Abstract:The N and P fertilization impact the nodulation and yield of soybean significantly, however, there are not many reports on these in the Northeast China where the soil fertility is relatively high. Split plot field experiments were conducted to study the effects of N (0, 20 and 50 kg/ha), P (0, 20 and 40 kg/ha) and N×P interaction on soybean growth, nodulation characteristics and yield. The results show that the high rate of individual N application increases the biological and grain yield of soybean, but decreases the number, dry weight, size and nodulation index of nodules. High rate of individual P fertilizer increases the grain yield, nodule number, dry weight, size, nodulation index, although the increments in grain yield are lower than those of the N treatments. Compared with the control and the individual N or P application, the interactive effect of N and P (N×P) demonstrates the highest biomass and yield, but there are no significant differences among the N, P and N×P treatments. The nodule number, dry weight, size and nodulation index with N×P are lower than those of the individual P application, and the nodule number, dry weight, size and nodulation index of the N2 treatment (N 50 kg/ha) are higher than those of the N1 treatment (N 20 kg/ha). The increased P application rate offsets the negative effect of high N application rate on nodulation to some extent. The effects of N, P and N×P treatments on nodulation characteristics indicate that the N and P have direct effect on the nodulation, and not via plant growth. Therefore, both N and P are the key factors to the nodulation and yield of soybean in Northeast China. To maximize soybean yield, the N and P application rates should be at 50 kg/ha and 40 kg/ha, and to maximize soybean nodulation and nitrogen fixation, the N and P application rates should be at 0, 20 N kg/ha and 40 P kg/ha.