Impact of precipitation variation on summer forage crop productivity and precipitation use efficiency in a semi-arid environment

Planting annual forage crops could provide fodder supplies, enhance the development of the livestock industry, and optimize cropping systems in semi-arid regions, but water shortages and variable precipitation limit forage production on the Loess Plateau. To explore forage production under variable precipitation conditions, we conducted 3-year field experiments to evaluate the crop production, water use, water use efficiency, and pre-cipitation use efficiency of three forage crops, soybean (Glycine max L.), oat (Avena sativa L.), and vetch (Vicia sativa L.), under three rainfall scenarios: a 30 % decrease in rainfall (R-30 %), normal rainfall (CK), and a 30 % increase in rainfall (R +30 %). The scenarios were implemented with rainfall-collection-redistribution devices. In 2017, under the CK scenario, the dry matter yield (DMyield) values of soybean, oat, and vetch were 3617.56, 5284.00, and 2631.00 kg ha -1, respectively, and the crude protein yield (CPyield) values were 555.20, 518.37, and 467.57 kg ha -1, respectively. Compared to those under the CK scenario, the soybean, oat, and vetch DMyield values under the R + 30 % scenario increased by 26.25 %, 13.16 %, and 26.38 % in 2016, but the water use efficiency for dry matter yield (WUEDM) increased by 28.04 %, 40.58 %, and 27.77 %, respectively, in 2018 under the R-30 % scenario. Compared to that of soybean, the precipitation use efficiency for crude protein yield (PUECP) of oat was significantly lower, by 32.58 %, 31.19 %, and 27.50 %, in 2018 under the R-30 %, CK, and R + 30 % scenarios, respectively. Across the three growing seasons, under the R-30 %, CK, and R + 30 % rainfall scenarios, oat had the highest DMyield and WUEDM, but soybean had the highest CPyield and PUECP. Therefore, oat and soybean are two suitable forage types for this region, and they could be integrated into existing cropping systems. Under wet conditions, we recommended incorporating oat into fallow-winter wheat and fallow-maize -winter wheat cropping systems during the fallow periods to produce forage. Under dry and normal climate conditions, we recommend planting soybean in fallow-winter wheat and fallow-maize-winter wheat cropping systems to reduce soil water use and increase precipitation use efficiency.