The study was carried out at Xiang-Fang Experimental Station of NEAU in 1999-2001. The station is located at Harbin, Heilongjiang province (45?N and 126?E), PAR is about 1474MJm2 during growing period, mean monthly temperature is 18.5 between May and September. Effective accumulated temperature is 2800 . Average annual precipitation is around 550mm. The study includes three parts: fertilizer amount and plant density, cultivars, and source-reducing and sink-limiting. Four-factor saturated experimental design...