Abstract: Based on the data of wheat fields and soil moisture at the Xifeng Agrometerological Experiment Station from 1981 to 2010, the variation law of soil water and the relationship between the yield factors and soil water were discussed. The results showed that the maximum soil water storage occurred in growth stage before winter, followed by reviving to jointing stage, and the minimum in booting to mature stage. The maximum soil water consumption was observed in booting to mature stage, followed by growth stage before winter, and the minimum in reviving to jointing stage. It is also shown that the soil water storage at depths of 200 cm and 100 cm decreased and water consumption at depths of 200 cm and 100 cm increased with trend of fluctuations. The utilization efficiency of soil water increased in a linear trend and the turning point occurred in 1998. There is significant relationship between the infertility spikelet rate and soil water storage at depths of 200 cm and 100 cm. The correlation between soil water storage in different layers and TKW (thousand kernel weight) can be estimated through the method of hypothesis testing, and the deeper the layer of soil water storage, the higher the correlation coefficient was. The correlation between ear number and soil water storage in different layers in growth stage before winter and the period of reviving to jointing could pass 0.1 and 0.01 reliability testing respectively. The soil water storage in different layers in growth period and actual yields in test field were correlated prominently. The value of aj(t) was 20 kg in 1 ha at a depth of 1 mm in soil water during the second ten days in May. There is negative correlation between water consumption at 100 cm depth and infertility spikelet rate. The TKW and water consumption in different soil layers was closely correlated.

Key words: Loess Plateau in Gansu, soil water, variation, yield factors, influence