The effect of different preceding crops on the development, growth and yield of winter wheat

Abstract

The effects of different preceding crops on the growth, development and yield components of winter wheat (cv. « Kanzler ») were determined in field trials carried out over three seasons in a system with high inputs. The effects on grain yield were observed in a total of four seasons.At most of the sample dates after winter, wheat following wheat had a lower dry weight and a slightly lower number of shoots per unit area than the other treatments, but the differences were inconsistent within years. After winter in one season (1986/87) a large range in number of shoots per unit area was observed, but it diminished during the season and finally led to negligible differences in dry weight; in the succeeding seasons (1987/88 and 1988/89) there was a contrasting trend.Wheat after wheat compared with wheat after rapeseed yielded between 0.66 t ha-1 (1986/87) to 1.97 t ha-1 (1987/88) less, but in the last season (1989/90) the wheat following wheat outyielded wheat following rapeseed by 0.59 t ha-1. This was attributed to the optimum of nitrogen fertilization being exceeded in the wheat after rapeseed. Considering all seasons, the differences in grain yield could not be accounted for in terms of any single yield component.Take-all was apparent in three seasons and the higher disease incidence in wheat after wheat was associated with differences in growth and yield in 1987/88 and 1988/89 but in 1986/87 the incidence of take-all was considerably lower. It is suggested that the harmful influences of the disease were mitigated by wet seasonal conditions.Averaging over seasons, it was not possible to compensate for the detrimental influences of the preceding wheat crop on the grain yield of the subsequent wheat by increasing the amount of nitrogen fertilization from 210 kg N ha-1 to 250 kg N ha-1.