Rapsanbau im ökologischen Landbau – Auswirkungen von Vorfrucht, Reihen-abstand und Untersaat mit Weißklee auf den Ertrag

Summary

The demand for organically cultivated oil seed rape in Germany is very high. But the risk of cultivation due to the high demand of N-supply, preceding crop, weed manage¬ment and plant protection is very high as well. In a two-year experiment, the effects of (I) preceding crop (ryegrass-clover-mixture: (a) cut mowing vs. (b) mulching, (c) peas and (d) barley-pea-mixture), (II) row distance of oil seed rape (12.5 cm, 25 cm, 37.5 and 50 cm) and (III) underseed in autumn together with the oil seed rape (with and without white clover) were tested in a split-plot-design with four replicates at the ex-perimental farm of the Institute of Organic Farming (FAL) in Trenthorst. The results showed a very different yield level with 0.85 t ha-1 in 2004, and 1.68 t ha-1 in 2005, which is a result of a high pressure due to blossom rape beetles (Meligethes aeneus) in 2004. The highest yield of oil seed rape was realized after the mulched ryegrass-clover-mixture with 1.29 t ha-1 in 2004 and 2.48 t ha-1 in 2005, but only in 2005 it was significantly different to the cut mowing system. In both years yield was significantly higher after ryegrass-clover compared to pea or barley-pea-mixture. In comparison of the different row distances, yield was significantly lower at the row distance of 12.5 cm. The undersown white clover decreased the yield with the exception of the 12.5 cm plots. This effect is caused by the weed control done with a mechanical hoe in the plots without the undersown clover combined with the wider row distances. So in these plots the heavy clay soil were aerated, which stimulated the N-mineralisation during the time of high N-demand by the oil seed rape in early springtime.