Large quantities of nitrogen fertilizer are often applied to grassland with the aim of increasing the production of milk and meat from ruminant livestock. However, less than 25% of the fertilizer N is actually converted into animal protein. The remainder is subject to a variety of transformations in the soil, either before or after its uptake by the grass and consumption of the grass by livestock. Some of these transformations cause loss of N from the soil-plant-animal system, and result in some degree of pollution and potential harm in the wider environment. In this book the published information on the various transformations of nitrogen in temperate grassland systems is comprehensively reviewed. The effects of soil, weather and management factors are discussed and considerable emphasis is placed on soil-plant-animal interactions. The book also discusses the factors that influence the response of grassland to the application of fertilizer N, and how the optimum rate of application may be determined. In addition, N balances are described for different grassland systems, showing how annual inputs and outputs vary greatly depending on sward type and management. Overall, the book presents a valuable review of grassland nitrogen in temperate regions for advisers, researchers, teachers and students in agriculture and environmental science.
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Uptake of Nitrogen and Effects on Morphology
Biological Nitrogen Fixation and Interaction with
Consumption Digestion and Excretion of Nitrogen
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ammonia volatilization ammonium nitrate ammonium sulphate amount of nitrate animal application of fertilizer arable areas assessed atmosphere average biomass calcium ammonium nitrate calcium nitrate cattle crop decomposition defoliation denitrification differences digestibility dry matter dung effect etal excreted factors fertilizer N field grass swards grass-clover swards grassland grassland soils greater growing season growth harvested herbage yield immobilization increase influenced inorganic inputs irrigation Italian ryegrass Journal of Agricultural kg ha-1 kg N ha-1 leaf legume livestock long-term grassland lysimeters manure microbial mineralization N2 fixation nitrate leached nitrate-N nitrification nitrogen nutrient occur partly perennial ryegrass period plant material plant-available plots ploughing production protein rainfall rate of application rate of fertilizer ratio reduced response to fertilizer result roots Ryden senescence sheep silage slurry soil organic matter soil pH stolons supply swards receiving Table temperature tends tillers tion uptake urea urine volatilization of ammonia white clover Whitehead winter year1 Zealand