Effects of Straw Retention，Film Mulching，and Nitrogen Input on Soil Quality in Dryland Wheat Field

The effects of straw retention，film mulching，and nitrogen fertilizer on soil quality in dryland were assessed through a 5-year field positioning experiment. This experiment was conducted using a dual factor split plot design，and the main treatments were three cultivation models：conventional cultivation（CT），straw retention in field（SR），and film mulching cultivation（FM）. There were three nitrogen application rates for the split zone treatment：0，144，and 180 kg·hm-2. After the winter wheat harvest in the fifth year，soil samples of 0-20 cm in the topsoil were collected to measure soil physical and chemical properties and biological properties，such as bulk density（BD），soil porosity（SP），field capacity（FC），soil organic carbon（SOC），total nitrogen（TN），total phosphorus（TP），total potassium（TK），mineral nitrogen（NO3--N + NH4+-N），available phosphorus（AP），available potassium（AK），microbial biomass carbon（MBC），microbial biomass nitrogen（MBN），sucrase activity（SA），alkaline phosphatase activity（ALP），urease activity （UA），dehydrogenase activity（DHA），etc. Based on a two minimum data set（MDS），the soil quality index（SQI）was calculated using linear（LT）and nonlinear（NLT）scoring models，and the optimal SQI was found by fitting with winter wheat yield. The response of soil quality to straw retention，film mulching，and nitrogen fertilizer was analyzed. The results showed that the SP，FC，SOC，TK，SA，ALP，DHA，MBN，and MBC of the SR treatment were significantly increased by 10. 1%，40. 5%，28. 3%，14. 4%，22. 0%，8. 9%，48. 3%，35. 9%，and 62. 5% compared to those of the CT treatment，respectively. The SP，FC，NO3--N，AP，AK，ALP，and MBN of the FM treatment were significantly higher by 3. 1%，14. 6%，729. 0%，37. 4%，28. 2%，7. 2%，and 17. 7% compared to those of the CT treatment，respectively. The yield of winter wheat in the SR and FM treatments was significantly higher than that in the CT treatments by 25. 1% and 18. 6%，respectively. Compared with N0，the application of nitrogen fertilizer significantly increased SP，TN，NO3--N，NH4+-N，ALP，and MBN by 3. 4% to 407. 6%，whereas BD，SOC，and MBC/MBN significantly decreased by 3. 0% to 31. 7%. Under the three cultivation modes，nitrogen application significantly increased winter wheat yield，with an increase of 69. 4%-79. 1% compared to that of N0. There was no significant difference between the two nitrogen application levels. The SQI calculated based on the MDS2 nonlinear scoring model could more accurately evaluate the soil quality of dryland wheat fields. In NLT-SQI2，the SR，FM，and nitrogen fertilizer could increase the SQI of the soil，and the SQI reached the maximum at the level of SR combined with N180，followed by FM and CT. In summary，straw retention and film mulching combined with appropriate nitrogen fertilizer could maintain and improve soil quality，and straw retention yielded better results than film mulching. © 2024 Science Press. All rights reserved.