Research And Numerical Simulation For Water And Salinity Change At Demonstration Area Drip Irrigation Cotton Fields In Southern Xinjiang

Xinjiang is located in the northwest of China, abundant land resources, but a shortage of water resources. By the introduction of film with drip irrigation technology, water-saving effect is apparent, but cause serious soil secondary salinization problem. In this paper, take high, medium and low salt these three pieces of cotton field as research object, in which analyze the change of soil water and the accumulation characteristics of soil salt. Selecting seven pieces different salinization degree’s cotton fields to study cotton’s growth indicators in different development stages’ responses of different degrees of salinization, and work out the salt tolerance of cotton. Lead in cotton salt tolerance values as salt control standards, using HYDURS software to carry on the numerical simulation, set up soil water and salt migration model under the condition of drip irrigation, optimize irrigation system.The main conclusions of this paper and the research results are as follow:(1) Through the surveillance of growth period, there are big differences of the upper and under layer of soil water and salt distribution among the three different salt cotton fields, the salt is mainly concentrated on the upper soil, and the range ability of salt is quite high, the lower salinity is more stable. The accumulation of salt at emitter was smaller while more at interspaces of films in horizontal direction.(2) In the whole growth period of cotton, the moisture content of cotton fields’ salt has no obvious differences, but it appears as ladder shape in high, medium and low salt during the blooming period. Under the same conditions, the change of moisture content in high salt cotton field is less than lows’, and the moisture content of high salt cotton field is higher than middle and low salt cotton fields. Generally, the tendency of the change of the salinity soil salt cotton fields is minimal at bud time, maximum during the blooming period, at the open-boll period reduced and slightly lower before planting. High salt salinity variation is higher than the middle and low salt cotton fields.(3) In three consecutive years, the soil salt content appears an increasing tendency: the soil salt content is slightly higher than the previous year. The salt content in the emitter of cotton are lower than film, there are different degrees of desalination at the 0 to 40 cm of emitter surface, 60-100 cm deep underlying harvest salinity is higher than the same depth of the salt content of the seeding time. The degree of soil salt content accumulation at membrane is serious than emitter, each layer are in a state of salt accumulation, and the upper soil accumulation degree is greater than the lower.(4) In the whole growth period, the cotton salt tolerance index’s stress on salt become weakening with the development of growth period. The cotton plant height and dry matter quality key salt content are 0.56%, the key salinity of leaf area is 0.71%, branch number, cotton boll number, boll weight are 0.71%. Overall, there are no significant differences in low salt cotton processing, while the medium and high salt cotton processing in significant difference.(5) Correlation analysis between cotton salt tolerance index and salt, cotton plant height and dry matter of quality is very sensitive to salt, and the correlation is relatively high, however, because of leaf area index also affected by other factors, so salt sensitivity is relatively poor. Cotton branch sets, cotton boll number, boll weight correlation coefficient is lower than other indicators. Through the analysis found that S’s salt tolerance function fitting is better, the salt content of decrease cotton production 50% is 1.08%, the critical value of salinity tolerance is 0.5% and the limited value of salt tolerance is 1.82%.(6)Through simulate the cotton fields in nanjiang Baotou lake farm by using HYDURS software, found that simulated values and measured values anatomizes well with each other. Combined with the local irrigation system and climatic conditions, take cotton salt tolerance values as a salt stress standard, optimize irrigation system. The lower the soil salt contents the less need of irrigation water. Under certain conditions of the total irrigation can adjust the proportion of allocation of irrigation and the water cycle to control salt content.