Effects of gramineae-legume mixed sowing and deficit irrigation on yield, quality and water use of forage grass in Hexi region

In this study, single sown of forage maize (Zea mays) (Z), mixed sowing of forage maize and forage beans (Glycine max) (ZG) and forage maize dolichos lablab mixture (ZD) were planted in Hexi region in 2019. Six irrigation modes were set under each planting mode to study the effects of different planting and irrigation modes on the yield, quality and water use efficiency of forage grass. The results showed that: 1) the fresh and hay yield of ZG and ZD treatments was significantly higher (P < 0.05) than Z, the fresh grass yield increased by 19.1% and 16.4%, and the hay yield increased by 12.7% and 9.0%, respectively. Under the same planting method, the fresh and hay yield of water deficit in later stage (I4), mild water deficit in early stage (I5) and full irrigation (I6) was significantly higher (P < 0.05) than that of severe water deficit (I1). Compared with I1 treatment, their average fresh grass yield increased by 39.1%, 45.9% and 46.6%, respectively, and the average hay yield increased by 35.8%, 44.2% and 43.8%, respectively. 2) The results showed that mixed sowing treatments increased crude protein content, reduced starch, acid and neutral washing fiber, and further increased relative feeding value (RFV), and ZG treatment significantly (P < 0.05) increased crude protein, crude fat and crude ash yield compared with Z. The average crude protein, crude fat content and RFV of I5 treatment were significantly higher (P < 0.05) than that of I1. The yield of crude protein, starch, crude fat and crude ash of I5 treatment were the highest among the six irrigation modes. 3) The data showed that ZG and ZD treatments significantly improved (P < 0.05) the water use efficiency (WUE) compared with that under Z. The soil water storage and evapotranspiration of I5 and I6 treatments were significantly higher (P < 0.05) than I1, and the WUE of I5 was significantly higher (P < 0.05) than that under I4 and I6. The WUE, crude protein, crude fat and starch of ZG-I5 treatment were the highest in all treatments, and the fresh hay yield of ZG-I5 was just below that of ZG-I6. This treatment was the best suitable cultivation mode for green forage corn production in Hexi region.