| Rice is one of the important food crops in China, but changes in climate and environment has brought or will bring key effects to the rice production. Thus, it is necessary to identify the characteristics of regional climatic changes and to carry out research on population regulation techniques that are adaptable to climate change. This study analyzes the characteristics of changes in agro-climatic resources at the middle reaches of the Yangtze River, where double-season rice has been developed at various growth stages over the last50years. Based on this analysis, the different nitrogen fertilizer rate (NO-nitrogen application was Okg/ha; N90-nitrogen application was90kg/ha; N135-nitrogen application was135kg/ha; N180-nitrogen application was180kg/ha; N225-nitrogen application was225kg/ha) and transplanting density (D45-transplanting densities of45×104hills/ha; D30-transplanting densities of30×104hhills/ha; D22-transplanting densities of22×104hills/ha; D16-transpl-anting densities of16×104hills/ha) and number seedling of per hill (B1-1seedling per hill. B2-2seedlings per hill, B3-3seedlings per hill, B4-4seedlings per hill) has been employed to regulate populations, and a study on the effects of these three methods is carried out. Finally, the different population regulation theory and technique systems for early and late rice are developed. This will provide theoretical basis and technical guidance for high-efficient planting and high yield of double-season rice under the influence of climate change. The conclusions are as follows:1. Ascertain the agro-climatic resources change characteristics of double crop rice at various growth stages at the middle reaches of the Yangtze RiverThe agro-climatic resources, such as the mean temperature, mean daily maximal temperature and mean daily minimum temperature and>10℃accumulated temperature during early-season rice growth period were significantly increased. The increase speed of the mean temperature, mean daily maximal temperature and mean daily minimum temperature during the transplanting and returning green and to the tilling stage of early-season rice was1.05℃/10a,1.34℃/10a and0.84℃/10a respectively. The>10℃accumulated temperature during the transplanting and returning green stage to the tilling stage of early-season rice was significantly increased, the increase speed was35.48℃/10a, followed by the seeding and seedling-raising stage of early rice, the increase speed was26.48℃/10a. The sunshine hours only during the planting and returning green stage to the tilling stage of early-season rice was increased. The precipitation during the seeding and seedling-raising stage and the planting and returning green stage to the tilling stage of early-season rice were decreased. The increase speed of the mean temperature, mean daily maximal temperature and mean daily minimum temperature during the heading stage and the filling and ripening stage of late-season rice was0.42℃/10a,0.34℃/10a,0.57℃/10a;0.44℃/10a,0.48℃/10a,0.46℃/10a respectively, but the decrease speed of the sunshine hours and the precipitation during the heading stage and the filling and ripening stage of late-season rice was5.16h/10a,5.22mm/10a;7.87h/10a,18.40mm/10a respectively, the climate changed brought the temperature is low and less sunshine and excessive precipitation that had an adverse effect on rice during the transplanting and returning green and to the tilling stage and booting stage. Therefore, the regional climate changed would be beneficial to early rice production, but had a negative effect on the yield potential of late rice.2. The regulation of different transplanting density and number seedlings per hill can improve the adaption to regional climate change ability of double-season riceThe photosynthetic rate of early-season rice flag leaf increased with the increase of transplanting density, the photosynthetic rate of early-season rice flag leaf for different number seedlings per hill were B3>B4>B2. The photosynthetic rate, SPAD values of canopy leaves and canopy solar radiant interception rate of early-season rice for D45B3was the highest. The photosynthetic rate of late-season rice flag leaf decreased with the increase of transplanting density, the photosynthetic rate of late-season rice flag leaf for different number seedlings per hill are B2>B1>B3, the photosynthetic rate of late-season rice flag leaf for2seedlings with the transplanting density of22×104hills/ha (D22B2) was the highest. The number of seedlings per hill and the yield of early-season and late-season rice showed a single peak curve relationship. The yield of early-season rice for different transplanting density were D30>D45>D22, the yield of late-season rice for different transplanting density were D22>D30>D16. The higher would be obtained:33×104hills/ha for the early-season rice with3seedlings per hill and26x104hills/ha for the late-season rice with1seedling per hill.3. The regulation of different nitrogen fertilizer rates and transplanting density has significant effects on population characteristics, yield and its components of double-season rice of regional climate changeThe LAI of nitrogen rate of135kg/ha was the highest during late growth period of early-season rice, the LAI and dry matter accumulation increased with the increase of transplanting density, the solar radiation interception rate of canopy for early-season rice with the transplanting density of30×104hills/ha (D30) was the highest. The effect of nitrogen fertilizer rate on early-season rice grain number per panicle and seed setting rate were lower than that on the number of productive panicles and1000-grain weight. The effect of interaction of nitrogen fertilizer and transplanting density on grain number per panicle was significant. The yield of early-season rice for the nitrogen rate of135kg/hawas the highest, the yield of early-season rice for the nitrogen rate of180kg/ha was the second highest and they were10245.04kg/ha,9962.12kg/ha respectively. Both of the nitrogen rates of180kg/ha and transplanting density of22×104hills/ha (D22) for late-season rice would be obtain the highest solar radiation interception rate of canopy. The photosynthetic rate of late-season rice flag leaf for the nitrogen rate of180kg/ha was the highest during the heading stage and the photosynthetic rate of late-season rice flag leaf for transplanting density of22×104hills/ha was the highest. The canopy solar radiant interception rate of late-season rice for N180D16was the highest during the heading stage and during the milky stage N225D16was the highest. The nitrogen fertilizer rates had more effect on the late-season rice grain number per panicle and number of productive panicles, the number of productive panicles increased with the increase of transplanting density, but the grain number per panicle decreased with the increase of transplanting density. The late-season rice with the nitrogen rate of180kg/ha could get the maximum yield, the transplanting density had less effect on the yield of late-season rice, but the yield increased with the increase of transplanting density. In order to obtain the higher yield, the nitrogen rate and transplanting density were recommended as:N141.20kg/ha for the early-season rice with the transplanting density of36.60×104hills/ha and N190.30kg/ha for the late-season rice with the transplanting density of23.60×104hills/ha.4. The regulation of different nitrogen fertilizer rates and number seedlings per hill has significant effects on double-season rice of regional climate changeThe LAI of early-season rice increased with the increase of number seedlings per hill, in the booting stage the LAI of early-season rice increased0.3for3seedlings per hill in comparison with that under the condition of2seedlings per hill. Before the heading stage the LAI of early-season rice for the nitrogen rate of135kg/ha was the highest, but after the heading stage the nitrogen rate of180kg/ha was the highest. The solar radiation interception rate of canopy of early-season rice increased with the increase of nitrogen fertilizer rates, the solar radiation interception rate of canopy of early-season rice for different number seedlings per hill were B3>B2. The LAI of late-season rice increased with the increase of nitrogen fertilizer rates, the LAI of late-season rice for different number seedlings per hill were B2> B1.The number of productive panicles of early-season and late-season rice increased with the increase of nitrogen fertilizer rates, nitrogen fertilizer rates and the grain number per panicle showed a single peak curve relationship for early and late rice, The effects of different nitrogen fertilizer rates and number seedlings per hill on the grain number per panicle showed that both of the N135B3for early-season rice and N180B1for late-season rice were the highest. The yield of nitrogen rate of135kg/ha of early-season rice was the highest and nitrogen rate of180kg/ha was the second highest. The yield of early-season rice of3seedlings per hill was higher than that of2seedlings per hill. The yield of nitrogen rate of180kg/ha of late-season rice was the highest, but the yield of nitrogen rate of135kg/ha was higher than that of nitrogen rate of225kg/ha, the yield of lseeding per hill more than that of2seedlings per hill. The yield of nitrogen rate of180kg/ha for late-season rice of1seeding per hill was the highest and nitrogen rate of Okg/ha for late-season rice of1seeding per hill was the lowest.5. The population regulation theory and technique system will provide for adaptation to regional climate change of double-season riceAccording to the different climate change for double-seasons rice at each growth stages and take the high yield and high economic efficiency into consideration, the N fertilization rate, transplanting density and number seedlings per hill were recommended as:N141.20-145.20kg/ha for early-season rice with the transplanting density of33.40-36.60×104hills/ha of3seedlings per hill and N184.70-190.30kg/ha for late-season rice with the transplanting density of23.60-25.80×104hills/ha of lseeding per hill. |
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