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Indices of nitrate loss from arable soil - NT1520

This study will aim to extend existing MAFF-funded work on development of 15N isotopic dilution techniques (projects NT1510, NT1514 and NT1906) for indicating the potential of soils to leak nitrate. The study will be composed of 3 specific objectives outlined as follows, together with ways in which they might be achieved: 1. Measurement of gross mineralization, gross nitrification and CO2 production at 20 different sites included in the MAFF-LINK programme (CSA 3629). Selected sites will show a range of land management practices, soil types and locations within the UK. In addition, selected sites at the Rothamsted and Woburn experimental farms will be studied to complement the MAFF-LINK sites. At each site, 2 treatments will be performed - normal farming practice for fertilizer application and absence of fertilizer application. Soil sampling will be conducted in collaboration with that of the MAFF-LINK programme, with samples being obtained in spring prior to fertilizer application and after harvest. Gross nitrogen fluxes and CO2 production will be measured using 15N isotopic dilution. Analysis of gross mineralization and nitrification in replicate soil samples will allow calculation of the rate of N immobilization and hence the index of gross nitrification to gross immobilization; 2. Use of measurements of gross nitrogen transformations to calculate indices of nitrate over production; and 3. Comparison of indices with crop yields and measured and predicted nitrate losses, and assessment of the suitability of indices for the practical indication of nitrogen -saturated soils. Five sites will be selected for detailed characterisation of nitrate leaching losses; porous cups and resin bags will be installed at these sites and leaching losses measured for the duration of the project. Nitrate losses will be predicted using SUNDIAL and WELLN. The indices will be compared with crop yield, measured nitrate and simulated nitrate losses for all the sites. The indices developed in this study will be assessed for their ability to provide an indicator of nitrogen saturation in soils and verify model predictions. Results will allow MAFF to identify soils where nitrate supply is likely to exceed immobilization and is therefore susceptible to leaching.
Project Documents
• Final Report : Indices of nitrate loss from arable soil   (87k)
Time-Scale and Cost
From: 1998

To: 2000

Cost: £102,366
Contractor / Funded Organisations
Rothamsted Research (BBSRC)
Fields of Study
Fertilisers and Nitrate Pollution