Effects of Humic Acid on the Photosynthetic Characteristics, Essential Elements and Yield of Oryza sativa L. and Their Correlation Analysis

• ZHANG Qinyi, 
• LI Wenwei, 
• YANG Jing, 
• LUO Yacheng, 
• YANG Jieru, 
• WANG Huiqun, 
• XIAO Langtao