Study On Salt Ions Distribution And Migration Of Spatiotemporal In Cotton Fields With Long-Term Drip Irrigation In Xinjiang

Drip irrigation under mulch can only adjusted the root zone water and salt environment in a short period of time in theory, and it might lead to salt accumulation in the edge of "wetting front", increased ion poisoning of cotton, and then restricted the sustainable development of drip irrigation technology. In this paper, the combination of long-term fixed point monitoring and temporal and spatial variability is used. Five cotton fields in drip irrigation is been monitored from 2009 to 2013 in Paotai town of Shihezi,Xinjiang Production and Construction Corp. To clarify the influence of existing irrigation systems and ablation of snow to soil water and salt ions and analysis ions distribution and migration of time and space before and after the growth period and wintering period. Through seek salt ions distribution and migration of time and space in cotton fields with Long-term drip irrigation to provide theoretical basis for the development of drip irrigation. The main conclusion show as follows:(1)The distribution and migration of salt ions in cotton fields with Long-term drip irrigation before and after the growth period and wintering period in XinjiangApplication drip irrigation technology in 6 years, salinity, Cl-,SO42-,Na+,Ca2+,Mg2+are onto the surface before and after the growth period, the content of salinity and ions decreased with the increase of soil depth in 0-80 cm. Affected by groundwater levels and water quality, the content of salinity and above-mentioned five ions increased with the depth below 200 cm in cotton fields with drip irrigation. Under the current irrigation system, irrigation leaching the salinity and ions, lead to the content in 0-140 cm of salinity and Cl-,SO42-,Na+,Ca2+,Mg2+decreased apparently after cotton growth period compare before. In 5 years, freezing layer appeared a phenomenon of stagnant water and salt in wintering period the cotton field with drip irrigation, Cl-,SO42-,Na+,Ca2+,Mg2+gathered in freezing layer significantly. The snow melt leaching the salinity and ions in soil, after the snow melt the content of salinity and Cl-,SO42-,Na+,Ca2+,Mg2+reduced significantly compare with freeze-up. Na+ and Ca2+ are the most prominent change with total salt in eight ions in growth period and freeze-up period.(2)Study on salt ions distribution and migration of time and space in cotton fields with Long-term drip irrigation in XinjiangMonitoring of 16 years, the distribution characteristics of salinity and Na+, Ca2+,Mg2+,SO42-,Cl-are onto the surface throughout, the trend is particularly apparent in the first three years,total salt and five ions spread relatively evenly in 0-140 cm three years later. Exponential decay can regression the relationship between total salt, ions and drip period, that the content of salinity and Na+,Ca2+,Mg2+,SO42-, Cl-decreased year by year in 16 years application drip irrigation. Whereby, drip irrigation in 1-4a,the average salt off is 8665.10g/a, it’s rapid desalt stage,in 4-12 a is steady desalt stage, the average salt off is 1412.02g/a, when drip irrigation technology application 12 a,the content of salinity is in stable stage. Drip irrigation in 1-4a, the average Na+ off is 3172.86g/a,it’s rapid reduce stage,in 4-10 a is steady reduce stage,the average Na+ off is 795.13g/a,10 years later,the content of Na+ is in stable stage. For first four years,Ca2+ is still in rapid reduced stage,the average decline is 703.15g/a,from 4 to 12 it’s into steady reduce stage,the average decline of Ca2+ is 80.62g/a,after 12 years,the content of Ca2+ is stable stage. Mg2+ is in rapid reduce stage in first four years, the average decline of Mg2+is 340.10g/a,after the fourth year is steady reduce stage,the average decline of Mg2+ is46.94g/a. The first three years is rapid decline stage of SO42- and the average decline is 204.12g/a,from 3 to 16 is steady decline stage, the average decline is 37.12g/a. The rapid reduce stage of Cl- in the first three years,the average decline is 237.82g/a, 3to 10 a is steady stage and the average decline is 34.24g/a, the content of Cl-into stable stage in 10 years later.