Effects of Sowing Density, Fertilizer Amount in Seedbed and Seedling Age on Seedling Quality and Grain Yield in Paddy Field for Mechanical Transplanting Rice

An experiment of two factors(sowing density and fertilizer amount in seedbed) was conducted in plastic film seedling nursery using a late maturity japonica cultivar Wuyunjing 3.The seedlings of three different ages were transplanted into paddy field,and yield and yield components were tested.The main results were as follows:(1) The effect of seedling age on seedling quality and yield was predominant,and followed by fertilizer amount and sowing density.(2) The trend of grain yield reduction was obvious when seedling age was extended from 16 d to 21 d after sowing,although under dense sowing with less fertilizer application(treatments code M1 and M2),or thin sowing with more fertilizing(code X3).Therefore,transplanting at optimum seedling age is very important for mechanical transplanting.(3) The seedling quality indices,such as root-developing ability and sugar content in stem and sheath at seedling age of 21 d were superior to that at seedling age of 16 d(significantly different),but the grain yield in paddy field of 21 d seedling age was decreased because of plant and panicle number reduction.So the indices of vigorous seedling would be varied with seedling age.(4) Path analysis of yield components on yield showed that panicle number was the most effective(path coefficient 1.1112) followed by grains per panicle(path coefficient 0.6517) for mechanical transplanting rice.