ACKNOWLEDGEMENTS
Funding for this project was provided by the projects of Key subject of Ningxia province (2018BBF02016), China Agriculture Research System (CARS-38), Research and Demonstration on Key Technologies of Efficient Utilization Modern Artificial Grassland (2017BY082), and China Postdoctoral Science Foundation (2019M660877). We thank LetPub (www.letpub.com) for its linguistic assistance during the preparation of this manuscript.