Early sowing Ð a system for reduced seedbed preparation in Sweden

Conventional seedbed preparation for spring sown crops in Sweden includes 3±4 harrowings followed by sowing, but there is a great interest among farmers to reduce this tillage. Since the soil is normally at ®eld capacity after winter, the conventional system implies a major risk of soil compaction and the farmer has to wait for the soil to dry before seedbed preparation can be started. A new technique that has been made possible by new types of seed drills and improved tyre equipment is early sowing of spring cereals without harrowing. It was tested in 74 ®eld experiments in Sweden during 1992±1996, on soils with clay contents ranging from 6 to 57% (typically Eutric or Gleyic Cambisols). On an average, early sowing increased yield by 1% compared with that of conventional sowing. When early sowing was made more than 30 days before conventional sowing it increased yield by an average of 11%. There was no clear relation between yield response to early sowing and soil type. In four long-term experiments, there were no signi®cant differences in bulk density or in saturated hydraulic conductivity between early and conventional sowing. As an average for all experiments, number of emerged plants was 6% lower for early than that for conventional sowing, but this factor did not seem to be decisive for crop yield. In an experiment, when barley (Hordeum vulgare, L.) was grown after barley, there was a higher occurrence of leaf scald (Rhyncosporium secalis (Sacc.) Shoemaker) and net blotch (Dreschlera teres (Oudem) J.J. Davies) in early sown treatments, however, when all results are considered, the risk of increased plant pests due to early sowing seems small. In total, early sowing of spring cereals without harrowing may be bene®cial to farmers since it reduces the cost of tillage and increases crop yield potential by lengthening the growing period. # 2000 Elsevier Science B.V. All rights reserved.