| China’s agriculture has entered a multiple purpose period requiring paying equal attention to crop yield, quality and environmental protection. During "Twelve-Five" period, large-scale agricultural pollution control technology and water resources guarantee of the commodity grain bases in the Northeast area has become to be a key research direction of the water science and technology. And loss of nitrogen in agriculture is the important reason that non-point source pollution occur. It is therefore of great significance to study economic and environmental effects of water and nitrogen coupling in rice. In this passage, suitable soil moisture potential criterion, water requirement regulation, water production function, water sensitive index cumulative curve, dry matter accumulation law, nitrogen accumulation law; quality variation, water-nitrogen coupling pattern, water-nitrogen model and other contents for rice were researched based on soil moisture potential regulation and control experiment, water stress experiment, nitrogen controlling experiment and water-nitrogen coupling orthogonal experiment in central region of Liaoning province. The main results are as follows:(1) The experiment for high-yield soil water potential regulation were conducted during different stages of rice included tillering initial stage, tillering final stage, jointing stage, Heading stage, milk maturity stage. The results showed that soil moisture potential regulation and control was able to increase the rice yield at all growth stages after returning green, the suitable soil water potential criteria for middle-season rice at different growth stages were suggested,5～1OkPa for tillering initial stage, drought but not more than35kPa for tillering final stage,5～10kPa for jointing stage and Heading stage, not more than20kPa for milk maturity stage; re-watering post drought had obvious compensation effects to rice when soil suction potential was controlled in5-10kPa at tillering initial stage were discussed base on the results that tillers number, output, final root dry biomass and leaf dry weight were significant exceeding contrast; Based on the experiment for suitable soil water potential regulation, the paper analyses the variation of rice evapotranspiration (ET). The results showed that ET of each water controlling stage had decreases at different degree in comparison to the basin irrigation; reduce proportion of the treatment for water controlling at jointing stage and heading stage was least, but it has a most influence for yields; jointing stage and heading stage were key water requirement period, and water controlling should be implement as less as possible; tillering final stage could have a heavy drought because it was most insensitive to water. The diurnal variation law of ET in a typical day in controlling stage showed that the value of daily ET was change with the meteorological factor in the same day; ET was influenced by the value of soil water potential in the same meteorological condition, greater soil water suction comes small ET. Multiple and stepwise equations showed that global radiation intensity, relative humidity, and wind speed were meteorological factors which played a leading role in rice ET, they were main reason for ET change, and other meteorological factors could influence ET by means of affect them.2. Based on the experiment for high-yield soil water potential regulation, the paper analyses the variation of rice evapotranspiration (ET), so as to seek after the water requirement regulation of deficit irrigation for rice. The results showed that ET of each water controlling stage had decreases at different degree in comparison to the basin irrigation; reduce proportion of the treatment for water controlling at jointing stage and heading stage was least, but it has a most influence for yields; jointing stage and heading stage were key water requirement period, and water controlling should be implement as less as possible; tillering final stage could have a heavy drought because it was most insensitive to water. The diurnal variation law of ET in a typical day in controlling stage showed that the value of daily ET was change with the meteorological factor in the same day; ET was influenced by the value of soil water potential in the same meteorological condition, greater soil water suction comes small ET. Multiple and stepwise equations showed that global radiation intensity, relative humidity, and wind speed were meteorological factors which played a leading role in rice ET, they were main reason for ET change, and other meteorological factors could influence ET by means of affect them.(2) Soil water potential stress experiments were conducted on tillering stage, jointing stage, heading stage, milk maturity stage of rice in2011and2012respectively, so as to explore the change of rice evapotranspiration in each stage for water stress and returning water. The analysis for ET shows that soil water potential stress on single stage had a marked impact for rice evapotranspiration, and the impact will be continue for several stages after re-watering, the more closer to controlling stage the more influence of the impact; the periods and the extent for the impact depended on the stage and the status of water potential stress, treatment for water stress at tillering stage had the longest influence period for ET, and treatment for water stress at jointing stage had the most serious influence extent for ET; the ET was effected more seriously caused by water stress in earlier stage than in later stage; the difference of time division maybe the reason for different incidence of ET in stage after re-watering. The experiments were also conducted to search for the influence of rice yield caused by different status of soil moisture potential stress, and to discuss five water production function (Jensen, Minhas, Blank, Stewart, Singh) of rice in middle Liaoning Province. The results showed that yield reduced most seriously when water stress at tillering stage and jointing stage, and heading stage, milk maturity stage could suffer light drought; for rice in central region of Liaoning province, Minhas model was all reasonable, but Jensen model was the most suitable static water production function; It was relatively suitable for yield to evaluate sensitive degree of water potential stress in each stage with increasing rate for water productivity under the serious status of soil water potential stress, and the water productivity increasing rate could also explain the order of the sensitive index for each model; Jensen model water sensitive index cumulative curve of growth curve could used for yield prediction for rice in central region of Liaoning province, and could solve sensitive index for any rice period of time.(3)Different nitrogen application rate experiment (2012) showed that:The increase in the amount of nitrogen fertilizer will increase the biomass of rice root, stem, leaf and spike; dry matter accumulation of rice under different nitrogen level analysis showed that root dry weight in the process of normal nitrogen (N1) and low nitrogen (NO.5, NO) peaked on jointing stage, but high nitrogen treatment (N2.5, N2, N1.5) peak on the heading stage, it was showed that the increase of the nitrogen can prolong root dry matter accumulation; Stem dry weight peak on heading stage; leaf had the highest sensitivity for nitrogen and peaked in the final jointing stage; Ear dry weight has been in the growth process from the end of the final jointing stage to milk stage; total dry weight of each treatment in each period were increasing and stabilized by the end of the milk stage period, the decrease of nutritional organs such as roots, stems and leaves and the increase of total dry matter showed that the biomass of root, stem and leaf transferred to ear. Yield analysis showed that N application rate has a significant effect on yield, within a certain range, the higher N application rate, the greater the production; The correlation coefficient between yield and the final dry matter accumulation was0.996(P=0.001); Increasing nitrogen application promoted the rice tillering, and increased the yield of rice, the correlation coefficient between yield and ultimate tiller number was up to0.979(P=0.001); under different N levels, the tiller peak and times of each treatment were different, the peak time for N2.5, N2, N1.5delayed one week to peak time for N1, NO.5, NO, and there were significant difference among the peak of each treatment. Different N levels also had a significant impact on rice final nitrogen uptake, the more nitrogen rate, the greater the amount of nitrogen uptake; among the organs, ear has the highest nitrogen content, and the corresponding nitrogen uptake more, and yield was significantly positively correlated with ear nitrogen uptake and plant nitrogen uptake. Under different N levels, nitrogen agronomic efficiency, plant nitrogen uptake and valid spikes had a significant negative correlation, and the nitrogen grain production efficiency, nitrogen partial factor productivity, soi1N dependent rate was significantly negatively correlated with yield, plant dry weight, nitrogen uptake and valid spikes. Quality change for control of nitrogen test (2012) showed that increasing nitrogen could significantly improve the milled rice rate and brown rice rate, improve the rice milling quality under low nitrogen condition; with the increase of nitrogen, protein content increased significantly, but taste value of rice decreased significantly; brown rice rate and milled rice rate were significantly positive related with protein content, extremely significant negative related with amylose content, significantly negative related with the free fatty acid content; principal component analysis showed that, with the increase of nitrogen application rate, the comprehensive quality of the rice emerged a downward trend, no nitrogen treatment get the highest score, and nitrogen applied2.5times get the lowest score. The quality changes of water stress trial (2012) indicates that, milled rice rate and brown rice rate of moderate water stress treatment were higher than the water treatment of mild and severe stress; the drought in the late stage (heading, milk stage) was not conducive to the improvement of rice quality; positive and negative correlation for taste value and RVA characteristic indicated that RVA characteristic indexes of better eating quality of rice were:peak viscosity, breakdown value high, cool paste viscosity, Setback viscosity, consistence viscosity low. Principal component anaiysis show that, the rice quality of mild drought (less than15kPa) at each growth stage, were higher than the quality of moderate drought and severe drought, in the production, milk stage mild water stress was most worthy of promotion.(4) The results of water-nitrogen coupling multi-factor orthogonal test show that, rice ET reduced with soil moisture decrease and enhanced with the increase of nitrogen application rate. Nitrogen agronomic efficiency was the evaluation index for nitrogen fertilizer production efficiency, then the optimal combination was A2B1CxN1-2; regard nitrogen apparent efficiency as rice nitrogen recycling environmental efficiency indicators, then the optimal combination was A1B1C1N1-2; the optimal combination for the highest rice yield was A1B1C2N3; the optimal combination for quality water and nitrogen was AxBxCxN1; the indicator to evaluate merits of water-saving irrigation methods was water productivity, the optimum combination was A1-2B1C2-3N3. Combine the above five indexes into a comprehensive index, then under the same weights (0.2) of different index, the optimal combination to improve the comprehensive index was A1B1C2N2. Based on water stress test, nitrogen control test, water and nitrogen coupling orthogonal experiment in2012, this passage applied and modified three kinds of water and nitrogen coupling model which have been applied for wheat and compared its applicability and advantages and disadvantages, the results showed that Final production model of whole growth stage, the reproductive stages model (water nitrogen Jensen model) and its sensitive coefficient accumulative curves, and BP neural network model had higher degree of fitting, they could be used for the estimation of rice yield; The prediction accuracy of BP neural network model was the highest; the whole growth stage model needed the least data; but the most applicable model was water nitrogen Jensen model and its sensitive coefficient accumulative curves. |
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