| Distribution of precipitation is inconsistent and asynchronous with evaporation, creating conditions for severe summer and autumn droughts in the hilly region of southern China. Jiangxi Province is located in a hilly region of southern China, where seasonal drought regions are widely distributed. High temperatures have caused severe drought during the past fifty years. The drought disaster-affected acreage of rice was 0.63×10~6 ha in 2003. Seasonal drought often seriously affects rice production due to water stress. As a result, it is necessary to set up new water-saving rice cultivation systems to increase water use efficiency and reduce yield loss caused by drought. The physiology-ecological effect and technology integration of water-saving rice cropping, the feature of ecosystem function and eco - environmental effect of water-saving rice cultivation patterns, and synthetic evaluation mode of water-saving rice cultivation patterns were studied in the field experiment and trough cultivation experiment in this research. This research would lend itself to prove up more construction and function of water-saving rice cultivation systems, and set up sustainable water-saving rice cultivation systems. This research has the potential to aid in sustainable development and effective production of rice cultivation and optimum use of water in seasonal droughts hilly region of southern China. The results are as follows:The biological characteristics of introducing rice cultivars under condition of water-saving and effects of water-saving irrigation on rice growth and grain quality were studied by using 12 introducing rice cultivations and 3 local rice cultivations as material in the seasonal drought hilly region of southern China. The results showed the early rice, mid-season rice and late rice was under the condition of 10%, 28%, and 26% water-saving respectively, the introducing early rice cultivar Zhanghan 27, mid-season rice cultivar Liangyoupeijiu and Wuyunjing 7, late rice cultivar Nongxiang 16 and Zhongxiang 1 had higher economic benefit and ecological benefit, and had a bright prospect of application in the region. The effective panicle number and plant length in water-saving irrigation was lower than that in common irrigation, but the spikelet length, No. of spikelet per plant, seed setting rate and 1000-grain weight in water-saving was higher than that in common irrigation. Among which effects of water-saving irrigation on the effective panicle number, plant length and No. of spikelet per plant had notable discrepancy in some rice cultivars. Comparing with the common irrigation, the brown rice rate, milled rice rate, head rice rate, gel consistency, amylose content and alkali-spreading value was increased, but length/width, chalky grain rate and chalkiness was decreased. Therefore the rice grain quality could be improved in water-saving irrigation.The effect of amount of nitrogen and planting density on canopy apparent photo synthetic (CAP) rate, photosynthetic rate and chlorophyll content in flag leaves, yield components and grain yields were studied with indica hybrid rice Liangyoupeijiu in intermission irrigation in southern China seasonal drought hilly region. The results were as follows: as the increment of density, canopy apparent photosynthetic (CAP) rate increased before anthesis and decreased quickly during grain filling. Meanwhile photosynthetic rate in flag leaves, grain number per panicle, seed setting rate and 1000-grain weight decreased. As the increment of amount of nitrogen, canopy apparent photosynthetic (CAP) rate, photosynthetic rate and chlorophyll content in flag leaves, panicle number and grain number per panicle increased. But seed setting rate and 1000-grain weight increased. The result showed that the tiptop output of mid-season rice was 10299 kg/ha when the transplanting density was 281.3 thousand hills/ha and the applying amount N-fertilizer is 225kg/ha in controlling irrigation.In order to investigate the effects of drought tolerance on the yield, component factors, as well as water productivity of rice, the field experiment and trough cultivation experiment with rain-proof shelter were carried out in 2003 and 2004. The results followed that: irrigation when the soil water potential was higher than -30kPa had no significant effect on yield however would greatly save irrigation water and improve water productivity. It would be the optimal rice irrigation regime rice in this area. Meanwhile trough cultivation experiment with rain-proof shelter was carried out to investigate the effects of different water stress on the relative values of MDA, plasmalemma permeability, osmoregulation substances, protective enzyme activity. The results indicated that the relative values of MDA, plasmalemma permeability, soluble sugar, amino acid, and activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in leaves increased and then decreased after rewatering to saturated soil under optimal water stress (the soil water potential was higher than -30kPa). The change trend became stable with the advance of growth stage. When the soil water potential was below -30kPa, the relative values of MDA, plasmalemma permeability, soluble sugar, amino acid, and activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in leaves significantly increased, increases of MDA and plasmalemma permeability in better drought resistant cultivars were obvious less than those in weaker drought resistant ones, and increases of soluble sugar, amino acid, activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD in better drought resistant cultivars were obvious more than those in weaker drought resistant ones, and plasmalemma permeability, soluble sugar, amino acid, and activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) decreased from16 days to 40days after anthesis. These results suggest that water stress can induce physiological and biochemical changes in rice and changes of MDA content, plasmalemma permeability, osmotic regulators and antioxidative enzyme activities are correlated significantly to drought resistance of rice varieties.Based on field investigation and experimental data analysis, ecological economic principles were applied to study the material flow, energy flow, value flow and ecological environmental benefits of water-saving rice cultivation systems. The results showed that the net production and economical production in the three types of water-saving rice cultivation systems were 3.10×l0~5 to 3.78×10~5MJ/( ha·yr) and 1.77×10~5 to 1.98×10~5 MJ/ (ha·yr), respectively. The major input of energy was for fertilizers, which were 0.59×10~5 to 0.97×10~5 MJ/ (ha·yr). The output-input ratios of energy and light utilization efficiency of rice fields were 3.22 to 6.45:1 and 0.64 to 0.78, respectively. The net monetary values were 484 to 1166 dollar/ (ha·yr) and the cost-benefit ratios were 0.34 to 0.88. Higher energy conversion efficiency, light utilization efficiency, and economic efficiency were found in the water-saving irrigation double-cropping rice cultivation system and water-saving rice cultivation system of rice and rape rotation. However, the lower energy conversion efficiency and economic efficiency took place in water-saving rice cultivation system of flood-drought cultivation. The water-saving rice cultivation systems had a higher integral benefit than the local rice cultivation system, and could significantly save water and decrease the application of fertilizer and pesticide so that it could control agriculture non-point resource pollution.Study of water-demand regulations and water use efficiencies under condition of different water-saving rice cultivation patterns were carried by field-scale experiments. The results obtained showed that the evapotranspiration of rice or rape reduced by a wide margin, the water requirement, requirement intensity and coefficient of every stage changed greatly for the growth regulation function and compensation effect to crop of water-saving rice cultivation patterns. Thus, the new water requirement rules of water-saving rice cultivation patterns were formed. The water requirement intensities of the water-saving irrigation double cropping rice pattern, the double cropping rice pattern of flood-drought cultivation, and water-saving rice cultivation pattern of rice and rape rotation were 0.76mm/d,1.15 mm/d,0.32 mm/d lower than those of the conventional double cropping rice pattern, respectively. The leakage intensities of the water-saving irrigation double cropping rice pattern, the double cropping rice pattern of flood-drought cultivation, and water-saving rice cultivation pattern of rice and rape rotation were 0.12mm/d,0.16 mm/d,0.19 mm/d lower than those of the conventional double cropping rice pattern, respectively. The WUE of the water-saving irrigation double cropping rice pattern, the double cropping rice pattern of flood-drought cultivation, and water-saving rice cultivation pattern of rice and rape rotation was 30%, 48%, and 18% higher than that of the conventional double cropping rice pattern, respectively.Environment of cultivated land has been influenced unfavorably by single continuous cropping in paddy field, and seasonal drought often seriously affects rice production due to water stress. The soil physical and chemical characteristics, soil microorganism and soil enzyme activity of water-saving rice cultivation patterns were studied in the field experiment of five years in this paper. The results showed that, water-saving rice cultivation patterns had improved soil physical and chemical characteristics apparently. Water-saving rice cultivation patterns could not only provide water indispensable to life, but also ameliorate the condition of soil water content and ventilation. Soil microorganisms multiplied, and the double cropping rice pattern of flood-drought cultivation was best among all the water-saving rice cultivation patterns. The activities of catalase, phosphatase, urease, polyphenoloxidase were higher than those of the conventional double cropping rice pattern. The correlation and principal component analysis showed that soil urease, alkaline phosphatase activities, and catalase activities could be as a comprehensive index of soil fertility, and their enzyme activities were affected by soil chemical properties and other enzymes. Soil fertility could be evaluated objectively by principal component analysis.Research of water-saving rice cultivation patterns integrated benefit evaluation is a core problem concerning development of paddy field agriculture, soil and water environmental protection as well as coordinated economic and eco-environmental development. Based on the current situation of seasonal droughts hilly region of southern China, applying analytic hierarchical process theory, this paper established the mathematical model and indicators system for integrated benefit evaluation for water-saving rice cultivation patterns by taking the demonstration patterns of water-saving rice cultivation in the native "863" special project as a research project. The evaluation indictors system was proposed based on characteristics and principles of scientific, practical and concise. The indicators system included three aspects such as economic benefit, social and eco-environmental benefit and systematically reflects the features of water-saving rice cultivation patterns. The evaluating model and the indicators system were applied to evaluate synthetically the integrated benefit of water-saving rice cultivation patterns in seasonal droughts hilly region of southern China. The evaluation results showed that The integrated benefits of the water-saving irrigation double cropping rice pattern, the double cropping rice pattern of flood-drought cultivation, and water-saving rice cultivation pattern of rice and rape rotation was higher than that of the conventional double cropping rice pattern, especially of water-saving rice cultivation pattern of rice and rape rotation. The evaluation model played an important role in the evaluation and management of water-saving rice cultivation patterns in seasonal droughts hilly region of southern China. |
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