Abstract
One of causes attributed to yield of soybean that 4Mg.ha-1 is the insufficient offer of nitrogen (N). The soybean needs in average 80 kg of N to each 1 Mg of grains, or 320 kg of N to yield 4 Mg, amount to be provided from biological fixation of N (BFN) and soil. Besides of demand be higher than offer, there are twice of soybean cycle which the N is one critic factor. The first time is at…