The objective of this study was to evaluate the straw effect of four cover crops [grain sorghum ( Sorghum bicolor L. Moench), sun hemp ( Crotalaria juncea L.), pearl millet ( Penisetum americanum L.), and brachiaria ( Brachiaria brizantha cv. Marandu)] sown at two different times and a fallow area and its effects on soybean cultivated in succession in a no tillage system. The study was carried out from march/08 to april/09 in the experimental farm of the College of Engineering, a unit of the Universidade Estadual Paulista (UNESP), located in Selviria, a county of the state of Mato Grosso do Sul, (51degrees22?W and 20degrees22?S, with 335 m altitude), Brazil, in an Oxisol. The treatments consisted in the sowing of the four cover crops on March 27 and April 23 of 2008 and in the use of a fallow area. The experiment was set in the field according to a randomized complete block design with eight repetitions. Forage crops (sunhemp and B. brizantha) sown in two seasons do not change the soybean yield. Soybean yield on sorghum and millet sown in March was higher than that observed for the same crops sown in April. The grasses used are shown as a viable option for the production of dry matter for soybean sown in March.
