1809: Crop production and N leaching in arable organic farming

Olesen, Jørgen E.; Askegaard, Margrethe and Rasmussen, Ilse A. (2003) Crop production and N leaching in arable organic farming. Paper presented at NJF's 22nd Congress "Nordic Agriculture in Global Perspective", Turku, Finland, page 195. NJF.

Summary

The possibilities for increasing grain yields and reducing N leaching losses in organic ce-real production through manipulation of crop rotation design were investigated in a field experiment on different soil types in Denmark from 1997 to 2000. Three experimental fac-tors were included in the experiment in a factorial design: 1) proportion of grass-clover and pulses in the rotation, 2) catch crop (with and without), and 3) manure (with and with-out). Three four-course rotations were compared (Table 1). Two of the rotations had one year of grass-clover as a green manure crop, either followed by spring wheat or by winter wheat. The grass-clover was replaced by winter cereals in the third rotation. Animal ma-nure was applied as slurry in rates corresponding to 40% of the N demand of the cereals.
The largest effects on both dry matter and N yields were caused by differences between sites caused by differences in soils, climate and cropping history. The rotation without a green manure crop produced the greatest total yield. Dry matter and N yields in this rota-tion were about 10% higher than in the rotation with a grass-clover ley in one year of four. Therefore, the yield benefits from the grass-clover ley could not compensate for the yield reduction as a result of leaving 25% of the rotation out of production. There were no dif-ferences in dry matter and N yields in grains between the rotations, where either spring or winter cereals followed the grass-clover ley. There were only small yield benefits from the use of catch crops at the crop rotational level.

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