东北黑土区大豆生长、结瘤及产量对氮、磷的响应

氮肥和磷肥显著影响大豆的结瘤和产量。然而在土壤肥力较高、速效养分有效性差的东北地区，有关氮肥和磷肥施用量对大豆结瘤和产量影响的研究较少。本试验采用裂区田间试验，设置3个氮（N）水平（0、20 和 50 kg/hm2）和 3 个磷（P）水平（0、 20 和 40 kg/hm2），研究氮、 磷及其交互作用对大豆生长发育、 结瘤特征及产量的影响。结果表明, 单施氮肥大豆生物量和产量随着施氮量的增加而增加，而根瘤数量、 干重、 大小和结瘤指数呈逐渐下降的趋势。单施磷肥促进大豆生物量、 产量、 根瘤数量、 干重、 大小和结瘤指数的增加，但其增幅低于施氮处理下的增幅。氮磷对大豆生长和产量促进作用高于单施氮和单施磷处理，但差异不显著；氮磷处理下的根瘤数量、 干重、 大小和结瘤指数低于单施磷处理；氮磷处理下N2（N 50 kg/hm2）处理下的大豆根瘤数量、 干重、 大小和结瘤指数高于N1处理（N 20 kg/hm2）下的，随着施磷量的增加大豆根瘤数量、 干重、 大小和结瘤指数增加，施磷能够抵消氮对大豆根瘤产生和形成的抑制。氮、 磷及其交互作用对大豆根瘤的影响都是直接的，并且不是通过促进大豆生长间接促进的。因此氮和磷均是限制东北地区大豆结瘤和产量的因素，但氮是主导因素。若要获得大豆高产，氮肥施用量需要控制在50 kg/hm2，磷肥在40 kg/hm2；但若想最大的发挥大豆的结瘤固氮功能，那么应该不施或者减少氮肥的施用量到20 kg/hm2，磷肥仍在40 kg/hm2。

Responses of growth,nodulation and yield of soybean to different nitrogen and phosphorus fertilization management

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.