Coupling Effect of Residue Returning Depth and Mulch Coverage

Objective The aim was to clarify the effects of the combined use of different depths of vegetable residue incorporation and film mulching on soil fertility and crop yield in arid farmland, and to optimize the utilization of vegetable residue resources.

Method In the arid farmland of Yuzhong County, Gansu Province, a key summer vegetable production area on the plateau, an experiment was set up with different vegetable residue incorporation depths (10-50 cm) and film mulching conditions (mulched and unmulched) in a factorial design (12 treatments in total). The 0-30 cm soil fertility dynamics were systematically monitored, crop yield parameters (number of heads, individual weight, and total yield) were recorded, and the coupling coordination degree of soil moisture-soil fertility-crop yield under different treatments was calculated to determine the optimal field management combination.

Results ① Comprehensive soil fertility ranking showed a trend of 20 cm > 10 cm > 30 cm > 40 cm > 50 cm > control. At 20 cm incorporation depth, soil total nitrogen content across the four growth stages increased by 1.00%-8.01% compared to the control. Meanwhile, available phosphorus increased by 15.76%-21.93%, available potassium increased by 41.32%-103.70%, organic matter increased by 8.25%-36.88%, and soil moisture content increased by 5.17%-15.38%; ② Under mulching conditions, cabbage yield ranking showed 20 cm > 10 cm > 30 cm > control > 40 cm > 50 cm. Under unmulched conditions, yield ranking showed a trend of 40 cm > 20 cm > 10 cm > 30 cm > control > 50 cm; ③ The overall system coupling coordination showed a significant treatment × depth interaction effect, consistent with the trends in individual soil fertility and yield improvements, resulting in two optimal technical combinations of mulched with vegetable residue incorporated at 10 cm and unmulched with vegetable residue incorporated at 20 cm.

Conclusion The combination mulched with vegetable residue incorporated at 10 cm was suitable for arid areas with no irrigation, enhancing water retention and nutrient supply. The combination unmulched with vegetable residue incorporated at 20 cm was suitable for arid areas with some irrigation supplementation.