College of Agronomy Sichuan Agricultural University Chengdu 611130 P.R.China;
Sichuan Engineering Research Center for Crop Strip Intercropping System/Key Laboratory of Crop Ecophysiology and Farming System in Southwest China Ministry of Agriculture and Rural Affairs Chengdu 611130 P.R.China;
Yibin Academy of Agricultural Sciences Yibin 644000 P.R.China;