Journal
JOURNAL OF AGRICULTURAL SCIENCE
Volume 139, Issue -, Pages 115-127Publisher
CAMBRIDGE UNIV PRESS
DOI: 10.1017/S0021859602002435
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The effects of straw incorporation (early and late cultivation) and straw burning were contrasted in a split-plot study examining the impact of long-term straw residue management, and six fertilizer nitrogen (N) rates on soil mineral nitrogen, crop fertilizer N requirements and nitrate leaching losses. The experiments ran from 1984 to 1997 on light-textured soils at ADAS Gleadthorpe (Nottinghamshire, UK) and Morley Research Centre (Norfolk, UK). Soil incorporation of the straw residues returned an estimated 633 kg N/ha at Gleadthorpe and 429 kg N/ha at Morley on the treatment receiving 150 kg/ha per year fertilizer N since 1984. Straw disposal method had no consistent effect on grain and straw yields, crop N uptake, or optimal fertilizer N rates. In every year there was a positive response (P<0(.)001) to fertilizer N in straw/grain yields, N contents and crop N offtakes at both sites. Nitrate leaching losses were slightly reduced by less than 10 kg N/ha where straw residues had been incorporated, while fertilizer N additions increased nitrate leached at both sites. At both sites there was a consistent effect (P<0(.)001) of straw disposal method on autumn soil mineral N, with values following the pattern burn>early incorporate >late plough. The incorporation of straw residues induced temporary N immobilization compared with the treatment where straw was burnt, while the earlier timing of tillage on the incorporate treatment resulted in slightly more mineral N compared with the later ploughed treatment. Fertilizer N rate increased (P<0(.)001) soil mineral nitrogen at both sites. At Morley, there was more organic carbon in the plough layer where straw had been incorporated (mean 1(.)09 g/100 g) rather than burnt (mean 0(.)89 g/100 g), and a strong positive relationship between organic carbon and fertilizer N rate (r(2)=93(.)2 %, P<0.01). There was a detectable effect of fertilizer N on readily mineralizable N in the plough layer at both Gleadthorpe (P<0(.)001) and Morley (P<0(.)05). At Morley, there was a consistent trend (P=0(.)06) for readily mineralizable N to be higher where straw had been incorporated rather than burnt, indicating that ploughing-in residues may contribute to soil nitrogen supply over the longer term.
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