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To determine the immobilisation of N by incorporated straw and subsequent release (New code NT1506) - NT0502

Description
See NT1506.

NT0502. Immobilisation of N by straw incorporation and subsequent release of N.

This study will aim to investigate the role of the soil microbial biomass in soil N dynamics, following straw incorporation, in order to minimise nitrate leaching losses from agricultural systems. Methods will be developed and tested for the measurement of soil microbial biomass C, N, ninhydrin-N and ATP in soils containing recently added and actively decomposing cereal straw, together with microbiological activity (e.g. C and N mineralization) in such soils. After initial laboratory experiments, the methodology will be tested under field conditions, using unlabelled straw and fertiliser, and developed to permit analysis of large numbers of heterogeneous field samples of soils containing straw. ISN-labelled straw and fertiliser will then be used in a field experiment to assess the contributions of straw N, soil N and added fertiliser N to N uptake by the biomass as it decomposes incorporated straw. Research findings will be combined and analysed for evidence relating to the effects of cereal straw incorporation on autumn-winter solid nitrate leaching losses. It is anticipated that this research will enable the development of methodology for microbial biomass measurement in soils containing recently added decomposing straw, and that this methodology will also be applicable to the investigation of biomass and soil N dynamics following incorporation of other crop residues (e.g. potato haulms, rape straw, bean straw, sugar beet tops) and animal manures.
Objective
Develop and test methods to measure soil microbial biomass C, N, ninhydrin-N and ATP in soils containing recently added and actively decomposing cereal straw. Develop and test methods to measure soil microbial activity (e.g. soil C and N mineralization) in such soils. Use the methods initially in laboratory studies,to investigate microbial biomass and soil N dynamics following straw incorporation. Initiate a field experiment with unlabelled straw and fertiliser to test the methodology under field conditions. Develop methodology to permit the analyses of large numbers of heterogeneous field samples of soils containing straw. Use of N-labelled straw and fertiliser in a field experiment to assess the contributions of straw-N, soil N and added fertiliser N to the uptake of N by the biomass as it decomposes incorporated straw. Combine all research findings to obtain evidence on the merits of cereal straw incorporation on decreasing autumn-winter solid nitrate leaching losses.
Time-Scale and Cost
From: 1991

To: 1995

Cost: £275,000
Contractor / Funded Organisations
Rothamsted Research (BBSRC)
Keywords
              
Fields of Study
Fertilisers and Nitrate Pollution