| From 2002 to 2003, the experiments were carried out at Xinghua, where the rice-fish culture was most concentrated and largest in Jiangsu province. With the conventionally-cultured rice as the contrast, the biological characteristic and adaptability, including the population development and individual growth of rice in rice-fish system were studied. Aim at the improvement of practical techniques, a series special experiments, sowing methods, sowing date, varieties selecting, planting density, and fertilizing technique, etc, were designed to analysis the rule high yield and good quality of rice in rice-fish culture. The main results were as follows:1. Because of being submerged by 20-40cm depth water from tilling stage to the time 7-10 days before harvest, rice in rice-fish system showed some changes in biology and morphology. Compared with the rice sowed in the same date in conventional culture, the rice in rice-fish culture showed:(1)The elongation stage was brought forward, the period from elongation stage to heading stage was retarded for 7-10 days, and the maturity was put off a little. The biomass, LAI and the coronal leaf area in every stage increased. The filling velocity of grain was higher than that of conventionally-cultured rice in early phase, while lower in late phase, and the active filling period came earlier.(2)The total number of leaves of rice in rice-fish system was more than that of traditional culture rice, the plant's height and the number of roots were enhanced. The basal nodes became wider, and the roots' vigor reduced in late phase.(3) The blowhole in stem and sheath developed, the ability of plant for aerating was stronger, the number and the area of vascular bundle were less than the contrast, and the development of vascular bundle was restrained. This discovery was reported for the first time.(4)The ears per mu, the grains per ear and the seed setting rate of rice in rice-fish culture decreased, while the grain weight increased. The rice quality, including milling quality, appearance quality and nutrition quality, were all improved.2. Different cultural approaches affected the yield and quality of rice in rice-fish system significantly. Some improved techniques could be applied to the rice production in rice-fish culture.(1) Compared with the replanting rice sowed in the same date, the whole duration of direct-seeding rice was shorter, and the percentage of effective panicles from stems and tillers was lower in the condition of rice-fish, the effective ears were also reduced. Percentage of seedling and effective panicles from stems and tillers of dry land direct seeding was higher than that of wet land direct seeding. The number and the weight ofdry matter of roots increased, but N accumulation by the plant up the soil reduced. The seed setting rate and the 1000-grain weight increased, but the grains per ear decreased, so the yield reduced and rice milling quality, appearance quality declined.(2) According to the whole stage, population characteristics, disease resistance, yield and quality, 4 late maturity japonica varieties (86You 8, Changyou 1, Huajing 3, Wuxiangjing 14), which showed better adaptability, were selected.(3) Rice in rice-fish, when the sowing date was put ahead properly, could make full use of good conditions in paddy field to get enough tillers and dry biomass, and increase the functioning leave areas of coronal layers and height of plant to adapt the deep water environment, and to achieve the high yield and good quality. However, sowing and replanting early will aggravate rice stripe viruses(RSV), so some approaches for prevention and cure must be strengthened. The proper sowing date in Jiangsu Lixiahe Area was in the middle of April.(4)According to the results of planting density experiment, while the planting density of the late maturity japonica varieties is about 1,2000 caves per mu, with 3 seedlings per cave for general rice and 2 seedlings per cave for hybridized rice, it would be able to achieve the high yield and good quality, the growth of crabs and shrimps w...
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