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  • 1
    Electronic Resource
    Electronic Resource
    The relation between fertilizer nitrogen applications and nitrate leaching from grazed grassland (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 8 (1992), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.1992.tb00894.x
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  • 2
    Electronic Resource
    Electronic Resource
    Mitigation options for diffuse phosphorus loss to water (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 14 (1998), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. Agriculture contributes significant loads of P to surface waters. The reductions in these diffuse P inputs necessary to help prevent eutrophication problems and/or assist in the restoration of water quality will require controls over both nutrient inputs and their subsequent transport in land runoff. Specific mitigation options include nutrient budgeting, input management, soil conservation, land use management and the establishment of riparian, and other buffer zones. The variable nature of diffuse P loss suggests that the best approach to control is through integrated management at a range of scales. Critical control concepts at the farm level include targeting source areas adequately, maintaining P input loading rates within recommended limits and avoiding high-risk management actions. Since eutrophication is a natural phenomenon and with potential conflicts with the need to meet production targets and/or minimize loss of other nutrients (N), some assessment of acceptable levels of P loss, of cost effectiveness of options and some prioritization of goals are necessary to find optimal solutions. As the requirements of individual waterbodies differ, these solutions need to be site specific and their successful adoption requires an appreciation by farmers of the importance of minimizing agricultural P loss both as individuals and collectively within a catchment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.1998.tb00638.x
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  • 3
    Electronic Resource
    Electronic Resource
    Ionic contents of leachate from grassland soils: a comparison between ceramic suction cup samples and drainage (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 13 (1997), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.1997.tb00559.x
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  • 4
    Electronic Resource
    Electronic Resource
    Phosphorus budgets for two contrasting grassland farming systems in the UK (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 14 (1998), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. Phosphorus budgets have been compiled for two contrasting grassland farming systems in the UK; intensive dairy farming and extensive hill sheep production. Balance sheets of inputs, recycling of P through the soil–plant–animal pathway and outputs are presented to determine the potential rate of P accumulation in the two systems. A typical 57 ha intensive dairy farm with 129 lactating cows imports 2.48t P via fertilizer, bedding and concentrates, plus a small amount from the atmosphere, of which 0.98t are exported in milk, calves and transfer from soil to the aquatic environment. Therefore 1.5t of P are retained within the farm each year, which equates to an accumulation rate of 26 kg/ha in the plant-soil system. This surplus occurs despite a fertilizer input of only 16 kg/ha. However, a large proportion of P, equivalent to 27 kg/ha, is imported in feed concentrates.For the typical 841 ha hill sheep farm supporting 694 Blackface ewes, P inputs and outputs are 0.66 and 0.42 t/yr, respectively. Therefore, approximately 0.24t P are retained within the farm, which is equivalent to an accumulation rate of 0.28 kg/ha per yr. In comparison to the small annual inputs and outputs of P on the hill farm, much P, 2.48t, is recycled through the plant-soil and plant-animal-soil pathways on the hill sheep farm. For both farming systems there is a net input of P, although the rate of accumulation is ten times greater for the dairy farm where the annual retention of P represents 60% of the total P inputs, compared with 36% on the hill sheep farm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.1998.tb00635.x
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  • 5
    Electronic Resource
    Electronic Resource
    Relationships between soil thermal units, nitrogen mineralization and dry matter production in pastures (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 14 (1998), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. Nitrogen (N) is of enviromental concern if it leaches or is released as nitrous oxide (N2O,). In order to utilize N efficiently in grazed pasture systems, the fluxes of N from various sources need to be quantified. One flux is N mineralization from organic sources. Previous work has examined incubation and chemical extraction of soils as methods to determine N mineralization potential. This paper re-examines new and previously published data on net mineralization, with the aim of examining the relationships between soil thermal units, net N mineralization (measured using acetylene incubations) and dry matter production in pastures. Net N mineralization is expressed as N turnover (net N mineralization as a % of total soil N). Relationships are developed between soil thermal units, dry matter production, and N turnover. These relationships have potential in advising farmers on potential N mineralization from soil organic matter. A second use of such relationships is the modelling of N transformations in pasture systems. Further work should explore the effect of soil moisture on such relationships and examine the relationship between soil thermal units and uptake of N by pasture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.1998.tb00615.x
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  • 6
    Electronic Resource
    Electronic Resource
    Nitrous oxide emissions from grazed grassland (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 13 (1997), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.1997.tb00600.x
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  • 7
    Electronic Resource
    Electronic Resource
    Nitrogen cycling and losses from dairy farms (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 9 (1993), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. The concern over leakage of nitrate into waters and loss of other forms of N to the environment demands an appraisal of N flows within complete systems. The grassland N cycle is complex, with interactive controls over fluxes and transformations, and has the potential for considerable losses. Although there are data from experimental systems, a total comprehension of flows is not yet possible.Intensive dairy farming has a number of opportunities for leaks. A ‘model’ system in SW England has an annual input of 25.6 tonnes of N: of this only 20% is transferred into protein or milk, a further 46% is lost to the wider environment, 34% is as yet unaccounted for and much is recycled. Recent research has provided new techniques to decrease losses. To meet the joint requirements of production and environmental concerns we need to consider N flows and supplies on an integrated, whole farm basis, and to take better account of mineral N in the soil profile in relation to current crop demand, local climate and past sward management.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.1993.tb00937.x
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  • 8
    Electronic Resource
    Electronic Resource
    Simulation of water retention and hydraulic conductivity in soil using a three-dimensional network (2000)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 51 (2000), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The conduction of water by soil is fundamental to the way in which soils transport nutrients and pollutants into groundwater. The derivation of relations between water flow and void structure has relied on the implicit assumption that water flows through aligned unconnected cylindrical capillary tubes. We describe a three-dimensionally interconnected model of void structure, called Pore-Cor, which simulates the intrusion of a non-wetting fluid and drainage of a wetting fluid. The model is calibrated by fitting it to the water retention curves of a sandy soil at four depths. The experimental drainage pressures are related to the radii of the entries to the voids by the Laplace equation. The necessities of using this equation, and of employing a simplified void geometry, introduce major approximations into the modelling. Nevertheless, the model is sufficiently precise and versatile to predict trends in other properties usefully. It is illustrated in this work by a close correlation between a predicted and experimental change in saturated hydraulic conductivity with depth, and a realistic unsaturated hydraulic conductivity curve. The saturated and unsaturated hydraulic values are shown to be much more realistic than those predicted by the aligned cylinders model. In addition, the simulations by Pore-Cor indicate that the void network within the sandy soil is acting in a structured rather than a random manner. The Pore-Cor model is currently being used to explain the matrix-flow characteristics of tracers and pollutants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2389.2000.00294.x
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  • 9
    Electronic Resource
    Electronic Resource
    Opportunities for reducing the environmental impact of dairy farming managements: a systems approach (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Grass and forage science 51 (1996), S. 0 
    Details
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Dairy farming systems are important sources for the emission of a number of materials that include various forms of nitrogen (NO3−, N2O and NH3) with potential environmental impact. The present paper is a systems synthesis study and assesses the likely impact of changes in management on N flows and losses. These include tactical fertilizer adjustment, slurry injection, maize silage production and the use of white clover as an alternative to fertilizer N. Implications for greenhouse gases (N2O and CH4) and support energy have also been considered. Substantial reductions in inputs and total and proportional losses by all die options considered were predicted by this study. Thus, using a tactical approach to fertilizer application and injecting slurry or using 50% maize silage reduced overall N losses from 160 (under conventional management) to 86 and 109kg Nha−1 respectively. Combining both possibilities reduced losses further to 69 kg ha−1. Although use of white clover, especially at low contents in the sward, was the most effective regime to reduce losses, this was at some cost to production so that losses per livestock unit (LU) did not always differ from those under other managements. Changing the N management had consequences for greenhouse gas emission with an estimated maximum 70% reduction in N2O release. The effects on CH4 emissions were relatively small. Substantial reductions in support energy costs were also obtained: these arose mainly from the reduction in fertilizer N use, which represented 66% of the total support energy in the original system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2494.1996.tb02034.x
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  • 10
    Electronic Resource
    Electronic Resource
    Use of a systems synthesis approach to model nitrogen losses from dairy farms in south-west England (2005)
    Oxford, UK : Blackwell Science Ltd
    Grass and forage science 60 (2005), S. 0 
    Details
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Nitrogen (N) budgets were determined for six typical, moderately intensive dairy farms in south-west England. Proportionately, only 0·12–0·17 of the N input to the farms was recovered in agricultural products, leaving annual N surpluses equivalent to 249–376 kg N ha−1. A sequence of models (MANNER, NCYCLE and SUNDIAL) was used, together with the estimated N balance of the dairy cows and standard ammonia emission factors, to estimate N losses for each farm. Total estimated losses were equivalent to 137–220 kg N ha−1 year−1. Leaching accounted for 0·26–0·45 of the total loss, ammonia volatilization for 0·27–0·39 and denitrification for 0·17–0·36. When residual N from manure applications was included, there appeared to be an annual accumulation of soil N, equivalent to 66–158 kg N ha−1 when averaged over the whole farm area. The amounts of N lost by leaching, volatilization and denitrification, and accumulated as soil-N, were determined by a combination of farm properties, including N input, soil type, drainage, characteristics of the manure produced and type of fertilizer. The sum of estimated losses and change in N retained on the farm was between 0·85 and 1·11 of the N surplus (input minus output) determined from the farm budget. This suggests that losses and the change in soil-N were underestimated on some farms and overestimated on others (by up to −50 and +23 kg N ha−1 respectively). Much of the discrepancy between estimates and the surplus was attributed to difficulties of fully integrating inputs and outputs between the different models and stages of the modelling procedure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2494.2005.00474.x
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