Introduction Experiment of Annual Oat Forage and Screening of Microbial Fertilizer in Qinghai–Tibet Plateau

We conducted experiments to screen annual forage oats suitable for cultivation at high altitude (4200 m), and to establish a green fertilization system with microbial fertilizers and manure organic fertilizers in order to provide technical support for a sustainable forage production system in the pastoral areas of the Qinghai–Tibetan Plateau. The experiment followed the principle of randomized block design to systematically analyze the agronomic traits, yield quality, and soil health of oats among different treatments, and to screen for adaptable oat varieties and the optimal application rate of microbial fertilizers with organic manure. The results showed that the following: (1) The results of the oat variety screening test showed that the yield and quality indexes of ‘Qing Yin No. 2’ and ‘Bai Yan No. 7’ introduced in high altitude areas were higher than those of other oat varieties, with high membership function values of 0.69 and 0.65, respectively. (2) The combined application of microbial fertilizer and organic fertilizer showed that the combined application could significantly improve the growth and photosynthetic characteristics of ‘Bai Yan No. 7’. The combination of the two also improved the yield quality of ‘Bai Yan No. 7’; the hay yield with the BHC3 treatment was 8508.00 kg·hm −2 , significantly higher than the BCK treatment ( p < 0.05). Regarding soil fertility, under the BHC3 treatment, compared with the BCK, soil nutrient contents and soil enzyme activities were also significantly improved ( p < 0.05). At the same time, the combination of the two treatments also significantly improved the growth and photosynthetic characteristics of ‘Qing Yin No. 2’. The combination of the two also improved the yield quality of ‘Qing Yin No. 2’, and the hay yield with the QDY4 treatment was 8707.67 kg·hm −2 , which was significantly increased by 25.37%, compared with that of QCK. Regarding soil fertility, under the QHC2 treatment, compared with the QCK treatment, soil nutrient contents and soil enzyme activities were also significantly improved. To sum up, ‘Qing Yin No. 2’ and ‘Bai Yan No. 7’ can better adapt to the ecological environment in high altitude areas, and are suitable for planting in areas with an altitude of 4200 m. The combined application of Trichoderma harzianum , Bacillus licheniformis , and organic fertilizer can improve the yield, nutritional quality, and soil fertility of ‘Qing Yin No. 2’ and ‘Bai Yan No. 7’. The best treatment for ‘Qing Yin No. 2’ is QDY4, that is, 15.00 kg of Bacillus licheniformis is applied per hectare, and 18,000 kg of cattle and sheep manure organic fertilizer is applied per hectare. The best treatment for ‘Bai Yan No. 7’ is BHC3, that is, 6.00 kg of Trichoderma harzianum is applied per hectare, and 18,000 kg of cattle and sheep manure organic fertilizer is applied per hectare. With the above treatment, the forage grass grows best, the soil nutrient content in the forage grass field is the highest, and the input–output ratio is the highest.