Atrazine em pós-emergência no consórcio do sorgo com capim-marandu

Abstract

This work aimed to evaluate the effect of doses of herbicide atrazine in post-emergence of sorghum intercropped with marandu grass, conducted in Uberlândia-MG in 2011. The Brachiaria brizantha cv. Marandu and Hybrid Sorghum 1G282 were used to compound the intercropping. We used a density of 140 000 plants / ha-1 and 0.45 m spacing between rows for the grain Sorghum. We adopted the amount of 420 points of cultural value ha-1 for marandu grass. The treatments consisted of five doses of the herbicide atrazine base (0, 1000, 2000, 3000 and 4000 g ha-1) applied at post-emergence in intercropping system. The experimental design was in randomized block with four replications. The plots consisted of four rows of five meters, and the two central lines were considered useful ones. We evaluated the zootechnical and agronomic characteristics of interest to marandu grass and grain sorghum.There was effect of interaction between doses of herbicide atrazine and cropping system for variables: neutral detergent fiber, acid detergent fiber, total digestive nutrients and non-fiber carbohydrates. In monocropping system, the grain sorghum had higher plant height, productivity of dry matter and grains as compared with intercropping system. They were observed effects of cropping system to neutral detergent fiber, acid detergent fiber, total digestive nutrients and non-fiber carbohydrates. There was effect of doses to total carbohydrates, total digestive nutrients and non-fiber carbohydrates. We conclude that sub doses of atrazine assessed at post-emergence is not efficient in controlling Marandu grass in intercropping, and did not influence the chemical bromatological composition of the materials. The herbicide atrazine negatively influenced the nutritional value of sorghum intercropped with Marandu grass. The monocropping of sorghum results in higher production of dry matter and grains compared to intercropped with Marandu grass.