Effect of previous crop, cultivar, sowing date and nitrogen on weed biomass and species composition.
A rotational experiment was begun in 1994 to investigate the effect of crop, cultivar, sowing date and nitrogen on weed biomass and species composition. The greatest effect on weed biomass in the second rotational year was that of crop grown in year 1 and year 2 as well as the interaction between them. Greater weed biomass was observed in rape than wheat in the second rotational year. A first wheat following rape had more weed biomass than a second wheat. Differences in weed biomass in the current crop may be attributable in part to sowing date. Wheat biomass differed between cultivars of wheat but no effect was seen on weed biomass: Positive effects of previous nitrogen application were evident for both crop and weed biomass in early assessments. Species composition was affected by previous crop as well as sowing date of the current crop.