1. Postgraduate Student, Centre for Agricultural Water Research in China, China Agricultural Univ., Tsinghuadong St. No. 17, Beijing 100083, China.
2. Ph.D. Student, Centre for Agricultural Water Research in China, China Agricultural Univ., Tsinghuadong St. No. 17, Beijing 100083, China.
3. Professor, Centre for Agricultural Water Research in China, China Agricultural Univ., Tsinghuadong St. No. 17, Beijing 100083, China (corresponding author).