Effects of different planting densities and fertilization levels on yield and quality of sweet sorghum grown under covering film cultivation in the dry land of Qinghai

In this experiment, Jitian 5 and Jiutianza 3 were used as materials in an experimental study on the effects of different planting densities. Linespacing×plant spacing: (40 cm×40 cm, 40 cm×30 cm, 40 cm×20 cm) and amount of urea (0, 150, 225 kg·ha-1) in the topdressing on the yield and quality of sweet sorghum were studied at an altitude of 2 040 m on dry land in Qinghai by covering film cultivation. The results showed that the fresh and hay yields of two cultivars were the highest at the spacing of 40 cm × 20 cm (120 000 hole·ha-1). The yield of fresh grass was 99.75 and 108.17 t·ha-1.The hay yieldswere 17.89 and 22.58 t·ha-1, respectively. The yield was higher and quality was better at 150 kg·ha-1 urea at the jointing stage. The crude protein of the two cultivars was 5.47% and 4.80%, crude fat was 5.67 and 7.57 g·kg-1, acidic detergent fiber was low, and comprehensive performance was good. In conclusion, a planting density of 120 000 hole·ha-1 and topdressing urea of 150.0 kg·ha-1 at the jointing stage are most suitable for sweet sorghum in the Qinghai dry land