Variability of weed infestation in two wheat varieties (Triticum Aestivum L.). I - as influenced by sowing date and post-emergence weed control

Abstract

The density of weed infestation of a crop is influenced by its sowing date due the variability of the control of the spontaneous flora in pre-emergence, depending on the level of weed emergence before sowing.

In this study the effect of different sowing dates of two wheat varieties (Sever and Centauro) and post-emergence weed control was analyzed in terms of weed infestation and crop performance. The trials were carried out over four years (1996/97 until 1999/00) on the farm Revelheira belonging to the Regional Directorate of Agriculture in the Reguengos de Monsaraz municipality.

When sowing was carried out in the beginning of November and without post-emergence weed control weed infestation during the crop cycle was much higher when compared to the sowing date at the end of November. Consequently, yield reduction was much more pronounced at the early sowing date. Thus, for early sowing dates, post-emergence weed control under Mediterranean conditions seems to be essential to avoid severe weed infestation and unacceptable crop yield reductions.