Dry direct-seeded rice-wheat rotation system: Lower water and carbon footprint and higher carbon production efficiency and net ecosystem economic benefits

Securing food and energy supplies presents a significant challenge to human survival and progress. The rice-wheat rotation is one of the main food crop systems in China. However, no comprehensive assessment of the water footprint (WF), carbon footprint (CF), carbon production efficiency (CPE), and net ecosystem economic benefits (NEEB) of different rice-wheat rotation systems has been reported. This study was conducted to assess the productivity, WF, CF, CPE, and NEEB of dry direct-seeded, wet direct-seeded, and transplanted rice-wheat (TR-W) rotation systems. The objective was to provide theoretical guidance for the development of clean and sustainable rice-wheat rotation production technology systems. We used a split-plot design, with the main plots being the dry direct-seeded, wet direct-seeded, and transplanted rice planting methods, and the subplots consisting of two rice genotypes. Dry direct-seeded rice was mainly rainfed, ensuring that the soil remained relatively dry so that the soil is kept aerobic during the whole reproductive period of rice. Wet direct-seeded rice continues to keep the soil moist after sowing; the plots were maintained under a water layer of 3–10 cm following the emergence of 4.5 leaves, a condition that persisted until two weeks prior to the rice harvest. Transplanted rice was maintained under a water layer of 3–10 cm following transplanting until 2 weeks prior to the rice harvest. Subsequent to the rice harvest, the above-ground rice stubble was removed, and the ground was tilled with a rotary tiller in preparation for the subsequent wheat planting. Results demonstrated that the annual yield from the dry direct-seeded rice-wheat (DR-W) rotation system was comparable to the wet direct-seeded rice-wheat (WR-W) rotation system, while significantly lower than that of the TR-W rotation system. However, the WF of DR-W rotation system was 45.96% and 33.94% lower than that of WR-W and TR-W rotation systems, respectively, and the CF was 35.57% and 25.87% lower than that of WR-W and TR-W rotation systems, respectively. Therefore, its water and carbon production efficiencies were higher than those of WR-W and TR-W rotation systems. In addition, NEEB in DR-W and TR-W was comparable and significantly higher than that in WR-W. The DR-W rotation was a promising rotation system according to the comparable annual yield, lower water and carbon footprints, higher CPE, and comparable or higher NEEB in comparison with other rice-wheat rotation systems. We suggest that the DR-W rotation should be promoted as the primary production mode for the rice-wheat rotation.