Project NT1505 has already been evaluating the effects of straw incorporation and burning treatments on soil nitrogen supplies over 13 years (1998—1997) using a light loam at ADAS Gleadthorpe and a medium loam at Morley Research Centre. Detailed measurements have already been made of the impacts of straw incorporation and cultivation timing on crop yields, optimum fertiliser nitrogen rates, crop nitrogen offtakes and nitrate leaching losses using a replicated split plot design, with 6 fertiliser nitrogen rates superimposed on 3 contrasting cultivation treatments. Results have been published up to 1994. This study will aim to interpret and publish the most recent 4 years of data up to the end of the study in March 1998. Results from project NT1505 will be collated and analysed; the analysis will evaluate the effects of the contrasting straw disposal methodologies on soil mineral nitrogen supply, crop yields, crop nitrogen offtakes and optimum fertiliser requirements. Additional analyses will examine effects of straw incorporation vs. burning treatments on nitrate concentrations in drainage waters and resulting nitrate- nitrogen losses. At harvest, topsoil samples will be taken and analysed for organic carbon, total nitrogen and readily mineralisable nitrogen, via anaerobic incubation. Effects of long-term straw management treatments and fertiliser nitrogen additions on these soil properties will be examined. Publication of data will focus on the impacts of straw incorporation on soil mineral nitrogen supply, optimum fertiliser nitrogen requirements and nitrate leaching losses, as well as implications of the management regimes for soil quality and long-term soil fertility.