EFFECTS OF HERBICIDES ON INTERCROPPED MAIZE AND Brachiaria brizantha WEED CONTROL, GROWTH AND YIELD

Abstract

This study had the objective of evaluating weed control, growth and yield of intercropped maize and Brachiaria brizantha, as function of herbicide doses of nicosulfuron. Six nicosulfuron doses (0 g ha-1, 2 g ha-1, 4 g ha-1, 8 g ha-1, 16 g ha-1, and 32 g ha-1) were evaluated in a tank mixture with atrazine (1,500 g ha-1). Additionally, two weeded controls were tested represented by both species in monoculture. The weed species Brachiaria plantaginea, Sorghum arundinaceum, and Brachiaria decumbens were controlled effectively by nicosulfuron with the highest used doses. The perennial species Cyperus rotundus and Artemisia verlotorum were not controlled by the herbicides. Initially, maize presented a higher growth rate than Brachiaria brizantha causing a reduction in the biomass yield rate and the leaf area index (LAI) of the intercropped forage. This effect was increased on higher rates of nicosulfuron. The maize biomass yield was smaller in the atrazine treatment as related to those treated with the nicosulfuron + atrazine mixture and the weeded control. During the critical period of competition, the aerial biomass yield and the LAI of maize were superior to the intercropped Brachiaria brizantha. These characteristics allowed a good maize grain yield independently of the adopted management.

KEY-WORDS: Crop-livestock integration; no-tillage; atrazine; nicosulfuron.