Effects of Agronomic Measures on Mechanical Transplanting Long-Age Seedlings of Super Rice in Rapeseed(Wheat)-Rice Planting Area of Chengdu Basin

The effects of agronomic measures including sowing norm,date and types of seedling tray on rice long-age seedlings,were studied by using super rice,II-you 602,in wheat(rapeseed)-rice planting area in Chengdu basin.The results indicated that in normal sowing time,though rooting ability of long-age seedlings decreased from 30 to 42 days after sowing,the population size of seedlings declined slowly,root-shoot ratio,width of stem base and dry weight per unit seedling height increased.However,between 42 and 54 days after sowing,the population size of seedlings decreased sharply,root-shoot ratio and dry weight per unit seedling height began to decline,and rooting ability of long-age seedlings continued to fall.With postponement of sowing time,the population size of seedlings increased,but root-shoot ratio,rooting ability and dry weight per unit seedling height not improved dramatically and even declined.The sowing norm of 431.03 to 554.19 g m-2 was beneficial to population size and individual quality.The effects of plastic cell-tray were better when seedling age over a certain phase(about 40 days after sowing),the descending of seedling quality and population size was slower,whether further seedling age was prolonged or sowing norm properly increased.The above results showed that sowing date of around April 15,sowing norm of 431.03 to 554.19 g m-2,using hard plastic cell-tray and seedling age of about 42 days were good for raising mechanical transplanting long-age seedlings by the dry raising method of rice seedlings in Chengdu basin.