| In order to understand the plant growth characteristics and seedling-raising techniques for machine-transplanted mid-season hybrid rice, the study was executed in Pixian county of Sichuan province from 2007 to 2009, and it included six experiments:seedling age+ variety; nitrogenous fertilizer+PP333; seedling raising method+sowing rate; pore number of plastic tray+pore diameter of plastic tray; seedling raising method+nitrogenous fertilizer and transplanting method+variety. In the five nursing seedling experiments, it researched the growth characteristics of machine-transplanted rice with long seedling age; in the transplanting method+variety experiment, conventional tillage & transplanting and optimized-broadcasting rice were selected as CK, the seedling growth characteristics in turning green period, population quality indices between heading stage and mature stage, grain-filling properties, grain yield and quality were researched. Based on the experimental results and production demonstration, the seedling-raising techniques for machine-transplanted mid-season hybrid rice were summarized in this paper. The main results are as follows:1. Two years experiments showed that,36 days after sowing was the optimum stage of machine-transplanted mid-season hybrid rice seedling,44 days and 52 d after sowing was respectively the over-optimum stage and serious over-optimum stage of machine-transplanted mid-season hybrid rice seedling. In the over-optimum especially serious over-optimum stage of machine-transplanted rice seedling, the seedling quality decreased rapidly, i.e. the plant height increase rapidly while the dry weight per 100 plants and root vigor decrease rapidly. /Meanwhile, the MDA content of seedling leaf increased in line. Premature or late sowing date wasn't be propitious to raising seedling for mid-season hybrid rice. The ratio of weight/height, seedling root number, and root length and height uniformity of 35 d seedling age decreased significantly, the plant height of 55 d seedling age increased rapidly, while the weight of 100 seedlings decreased, the seedling was decrepit. Adjust the sowing date that control the seedling age between 40～45 d, the rates of seed emergence, height uniformity, root vigor and roots twisting power were ameliorated significantly. Thereby, the seedling individual diathesis and seedling block quality of machine-transplanted rice with long seedling age were ameliorated effectively.2. According to GB/T 6243-86, optimum selecting the seedling raising technology factors can effectively improve the machinerice-transplanted quantity. For dry-raised seedling by two-layers plastic film, the machinerice-transplanted quantity of 45 d seedling age was better, which partial floating rate was 8.07%, hurting rate was 16.03%, whole partial floating rate was 6.74%, crooking rate was 11.81%, empty rate was 8.90%, and overturning rate was 9.53%. Soaking seeds with 100 mg/L PP333 and spraying seedling leaf with 250 mg/L PP333 in 2.5 leaf age combining the application of 6 g/m2 nitrogenous fertilizer in 1.5 leaf age, the rate of empty-hole can decrease to 8.5%. For dry-raised seedling in plastic trays, combining the application of 6 g/m2 nitrogenous fertilizer in 1.5 leaf age and transplanting age, the rate of empty-hole can decrease to 7.05%. Adjusting the pore number and pore diameter of plastic tray to 728 and 2 mm can effectively improve the machinerice-transplanted quantity respectively. Which partial floating rate was 6.00%, hurting rate was 10.00%, whole partial floating rate was 3.50%, crooking rate was 8.70%, empty rate was 7.64%, and overturning rate was 7.36%. Moreover, the seedling raised with newspaper and bottomless on upland fields, and the sowing rate of 277.78-416.67 g/m2 gained the better machinerice-transplanted quantity, which empty rate were 7.02% and 8.07% respectively.3. The growth period of machine-transplanted mid-season hybrid rice with long age seedlings was longer than the conventional tillage & transplanting rice and optimized-broadcasting rice, which was about 6 days. In turning green period, the growth of machine transplanted rice with long age seedlings was slow, the root vigor, root number, length of the longest root and dry matter accumulation of which were worse than other transplanting mothods. After transplanted 15 d, the seedling SOD enzyme activity difference between machine-transplanted rice and conventional tillage & transplanting rice was obvious. In turning green period, the seedling POD enzyme activity difference between machine-transplanted rice and optimized-broadcasting rice was from 41.42 to 53.05 △A470·g-1FM·min-1; Compared to the conventional tillage & transplanting rice, the POD enzyme activity difference decreased in the days after transplanted 25-30 d. In turning green period, the seedling CAT enzyme activity difference among the three transplanting methods were jarless relatively, the difference range were 24.64-28.21μmolH2O2·g-1FM·min-1 and 13.76-16.99μmolH2O2·g-1FM·min-1 respectively. After transplanted 12 d, there was scarcely any tiller of machine-transplanted rice, the tillers main bourgeon in the later of turning green period, and the tiptop number of tiller appeared after transplanted 36 d, which was the same as conventional tillage & transplanting rice and optimized-broadcasting rice. But the tiptop number of tiller and the finally number of tiller are lower, which are 15.38/hole and 12.73/ hole respectively.4. The population quality indices between heading stage and mature stage of three transplanting methods were different. Between heading stage and mature stage, the ratio of high effective leaf area of the conventional tillage & transplanting rice and optimized-broadcasting rice was 0.79, which was higher than machine-transplanted mid-season hybrid rice 0.12. In heading stage, the Leaf area index (LAI) of the conventional tillage & transplanting rice and optimized-broadcasting rice were 8.02 and 8.03, which was higher tan machine-transplanted mid-season hybrid rice significant. In mature stage, the leaf area index (LAI) difference of three transplanting methods was inconspicuousness. Between heading stage and mature stage, the LAI decay rate of three transplanting methods was inconspicuousness, which was about 0.144/d. The light permeating percentage difference which was the 1/2 plant height of three transplanting methods was extremely notable. In heading stage, the light permeating percentage of machine-transplanted mid-season hybrid rice was 30.5%, which was higher than the conventional tillage & transplanting rice and optimized-broadcasting rice 5.36% and 8.82% respectively. In mature stage, the light permeating percentage of machine-transplanted mid-season hybrid rice was 24.78%, which was higher than the conventional tillage & transplanting rice and optimized-broadcasting rice 8.49% and 10.00% respectively. So, compared to the conventional tillage & transplanting rice and optimized-broadcasting rice, the NAR, leaf area index and ratio of high effective leaf area were lower, but the LAI attenuation rate and light permeating percentage were higher. Among the three varieties, the light permeating percentage of Gangyou 906 was better; LAI of Chuanxiang 9838 was bigger, while the NAR and RLA of Gangyou 188 were higher. 5. Compared to the conventional tillage & transplanting rice and optimized-broadcasting rice, the grain-filling ablity of machine-transplanted mid-season hybrid rice with long age seedlings was weaker. The concrete embody were as followes:the superior, inferior grain Ro was small, the actual grain-filling time was short, the average grain-filling rate was slow and the increasing of grain weight was slow. The superior grain average Ro of machine transplanted rice was 0.178 g/100 grains, which lower than the conventional tillage & transplanting rice and optimized-broadcasting rice 0.132 g/100 grains and 0.096 g/100 grains respectively. The inferior grain average Ro of machine-transplanted rice was 0.124 g/100 grains, which lower than the conventional tillage & transplanting rice and optimized-broadcasting rice 0.003 g/100 grains and 0.005 g/100 grains respectively. The actual grain-filling time of machine transplanted rice superior and inferior grain were all shorter, which were 19 d and 24 d respectively; the average grain-filling rate of machine-transplanted rice superior and inferior grain were all lower, which were 1.078 mg-grain-1·d-1 and 0.603 mg-grain-1·d-1 respectively. In the three varieties, the superior actual grain-filling time of machine-transplanted Gangyou 188 was fewer than Chuanxiang 9838 two days, but the inferior actual grain-filling time of Gangyou 188 was longer, which was 26 days, and the average grain-filling rate of superior grain and inferior grain of Gangyou 188 were 1.174 mg-grain-1·d-1 and 0.685 mg-grain-1·d-1.6. Seedling-raising techniques have big effects on the grain yield of machine-transplanted rice.The better seedling age was 45 d (sowing date was from lth April to 6th April), suitable variety wasⅡyou 498, which grain yield can reach to 9.53 t·ha-1 at 45 d seedling age, grain yield of Chuanxiang 9838, Gangyou 527 and Gangyou 305 were medium, the grain yield of prematurely hybrid paddy rice Zhongyou 448 was lower. Nitrogenous fertilizer, PP333 and seedling raising methods, sowing rate can obtain higher grain yield, which were 9.95 t·ha-1 and 9.70 t·ha-1 respectively. For dry-raised seedling in plastic trays, combining the application of 6 g/m2 nitrogenous fertilizer in 1.5 leaf age and transplanting age, the grain yield can reach to 10.41 t·ha-1. Increasing the pore number and decreasing the pore diameter were propitious to increase the grain yield of machine-transplanted rice. The grain yield of 728 pore+2 mm pore diameter was higher, which was 9.73 t·ha-1, the grain yield of 182 pore+1 mm pore diameter was lower, which was 7.50 t·ha-1.The Grain yield difference of three transplanting methods was extremely notable, the grain yield of optimized-broadcasting rice was higher, which actual grain yield was 10.25 t·ha-1; the grain yield of machine-transplanted rice was lower, which actual grain yield was 9.50 t·ha-1; the grain yield of conventional tillage & transplanting rice was mid, which actual grain yield was 10.13 t·ha-1. Analyzing the grain yield composing factors, the effective panicle of machine-transplanted rice was higher than the other transplanting mothods, the difference was extremely notable; the grains per panicle of optimized-broadcasting rice was higher than the other transplanting mothods, the filled grains per panicle difference between optimized-broadcasting rice and conventional tillage & transplanting rice was not notable, but all of them were higher than machine transplanted rice, the difference was extremely notable. The 1000-grain weight of three transplanting methods was not notable. In the three varieties, the grain yield of Gang you188 was higher. The effects of transplanting mothods on the milled rice rate, head rice rate and the grain amylase RVA were small, while have big effects on the chalky rice rate and setback numerical value.
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