Abstract:Field scale autumn irrigation experiments were conducted on the salinity soil in Hetao Irrigation District to study the variation of soil nutrient in autumn irrigation, freeze thawing and growth periods of maize with different mulching approaches. Seven treatments were contained as follows: mixed chopped maize straw mulching amount of 1.2 (F1.2), 0.9 (F0.9), 0.6 (F0.6) and 0.3 kg/m 2 (F0.3), as well as the whole maize straw (YZ) mulching, plastic film (DM) mulching, and no mulching (CK). Results showed that water table was high after autumn irrigation, soil water had a recharge and discharge relationship with groundwater during the autumn irrigation and freeze-thawing periods. The transfer and migration of soil nutrient occurred simultaneously. The changing law of soil nutrient was complex during the autumn irrigation and freeze-thawing periods. The soil surface mulching altered the water-soil environment of soil. The nutrient content had differences between treatments. The rangeability of whole effect nutrient was small during the experiment period. But the rangeability of available nutrient was large. Analyzing the feeder capability of surface soil before seeding stage of maize, it was showed that the treatment of straw mulching had small soil total N content but got huge supply intensity. It required nitrogen when the spring sowing happened. The treatment of straw mulching had small soil total P content but owned huge supply intensity. It needed phosphorus fertilizer for the spring sowing, which could ensure the growth of crops. Generally, the soil total K content and the potassium supply intensity of straw mulching treatments were higher than those of CK. Compared with CK, straw mulching made the surface soil be capable of satisfying the potassium fertilizer demand during the growth period. After the experiment period, the whole soil N content of DM in surface soil was decreased by 0.10 g/kg under the same fertilizer condition. The rangeability of other treatments was small. The soil total P content of each treatment was increased after experiment, and the soil total K contents of CK and DM were also increased, but the soil total K contents of F1.2 and F0.9 were decreased. The available N contents of YZ, F1.2 and DM were increased. The available K and P contents for each treatment were increased after experiment. The soil organic matter contents of F1.2, F0.9 and CK were increased after experiment, however, it was decreased for other treatments.
