Effects of crop rotation and reduced nitrogen fertilisation on Apera spica-venti populations in a long-term experiment.

Apera spica-venti is one of the most serious annual grass weeds in Germany and may cause considerably yield losses in untreated fields. A long-term field experiment was conducted investigating the effects of crop rotation and nitrogen fertiliser use on A. spica-venti populations. A six-field cash-crop rotation with 67% winter cereals and a six-field fodder crop rotation with 50% winter cereals were studied. The rate of tillering was in the fodder crop rotation significantly higher than in the cash crop rotation. The halving of nitrogen fertilizer dose caused a significant increase in the tillering rate. Most plants of A. spica-venti emerged in winter wheat. There was an increase of emerged A. spica-venti in winter wheat from year to year.