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Nitrate leaching from organic arable crop rotations: effects of location, manure and catch crop
Authors:M Askegaard  JE Olesen  K Kristensen
Institution:Department of Agroecology, Department of Animal Breeding and Genetics, Danish Institute of Agricultural Sciences, PO Box 50, 8830 Tjele, Denmark.;Department of Biometry Research Unit, Department of Animal Breeding and Genetics, Danish Institute of Agricultural Sciences, PO Box 50, 8830 Tjele, Denmark.
Abstract:Abstract. Nitrate leaching from crop rotations supporting organic grain production was investigated from 1997 to 2000 in a field experiment at three locations in Denmark on different soil types. Three experimental factors were included in the experiment in a factorial design: (1) proportion of N2-fixing crops in the rotation (crop rotation), (2) catch crop (with and without), and (3) manure (with and without). Three, four-course rotations were compared, two at each location. The nitrate leaching was measured using ceramic suction cells. Leaching losses from the crop rotation with grass–clover green manure and without catch crops were 104, 54 and 35 kg N ha?1 yr?1 on the coarse sand, the loamy sand, and the sandy loam, respectively. There was no effect of manure application or time of ploughing-in the grass–clover green manure crop on the accumulated nitrate leaching from the entire rotation. Catch crops reduced nitrate leaching significantly, by 30–38%, on the sandy soils. At all locations catch crops reduced the annual averaged nitrate concentration to meet drinking water quality standards in the crop rotation with green manure. On the coarse sand there was a time lag between the onset of drainage and the start of N-uptake by the catch crop.
Keywords:Nitrate leaching  organic farming  crop rotation  catch crop  organic manure
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