Changes of Weed Flora due to Nitrogen Addition in Sunflower

Abstract

A field trial was conducted in Domokos region, in central Greece with Helianthus annuus, hybrid ‘LG 5658’ in order to evaluate the effects of different N fertilization and weed control methods on sunflower yield and weed flora. ANOVA showed that the interaction of fertilization and weed control had a significant effect on grain yield. Moreover, this study revealed that the density of the common weeds Amaranthus retroflexus, Abutilon theophrasti, Xanthium strumarium and Echinochloa crus-galli was increased by 60, 40, 33 and 23% in the plots of high N rate without any herbicide use. On the contrary, weeds like Datura stramonium and Convolvulus arvensis were not significantly affected by fertilization. This different responsiveness of the several weed species could be further exploited through programs of integrated crop and weed management. Moreover, our findings related to the differences in herbicide efficacy resulting from different N levels may alter weed flora and explain possible weed control failures.