In Brazil the cultivation of soybean is almost all done under no-till system, and the soybean is the Brazilian culture with fastest growing in the last three decades and corresponds to 49% of the grain planted area in Brazil. The increasing productivity is associated to technological advances, the management and efficiency of producers. Cultivated especially in the Midwest and South regions, soybean has established itself as one of the leading products of domestic agriculture and trade balance. Soybean was responsible for the formation of a complex structure of production, storage, processing and marketing in all countries where it is growing on a large scale. The great demand in the international market provided rapid expansion of this crop in Brazil, which occurred by the replacement of other cultures by soybean culture, and especially by the conquest of new agricultural frontiers. In relation to nitrogen fertilization efficiency in soybean crop, there are many doubts about the subject. In some situations, as in production systems under no-till with a high amount of straw on the soil, nitrogen fertilization can reduce the problem of nitrogen deficiency and also increase soybean crop yield, however, there is a limit of dose of nitrogen to be used and the soybean grain yield increase and the soybean price must compensate the nitrogen fertilization investment. This book will present results of researches conducted in the Northwest region of São Paulo State (Brazil), involving nitrogen fertilization in soybean under no-till system on the straw of sugarcane and on the straw of forage sorghum intercropped with Congo grass.