Studies On Climate Change In Middle Reach Of Yangtze River And Adaptive Technique For High Yielding Production Of Double-cropping Rice

Climate change has become an undoubted fact and a main reason why rice yield stagnates and breeding technology advancement just maintains the rice yield level. How to reply to climate change, to fully use recent breeding achievements and to enhance the integrate productivity of crop has become an attractive question. According to the lack of study on climate change and its coping technology, and the actuality of current coping technology can not well guide the crop system production of certain area, the double-season rice in middle reach of the Yangtze River was selected as research object in this study. Firstly, the change characteristics of agricultural climate resources of the last50years and its influences on double-season rice were analyzed in order to put forward adaptive requirements. Then some adaptive coping technologies including variety type, variety combination pattern, sowing date arrangement and so on were investigated. Finally, a coping theory and technology system which will provide theoretic and technical guidance for sustaining high and steady yield of double-season rice in middle reach of the Yangtze River. Some valuable results were obtained as follows.1. Change characteristics of agricultural climate resources in middle reach of the Yangtze RiverChange characteristics of agricultural climate resources of50meteorologic stations from1960to2005were analyzed in order to provider theoretic basis for adaptive coping technology study and coping countermeasure establishment. During last50year, the mean annual temperature increased by0.179℃/10a, annual mean daily maximal temperature increased by0.145℃/10a, annual mean daily minimum temperature increased by0.23℃/10a,≥0℃accumulated temperature increased by70.8℃/10a,≥10℃accumulated temperature increased by66.3℃/10a, annual sunshine hours decreased by57.2h/10a, and annual precipitation increased by5.1mm/10a. While the increase speed of the mean annual temperature, annual mean daily maximal temperature and annual mean daily minimum temperature in temperature-defined growth season was0.08℃/10a,0.07℃/10a and0.09℃/10a respectively, obviously lower than those of the whole year. Therefore, the main change characteristic was that the temperature in temperature-defined growth season increased more obviously than the other season, and the increase speed of the annual mean daily minimum temperature was the most obvious. The increase speed of the mean annual temperature, annual mean daily maximal temperature and annual mean daily minimum temperature,≥10℃accumulated temperature during early-season rice growth period was0.20℃/10a,0.20℃/10a,0.22℃/10a and48.9℃/10a respectively. The increase speed of the mean annual temperature, annual mean daily maximal temperature and annual mean daily minimum temperature,≥10℃accumulated temperature during late-season rice growth period was0.09℃/10a,0.03℃/10a,0.17℃/10a and14.6℃/10a respectively. All of them less than those during early-season rice growth period. The decrease speed of sunshine hours during late-season rice growth period was42.7h/10a, more than18.6h/10a during early-season rice growth period. It could be concluded that the climate change influence and its coping technology was different between early-season rice growth period and late-season rice growth period. At the same time, another main change characteristic was spatial variation. There were synchronal increase trend for heat, sunshine hour and precipitation in the Dongting Lake area of Hunan Province, the Jianghan Plain area of Hubei Province, the Jingdezhen and Zhangshu area of Jiangxi Province. It could be concluded that the yield and yield potential of double-season rice will enhance sharply because of the heat, sunshine hour and precipitation in these area increase synchronously.2. Change characteristics of safe dates for double-season rice production in middle reach of the Yangtze RiverIn order to provide technical instruction for safe production of double-season rice, the change characteristics of safe dates for double-season rice production were analyzed on the basis of analysis on change of agricultural climate resources. The results indicated that the change climate trend was-0.9d/10a for safe sowing of early-season rice seedling raising in dry nursery, was-1.6d/10a for safe sowing of early-season rice seedling raising in wet nursery, was-2.1d/10a for safe transplanting of early-season rice, was-0.8d/10a for safe full heading of late-season hybrid indica rice, was0.01d/10a for safe full heading of late-season inbred indica rice, was1.1d/10a for safe maturity of late-season rice, was0.2d/10a for days of safe growth season of the double-season rice whose early rice seedling raised in dry nursery, and was0.3d/10a for days of safe growth season of the double-season rice whose early rice seedling raised in wet nursery. Compared with the safe date of the first25years from1960to1984, the safe date with80%guarantee rate of the second25years from1985to2009was March24th and delayed by3days for sowing of dry nursery seedling of early-season rice, was April8th and advanced by3days for sowing of wet nursery seedling of early-season rice, was April26th and advanced by4days for transplanting of early-season rice, was September1st and advanced by3days for full heading of late-season hybrid indica rice, was September9th and delayed by1days for full heading of late-season inbred indica rice, was October16th and no difference for maturity of late-season rice. Furthermore, the days of safe growth season with80%guarantee rate of the second25years from1985to2009was213and shortened by4days for dry nursery seedling of early-season rice, and was196and prolonged by1day for wet nursery seedling of early-season rice compared with the days of safe growth season of the first25years from1960to1984. The results above indicated that the safe production season in this region did not change obviously like as the northeast and other regions. Therefore, the planting mode and variety pattern selection can not follow like sheep the global warming, must be decided according to change concrete instance of agricultural climate resources of different regions.3. Adaptive variety type and its character to climate changeIn order to put forward adaptive variety type and its character to climate change, the super hybrid rice, common hybrid rice and inbred rice were selected as material in this study by combining the results of this study with the influence and adaptive requirements of climate change on double-season rice. The results indicated that super hybrid rice varieties had more dry matter accumulation, longer growth duration, lower transpiration rate but equivalent net photosynthetic rate in upper functionary leaves, higher net photosynthetic rate but equivalent transpiration rate in lower functionary leaves compared with common hybrid rice and inbred rice. At the same time, super hybrid rice had wonderful plant configuration such as good plant type, reasonable canopy structure and so on according to the results achieved in other relative research. Therefore, double-season super hybrid rice could meet well the demands such as more dry matter production and accumulation, longer growth duration, drought tolerance, higher photosynthetic rate and shadow tolerance brought forward by climate change for double-season rice to adapt. Furthermore, double-season super hybrid rice had higher yield and yield potential than other rice variety. The results above indicated that double-season super hybrid rice was the adaptive variety type to climate change in this region from climate change adaptation and yield to consider.4. Adaptive variety pattern to climate changeIn order to know adaptive variety pattern in different double-season rice planting area, an adaptive study was conducted on the basis of former research. The results in this study showed that the yield of early-season rice higher than that of late-season rice, but the yield stability lower than that of late-season rice. The factor resulting in yield stability for early-season rice was the number of effective panicle. However, the influence factor was complex including number of effective panicle, number of spikelets per panicle, number of full spikelets per panicle and seed-setting rate, but the number of effective panicle was the first factor among them for late-season rice. If the safe and high utility of agricultural climate resources and production practice of different region were considered integrative, we could think the variety pattern of early-season rice with early maturity and late-season rice with late maturity in northern and eastern Hunan, of early-season rice with late maturity and late-season rice with late maturity or early-season rice with late maturity and late-season rice with middle maturity in mid and southern Hunan should be selected.5. Adaptive sowing date arrangement to climate changeA interval sowing date trial in different area in Hunan Province was conducted for bring out the adaptive variety pattern and suitable sowing date to climate change. The results showed that super hybrid rice with late maturity variety could be selected in early-season rice production in all double-season rice planting area of Hunan Province, and the suitable sowing date was March25th in northern region, was March20th in mid and southern region. In late-season rice production, the selection of variety pattern and sowing date arrangement was relatively complex and must be decided according to latitude. In northern region of Hunan Province, super hybrid rice with early or middle maturity could be chosen, and suitable sowing date could be arranged at June25th around. In mid and southern region of Hunan Province, super hybrid rice with late maturity could be chosen, and suitable sowing date could be arranged at June20th around.