Resource use efficiencies and economic benefits of winter wheat-summer maize cropping system with double mechanical grain harvest

The evaluation of the mechanical grain harvest of winter wheat-summer maize cropping system and water-saving planting pattern of winter wheat without reduction in annual grain yield is an important way to improve the economic and ecological benefits of winter wheat-summer maize double cropping system in the Huang-Huai-Hai Plain. In this study, field experiments with the traditional winter wheat-summer maize cropping system (CK) and mechanically grain-harvested winter wheat-summer maize cropping systems (TR) were conducted at Jiaozhou of Shandong Province, Daming of Hebei Province, and Xinxiang of Henan Province from 2018 to 2020 to determine their annual yield, climate resource allocation and utilization, and economic benefits. The results showed that annual climate resources were redistributed through extremely late sowing (Mid November) of winter wheat and extremely late harvesting (Early November) of summer maize for TR, which affects the grain yield of wheat and maize. Compared with CK, TR decreased the grain yield of winter wheat by 9.2% across years and experimental sites owing to the reduction in biomass, spike number, and 1000-kernel weight. However, the yield of mid-late-maturing summer maize varieties in TR increased by 8.1% across years and experimental sites compared with that in CK, and the increase in kernel weight contributed to the yield increase in maize in TR. Moreover, there was no significant difference in the total biomass of summer maize between CK and TR, but the harvest index of summer maize in TR was higher than that in CK. Therefore, no significant difference in annual grain yield was found between TR and CK. The grain water content of summer maize at harvest for TR was between 14.1% and 16.8% and was significantly lower than that for CK. In addition, compared with CK, TR reduced water consumption during the winter wheat season and annual by 15.3% and 6.0% across years and experimental sites, respectively; but increased their WUE by 15.2% and 8.4%, respectively. Although the output and economic benefits of winter wheat under TR treatment reduced, the output and economic benefits of summer maize increased by 8.7% and 16.2% across years and experimental sites, respectively. As a result, the annual economic benefit of TR increased by 5.6% across years and experimental sites compared to that of CK. The results indicated that the establishment of doubl mechanical grain harvest of combined the extremely late sowing of winter wheat and extremely late harvesting of summer maize with mid-late maturity could help to achieve water-saving for winter wheat and mechanical grain harvesting of summer maize, ensuring a higher annual grain yield and economic benefit. This study provides ideas for improving the mechanization of winter wheat-summer maize double cropping system and the sustainable use of water resources.