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Immobilisation and mineralisation of N under grassland and short-term/long-term release after ploughing - NT1502

In cropping systems, it is important to take full account of soil mineral N supply, enabling fertilizer N to be used as efficiently as possible for production so that losses to the environment are minimised. This is particularly challenging for grasslands because management can greatly influence accumulation and release of N. This study will aim to improve understanding of the factors controlling net release (e.g. sward age and composition, past/current management and soil and environmental conditions) so that accurate prediction of N release from pasture and after ploughing can be improved. The study will be composed of 3 main objectives outlined as follows, together with ways in which they might be achieved: 1. Development of a scientific basis for estimating N release from soil organic materials in soil supporting grass swards. Net release of mineral N from 3 grassland sites (with known background managements and histories) will be determined with respect to background management, moisture/temperature response characteristics and soil organic matter characteristics. Soil-site management variables will be extended by making restricted measurements of net mineralization of further sites with documented histories and characterising their organic matter; 2. Determination of the short and long term effects of cultivation of grassland soils on the release of nitrate through enhanced mineralization. The effects of cultivation on release of mineral N and increased availability to plants or losses to leaching will be examined at 3 different sites. Effects of cultivation on changes in soil organic matter and effects of subsequent management on rates of release and leaching losses will also be determined; and 3. Provision of predictive capacity for mineralization of N in grassland. Information obtained from the study will be synthesized and used to test the capability of existing mineralization models. The most suitable model will be developed to allow prediction of effects for both production and environmental criteria.
Time-Scale and Cost
From: 1995

To: 1998

Cost: £241,193
Contractor / Funded Organisations
ADAS UK Ltd., Institute of Grassland and Environment Research (IGER)
Fields of Study
Fertilisers and Nitrate Pollution