| The area of paddy occupied 28% of total crops area, but the water consumptionoccupied 65% of total agricultural water consumption and 54% of total national waterconsumption. The average dosage of nitrogenous fertilizer in single season rice was180 kg.hm-2, and was 75% higher than the world average level. Traditional irrigationand fertilization didn't benefit the high yield potential of rice, while tensed up thewater supplying and caused environmental pollution. So taking feasible irrigationmode to improve the water use efficiency was very important to guarantee foodsecurity and for the sustainable development of agriculture. The researches onmechanism of different degree of stress on yield and quality in different period of ricegrowth, and the study of rice physiological character, yield and water use efficiency indifferent levels of water and fertilizers, which was the theory base of water-savedagriculture to improve the irrigation mode. This paper studied the influence of waterstress in different period and different degree on growth, physiology, yield and qualityof rice, and discussed the sensibility of rice to water stress in different growth periods.It also studied the influence of varied soil water and fertilizers on physiologicalcharacter, yield and water use efficiency, and compared the physiological andecological characters of intermittent irrigation, semi-dry cultivation, dry cultivationand continuous flooding irrigation. The experiments were carried in basins,non-weighting lysimeters and field in 2005 and 2006, which the purpose was tosupply the theory direct of best water management and precise fertilizer in south ricefield. The results showed as follows.(1)The influence of water stress on rice growth, physiological character, yieldand quality in different growth periods.Dealing with low-degree water stress during tillering stage, the total dry weightof plant root, leave, stem, fringe and the upper-ground was heavier than CK, whichshowed positive effect. While high-degree was opposite. The leaf area index of ricewas higher than CK under low-degree water stress treatment during grain filling stage.The LAI of Liangyou peijiu and Honglianyou 6 were respect 5.80% and 11.57%higher than CK, while high-degree treatment was opposite.Compared with CK, the leaf photosynthetic rate was enhanced and the water useefficiency was improved prominently under the low-degree water stress. The value ofleaf SPAD, chlorophyll a, chlorophyll b and total content of boot leaf were all lowerthan CK during heading stage, which was positive correlation with water stress. Thecarotenoids content, chlorophyll a, chlorophyll b increased as soil water increased.The water potential of leaf decreased as water stress increased during panicleinitiation stage and tillering stage, and water potential decreased obviously whenhigh-degree water stress. The content of MDA increased as water stress strengthened, was 1.74 and 1.51 times higher than CK during tillering stage and heading stage,which showed high-degree water stress, accelerated the leaf aging. The content ofproline increased as water stress strengthened, and high-degree treatment showedprominently increased. The root activity was highest under low-degree stresstreatment and was lowest under high-degree treatment during panicle initiation stage.The root activity of Liangyou peijiu and Honglianyou 6 were respect 19.15% and13.64% higher than CK.Water stress influenced reproductive panicle number obviously. Low-degreewater stress increased individual reproductive panicle number and grain number, so itcould increase yield and showed positive effect. High-degree water stress limited theyield potential and decreased the yield. The water stress in panicle initiation stage andheading stage influenced yield obviously, because of water stress distressingindividual grain number, 1000-grain weight. Water stress in grain filling periodinfluenced 1000-grain weight obviously, low-degree didn't influence yield and yieldcomponent and high-degree decreased yield. At the station of low-degree stress, thewater use efficiency was highest in different periods. Feasible water stress duringtillering stage and grain filling stage could enhance the water use efficiency.Low-degree water stress could improve the milling quality, cooking quality andnutritional quality of rice during tillering stage and grain filling stage, but high-degreewater stress in tillering stage depressed the milling quality, cooking quality andnutritional quality of rice; Low-degree and mid-degree water stress could improveduring panicle initiation stage; Mid-degree water stress prominently increasedchalkiness during heading stage; high-degree water stress prominently increasedchalky rice and chalkiness, as water stress aggravated, the protein content increasedand amylase content decreased.(2)The influence of water stress on nitrogen nutrition characters.The dry weight of shoot and total dry weight of plant increased as nitrogen levelsincreased at the same soil water potential, but the root-shoot ratio was theopposite.The net photosynthetic rate, chlorophyll a, chlorophyll b and total content,value of leaf SPAD and leaf water potential depressed as the soil water stressstrengthened at the same nitrogen level, while the chlorophyll a/b, MDA content andthe activity of peroxidase enhanced respectively. Chlorophyll a, chlorophyll b andtotal content, value of leaf SPAD increased as the nitrogen level improved at the samesoil water potential, but leaf water potential, chlorophyll a/b and MDA contentdecreased.The grain yield decreased as soil water potential reduced at the same nitrogenlevel. When the soil water potential was medium, the yield was HN＞MN＞LN; whileyield was MN＞HN＞LN under the conditions of well-watered soil or of severe soildrought. The water use efficiency of rice in LN was highest under the status of mildsoil drought, but the water use efficiency of rice in NN and HN status reduced as soil water stress enhanced. The result indicated that high-level fertilizer had negativeeffect on increasing the grain yield under water-saving irrigation.Under the same water treatment, the brown rice rate, milled rice rate and headmilled rice rate improved as nitrogen nutrition increased; under the same nutritiontreatment, the brown rice rate, head milled rice rate and milled rice rate improved assoil water potential fell. Under the same water treatment, chalky rice rate andchalkiness both decreased as nitrogen nutrition increased; under the same nutritiontreatment, chalky rice rate and chalkiness increased as soil water potential decreased.At the same level of soil water potential, protein content of rice increased as nitrogenincreased; at the same level of nitrogen, protein content increased as water stressstrengthened.(3)The influence of different irrigation modes on rice physiological character,yield, quality and water use efficiency.Compared with continuous flooding irrigation, photosynthetic rate, leaf areaindex and water use efficiency of leaves under intermittent irrigation condition wereincreased while leaf transpiration rate was decreased; water use efficiency of leavesunder semi-dry cultivation was higher; photosynthetic rate, transpiration rate, leaf areaindex, and water use efficiency of leaves decreased under dry cultivation while leaveswere senile in premature period.The daily change of rice net photosynthetic rate in different irrigation excited"middle rest". The net photosynthetic of intermittent irrigation was higher than thatunder the continuous flooding irrigation in different period, but the net photosyntheticrate of dry cultivation decreased prominently. The transpiration rate of continuousflooding irrigation was lower than that of intermittent irrigation, semi-dry cultivationand dry cultivation in grain filling stage. The intermittent irrigation improved thecontent of chlorophyll, and rainfed cultivation prohibited the production ofchlorophyll. The water potential of leaf decreased and MDA content, proline content,POD activity enhanced as irrigated water decreased.The difference of temperature and humidity between day and night ofintermittent irrigation were both larger than that of continuous flooding irrigation.Rice group absorbed more sunlight. So the intermittent irrigation benefited the ricegroup environment and rice development.The water consumption of continuous flooding irrigation was higher than that ofintermittent irrigation, semi-dry cultivation and dry cultivation(rainfed) duringdeveloping stage, the order was intermittent irrigation＜semi-dry cultivation＜drycultivation(rainfed); the yield of intermittent irrigation increased, while the semi-drycultivation and dry cultivation(rainfed) were opposite; the water use efficiency ofintermittent irrigation was highest, follows as semi-dry cultivation, continuousflooding irrigation and dry cultivation(rainfed). The yield and water use efficiencychanged from increasing to decreasing, which showed secondary curve. The head milled rice rate, milled rice rate and grain length of intermittent irrigation were higherthan others, and chalky rice rate and chalkiness were lower than others; Amylosecontent decreased, gel consistency and protein content increased as waterconsumption decreased. It showed that intermittent irrigation was the best method ofpaddy in the southward.
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