No tillage with previous plastic covering increases water harvesting and decreases soil CO₂ emissions of wheat in dry regions

In arid and highly populated areas, water shortage and soil CO₂ emission (CE) are seriously threatening the sustainability of agriculture. Optimization of tillage, irrigation, and nitrogen (N) application within cropping systems are keys to reducing CE. We hypothesized that an integrated system could increase crop yields and improve water harvesting, while reducing CE and enhancing C sequestration potential from crop production. In 2016–2018, this hypothesis was tested under spring wheat of maize-wheat rotation in field experiments in the arid inland irrigation of China. This research evaluated how no tillage, reduced the supply levels of irrigation and N affect crop yield, water harvesting, and CE, C sequestration potential of following spring wheat after plastic-mulched maize. Across the three study years, tillage practice, irrigation level, and N level individually had a significant effect on grain yield, water harvesting, and CE characteristics of wheat in each year, but the interaction among the three factors was hardly significant. No tillage with previous residual plastic covering (NTP), reduced irrigation, and reduced N application increased grain yield, improved water harvesting of wheat, but decreased CE. On average, NTP practice combined with a reduction of 20 % in irrigation and N supply levels (i.e., the optimized system, NTPI2N2), increased grain yield, soil water storage between pre-sowing and post-harvesting (wheat harvesting), and the ratio of transpiration to evaporation (T/E) by 13.6, 150.0, and 79.7 % (P < 0.05), respectively, compared to conventional tillage with local conventional high supply level in irrigation and N (i.e., the control, CTI2N3). The optimized system reduced CE and carbon emission intensity (CEI) by 31.3 % and 39.0 % (P < 0.05) compared to the control treatment, respectively. However, the optimized system had 7.5, 12.6, 7.5, and 57.4 % (P < 0.05) greater net primary production (NPP), net ecosystem production (NEP), carbon in harvested wheat (harvest-C), and the ratio of NPP/CE than the control. It indicates that the optimized system had greater potential for enhancing soil C sequestration. Therefore, no tillage with previous residual plastic covering from the previous maize combined with a 20 % reduction in both irrigation and N levels is a promising strategy to improve water harvesting, reduce CE, and enhance soil C sequestration potential of wheat production in dry regions.