Trade-offs between winter wheat production and soil water consumption via leguminous green manures in the Loess Plateau of China.

• Both Δ Y R and Δ WUE R in the LGM systems were over 5% when rainfall was adequate. • Soil in the LGM systems was 39.7 % times more desiccated than that in the fallow system. • LGMs yielding ≥1926 kg ha−1 reduced wheat yield in this dry-land region. • The safety threshold of soil water consumption by the LGMs was 26.2 mm (0−200 cm). • The minimum annual rainfall for applying the LGM approach was estimated to be 551 mm. The growth of leguminous green manure (LGM) in place of bare fallow in summer improved soil fertility but resulted in reduced soil water storage and crop yield in semiarid regions of the Loess Plateau. To balance the contradiction between yield production and soil water consumption in LGM systems, we investigated the effects of replacing fallow with three LGMs on the relative changes in grain yield and water use efficiency of winter wheat (Triticum aestivum L.), the plant available water distribution pattern, and the soil desiccation characteristics in the 0−200 cm layer from 2009 to 2018. Additionally, we assessed the correlations between Δ soil water storage, LGM biomass, and annual precipitation with Δ grain yield, and Δ soil water storage with LGM biomass over 10 years. Results showed that the relative changes in wheat yield and water use efficiency in the LGM systems were all negative in a dry year, however, they were all positive and over 5 % when rainfall was adequate. There were strong positive correlations between the annual precipitation with Δ soil water storage (R2 =0.59) and Δ grain yield (R2 =0.67). The minimum annual rainfall for applying the LGM approach was estimated to be 551 mm. Conversely, the slight correlations between the LGM biomass with Δ soil water storage (R2 =0.125*) and Δ grain yield (R2 =0.25**) under the LGM systems were all negative. Compared to the fallow system, for every 71.4 kg ha−1 of LGM aboveground biomass produced, the soil water storage during the fallow period was reduced by 1 mm, and for 1 mm of soil water storage decreased, the wheat yield was reduced by 18.9 kg ha−1 in the LGM systems. Consequently, managing the LGM aboveground biomass within 1926 kg ha−1 or less may be an efficient option to reduce the risks of wheat yield and soil water balance due to replacing fallow with LGMs on the Loess Plateau and in similar dry-land regions. [ABSTRACT FROM AUTHOR]