Influência do regime hídrico e de herbicidas pré-emergentes aplicados sobre diferentes quantidades de palha para o controle de Digitaria insularis (L.) Fedde

Abstract

The sourgrass (D. insularis) is a weed that is difficult to manage in soybean crops, pre-emergent herbicides are often positioned for their control, however in the application of these products the following aspects must be observed: the amount of straw, the amount of rainfall and the physicochemical characteristics of the herbicides. Given the above, the objective of this work was to evaluate the control of D. insularis by pre-emergent herbicides positioned in different water regimes and amounts of straw. The experiment was carried out in a greenhouse at the Federal University of Grande Dourados, Dourados - MS, the experimental design adopted was completely randomized, organized in a 6 x 3 factorial scheme, in the first factor the water regimes were allocated (1- 5 mm after 48 hours 10 mm; 2- 20 mm after 48 hours 10 mm; 3- 5 mm after 5 days 20 mm; 4- 5 mm after 10 days 20 mm; 5- 5 mm after 15 days 20 mm and 6 5 mm after 20 days 20 mm ) and pre-emergent herbicides (diclosulam (29.4 gia ha -1 ); flumioxazin + imazetapyr (50 + 106 gia ha -1 ) and diurom + sulfentrazone (420 + 210 gia ha -1 )) these factors were isolated for the amount of straw (without straw and 3 t ha -1 of straw from Zea mays L. + Brachiaria ruziziensis Germain & Evrard). D. insularis was sown in the amount of 0.1 g of seeds at a depth of 2 cm in polyethylene pots and at 42 days after the emergence of weeds the control of D. insularis was evaluated through visual notes of 0-100 % and reduction of dry mass of the aerial part. When applied directly to the soil, diclosulam presented the smallest controls in the water regime 3, 4, 5 and 6 with 89.29%, 82.25%, 80% and 77.25%, respectively. It was also observed in the application on straw, less control with diclosulam in the water regime 6 (70.50%), the other herbicides diurom + sulfentrazone and flumioxazin + imazetapyr did not present significant differences in the water regimes presenting superior control of D. insularis. It is concluded that the herbicide diclosulam is influenced by the drought intervals after application, because the greater the drought interval after application, the smaller the control and reduction of dry mass in the quantities of straw studied. The herbicides diurom + sulfentrazone and flumioxazin + imazetapyr showing superior control of D. insularis in the studied water regimes, both in applications on straw and directly on the soil.