1Key Laboratory of Plant Nutrition and Agri-environment in Northwest China, Ministry of Agriculture, Yangling, College of Natural Resources and Environment, Northwest A & F University, Yangling, Shaanxi 712100, P. R. China,
2College of Forestry, Northwest A & F University, Yangling, Shaanxi 712100, P. R. China
1Key Laboratory of Plant Nutrition and Agri-environment in Northwest China, Ministry of Agriculture, Yangling, College of Natural Resources and Environment, Northwest A & F University, Yangling, Shaanxi 712100, P. R. China,
2College of Forestry, Northwest A & F University, Yangling, Shaanxi 712100, P. R. China
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Corresponding author:
Zengchao Geng , Tel: +86-13992812200,
Received: 17 September 2016 • Revised: 13 March 2017 • Accepted: 5 July 2017