Effect of weed seed production prevention and 10-year herbicide direct spray on weed density in corn during sucessive years

摘要

A ten-year corn field experiment was conducted at Ponta Grossa (Parana, Brazil) to evaluate the effect of weed seed production prevention and herbicide direct spray on weed density in successive years, under two different tillage treatments (conventional and no-till). The main weeds in the area were Alexandergrass (Brachiaria plantaginea), crabgrass (Digitaria ciliaris), wild poinsettia (Euphorbia heterophylla), pusley (Richardia brasiliensis) and arrowleaf sida (Sida rhombifolia). The prevention of weed seed production during ten years reduced weed density over 99%. There was no difference between conventional tillage and no-till for density reduction. Weed density reduction varied but was greater during the first years for all species. Weed density in successive years, when there was weed seed production (check), varied, according to climatic and cultural conditions. Direct spray herbicide application was efficient in controlling weed seed production, when the species were susceptible to the herbicides. Increasing crabgrass density was observed under conventional tillage with direct spray due to poor control. The fitting equation in the treatments without seed production and herbicide direct spray was a negative exponential. Weed density results were confirmed by weed seed bank evaluation.