Abstract

Winter oilseed rape can take up more nitrogen during autumn than cereal crops and requires high amounts of nitrogen (N) for maximum yield. In organic farming clover-grass leys are often the previous crop to winter oilseed rape since large amounts of nitrogen are mineralised during the autumn, after ploughing the ley, and the following growing season. Whether the Nsupply to winter oilseed rape is affected by harvesting the ley once or twice or keeping it as a green mulching crop are discussed in organic farming. Winter oilseed rape gives a good residual- N effect on the following crop but increased amounts of soil mineral nitrogen (Nmin) is often found at harvest of oilseed rape and late autumn which increases the risk for N-losses during winter. Consequently there is a need to optimise the N-supply to winter oilseed rape and reduce the risk for N-losses. This is especially important in organic farming where N often is a limiting source. In five field trials (2001-2006) the effect of three treatments of a clover- grass ley (no harvest, one harvest, two harvests) on Nmin, net N-mineralisation, N-uptake and seed yield of organically grown winter oilseed rape (with and without application of dairy slurry in the spring) was studied. In the subsequent year the effect on Nmin, N-uptake and grain yield was studied in winter wheat (following early soil cultivation/ploughing) and in spring wheat (following early soil cultivation/ploughing, catchcrop/late ploughing and no catchcrop/late ploughing). Different amounts of above ground ley crop incorporated into the ground (in the three treatments) had no impact on oilseed rape seed production or Nmin in late autumn after ploughing the ley, in early spring or at harvest of the following winter oilseed rape. The reason for this could be that the roots are of more importance for the N-supply after leys and were most likely similar in all treatments. The impact of the slurry application to the winter oilseed rape was surprisingly small and increased yield with 300 kg ts/ha. In late autumn after harvest of oilseed rape Nmin was reduced by 50 % with catch crop (or spontaneously occurring crop) and late ploughing compared to where winter wheat was sown after early cultivation and ploughing or early cultivation followed by late ploughing. The results showed that catch crop (or spontaneous crop) and late ploughing (followed by spring wheat) were efficient methods to reduce the risk for N-losses after winter oilseed rape. Subsequent wheat yield was relatively high, indicating a sufficient N-supply, but was not affected by the ley treatments, slurry application or various soil cultivation (with or without catchcrop) after harvest of oilseed rape. Yield of winter and spring wheat was similar and with a price 0,5 kr/kg higher for spring wheat, economically as well as environmentally the best choice of subsequent crop to winter oilseed rape was spring wheat

Keywords

höstraps; efterverkan; ekologisk odling

Published in

Rapport (Avdelningen för precisionsodling, Sveriges lantbruksuniversitet)
2008, number: 16
ISBN: 978-91-85911-24-0
Publisher: Avdelningen för precisionsodling, Institutionen för markvetenskap, Sveriges lantbruksuniversitet

SLU Authors

• Engström, Lena

  • Department of Soil Sciences, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Agricultural Science


Permanent link to this page (URI)

https://res.slu.se/id/publ/18288