Conventional seedbed preparation for spring sown crops in Sweden includes 3
-4 harrowings followed by sowing, but there is a great interest among farme
rs to reduce this tillage. Since the soil is normally at field capacity aft
er 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 c
an 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 w
ithout harrowing. It was tested in 74 field experiments in Sweden during 19
92-1996, on soils with clay contents ranging from 6 to 57% (typically Eutri
c or Gleyic Cambisols). On an average, early sowing increased yield by 1% c
ompared with that of conventional sowing. When early sowing was made more t
han 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 significant differ
ences in bulk density or in saturated hydraulic conductivity between early
and conventional sowing. As an average for all experiments, number of emerg
ed plants was 6% lower for early than that for conventional sowing, but thi
s 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 oc
currence of leaf scald (Rhyncosporium secalis (Sacc.) Shoemaker) and net bl
otch (Dreschlera teres (Oudem) J.J. Davies) in early sown treatments, howev
er, when all results are considered, the risk of increased plant pests due
to early sowing seems small. In total, early sowing of spring cereals witho
ut harrowing may be beneficial to farmers since it reduces the cost of till
age and increases crop yield potential by lengthening the growing period. (
C) 2000 Elsevier Science B.V. All rights reserved.