From Anders Borgens List of Publications
Winter cereals under-sown in spring crops - an ecological way to reduce soil tillage.
Proceedings from IFOAMs 13th International Scientific conference, Basel
Keywords: Crop rotation, soil tillage
The aim of organic plant production is (among others) to maintain soil fertility, prevent leaching and reduce energy consumption. In organic plant production this goal is mainly achieved by clover-grass fields which is established under sown in a spring crop without soil tillage. Clover-grass can mainly be used as fodder for ruminants and other grassing animals, but many organic farms with low stock density wishes to reduce the frequency of clover-grass fields in the crop rotation in order to increase the salable plant production. However, this normally increases the soil tillage intensity in the system, which again results in leaching of nutrients, increased energy consumption and reduced humus content in the soil.
Direct drilling as it is used in conventional agriculture could be a way to reduce soil
tillage also in the organic cereal production, but problems with weeds have been the major
obstacle to implement this method. To solve this problem, the idea arose, if winter
cereals could be under sown in a spring crop in the same way as grasses and clover crops
Material and methods
Plots with winter wheat and winter ray were sown into a barley field in the beginning
of April, which is normal sowing time for spring cereals in Denmark. The plots were sown
the same day as the barley. Control plots with winter cereals were sown in plots prepared
with a rotary cultivator in September after harvest of the barley. No pesticides were used
in the assessment period, but the cropping conditions were not organic in this experiment.
Results and discussion
Most of the tested varieties of winter wheat and winter ray tilled already in the first year which prevented the winter cereals from regrowth after harvest. However, the winter wheat variety 'Stava' and one variety of perennial ray did not head in the first year, and grew well again after harvest. The yield of the barley was reduced as a result of the under sown crops, but compared with the reduced costs for establishment of the subsequent crop, this was acceptable in the wheat, but not in this variety of perennial ray. The nutritional status of the under-sown crops were much better than the crops sown after harvest, but the yield in wheat was very much reduced because of heavy infection by BYDV (Barley Yellow Dwarf Virus). Hence, the resulting yield was the same in the wheat under-sown and after-sown.
New on going experiments conducted under organic conditions with peas as cover crop shows that other varieties of both winter wheat and winter ray can be used for this cropping system. Peas are not hosts for BYDV and they are more likely to be able compensate for the competition of nitrogen.
At the present stage more research/development is needed, and the system can not be
recommended for commercial production yet. Future research should concentrate on the
choice of suitable varieties with high vernalization needs and tolerance against BYDV.
More focus should be put on mechanical weed control in the first year, plant density and
possibly mulching after harvest. Swedish and Finnish studies have found problems with pest
flies (Mayetiola destructor and Oscinella frit).
Winter cereals can be established by under sowing in a spring crop. A necessary
prerequisite is that a varieties with a very high vernalization need is used. This
cropping system will minimize the leaching of nutrients, the and brake down of humus in
the soil, problems with annual weeds and the time and energy consumption in the
production. Other problems arise instead, like BYDV, insects and perennial weeds. Further
experiments with the development of the system is therefore needed.
Borgen, A. (1999). Vintersæd etableret som udlæg i dæksæd. Forskningsnytt om Økologisk Landbruk i Norden. 6:6-8.