1College of Agronomy, Northwest A & F University, Yangling, 712100 Shaanxi, China.
2The Research Center of Recycle Agricultural Engineering and Technology of Shaanxi Province, Yangling 712100 Shaanxi, China.
3College of Forestry, Northwest A & F University, Yangling, 712100 Shaanxi, China.
4Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
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