The consolidation of the no-tillage system in the Cerrado still faces difficulties regarding the establishment of cover crops. In this sense, has chosen by the technique of oversown aiming to take advantage of the moisture at the end of the rainy season. However, there is not always successful the establishing of the crops with this sowing system. Thus, the aim of this study was to evaluate the initial development of Urochloa ruziziensis in oversown on stage R5.3 and agronomic performance of soybean under different spacing between the lines of cultivation. The field experiment was carried out in the Barra do Garças (MT) Brazil, in 2010/2011 crop season. The experimental design was randomized blocks in a 5x2 factorial arrangement with four replications, characterized by five different row spacings (0.40; 0.45; 0.50; 0.55 and 0.60 m) and two soybean cultivars (P99R01 and M-Soy 9144RR). We evaluated the plant height, number of pods plant-1, thousand grain weight, number of plants of U. ruziziensis at 7, 14 and 21 days after emergence (DAE), index of closing of lines (ICL), photosynthetically active radiation (PAR) below the canopy and PAR intercepted at 30, 45, 60 and 75 DAE and the yield of grain. Regardless of cultivar, the spacings of 0.45 m to 0.50 m yielded the highest values in plant height, number of pods plant-1, number of plants of U. ruziziensis and yield of grain. There was no effect on weight of thousand grains. Regardless of cultivar, row spacing below of 0.50 m provide higher IFL, higher PAR interception and a lower incidence of PAR below the canopy.
Glycine max; cover crops; productivity; photosynthetically active radiation
