Effects of seedling raising methods and sowing rates on machine-transplanted long-age rice seedling

In order to develop a new technology of rice seedling raising for mechanical transplanting, the effects of seedling raising method and sowing rate on seedling and transplanting quantity were studied using Chuan-Xiang 9838 as test material by field experiments. The results showed that the seedling rate decreased with the increasing of sowing rate. The effects of seedling raising methods on the seedling quality were highly significant. Similarly, sowing rates showed highly significant difference on plant height, stem width, roots number, roots length, root vigour, malondialdehyde and ratio of weight and height, while significant difference on dry weight per hundred plants. The root force of seedling block with non-woven fabrics on upland field was the weakest (6.48 kg/m2), but that with two-layers plastic film was the strongest (18.70 kg/m2). According to GB/T 6243-86, the transplanting quantity that raised with newspaper on upland field was the best, followed by bottomless one. Sowing rate of 277.78 g/m2 showed lower seedling injury rate, seedling hook rate and sowing leakage rate. And sowing rate of 416.67 g/m2 showed lower seedling floating rate, entire seedling floating rate and overturned rate of transplanting. As far as machine-transplanted long-age rice seedling was concerned, the seedling raised with newspaper and bottomless on upland fields, and the sowing rate of 277.78-416.67 g/m2 were recommended.