Study On Water-Fertilizer-Salt-Yield Regularity And Optimal Irrigation Schedule Of Rice By Drip Irrigation Under Plastic Film

Based on research status at home and aboard, adopting methods including comparison design,general rotary combination design and computer numerical simulation, by taking rice as research object and relying on a series of field experiments, systematic researches have been done on water production function model, water-fertilizer coupling model, law of soil water and salt movement and optimized irrigation schedule of rice by drip irrigation under plastic film, respectively. The main research results are as follows:1. Irrigation and fertilizer amount plays a really important part in physiological characters of rice,which means that lower amount of water and fertilizer may make physiological characters of rice even worse, including worse plant height, filled seed ratio and kernel weight, causing apparent yield reduction. While to the quality of rice, each quality index decreases with the reduction of moisture content under different water conditions.2. In the experiment soil, under the condition of drip irrigation under plastic film, these three factors including irrigation quota, N and P2O5 fertilizer and yield of rice coincide with the model of three-factor quadratic regression with regression coefficient of one degree term, two degree term and N-P2O5 interaction item reaching significant level. The importance of such three factors can be listed as irrigation quota> N> P2O5. There is a positive correlation between yield predicted by the model mentioned above and the actual yield of rice (R2=0.981). In addition, optimal combination of water quota, N and P2O5 fertilizer was obtained under different target yield by solution of the models. With the experiment lasting for 2 years, the verification shows that yield, WUE are consistent with optimal combination target yield and WUE. Such optimal combination scheme can provide theoretical basis to the promotion of rice by drip irrigation under plastic film.3. Salt amount in the paddy field is higher in tillering and milk stage, while in jointing-booting stage and heading-flowering stage it is lower. With migration of soil water, irrigation water has played an important role in effectiveness of salt leaching, and the amount of salt content decreases, remaining the state of high desalination in plough layer of the soil and transferring to deeper layer. In addition, soil salt leaching magnitude varies with different irrigation level. Effectiveness of leaching in which irrigation level is higher than 100% of field capacity is apparently superior to that of 80%-90%, while the effectiveness of leaching is negligible under 60%?70%. Thus, in a word, irrigation level higher than 80%?90%? ? can be useful for preventing soil secondary saline-alkalization and improving environmental quality.4. Influence on yield of rice by soil water is highest in jointing-booting stage, while in heading-flowering stage and tillering stage it is smaller with the influence smallest in milk stage Sensitivity index of water production function calculated by Jensen model can be listed as jointing-booting stage> heading-flowering stage> tillering stage > milk stage, which is similar to normal pattern of water consumption. Furthermore, lower limit of soil moisture remains 90%?100%? ? in each growth period, which can ensure high production and a rather highly WUE of rice, realizing consistence between high production and high efficiency. On this basis, the optimized irrigation schedule determined by dynamic solution of the models can be described as follows: irrigation level is 750 m3/hm2 in tillering stage, 2125 m3/hm2 in jointing-booting stage, 1050 m3/hm2 in heading-flowering stage and 325m3/hm2 in milk stage, respectively.In this dissertation, the production function model and the optimal irrigation schedule, the water and fertilizer coupling model and the optimal combination scheme and the water and salt transport law,of rice by drip irrigation under plastic film have been done, which can provide the theoretical basis to efficient utilization of water-fertilizer of rice by drip irrigation under plastic film and the promotion of such technique in Ningxia.