What causes soybeans to produce many flowers but few pods?

At present, many farmers growing soybeans have found that in some plots the soybean plants produce many flowers but few pods. The reasons can be found through a "five checks." First, check the soil structure and analyze whether the soil pH value is too high, and whether the field has been repeatedly cropped with soybeans or is a continuous cropping field; second, check the fertilizer content and analyze whether the ratio of nitrogen, phosphorus and potassium in the applied chemical fertilizer is reasonable; third, check the planting structure and analyze whether the planting density is reasonable; fourth, check the plant roots and analyze whether pests and diseases have occurred on the roots; fifth, check the soil moisture and analyze whether the moisture content is too high or too low, since both excessive drought and excessive waterlogging will affect the pod-setting rate. Only by carefully checking and analyzing in detail can conclusions be drawn and proper measures taken to prevent flower drop and poor pod set and to increase yield.