In 2008, at four ecological regions: Shandong Agricultural University, Wenkou, Yanzhou and Laizhou. ZhengDan958 (ZD958) and DengHai661 (DH661) were used for experimental materials, and planted by five different densities which were 22500, 45000, 67500, 90000 and 112500 plant?ha~(-1). In 2009, Denghai 661 as the test material and planted by 8 different densities, which were 30000, 45000, 60000, 75000, 90000, 105000, 120000 and 135000 plant?ha~(-1), also used Nongda 108 and Danyu 34 as the test material, they...