In modem cropping systems, there is a tendency to reduce tillage intensity
in order to decrease soil erosion, leaching of pesticides and nitrate and p
roduction cost. These changes in tillage practices are expected to markedly
alter the efficiency of weed control and, thus, weed populations. There is
a lack of information on how reduced tillage systems, especially no-tillag
e, affect the development of weed populations and the efficiency of weed co
ntrol under humid temperate climate, which is typical for large parts of Eu
rope.
An experiment was conducted on a sandy loam and a loamy silt soil in the Sw
iss midlands to investigate the impact of the time of chemical weed control
on weed populations in different tillage systems. Pre- and post-emergence
herbicides were applied in conventional tillage (CT) with mouldboard plough
, minimum tillage (MT) with chisel plough, and no-tillage (NT) in a 'winter
wheat - oilseed rape - winter wheat - maize' crop rotation. All crop resid
ues were left on the fields and no stubble tillage was done. In this report
, data of winter wheat are presented.
In winter wheat grown after maize and winter wheat grown after oilseed rape
, the density of weed species was significantly affected by tillage systems
. The rank order of tillage systems in winter wheat grown after maize and w
inter wheat grown after rape was NT < MT < CT and CT < MT < NT, respectivel
y. Perennial weed species were more abundant in NT and MT than in CT. Gener
ally, the efficiency of postemergence weed control was better than that of
pre-emergence weed control.