Productivity and water use in forage-winter wheat cropping systems across variable precipitation gradients on the Loess Plateau of China.

Fallow-winter wheat (Triticum aestivum L.) (F-W) is the major cropping system for wheat production on the Loess Plateau of China. Integrating forage crops into the summer fallow season could improve crop yield, water productivity, and rainwater use efficiency, but this process is limited by the inter- and intra- annual variable precipitation. A 3-year (2016–2019) field experiment was conducted on the Loess Plateau to investigate the effects of fallow-winter wheat, oat (Avena sativa)-winter wheat (O-W), soybean (Glycine max)-winter wheat (S-W), and vetch (Vicia sativa)-winter wheat (V-W) systems on dry matter yield, water use, water productivity, and precipitation use efficiency under three interannual rainfall scenarios: a 30% decrease in rainfall (R-30%), normal rainfall (CK), and a 30% increase in rainfall (R+30%) by a rainfall-collection-redistribution device. In 2017–2018, under the CK scenario, the F-W, O-W, S-W, and V-W system wheat yields were 3.39, 3.63, 4.30, and 3.24 t ha−1, respectively, and the system yield values were 11.28, 16.72, 16.40, and 14.27 t ha−1, respectively. Compared to the CK scenario, the F-W, O-W, S-W, and V-W system yields increased by 22.9%, 34.5%, 20.4%, and 33.8% in 2016–2017 under the R+ 30% scenario, but the system water productivity decreased by 19.9%, 41.8%, 19.6%, and 32.4% in 2017–2018 under the R-30% scenario. Compared to those of the F-W system, the O-W, S-W, and V-W system yields significantly increased by 48.2%, 45.4%, and 26.5%, respectively, and the system water productivity increased by 51.5%, 47.3%, and 25.17%, respectively, in 2017–2018 under the CK scenario. The system precipitation use efficiency also increased by 29.3%, 42.9%, and 28.9% in 2018–2019 under the R+ 30% scenario. Across the three growing seasons, the F-W system had the highest wheat yield in the dry growing season. The S-W system had the highest dry matter yield, water productivity, and precipitation use efficiency in the normal and wet growing seasons. Therefore, we recommend the F-W system for local farmers when considering saving more soil water and maintaining wheat yield in the dry growing season. In normal and wet growing seasons, we recommend the S-W system for local farmers considering that the system increases productivity and improves environmental sustainability. • The O-W system had the highest forage yield, but it decreased the winter wheat yield in dry conditions. • The S-W system increased productivity and precipitation use efficiency in normal and wet conditions. [ABSTRACT FROM AUTHOR]