Resumen
Rice is considered by FAO as one of the most important foods to world food security and nitrogen (N) is the nutrient that most often affects the productivity of this crop, with its dynamics in the soil-plant system changed by management used. With the objective of evaluating the yield and quantities of nutrients in the phytomass of cover crops; and to evaluate the influence of the isolated and combined use of cover crops and urea as N sources on the growth, productivity and grain quality of upland rice cultivars irrigated, in the implantation of the no-tillage system, was carried out a study in an Oxisol (Rhodic Haplustox), cerrado (savannah) phase at the Experimental Farm of UNESP/FEIS, in Selvíria-MS, Brazil. The experimental design was in randomized blocks, with four repetitions, in a 4x2x3 factorial scheme. The treatments were a combination of four cover crops: velvet bean (Mucuna aterrima), sunn hemp (Crotalaria juncea), millet (Pennisetum glaucum) and spontaneous vegetation (fallow in off-season); and two rice cultivars: Primavera and IAC 202; and three N rates: 0, 50 and 100 kg ha-1 as urea. The millet, followed by sunn hemp, produced the highest yield of dry phytomass and accumulation of nutrients. The succession sunn hemp-rice promoted higher grain yield, regardless of the N rate applied, while the cultivar IAC 202 was the most productive than Primavera. The increase of the N rate caused a drop in the number of spikelets seedless per panicle, with positive effects on grain yield. These results contribute with information about the cover plants and more efficient N rates to increase the quality and yield of rice crop.