| A series of experiments about cultivars climatization, sowing methods,sowing date and regime of N saving and water saving were carried out to established a novel practical technique for high-yielding of direct seeding rice under non-tillage on the farm of Yangzhou University during 2003~2004. The main results were as follows:1. Under the high-yielding culture management, the comprehensive productivity of four mainly-popularized rice varieties in Jiangsu, Guanglingxiangjing, lianjiajing 1, wuxiangjing 14 and fengyouxiangzhan were compared. And the results showed that, wuxiangjing 14, lianjiajing 1 not only have higher yield (650~700kg/mu), and their grain quality reach the national standard, which were the suitable direct seeding varieties in mid-Jiangsu on wheat stubble. And the reasons for their high yield are :(1 ) Its whole growth duration is rather long, and it ripe safely; (2) Their population photosynthesis capacity is strong, and has a larger productivity at the mid-and late stage of the growth duration. Their LAI, photosynthesis potential and net assimilation rate is also rather high, and finally has a high biomass. (3) Relatively higher grain number per mu was formed by more ears and larger ear type of the population, and the seed setting percentage and 1000-grain weight were also on a rather high level.2. The rice was cultivated under No tillage and mulching stalk on wheat stubble. Compared with concentrative hill sowing (seeds were converged in hill) method and broadcast sowing in the field, the scattered hill sowing (seeds were separated in hill) not only noteably enhance the rice quality remarkably as well as the productivity. The yieldenhancement was realized through increasing the ears per mu, the grains per ear and the seed setting rate at the same time. In the process of yield formation, the photosynthesis potential, net assimilation rate and the dry matter accumulation at the main growth stage all showed some superiorities. In contrast with direct broadcast sowing (the control) , the direct hill sowing had a smaller growth potential at the early stage, but a larger growth potential which favors the formation of the yield at the mid-and late stage. Competition among plants were less stronger in concentrative hill sowing than that in scattered direct hill sowing, the yield of each hill of the scattered hill sowing increased by 10.1%, and the grain weight of each stem incresed by 4.4%.3. After the wheat was harvested in mid-Jiangsu, various direct seeding ways of premature late indica varieties were carried out during June 5th and 25th, all the results showed that: With the retardation of the sowing date , the growth duration of rice was shortened from 145 d to 131 d, mainly of which was the vegetative growth stage. The LAI and the accumulation of dry matter at main growth stage decreased, and the photosynthesis potential and net assimilation rate had a trend of decreasing at the mid-and late- stage with the retardation of the sowing date. The seed setting percentage and the 1000-grain weight changed very little, but because the ear number per mu, especially the grain number per ear decreased, so the yield decreased as the retardation of the sowing date. The sowing early as possible after wheat harvest in mid-Jiangsu region is a key measure for high yield, good quality and high efficiency.4. Aim at the shortcoming that over topdressing of N in current high yield cultivation of direct seeding rice on wheat stubble, regime of N saving with decreasing N topdressing while enhancing the plant density were carried out for two years. The N assimilation, the dynamics of leaves and tillers, photosynthesis production, accumulation of dry matter, yield and quality characteristics were analysesed comparatively. It was believed that the basic seedlings per mu should be 200 thousand, and N topdressed should be about 10 kg per mu, the aim of high-yielding (650~700 kg/mu)and good quality would be achieved as the conventional derect seeding with high N topdressing cultivation. 40%~50% N topdres...
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