Population dynamics of Brachiaria plantaginea (Link) Hitch. by soil and herbicide managements. 2. Emergence

Abstract

A field experiment was carried out in Londrina, Paraná State, Brazil, on a "Latossolo Roxo distrófico", with 75% of clay and 2.7% of organic matter. The objectives were to determine annual pre- and post-emergence rates of Brachiaria plantaginea (Link) Hitch. in soybeans for predictive uses in weed control. Soil and herbicide managements in soybeans, followed by wheat were established during five years. Emergence rates of BRAPL changed with the year. In 1991/92, the highest annual emergence rate was 29.8%. At this year, before sowing, emergence rates were averaged in 73.9% of the annual emergence, being higher when cultivation intensities were lower. In the other years, rates were lower than 18.2%. After soybean sowings, under weed control, emergence rates varied between 5.1% and 9.6% under moldboard tillage; 4.8% and 8.7% under disc plowing; 2.2% and 6.3% under escarification and heavy disc, and 0.3% and 4.3% under no-till. In reinfestations, without herbicide control, emergence rates for this species tend to decrease.