crops can increase C levels over the cropping cycle. Use of no-till, green manures and agroforestry are other beneficial practices. Overall, improving the productivity and sustainability of existing agricultural lands is crucial to help reduce the rate of new land clearing, from which large amounts of CO2 from biomass and soil are emitted to the atmosphere.Some regional analyses of soil C sequestration and sequestration potential have been performed, mainly for temperate industrialized countries. More are needed, especially for the tropics, to capture region-specific interactions between climate, soil and management resources that are lost in global level assessments.By itself, C sequestration in agricultural soils can make only modest contributions (e.g. 3-6% of total fossil C emissions) to mitigating greenhouse gas emissions. However, effective mitigation policies will not be based on any single ‘magic bullet’ solutions, but rather on many modest reductions which are economically efficient and which confer additional benefits to society. In this context, soil C sequestration is a significant mitigation option. Additional advantages of pursuing strategies to increase soil C are the added benefits of improved soil quality for improving agricultural productivity and sustainability.

Notes: Abstract. Field measurement of landfill methane (CH4) emissions indicates natural variability spanning more than seven orders of magnitude, from less than 0.0004 to more than 4000 g/m2 per day. This wide range reflects net emissions resulting from production (methanogenesis), consumption (methanotrophic oxidation), and gaseous transport processes. The determination of an ‘average’ emission rate for a given field site requires sampling designs and statistical techniques which consider spatial and temporal variability. Moreover, particularly at sites with pumped gas recovery systems, it is possible for methanotrophic microorganisms in aerated cover soils to oxidize all of the CH4 from landfill sources below and, additionally, to oxidize CH4 diffusing into cover soils from atmospheric sources above. In such cases, a reversed soil gas concentration gradient is observed in shallow cover soils, indicating bidirectional diffusional transport to the depth of optimum CH4 oxidation. Rates of landfill CH4 oxidation from field and laboratory incubation studies range up to 166 g/m2 per day, among the highest for any natural setting, providing an effective natural control on net emissions. It has been shown that methanotrophs in landfill soils can adapt rapidly to elevated CH4 concentrations with increased rates of CH4 oxidation related to depth of oxygen penetration, soil moisture, and the nutrient status of the soil.Estimates of worldwide landfill CH4 emissions to the atmosphere have ranged from 9 to 70 Tg/y, differing mainly in assumed CH4 yields from estimated quantities of landfilled refuse. At highly controlled landfill sites in developed countries, landfill CH4 is often collected via vertical wells or horizontal collectors. Recovery of landfill CH4 through engineered systems can provide both environmental and energy benefits by mitigating subsurface migration, reducing surface emissions, and providing an alternative energy resource for industrial boiler use, on-site electrical generation, or upgrading to a substitute natural gas. Manipulation of landfill cover soils to maximize their oxidation potential could provide a complementary strategy for controlling CH4 emissions, particularly at older sites where the CH4 concentration in landfill gas is too low for energy recovery or flaring. For the future, it is necessary to better quantify net emissions relative to rates of CH4 production, oxidation, and transport. Field measurements, manipulative studies, and model development are currently underway at various spatial scales in several countries

Notes: Book Reviewed in this article: Phosphorus loss from soil to water: Edited by H. Tunney, O. T. Carton, P. C.

Notes: Abstract. Variously timed sub-optimal irrigation strategies were applied to sugarbeet grown on a light soil (loamy sand or sandy loam) over four seasons (1991 to 1994) to investigate the effect on crop growth and nitrate leaching risk. Data from the two dry seasons, (1991 and 1994) are reported here. In the driest year (1991) soil mineral N levels after autumn harvest were negatively related to crop water use (P 〈 0.05). In this season, there was little drainage from the soil profile, and full irrigation reduced residual soil N by 31 kg N/ha (0-90 cm) compared with the unirrigated treatment (79 kg N/ha). The potential for N leaching during the ensuing winter was consequently more than halved. In 1991 and 1994 there was a strong positive linear relationship between dry matter yield, N uptake and water use, but a negative relationship between plant N concentration and water use. These relationships were a function of the severity and not the timing of drought. The additional N uptake associated with increased irrigation and crop water use was biased towards a large concentration in the aboveground crop (tops), which are normally returned to the soil. The C:N ratio of sugarbeet tops was affected by crop water supply with droughted crops having lower values. This would also influence N release and subsequent leaching risk. However, the effects of drought on N leaching risk were relatively small when compared with other root crops such as potatoes.

Notes: Abstract. The effects of tree crops on the soil physical properties of former agricultural land were compared with those of ley in a rotation with cereals on adjacent sites. Five sites in southern Sweden were investigated focussing on soil water retention characteristics, dry bulk density, macroporosity and saturated hydraulic conductivity. Three of the sites were on light textured soils and two on clay soils. The tree crops were 30 to 35-year-old hybrid aspen, Populus deltoides, and silver birch, Betula pendula, and the ley crops were one to five years old.The light-textured soils under tree crops showed bimodal pore size distributions in the macropore region, whereas under ley crops they showed unimodal distributions. Dry bulk densities were generally smaller and the macroporosities larger under tree crops compared with leyicereal crops. Saturated hydraulic conductivities tended to be larger under tree crops. Slopes of the linear regression lines between saturated hydraulic conductivity and each of the parameters dry bulk density, porosity and macroporosity were steeper in the soil under agricultural crops than under tree crops.Observed differences in physical properties were considered to be an effect of land use, which had brought about changes in aggregate stability, pore size distribution and pore continuity.

Notes: Abstract. Phosphorus concentrations and outputs have been compared and contrasted in six small agricultural catchments in the west and northeast of Scotland. The loss of P from soils to stream waters was more from catchments with intensive dairy cattle farming in the west than from the less intensively stocked/arable catchments in the northeast, with striking differences being seen between the two regions. In the northeast, intensive animal farming caused less P loss in drainage water than arable management.Larger mean annual concentrations were seen in the west (0.076-0.142 mg PO4-P/l as molybdate-reactive phosphate–MRP) compared with the northeast (0.012-0.025 mg PO4-P/l), a feature caused by the combination of limited P-retention in the western Gleysols and smaller inputs to the largely-podzolic northeastern catchments. Stream concentrations were decreased by dilution during winter storm flows and increased during summer baseflow and at the beginning of soil rewetting in autumn.

Notes: Book Reviewed in this article: Freshwater Contamination By B. Webb (editor).

Notes: Book Reviewed in this article: Biotechnical and soil bioengineering slope stabilization. A practical guide for erosion control By D. H. Gray & R. B. Sotir.

Notes: Abstract. This paper reports results from a four year study to investigate the suitability of porous ceramic cups to measure solute leaching on shallow chalk soils. Measurements were carried out in one field following surface applications of nitrate and bromide tracers and in two fields after only bromide was applied. Soil water samples were collected from porous cups at 30,60 and 90cm depth after every 25 mm of drainage, and soil samples from 0–30, 30–60 and 60–90 cm were collected monthly eachwinter. Soil matric suctions andvolumetric moisture content were measured in one winter. Leaching losses, measured with ceramic cups were compared with those measured by soil analysis. Porous cups installed in chalk at 60 and 90 cm depth were only able to collect samples regularly when soil matric suctions were less than 15 kPa. Water held at such low suctions is likely to move quickly through relatively large fissures in the chalk. The slow rate of equilibration between solute concentrations in water moving in macrofissures and those in water moving through micropores of the chalk matrix, means that porous cups may not provide good estimates of leaching losses if they are installed in chalk rock.

Notes: Abstract. Nitrate leaching after one year of a cut grass/clover ley was measured in two succeeding years to investigate how the postponing of ploughing leys from early to late autumn or spring, in combination with spring or winter cereals affected leaching of nitrate. The experiment was conducted as three field trials, two on a coarse sandy soil and one on a sandy loam soil. For calculation of nitrate leaching, soil water samples were taken using ceramic suction cups. The experiments started in spring in a first year ley and ended in spring three years later. Total nitrate leaching for the three year periods for each trial ranged between 160–254 and 189–254 kg N/ha on the coarse sand and 129–233 kg N/ha on the sandy loam. The results showed that winter wheat (Triticum aestivum L.) did not have the potential for taking up the mineralized N in autumn after early autumn ploughing of grass/clover leys, and that the least leaching was generally found when ploughing was postponed until spring, and when winter rye (Secale cereale L.) was grown as the second crop rather than spring barley (Hordeum vulgare L.). Nevertheless, leaching was generally high in the winter period even when winter rye was grown. On these soil types ploughing out should be postponed, whenever possible, to spring. Crop systems that maximize the utilization of mineralized N and thereby minimize nitrate leaching need to be further developed. Based on N balances, the data were further used to estimate the biological N fixation by the clover.

Notes: Abstract. Ceramic suction cups were used to obtain samples of soil solution from permanently grazed swards receiving 200 kg N/ha/y. The suction cups were installed in 1 ha plots at 10, 30 and 60 an depth in a poorly drained, heavy clay soil in S. W. England. The plots were hydrologically isolated from each other by perimeter drains which channelled surface runoff water into v-notch weirs. In one treatment, artificial drainage by a system of field and mole drains also converged to outfalls through v-notch weirs, which enabled samples to be taken. Nitrate and a range of other ionic constituents were examined over a 12 month period in soil solutions taken from the suction cups and compared with leachate obtained from the field drains and surface channels. Field drain samples frequently exceeded the EC limit of 11.3 mg nitrate-N/1, but concentrations in suction cups obtained during the same period did not, and were up to ten-fold less. Although correlations for ions were found between different sampling depths and drainage samples, no clear patterns emerged. It was concluded that suction cups were inappropriate for the determination of the overall leaching losses in this soil type, but provided useful data on changes in ionic concentrations which occurred in different soil horizons through to drainage outfalls.

Notes: Abstract. The impact of soil erosion on soil productivity was estimated for a Rhodic Ferralsol and a Eutric Cambisol in Santa Catarina, southern Brazil. Over equivalent periods, total soil losses were an order of magnitude different (868 and 68 t/ha respectively on the bare soil control), yet the impact on maize yield per tonne of soil lost was far greater at the Cambisol site with less erosion. Similar interesting contrasts between sites were found for the other measures of impact with decline in pH and phosphorus and increase in free aluminium being the most obvious induced soil differences. The results demonstrate the variable nature of erosion impact according to soil type and they highlight the importance of examining a number of measures of impact before pronouncing on the sustainability of any particular agricultural practice.

Notes: Abstract. Mubangwe Farm, northern Malawi, was brought into cultivation from savanna vegetation with Brachystegia between 1970 and 1983 to produce tobacco, maize and groundnuts. Because of poor yields even with inputs of lime, N, P and K the fields were soon abandoned. The soils were only moderately acidic with little likelihood of Al toxicity. They held only small amounts of exchangeable Ca2+ (down to 0.01 cmolc/kg) particularly at depth. Phosphorus availability was low particularly in the subsoil. A minus-one pot experiment showed that the growth of sorghum in topsoil samples was limited by lack of N, P, S and Ca. The lower availabilities of P and Ca in the subsoil are therefore likely to be major limitations to growth, allowing only limited root penetration. The loamy sand to sandy clay soils generally had small available water capacities (down to 0.07 cm3/cm3) which, with restricted root development, may have lead to drought in dry periods during the growing season. The findings emphasize the need to measure both subsoil and topsoil properties when new areas of land are being developed for crop production.

Notes: Abstract. Nitrogen (N) leaching losses from a shallow limestone soil growing a five course combinable croprotation (oilseed rape, wheat, peas, wheat, barley) were measured from 1990 until 1995 using porous ceramic cups, at 60 cm depth, and drainage estimates. The crops were grown with three husbandry systems and two levels of N fertilizer. The husbandry systems were designed to reflect local practice (Standard), the best possible techniques to reduce N loss (Protective) and an Intermediate system which was a compromise between the two. Nitrogen was applied at full and half recommended rates. Drainage started during September in four years and November in one year, with above average drainage in three years. Losses of N were largest after peas (58 kg/ha) and oilseed rape (42 kg/ha), and least (17 kg/ha) before peas sown in spring after a cover crop. Over five years, the Protective management system, which used early sowing and shallow cultivation wherever possible, lost least N (31 kg/ha/y) and the Standard system, with conventional drilling dates and ploughing as the primary cultivation, lost most (49 kg/ha/y). Halving the N fertilizer decreased N loss by 11 kg/ha/y, averaged over the rotation. None of the treatments gave mean drainage water nitrate concentrations of less than 50 mg/l, averaged over the five years. Changes to arable cropping alone will not eliminate the need for other measures to control nitrate concen-trations in public drinking water supplies.

Notes: Abstract. Soil salinity and alkalinity reduce plant production and alter species composition of meadow grasslands in western Jilin Province, China. This study was designed to compare the survival and growth of three grass species (Aneumlepidium chinense, Puccinellia tenuijlora and Hordeum brevisubulatum) transplanted into saline-alkali soils in the field, and to evaluate the effects of gypsum amendments on soil properties and growth of these species. Gypsum treatments decreased soil pH, electrical conductivity, and chloride and sodium levels; water infiltration and calcium levels were increased. Survival of grass transplants was increased by gypsum treatments. Tiller number and height, and grass yields were all increased by the application of gypsum. Improvements in plant growth and survival with gypsum treatment appeared to be due to reduced chloride levels and increased Ca availability in the soil, and to changes in soil structure leading to improved infiltration rates. Revegetation of salinelalkaline soils in this region would be improved by application of gypsum in the range of 14–19 t/ha.

Notes: Abstract. Methane (CH4) is an important greenhouse gas. Flooded rice fields (paddies) are a significant source of atmospheric CH4; estimates of the annual emission from paddies range from less than 20 to 100 million Tg, with best estimates of 50 × 20 Tg. The emission is the net result of opposing bacterial processes: production in anaerobic microenvironments, and consumption and oxidation in aerobic microenvironments, both of which occur sequentially and concurrently in flooded rice soils. With current technologies, CH4 emission from rice fields will increase as production increases. Over the next 25 years rice production will have to increase by 65% from the present 460 Mt/y to 760 Mt/y in 2020. The current understanding of the processes controlling CH4 fluxes, rice growth and rice production is sufficient to develop mitigation technologies. Promising candidates are changes in water management, rice cultivars, fertilization, and cultural practices. A significant reduction of CH4 emission from rice fields, at the same time that rice production and productivity increase at the farm level, is feasible, although the regions where particular practices can be applied, and the trade-offs that are possible, have still to be identified.

Notes: Abstract. Increases in the emissions of globally important nitrogen (N) oxide gases have coincided with significant changes in land use in the tropics. Clearing of tropical forests and savannas for agriculture currently represents the most extensive alteration of land cover on the planet. Over the last several decades, N fertilizer use has increased globally, and in China and the developing world, use has recently surpassed that in the developed world. The potential contribution of land-use change in the tropics to the increase in N oxides is great, yet only a few studies have measured N oxide emissions after tropical land conversion. Our summary of available research shows some conversions to pastures and a few management practices, especially those using N fertilizers, increase emissions beyond those found in undisturbed ecosystems. However, not all studies show unequivocal increases in emissions. Accordingly, we call for a mechanistic understanding of the processes controlling trace gas fluxes to adequately predict under what conditions increased emissions may occur. More measurements are needed to build and test models that may improve management of N fertilizer use in tropical agricultural systems. Given the expected expansion of agriculture and increased use of N fertilizers in the tropics, increased emissions of N oxides from the tropics are likely.

Notes: Abstract. Grazing animals on managed pastures and rangelands have been identified recently as significant contributors to the global N2O budget. This paper summarizes relevant literature data on N2O emissions from dung, urine and grazed grassland, and provides an estimate of the contribution of grazing animals to the global N2O budget.The effects of grazing animals on N2O emission are brought about by the concentration of herbage N in urine and dung patches, and by the compaction of the soil due to treading and trampling. The limited amount of experimental data indicates that 0.1 to 0.7% of the N in dung and 0.1 to 3.8% of the N in urine is emitted to the atmosphere as N2O. There are no pertinent data about the effects of compaction by treading cattle on N2O emission yet. Integral effects of grazing animals have been obtained by comparing grazed pastures with mown-only grassland. Grazing derived emissions, expressed as per cent of the amount of N excreted by grazing animals in dung and urine, range from 0.2 to 9.9%, with an overall mean of 2%. Using this emission factor and data statistics from FAO for numbers of animals, the global contribution of grazing animals was estimated at 1.55 Tg N2O-N per year. This is slightly more than 10% of the global budget.

Notes: Abstract. Increases in the atmospheric concentrations of nitrous oxide (N2O) contribute to global warming and to ozone depletion in the stratosphere. Nitric oxide (NO) is a cause of acid rain and tropospheric ozone. The use of N fertilizers in agriculture has direct and indirect effects on the emissions of both these gases, which are the result of microbial nitrification and denitrification in the soil, and which are controlled principally by soil water and mineral N contents, temperature and labile organic matter.The global emission of N2O from cultivated land is now estimated at 3.5 TgN annually, of which 1.5 Tg has been directly attributed to synthetic N fertilizers, out of a total quantity applied in 1990 of about 77Tg N. This amount was 150% above the 1970 figure. The total fertilizer-induced emissions of NO are somewhere in the range 0.5-5 Tg N. Mineral N fertilizers can also be indirect as well as direct sources of N2O and NO emissions, via deposition of volatilized NH3 on natural ecosystems and denitrification of leached nitrate in subsoils, waters and sediments.IPCC currently assume an N2O emission factor of 1.25 ± 1.0% of fertilizer N applied. No allowance is made for different fertilizer types, on the basis that soil management and cropping systems, and unpredictable rainfall inputs, are more important variables. However, recent results show substantial reductions in emissions from grassland by matching fertilizer type to environmental conditions, and in arable systems by using controlled release fertilizers and nitrification inhibitors. Also, better timing and placement of N, application of the minimum amount of N to achieve satisfactory yield, and optimization of soil physical conditions, particularly avoidance of excessive wetness and compaction, would be expected to reduce the average emission factor for N2O. Some of these adjustments would also reduce NO emissions. However, increasing global fertilizer use is likely to cause an upward trend in total emissions even if these mitigating practices become widely adopted.

Notes: Abstract. The validity of the model described in Greenwood & Karpinets (1997) was tested against the results of single year, multi level K fertilizer experiments. Measurements of plant mass, %K in the plant and K activity ratio in soil had been made at harvest and at intervals during the growing season on spring wheat, summer cabbage and turnips. Reasonably good agreement was obtained between these measurements and simulated values when the two ‘crop’ parameters (defining the dependence of critical and maximum possible %K on plant mass) were adjusted for each crop. Also good agreement was generally obtained for plant weight and plant %K at harvest in less detailed experiments on 10 other crops. Values of the two ‘crop’ parameters for 12 of the crops were strongly correlated with one another suggesting that a single ‘crop’ parameter may be all that is required to define most inter-species differences in plant-K demand.Simulations with the model indicate that, in central England, no response of 10 crops to K fertilizer would be likely on soils containing more than 170 mg of 1 M ammonium nitrate extractable-K/kg of soil and having clay contents of between 15 and 45%. Shortcomings of the model and opportunities for advance are discussed.A simplified version of the model runs on the Internet at:

Notes: Abstract. As part of a study of recession farming on the ‘fadama’ lands on a segment of the Komadugu-Yobe floodplain, a survey was carried out to investigate the local farmers’ perception of soil types and management practices. The farmers are clearly aware of the differences in soil type on the fadama and they possess unique skills in managing their farm lands. The farmers classify fadama soils for recession farming by assessing soil texture and soil drainage conditions by feel and observation. Integrating such local knowledge into soil surveys will lead to better practical definition of mapping units and give soil names that have more meaning for the farmers.

Notes: Abstract. The large boreal peatland ecosystems sequester carbon and nitrogen from the atmosphere due to a low oxygen pressure in waterlogged peat. Consequently they are sinks for CO2 and strong emitters of CH4. Drainage and cultivation of peatlands allows oxygen to enter the soil, which initiates decomposition of the stored organic material, and in turn CO2 and N2O emissions increase while CH4 emissions decrease. Compared to undrained peat, draining of organic soils for agricultural purposes increases the emissions of greenhouse gases (CO2, CH4, and N2O) by roughly 1t CO2 equivalents/ha per year. Although farmed organic soils in most European countries represent a minor part of the total agricultural area, these soils contribute significantly to national greenhouse gas budgets. Consequently, farmed organic soils are potential targets for policy makers in search of socially acceptable and economically cost-efficient measures to mitigate climate gas emissions from agriculture. Despite a scarcity of knowledge about greenhouse gas emissions from these soils, this paper addresses the emissions and possible control of the three greenhouse gases by different managements of organic soils. More precise information is needed regarding the present trace gas fluxes from these soils, as well as predictions of future emissions under alternative management regimes, before any definite policies can be devised.

Notes: Abstract. The projected increase in sewage sludge used on land within many countries in the European Community will provide a major source of entry for several heavy metals into the soil. Although the application rate of sewage sludge to agricultural land is constrained by maximum annual additions of heavy metals, there is a need to know the sensitivity of those soils to heavy metal inputs which are physically suited for application. A rulebased classification using weighted parameters designed to assess the metal binding capacity of soil and the risk of groundwater pollution has been applied to soils data held within the Macaulay Land Use Research Institute's National Soils Inventory The classification uses soil pH, organic matter content, texture and soil colour as a surrogate for iron oxide concentration. The results indicate that some metals, for example cadmium and zinc are potentially more mobile in soils than others such as lead, but that the majority of soils display a strong or very strong binding capacity for all the metals. However this pattern can only be sustained if the soil pH values are maintained at their present values; a fall of one pH unit marks a dramatic shift towards the weak and moderate binding classes. The approach is largely unvalidated but does provide a useful framework for incorporating our mechanistic understanding of processes into wide area soil quality assessments and in identifying future research opportunities.

Notes: Abstract. Kriging is used to provide detailed quantitative information for a range of soil characteristics across the floodplain of the River Gambia. Application of spatial statistics to a large area with a coarse grid of data points produces spurious patterns unless the area is first partitioned into soil-geomorphic mapping units, each of which has a unique pattern of spatial variation. Even combining classical soil survey method with spatial statistics, the large short-range variability of acid sulphate soils means that single factor maps conceal a large element of uncertainty. A more robust procedure is to map the probability of occurrence of critical values of key characteristics.

Notes: Abstract. Field experiments undertaken at 14 sites, on a range of soil types, in lowland England, during the cropping years 1989–1993, tested the effectiveness of cattle or pig slurry as a source of nitrogen for cereal cropping. Slurry was applied in autumn, winter and spring, to autumn and spring sown cereal crops. Assessments included slurry nitrogen efficiency relative to N in spring applied fertilizer in terms of both grain yield and grain protein production, apparent crop recovery and content of mineral nitrogen in soil profiles. Crop response to nitrogen was poor at seven sites where high residues of soil mineral nitrogen (SMN) were present. On the seven responsive sites, spring slurry applications proved more efficient (mean 40%) as a source of N than autumn (mean 24%) or winter applications (mean 32%). These differences were smaller than reported in a number of other studies, probably as a result of relatively low excess winter rainfall, resulting in less nitrate leaching during the period of the investigation. Rapid incorporation into the topsoil of slurry applied in autumn, increased (28 kgN/ha) the SMN of samples taken early in the winter. However this increase did not lead to a consistent improvement in crop N uptake. Slurry dressings, whenever applied, can be expected to make a significant contribution to the N requirement of the succeeding crop and need to be taken into account when calculating the appropriate spring fertilizer application.

Notes: Abstract. Soils in areas with high livestock density contribute to the eutrophication of aquatic ecosystems through loss of nutrients, especially phosphorus (P). In order to identify the potential for P loss from such soils we determined phosphorus extracted by water (H2O-P), by double lactate (DL-P), and P sorption capacity (PSC) and degree of P saturation (DPS) in soil samples from two counties, one with low (Harle-catchment) and the other with very high livestock density (Vechta). Both catchments are hydrologically connected with the tidal areas of the North Sea.The mean concentrations of H2O-P (0.4mmol/kg) and DL-P (3.9 mmol/kg) were lower in the Harle-catchment than in the Vechta area (1.2 mmol/kg, 6.8mmol/kg). Although oxalate-extractable Al (Alox) and Fe (Feox) and the derived PSCs varied according to soil type and to land use, the livestock density and the resulting high concentrations of oxalate-extractable P (Pox) were shown to be the main reason for the very high DPS of up to 179% in the county of Vechta. These values exceeded DPS reported from other intensive pig feeding areas in western Europe and indicate the potential for significant P loss. Less than 40% of the variation in Pox could be explained by the routinely determined H2O-Por DL-P. Geostatistical analyses indicated that the spatial variability of Pox depended on manurial history of fields and Alox, showed still smaller-scale variability. These were the major constraints for regional assessments of P losses and eutrophication risk from agricultural soils using available soil P-test values, digital maps and geostatistical methods.

Notes: Abstract. Although gypsiferous soils cover approximately 100 million ha in the world, it is only in the past two decades that their pedogenic and agronomic properties have been better understood and their classification improved. There is still no method to assess adequately their production potential.This paper focuses on gypsum accumulation forms as diagnostic criteria for a rapid soil suitability appraisal in the field. Pseudomycelia, gypsum spots, powdery coatings and other localized in situ precipitations usually indicate soils with less than 15% gypsum. Depending on their intensity and depth of occurrence in the root zone, they define a soil environment which is suitable for semi-sensitive and semi-tolerant crops. Continuous gypsum accumulations characterize soils or horizons with high (e.g. more than 25%) gypsum contents, and these can be used only for tolerant crops.The land use potential of gypsiferous soils is primarily determined by: (a) the depth of the impermeable layer, (b)the gypsum content within the root zone, and (c) the crop tolerance level. A method is proposed to assess the land suitability of gypsiferous soils on the basis of these criteria.

Notes: A standardized dataset of derived soil properties for the 106 soil units considered on FAO-UNESCO's 1:5 million scale Soil Map of the World is presented. It was derived from a statistical analysis of the 4353 soil profiles held in the WISE (World Inventory of Soil Emission) database, which was developed at the International Soil Reference and Information Centre (ISRIC) for the geographic quantification of soil factors that control processes of global change. Median values are presented by soil unit for selected soil properties including: pH(H2O); organic carbon content; cation exchange capacity; sum of exchangeable Ca2+, Mg2+ and K+; exchangeable sodium percentage; bulk density; total porosity; available water capacity; soil drainage class; and gravel content class. Medians for these variables are presented both for the topsoil (0–30 cm) and subsoil (30–100 cm), where applicable. The data set can help to refine ratings for soil quality in global environmental models pending the availability of comprehensive georeferenced databases on soil and terrain resources such as SOTER, the World Soil and Terrain Database. In a Geographical Information System (GIS) it can be linked to the units shown on the digital Soil Map of the World through the legend code.

Notes: Abstract. The effect of grazing pressure on infiltration, runoff, and soil loss was studied on a natural pasture during the rainy season of 1995 in the Ethiopian highlands. The study was conducted at two sites with 0–4% and 4–8% slopes at the International Livestock Research Institute (ILRI) Debre Zeit research station, 50 km south of Addis Ababa. The grazing regimes were: light grazing stocked at 0.6 animal-unit-months (AUM)/ha; moderate grazing stocked at 1.8 AUM/ha; heavy grazing stocked at 3.0 AUM/ha; very heavy grazing stocked at 4.2 AUM/ha; very heavy grazing on ploughed soil stocked at 4.2 AUM/ha; and a control with no grazing. Heavy to very heavy grazing pressure significantly reduced biomass amounts, ground vegetative cover, increased surface runoff and soil loss, and reduced infiltrability of the soil. Reduction in infiltration rates was greater on soils which had been ploughed and exposed to very heavy trampling. It was observed that, for the same % vegetative cover, more soil loss occurred from plots on steep than gentle slopes, and that gentle slopes could withstand more grazing pressure without seriously affecting the ground biomass regeneration compared to steeper slopes. Thus, there is a need for developing ‘slope-specific’ grazing management schedules particularly in the highland ecozones rather than making blanket recommendations for all slopes. More research is needed to quantify annual biophysical changes in order to assess cumulative long-term effects of grazing and trampling on vegetation, soil, and hydrology of grazing lands. Modelling such effects is essential for land use planning in this fragile highland environment.

Notes: Abstract. An effective fertilizer recommendation system requires information on seasonal, soil-related and cultural variations in soil mineral nitrogen (N) and nutrient requirements of the crop. This can be provided by dynamic N turnover models, such as listed by Plentinger & Penning De Vries (1996). In this paper, we describe a survey of farmer opinion designed to ascertain what farmers want from such a decision support system. Over 100 farmers were surveyed. Surveyed farmers requested that default values be available for all model inputs. Inputs should be entered both by windows-based menu (for clarity) and tabular format (for speed), have user-selected units, and be fully supported by context-sensitive help. The system should have a hierarchical structure allowing access to fixed parameters, and be compatible with commonly used farm recording packages. Recommendations should be provided both for the field (single and optional application rates), and in tabular format across the whole farm. Simulations should be easily rerun using more recent crop and weather data. Turnover processes underlying recommendations should be illustrated by flow diagrams of flux between pools, pie charts of fertilizer fate, bar charts of movement down the soil profile and graphical plots of changes in N status against time.

Notes: Abstract. Ten chalk topsoils (0-25 cm) were repacked into columns in the laboratory. After leaching similar to one year's throughflow in the field, loss of K was equivalent to between 9 and 74kg K/ha. This represented between 3 and 30% of the initial exchangeable K with which loss was poorly correlated. Loss was dependant on the soil solution concentration and was inversely proportional to potassium buffer power.The loss of magnesium in the same columns was between 10 and 22 kg Mg/ha (6-21% of the initial exchangeable Mg). Magnesium loss was poorly correlated with exchangeable Mg.When KCl fertilizer was incorporated into the soils, the increase in leaching of potassium was 1–35% of the K addition. Application to the top of the column resulted in less leaching than when the K was incorporated. Leaching of magnesium was increased by up to 5 kg Mg/ha.Potassium leaching may be delayed by the underlying A/C horizon but pure chalk, with an extremely low buffer power for K, has little ability to retain K. Extremely calcareous topsoils were the most leaky although in practice it is the organic chalk soils on which it is most difficult to attain adequate K levels. On all chalk soils, maintenance of a high K level with K fertilizer is likely to cause unnecessary long-term leaching losses. Annual, rather than biennial, fertilizer applications are to be preferred.

Notes: Abstract. The effects of straw disposal by burning and incorporation on soil and crop nitrogen (N) supply, were investigated on two light textured soils in central (ADAS Gleadthorpe) and eastern England (Morley Research Centre) over the period 1984 to 1995. Nitrogen balance calculations showed that after 11 years of contrasting straw incorporation versus burn treatments, the cumulative N returns in straw were c. 570kg/ha at Gleadthorpe and c. 330 kg/ha at Morley However, these N returns via straw incorporation were not reflected in increased total soil N levels in autumn 1994. There were no differences (P 〉 0.05) between straw disposal treatments in autumn soil mineral N supply, readily mineralizable N or organic carbon. Similarly, there were no consistent differences between the treatments in terms of crop yield, crop N uptake or optimum fertilizer N rates. Fertilizer N applications of 200 kg N/ha/y increased topsoil organic carbon from 1.18 to 1.28% and total N content from 0.091 to 0.102% on the loamy sand textured soil at ADAS Gleadthorpe, but not at Morley. Previous fertilizer N applications increased the quantity of nitrate-N leached in drainage water by c. 20 kg/ha at Gleadthorpe and c. 60 kg/ha at Morley overwinter 1994/95, and by 10–20 kg/ha at both sites overwinter 1995/96. There was some indication overwinter 1994/95 that straw incorporation reduced nitrate-N leaching by 10–25 kg/ha, but there were no differences between treatments overwinter 1995/96.

Notes: Abstract. Formulation of nitrogen balances on farms requires accurate information on all inputs of the nutrient. N2-fixation by legumes, particularly forage legumes, is an important input which is difficult to measure. Simple regression models have been established from the literature for predicting N2-fixation by grass–white clover (Trifolium repens) mixtures using dry matter yields.Linear relationships were obtained between the N2- fixation (Nfix) and the extra dry matter production of mixed swards (Md) compared with pure grass swards. Nitrogen fixation was given by Nfix= A + 0.067Md where A is the intercept having a value of 6.8 for cut swards and -168.1 for grazed swards. A common slope was adopted because the F statistics showed that slopes fitted separately were not significantly different. The value of the negative intercept represents the supply of N to the grazed sward from soil and excreta-derived N. The regression equation for the cut sward gave reasonable predictions (r2= 0.953) of values of N2-fixed for experimental data not used in establishing the relationship. For grazed grass, the approach over-estimated the N2- fixation by an average of 15%.

Notes: Book reviewed in this article: Agricultural Recycling of Sewage Sludge and the Environment By S. R. Smith.

Notes: Book reviewed in this article: No-tillage seeding: science and practice By C. J. Baker, K. E. Saxton & W. R. Ritchie.

Notes: Abstract. The rates of CO2 production and decomposition of 13C-enriched Lolium perenne leaves and roots in soil from the surface five cm of two upland stagnohumic gley soils were measured in laboratory experiments. One of the soils had been limed (pH 6.8) 13 years earlier. The other was unlimed (pH 3.7). Liming increased the rate of CO2 release from soil to which no L. perenne had been added. About 30% of the 13C in L. perenne leaves remained in both limed and unlimed soil after 224 days. By contrast, less 13C-remained in the limed soil amended with L. perenne roots (44%) than in the limed soils (55%). Although the daily rate of CO2 from the plant material-amended soils was initially greater in the improved than in the unimproved soil, it subsequently declined more rapidly.

Notes: Abstract. The characteristics and variability of soils within a 30 ha experimental site in N. E. Nigeria are analysed in relation to tree establishment. Profile description and analyses for some 480 surface samples of the sandy to clayey surface soils from Lake Chad lacustrine sediments provide baseline properties against which any subsequent modifications resulting from agroforestry practices can be assessed and to which initial tree performance can be related. This has been undertaken using principal component and spatial analyses. Inherited soil properties show spatial variations across the site which can be related to the soil textural parameters. The initial survival of trees planted for agroforestry experimentation shows strong correlations with the inherited characteristics of the soil rather than with acquired soil properties.

Notes: Abstract. Field measurements of cumulative infiltration and of the matric potential prior to infiltration were made with double-ring infiltrometers and tensiometers, respectively, on two sandy loams in north-east Scotland. The time to ponding for constant-rate infiltration was also measured in the same infiltrometers by applying water at a constant rate until ponding commenced. Under the range of initial potentials studied (-2 to - 17 kPa), an exponential relation was adequate to describe the relation between sorptivity and initial matric potential. The time to ponding was also strongly dependent on initial matric potential and increased dramatically as the soil became drier. Measurements of time to ponding were in good agreement with values predicted from the theory of Clothier et al. (1981) using values for sorptivity and the A parameter obtained from the cumulative infiltration experiments. Measurements and predictions clearly showed the importance of the sorptivity versus initial matric potential relation in controlling the time to ponding of such sandy soils. These results have implications for determining the generation of runoff and the establishment of stream flows, as well as determining optimum rates and design of irrigation.

Notes: Abstract. Use of either three or six occasions to spread similar total amounts of slurry was investigated over the late winter/early spring period in two years, on plots with underdrainage. Slurry was spread on four 7 m by 25 m plots which were instrumented to allow collection of drainflow and runoff. The ‘mobile water’ pore space allowed transport of a small proportion of applied slurry through the 0.75 m soil profile. Evidence of a polluted ‘mobile water’ pulse occurred after periods of up to 48 hours following spreading, suggesting subsurface rather than overland flow. Timing of the pulse depended on whether subsequent rainfall accelerated the flow The contaminated flow persisted for 6–12 hours. The worst contamination of 39 mg/l NH4+ -N occurred under ‘bypass flow’ conditions, when 52 mm of rain fell during the 48 hours after a 5.2 mm application. Two contributory factors appeared important. The first was the long duration of the high intensity storm and the second was an extended period of severe frost believed to have created fissures associated with frost heave. Making several applications of slurry in amounts less than 35 m3/ha is preferable to fewer larger applications during spring, for cereals on medium to heavy soils. This recognises the likelihood of there being underdrainage on arable land and the optimal use of well-drained, partially frozen ground to avoid compaction by slurry tankers.

Notes: Abstract. When Albania emerged from its seclusion in 1991, the scientific community had its first opportunity to interact with its international counterparts. Soil resource assessment was made with systems developed in the early 1950s, laboratory facilities to provide supporting data were poor, and it was recognized that a new assessment was urgently needed.The country faces a major challenge in reforestation and soil conservation against a background of overgrazing by sheep and goats and clearing of trees and scrubs for fuelwood. Even orchard and olive trees were used as fuelwood during the winters of 1990 and 1991. Since then, gully and rill erosion has accelerated on many of the sloping lands. In addition to reforestation and conservation measures to reduce the pressures on the sloping land, it is necessary to enhance productivity on the fertile valley bottom soils where most of the agriculture is confined. In the recent past, grain yields have declined due to reduced fertilizer use (low purchasing capacity), and poor management practices. More recently productivity has slowly improved, but land degradation, particularly erosion, has visibly increased.USDA Natural Resources Conservation Service in collaboration with the Land Resources Institute of Albania, initiated work on a new national soil map through collation of existing information and field studies. The land unit for land use planning, evaluation, and general management decisions, is the Major Land Resource Area (MLRA). Each MLRA encompasses geographically associated soils, the majority of which have broadly similar patterns ofclimate, water resources, and land uses. The MLRAs presented here are based on the soil map of Albania at 1 : 200 000 scale. The MLRA information provides an overview of the landscape and natural resources. It can be used to assess land suitability for various crops, opportunities to achieve self sufficiency in food production, selection of areas for both field crops and highvalue crops for export, and identification of appropriate farming system technologies. Each MLRA will have a set of degradation processes which can be flagged, therefore each of them becomes a unit for decision making with respect to investments in research and mitigating technologies. The task is far from complete. Appropriate databases are needed to support the decisions that are being made at national level. To complement the MLRA and related database, decision support systems are needed for the important task of developing policy options.

Notes: The binding of metal to humic substances is problematical. The approaches for studying metal binding to organic matter are briefly reviewed. Ion-selective electrodes (Cu2+ and Pb2+) were used to measure metal complexation by a whole peat and an extracted humic acid (HA) fraction. Scatchard plots and calculation of incremental formation constants were used to obtain values for the binding constants for the metals onto both peat and HA. Both the peat and the humic acid had a larger maximum binding capacity for Pb2+ than for Cu2+ (e.g. at pH = 5 HA gave 0·188 mmol Cu2+ g−1 and 0·564 mmol Pb2+ g−1: peat gave 0·111 mmol Cu2+ g−1 and 0·391 mmol Pb2+ g−1). Overall, the humic acid had a larger metal binding capacity, suggesting that extraction caused conformational or chemical changes. The binding constants (K1) for Cu2+ increased with increasing pH in both peat and humic acid, and were larger in the peat at any given pH (e.g. at pH = 5 HA gave log K1= 2·63, and peat gave log K1= 4·47 for Cu2+). The values for Pb2+ showed little change with pH or between peat and humic acid (e.g. at pH = 5 HA gave log K1= 3·03 and peat gave log K1= 3·00 for Pb2+). In the peat, Cu2+ may be more able to bind in a 2:1 stoichiometric arrangement, resulting in greater stability but smaller binding capacity, whereas Pb2+ binds predominantly in a 1:1 arrangement, with more metal being bound less strongly. Whole peat is considered to be more appropriate than an extracted humic acid fraction for the study of heavy metal binding in organic soils, as this is the material with which metals introduced into an organic soil would interact under natural conditions.

Notes: Excess salts may be removed from soil by leaching, but ponding water on the soil's surface and allowing infiltration requires large quantities of water. During such leaching water flows preferentially through macropores between aggregates, while the flow within aggregates is much less. Consequently, solute within aggregates is removed much more slowly, thus decreasing overall leaching efficiency. For this reason intermittent ponding can be more efficient because it allows time for solute to diffuse to the surfaces of aggregates during the rest period and subsequently be removed in macropore flow. We explored solute transport in aggregated soils under intermittent leaching in three ways: theoretically, by laboratory experiments on columns of porous ceramic spheres as analogues of aggregates, and by simulation. Solute movement during displacement is described by the mobile-immobile convection-dispersion equation. During the rest period flow ceases, and solute redistributes within the aggregates by diffusion, the key variable being the effective diffusion coefficient, De of the solute in the aggregates, and longitudinally by diffusion within macropores (though this was ignored in the simulation). We estimated De for our porous spheres from observations of solute outflow into finite volumes of stirred distilled water. The theory was validated against experiments on saturated columns for different aggregate-size distributions, flow velocities, and displacement and rest periods, with most parameters estimated independently. Experiments and simulations showed that water savings of 25% were possible under our laboratory conditions, increasing as aggregate size, flow velocity and duration of rest period increased. The potential of intermittent leaching in the field is considered.

Notes: Comparisons were made between the phenolic and carbohydrate signatures of soil profiles developed under grass, spruce and ash stands. Samples were collected from a brown earth soil which was originally under the same land use, but over the past 43 years has supported different monocultures. Distinct signatures associated with each litter type were recorded in individual profiles. A relatively undecomposed phenolic fraction from lignin and hydrolysable carbohydrate fraction from plants had accumulated in the soils under spruce and ash. This largely reflected the quantity and quality of the litter inputs from the spruce and ash compared with the grass. The phenolic and hydrolysable carbohydrate fractions accounted for as much as 60% of the total organic carbon concentration in the deep horizons. In the grassland profile both fractions were more decomposed than under ash and spruce suggesting that the forest profiles had rapidly accumulated a carbon pool with a comparatively slow rate of decomposition. This was most apparent from the spruce profile (which contained 398 mg g−1 C carbohydrate hydrolysed using trifluoracetic acid (TFA) in the C horizon compared with 165 and 45 mg g−1 C under ash and grass respectively). We conclude that the decay rate of these fractions is a function of the vegetation type.

Notes: Fractal dimensions were used to quantify the complex geometry of soil cracking patterns. Two fractal dimensions were measured to provide an adequate description of soil cracks: the mass fractal dimension, DM (which provides a measure of crack heterogeneity) and the spectral dimension, d (which provides a measure of crack connectivity). The cracking patterns generated by four soils were compared and related to their textural characteristics. As the clay content of the soil increased (6·1%–24·3%), so did DM (1·29–1·43), and d (1·03–1·33). Correlations indicated that there was a significant (P 〈 0·01) linear relation between the soil's clay content and the DM and d of cracks, the correlation coefficients obtained being equal to 0·965 and 0·840, respectively. Significant correlations (P 〈 0·01) were also observed between structural stability indices of the soil and the fractal dimensions of its cracks, increases in the stability of the soil, particularly of the clay fraction, being associated with cracks with greater fractal dimensions.

Notes: The relation between physical and mechanical responses and the structure of clay has been studied. Deformation in response to mechanical stress was measured on samples of Wyoming mont-morillonite and Saint Austell kaolinite in solutions of NaCl (0·005; 0·05; 0·5 and 5 M). Salt concentration was expressed in terms of osmotic potential of water and loading in terms of envelope pressure potential of water, and deformation was measured precisely under small mechanical stress. During shrinking and swelling, deformation was small and reversible, and consolidation was related to the largest mechanical stress applied previously in its history. The arrangement of the clay at equilibrium depends foremost on the type of clay mineral and physico-chemical properties of the liquid phase. For Na-montmorillonite suspensions, transition between gels with tactoids and rigid media with quasicrystals is abrupt and occurs at a potential of about −2000 J kg−1, whether the stress is osmotic or mechanical. Swelling indexes obtained under osmotic and mechanical stress are of the same order of magnitude. Deformation of smectite results from modifications of interassemblage and intra-assemblage organization.

Notes: We have developed a critical state, stress-strain analysis that predicts the entire sequence of states from start to the end of a constant cell volume triaxial test in p-q-v-ɛz, space, where p is the spherical stress, q is the deviator stress, v is the specific volume and ɛz is the axial strain. The analysis requires five soil properties to be specified, these being the critical state properties (M, λ and κ) and two elastic properties (any two of E, η, G and K—all four can be found from any two).In order to test the analysis, properties taken mostly from one series of constant cell volume triaxial tests are used to simulate the behaviour in a second test series. In both series the two soils (a sand loam and a clay loam) were tested at several different water contents. The first (property estimation) series of tests was performed using large samples, whereas the second (verification) series involved small samples. The behaviour is quite different in the two series. The elastic property E was not determined in the first series of tests but was estimated from the second series. Furthermore, for three very wet samples, λ had to be estimated by fitting the analysis to the data. The verification was not therefore fully independent of the input test data, particularly for the three wet samples. The stress strain analysis simulated the behaviour of both series of tests in all four dimensions of the p-q-v-ɛz space. The match in p-q-v space was good for all samples. On a q-ɛz plane, the value of q was under-estimated for several samples, but for most of the samples the match was good on this plane. The analysis was generally as good as, and sometimes better than, a previous analysis that deals only with the end point of the test in p-q-v space. The previous analysis did not take account of the elastic properties. The stress-strain analysis therefore seems to offer a useful framework for parameter estimation from constant cell volume triaxial tests. This extends the usefulness of the test itself, as the elastic properties may now be accounted for. The success of the analysis also strengthens the record of success of the critical state concept for unsaturated soils.

Notes: Measurements of N uptake by rice plants growing in a puddled flooded soil and the corresponding changes in soil solution NH: concentrations and the soil NH: diffusion coefficient are used to calculate how far root uptake properties and transport to the roots limit acquisition of N by rice. With root uptake parameters assigned values such that influx was maximal within realistic ranges, the minimum root length densities required to explain uptake were similar to measured root length densities in both N-fertilized and unfertilized soil. This suggests that most if not all of the root length was active in uptake and that uptake per unit root length was near maximal. A sensitivity analysis showed that the necessary minimum root length is very sensitive to root uptake properties within appropriate ranges. Transport to the roots was mainly by diffusion. Rates of diffusion will generally not limit uptake in well-puddled soils, but they may greatly limit uptake in puddled soils that have been drained and re-flooded and in unpuddled flooded soils. Uptake of fertilizer N broadcast into rice field floodwater and absorbed by roots in the floodwater or soil near the floodwater is not likely to be limited by root uptake properties or transport.

Notes: The derivation of pore size distributions from the soil water retention characteristic is complicated by the influence of the connectivity of the pore space on drainage. We examine this issue in the context of a random fractal pore network model. A two-dimensional one-parameter model simulates the drainage of water from an initially saturated pore network, explicitly accounting for the complex pore interactions which exist over a range of scales within the network. A parameter range is identified over which pore connections significantly hinder the advance of air into the network. The results demonstrate that connectivity between pores in a random structure can affect the drainage to an extent that in general it is not possible to obtain an accurate measure of the pore size distribution from the water retention data. These results, together with findings based on closely related multiscale network models, show that one should use with caution water retention models derived from fractal structures and based solely on pore size distributions.

Notes: The recent addition of trivalent metals to soil and their subsequent movement within the biosphere are of concern. For this reason, the sorption of chromium (Cr), yttrium (Y). rhodium (Rh), lanthanum (La), praseodymium (Pr) and gadolinium (Gd) in two contrasting acid soils has been determined. Except for Rh, the sorption of the other trivalent metals conformed well to the Langmuir equation with derived sorption parameters similar for all the trivalent species tested. Calculation of the buffer powers indicated that under both small (0·01 mmol kg−1) and large (1 mmol kg−1) trivalent metal soil loadings 〉 99·5% of the metals will be associated with the exchange phase with small quantities present in the bulk soil solution (〈0·5%). It seems that the slight availability of metals within the bulk soil solution will slow the rate of trivalent metal bioremediation of contaminated sites.

Notes: Compositional differences between soil solutions obtained by different methods have frequently been reported; variations in the soi1: solution ratio may explain these results. In this study we compared the amount and composition of phosphorus (P) in soil leachates and soil solutions from a temperate grassland soil in northeast Scotland and determined the influence of soi1:solution ratio on P fractions in soil water extracts. Leachates were collected from intact soil cores over 6 months, the cores were then destructively sampled, and soil solutions obtained by centrifuging. Molybdate reactive P (MRP) represented 71% of the total dissolved P (TDP) in soil leachates but only 54% in soil solutions. The MRP component in soil water extracts increased from 71% to 92% as the soi1:solution ratio increased from 1:15 to 1:15·4, while the dissolved organic P (DOP) component decreased from 26% to 6%. As the soil:solution ratio increased the amount of MRP extracted increased; by contrast the amount of DOP and dissolved condensed P (DCP) extracted remained constant. While the MRP component is regulated by soil sorption processes, the supply and amount of DOP and DCP is probably related to biological activity. Dissolved organic carbon (DOC) extracted at wide soi1:solution ratios contained a smaller proportion of P than that extracted at narrower ratios. The results indicate differences in the behaviour of P fractions in the soil at various soi1:solution ratios and that these are reflected in the P composition of soil solution and leachate.

Notes: In a pre-alpine meadow in the Toggenburg (Switzerland), casts of the earthworm Aporrectodea nocturna, initially detected 20 years ago around a newly planted hedge, now extend 170 m from the hedge. The abundance of A. nocturma decreased between 140 and 170 m from the hedge from 237 (site: An+) to 0 (site: An−) individuals m−2. The worm's activity and the macroporosity it has created have been studied using CAT scanning followed by automated image analysis of pores from 1·5 to 9 mm diameter. Brightness values in images from CAT scanning showed distinct local frequency maxima for stones, soil matrix and macropores. Measured diameters of pores were strongly linearly correlated with diameters of needles used to produce artificial pores. Pores from 1·5 to 3 mm were most abundant. The maximum number of pores from 1·5 to 9 mm (about 1600 m−2) was larger than the maximum number of all earthworms (about 480 m−2). Modelling the cast production of A. nocturna indicated that 23·8 kg m−2 were deposited on the soil's surface within 3 months. The measured macroporosity (1·5–6 mm) was one-quarter to one-sixth of the pore volume corresponding to the removed casts. Thus, net production of pores by earthworms was a result both of the burrowing activity and of the refilling with eroded cast material. Depth distributions of bulk density, total porosity and pores from 1·5 to 9 mm were different at An+ from those at An−. However, diffusion of butane was equal at An+ and An−. Three-dimensional reconstruction suggested that the disposition (continuity, interconnectivity) of pores was more important for gas diffusion than the structure (size distribution, frequency) and bulk soil parameters.

Notes: Humic acids from six Brazilian topsoils (three Latosols and three Podzols) and five soil fungal melanins were hydrolysed and the released amino sugars qualitatively and quantitatively determined by capillary gas-liquid chromatography. Melanins were obtained from liquid culture media, synthesized with nitrate or asparagine as a source of N, of Stachybotrys atra, Aspergillus glaucus, Eurotium echinulatum and Hendersonula toruloidea. Glucosamine (48–60%), galactosamine (39–52%), and traces of mannosamine were detected in all humic acids. The total amino sugar content ranged from 1351 to 2287 mg kg−1. In the fungal melanins analysed, mostly glucosamine (80–99%) and trace to small amounts of galactosamine and mannosamine (〈10%) were found in amounts ranging from 192 to 635 mg kg−1. The Occurrence of mannosamine in fungal melanins and fungal polysaccharides had not previously been found. The present study gives additional data to the theory that fungal melanins may play a role, as precursors, in the formation of soil organic matter.

Notes: We investigated dissolved organic matter (DOM) from soil, sewage sludges, water from waste disposal sites, and composts as sorbents and potential carriers for hydrophobic polycyclic aromatic hydrocarbons (PAHs) in soil. Partition coefficients (expressed log KDOC) for two 5-ring compounds were 4·8–4·9 for DOM from soil, 4·5–47 from composts, and 4·3–4·4 from sewage sludges. The DOM from compost and sewage sludge can influence the transport of non-ionic organic contaminants because of the large concentrations of dissolved organic carbon (DOC) released from these materials. Leachates from waste disposal sites did not sorb PAHs. The DOM from compost contained a large percentage of organic molecules 〉 14 000 Da (32–46%), whereas DOM from waste disposal leachates contained only 7-lo%, and so bound less PAHs. The percentage of total hydrophobic components, as characterized by XAD-8 chromatography, was 50 ± 9% for most of the DOM solutions and did not express the differences in affinity of the organic sorbents to PAHs in the same way as the KDOC values. Isolated molecular-weight fractions of DOM from composts sorbed benzo(k)fluoranthene in each fraction. The log KDOC values were 4·1–4·3 for both fractions, 〈 1000 and 1000–14 000 Da, and 4·8–5·0 for the fraction 〉 14 000 Da. The interaction of PAHs with DOM 〈 1000 Da cannot be explained by partitioning within intramolecular nonpolar environments of dissolved macromolecules; rather it seems to be due to the amphoteric properties of DOM. This type of interaction of PAHs with small DOM molecules might affect the mobility of hydrophobic organic chemicals in soils.

Notes: La stabilityé de la structure des horizons de surface et de profondeur de sols ferrallitiques du Congo est étudiée en fonction du mode de gestion des terres et de la teneur en carbone organique total des échantillons. Le rôle du carbone soluble à l'eau chaude dans l'agrégation est appréciéà partir de deux approches expérimentales, impliquant des extractions après chauffage en étuve ou en autoclave. Pour ce faire, des comparaisons sont faites entre les taux des macroagrégats stables (〉200 pm) à l'eau froide et à l'eau chaude. Les résultats indiquent que les situations culturales étudiées induisent des variations significatives des teneurs en carbone total. Le taux des macroagégats stables à l'eau froide est très fortement corrélé aux teneurs en carbone total et en carbone solubiliséà l'eau chaude. Toutefois, les taux des macroagrégats stables obtenus avant et après extraction du carbone à l'eau chaude ne sont pas significativement différents, ce qui peut remettre en question les résultats sur la fonction agrégeante des matières organiques solubles, déduits des seules approches statistiques.Hot-water soluble organic matter and aggregate stability. Methodological aspects and application to ferrallitic soils of the Congo〈section xml:id="abs1-2"〉〈title type="main"〉SummaryThe structural stability of surface and deeper horizons of ferrallitic soils of the Congo was studied in relation to the land use and the total organic carbon content of the samples. The role of hot-water soluble carbon in aggregation was assessed with two experimental approaches, one by heating in an oven and the other in an autoclave under pressure. The proportion of aggregates (〉 200 μm) stable in cold water were compared with that of macroaggregates stable in hot water. Cropping situation sunder study induced significant variations in total carbon content. Aggregate stability was highly correlated with both soluble and total carbon contents. However, amounts of water-stable aggregates obtained before and after solubilization of organic matter in hot water were not significantly different. This result would infirm the supposed aggregating role of soluble organic matter, inferred from statistical data only.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Notes: Two experiments in which early-weaned lambs (4–7 and 5–9 weeks of age) continuously grazed a perennial ryegrass-white clover sward are described. In both experiments groups of lambs were offered a proprietary concentrate ad libitum, 2/3 or 1/3 of ad libitum allowance, or no concentrate. Mean daily gains over 56 days in Experiment 1 increased from 88 g without concentrate to 275 g with ad libitum concentrate allowance; the range in daily gains over 71 days in Experiment 2 was 201 g to 253 g respectively. In both experiments mean faecal OM output from herbage decreased as concentrate OM intake increased.

Notes: Four groups of ewes grazed swards of red clover (Trifolium pratense cv. Hungaropoly) for 28-day periods ending 28, 14 or 0 (two groups) days before mating. One of the groups on red clover for the period immediately before mating continued on red clover during mating. At all other times before mating and for 7–8 weeks after mating commenced these ewes were grazed on a predominantly perennial ryegrass-white clover sward. A fifth (control) group was on the ryegrass sward throughout. There was no apparent adverse effect of red clover on ovulation rate, conception rate or embryo mortality.

Notes: A non-protein nitrogen additive containing ammonia, molasses and minerals was applied to precision-chopped forage maize to raise the crude protein content of the ensiled crop from approximately 8% to 10, 14 or 16%.The dry matter content, total nitrogen, water-insoluble nitrogen, and water-soluble nitrogen concentrations were measured at ensiling and 2 and 8 weeks later. The pH and lactic, acetic, propionic and butyric acid contents of the resultant silage were determined 2 and 8 weeks after ensiling.The levels of crude protein achieved were 10.8, 11.5 and 14.2%, which are equivalent to recoveries in the silages of 108, 82 and 89% of the applied nitrogen. After 8 weeks the water-insoluble nitrogen content of the treated silages had increased while the water-soluble nitrogen content had decreased. The increase in water-insoluble nitrogen may have been due to either decreased proteolysis or increased levels of microbial protein.There was a significant increase of 0.6 units in the pH of the silage when comparing the control to the highest rate of additive application. The additive increased the levels of lactic and acetic acid in the maize silage.

Notes: Methods of predicting the in vivo dry matter digestibility (DMD) of heather were examined in studies on ten samples of heather which had been fed to sheep in standard digestibility trials. DMD was predicted with similar accuracy from estimates of in vitro dry matter digestibility (in vitro DMD) and from the concentration of cell-wall constituents. In vitro DMD was found to be between 10 and 18 percentage units lower than DMD. Freeze drying the samples was the only modification to the technique which both increased in vitro DMD and the accuracy of the prediction of DMD. Other modifications attempted were the use of different liquor sources, changes in first-stage incubation time and dilution rate, and nitrogen supplementation of the inocula.The concentration of nitrogen or undigested dietary nitrogen in the faeces could not be used to predict the digestibility of heather with precision. It was concluded that the DMD of a heather diet could be satisfactorily predicted from the in vitro DMD of samples collected from sheep fistulated at the oesophagus.

Notes: The initial effect on the underlying sward of spraying bracken with 4.5 kg ha−1 a.i. asulam or 2.0 kg ha−1 a.i. glyphosate was to cause some damage which was greater if glyphosate was used rather than asulam or if treatment was carried out in August rather than in July. Agrostis species were especially susceptible while Festuca species were resistant. The recolonization of areas of bare ground after spraying was primarily by Holcus moliis, Anthoxanthum odoratum, Galium hercynicum and Potentilla erecta, but the population of the latter two species decreased as Agrostis became reestablished. If Digitalis purpurea, Urtica dioica or Cirsium arvense were present originally, heavy infestations developed following the use of asulam, with a smaller increase after glyphosate spraying. In all cases, by the end of three years after treatment, grasses occupied a greater area of the sward in treated than in control plots.

Notes: Three grass silages made in early June from S23 perennial ryegrass were compared in a 16-week feeding experiment with twelve Ayrshire cows. The silages were made from uniform herbage which received either formic acid (‘Add-F’) at the rate of 201 t−1, or a formalin-sulphuric acid mixture (‘Syiade’) at rates of 2.0 and 4.4 1 t−1. The silages were offered ad libitum either alone or supplemented with a cube containing 38% CP in the DM at the rate of 1.4 kg per 10 kg milk. The daily intakes of silage DM were not significantly different on the three silage treatments, and averaged 10.7, 11.0 and 11.0 kg per cow on the formic acid and the 2.0 and 44 1 t−1 formalin-acid treatments respectively. The mean daily yields of milk were 15.1, 13.3 and 13.7 kg per cow in the unsupplemented treatments, and 18.2, 18.1 and 18.0 kg per cow in the supplemented treatments on the formic acid and the 2.0 and 44 1 t−1 formalin-acid treatments respectively.On the basis of total animal production expressed in terms of metabolizable energy requirements, it was concluded that the differences between the three silages were small.

Notes: An experiment is described in which the amount of nitrogen fixed by the white clover component of a surface-sown hill sward was determined using small quantities of 15N-labelled ammonium sulphate. Between 11 July and 22 August 1974 25 kg ha−1 N was fixed. No evidence of a transfer of N from clover to the associated perennial ryegrass was detectable over this period although the N content of the grass growing with the clover was higher. The relative advantages of the isotope technique and the acetylene reduction assay are discussed.

Notes: Perennial ryegrass cv. S23 was preserved by fermentation (C), or with the addition of 8.7 1 formalin (35% w/w formaldehyde) per t fresh herbage (F) or of 9.0 1 equal mixture (by vol.) of formalin and formic acid (85% w/w solution) per t fresh herbage (FF). These three silages comprised the treatments in a three-period, crossover design in which urea (u) was given at the rate of 20 g per kg dietary DM to half the animals. Twelve calves were allocated to the treatment sequences when they were approximately 12 weeks of age from within groups which had previously received diets with or without urea.Calves ate significantly (P〈 0.001) less of silages F or FF than of silage C when each was offered alone, but when urea was given, intakes of silages F and FF were significantly (P 〈 0.001) increased such that the intakes of all three silages with urea were similar (23.6, 19.6, 19.3, 24.2, 24.2, 24.7 ± 0.51 g DM per kg LW for C, F, FF, Cu, Fu and FFu, respectively). Significantly (P〈0.01) more of the DM in silage C was digested than in F or FF and the addition of urea significantly (P〈0.05) increased the digestibility of DM from silage FF only (73.8, 71.3, 69.8, 74.6, 70.7, 72.5 ± 0.72% for C, F, FF, Cu, Fu and FFu, respectively). When the silages were given alone, calves spent longer eating and ruminating per kg DM ingested with F or FF than with C. The time spent on F and FF was significantly (P〈0.01) reduced by the addition of urea (303, 388, 411, 297, 299, 290 ± 18.9 min per kg DM ingested for C, F, FF, Cu and Fu and FFu, respectively).The results presented suggest that urea partially alleviated the reduction in voluntary intake by calves given herbage preserved using formalin, but the mode of action was not clear.