Abstract:Aiming to explore the effects of different spring irrigation quotas on soil water salt distribution and crop yield in salinization irrigation area under the condition of subsurface drainage. Taking the conventional spring irrigation level （2250m3/hm2） of open ditch drainage as the control group（CK）, four gradients of 100%, 90%, 80%, and 70% (W1, W2, W3, W4) of conventional spring irrigation water volume were set under the condition of subsurface drainage, total five treatments. Leaching effect of different spring irrigation volumes combined with subsurface drainage on moderately salinized soil was studied. Water and salt distribution, salt leaching effect, control effect on groundwater depth, oil sunflower yield and water use efficiency were analyzed. The results showed that because of the larger irrigation volume and less drainage, the soil moisture content in the root layer of CK treatment was higher, but there was no significant difference in W1 and W2 treatments. W1, W2 and W3 treatments all had better desalination effects after irrigation. The soil desalination rates in the root layer were increased by 18.47, 18.24, 7.75 percentage points compared with that of CK treatment （P<0.05). There was no significant difference between W1 and W2 treatments, and both were significantly higher than that of W3 treatments （P<0.05). Due to the smaller irrigation volume in W4 treatment, the soil desalination effect was significantly lower than that of other treatments （P<0.05). While leaching salt, W1 and W2 treatments had better leaching effect on soil salt isolates. At the same time, with the increase of irrigation leaching water, the ionic composition of the soil was developed in a benign. W2 treatment had the best time for the groundwater depth to drop after spring irrigation. The groundwater depth was dropped to 0.8m at the end of May, which was the best time for oil sunflower planting. W2 can better maintain soil moisture without affecting normal crop cultivation. The yield of oil sunflower in W1 treatment was significantly higher than that in the other four treatments （P<0.05), which was increased by 3.27%, 3.54%, 6.46%, and 17.98% compared with CK, W2, W3 and W4, respectively. The treatment with the highest soil water use efficiency was W2, which was not significantly different from W1, and significantly higher than CK, W3 and W4 （P<0.05). In view of the above, from the perspective of increasing production alone, W1 treatment was significantly higher than the other four treatments （P<0.05), which was an alternative mode. If it was limited by water resources, it can be used to reduce the amount of irrigation by 20% (W3 treatment), the desalination efficiency was slightly lower, totally 2.99 percentage points lower than that of open ditch drainage, and the improvement cycle can be increased to relieve soil salinization. From a multiangle comprehensive analysis of soil salt control, water saving, stable production, and water use efficiency, a 10% reduction based on conventional irrigation and a combination of underground drainage technology (W2) was an appropriate choice.
