Comprehensive benefit evaluation of monocropping and mixed cropping of different forages in the alpine region

This study aimed to explore the annual forage crops and planting patterns suitable for alpine pastoral regions in Qinghai. In this study, different varieties of broad bean (Vicia faba) and rapeseed (Brassica napus) were sown in monocropping and mixed with oats (Avena sativa). Plot experiments were conducted at Qinghai Bakatai Farm in 2020 to measure the production performance, nutritional quality, economic benefits, and soil nutrients of each treatment, and evaluate the comprehensive benefit. The hay yields of the tested treatments were found to range from 1 378.56 to 2 792.94 g·m⁻². Mixed cropping with oats increased hay yield, with the highest yields of 2 836.46 g·m⁻² and 2 668.79 g·m⁻² for the treatments of ‘Huayouza 62’ + oat and ‘Siyou 2’ + oat, respectively. The crude protein content of ‘Qinghai 13’ (20.13%) and ‘2005-00’ (18.34%) were significantly higher than that of other treatments (P < 0.05). Mixed cropping with oat decreased the crude protein and crude ash but increased the neutral detergent fiber, with no significant effect on crude fat and relative forage value (P > 0.05). Soils in the 0－20 cm layer with broad bean monocropping had higher total N, total P, nitrate N, ammonium N, and available P than soils with rapeseed monocropping. Although soils in the 0－20 cm layer with the rapeseed-oat mixtures had higher total N, total P, nitrate N, ammonium N, and available P than soils with rapeseed monocropping, these values were still lower than those of monocropping of broad bean. The values of net economic benefits were highest after ‘Qinghai 13’ + oat treatment and lowest after ‘Huayouza 62’ treatment. The multivariate data evaluation showed that ‘2005-00’ monocropping and ‘Qinghai 13’ monocropping performed excellently in the alpine region of Qinghai and could be further tested for promotion and utilization.