OPTIMISING TIME OF PLANTING AND HERBICIDE APPLICATION FOR CONTROL OF PROBLEM WEEDSIN MAIZE

摘要

Field trials in Waikato, Bay of Plenty and Manawatu investigated the efficacy of pre- and post-emergence herbicides for weed control in maize crops planted early, mid or late season with prior cultivation or into a stale seedbed. Achieving good control of broadleaf weeds was easier than for annual grass weeds. Some weed species germinated over a long period from spring to summer months. The residual activity of pre-emergence herbicides was not sufficient for season-long control of such weeds in the early and mid planted crops and a post-emergence herbicide was essential to control them and to maintain grain yields. When grass weeds were dominant, the pre- and post-emergence combination still did not provide season long control in the early plantings. In late planted crops, weed control was also poor in the absence of a post-emergence herbicide even though few weeds were present at the post-emergence application time. The weed seedbank was reduced where good weed control was achieved.