Effects of Drip Irrigation Volume on Soil Water-salt Transfer and Its Redistribution

Abstract

Because of the irrigation regime and natural factors,soil salinazation has become more and more severe in arid regions. A 3-year field experiment was carried out to investigate the effects of different drip irrigation regimes on soil salinity distribution and cotton yield at Aksu National Station for Farmland Ecosystem Scientific Research,Chinese Academy of Sciences. The results show that the distribution of soil salinity was affected by the redistribution of soil moisture content. Average soil moisture content was gradually increased in cotton growth season. The position of peak value of soil salinity under mulch was moved downward with the increases of drip irrigation volume,and it was moved vertically from 35 cm to 65 cm when the drip irrigation volume was increased from 3 000 m3/hm2 to 4 800 m3/hm2. The downward movement of the position of peak value of soil salinity under mulch was in an order of the treatment Ⅳ treatment Ⅲ treatment Ⅱ treatment Ⅰ after irrigation,which reveals that the increase of drip irrigation volume could promote soil desalinization. Soil salinity was moved gradually from deep soil to topsoil and from the soil layer under mulch to the inter-mulch soil layer simultaneously. With the increase of drip irrigation volume,the average soil salt content was decreased in rhizosphere (0-40 cm in depth) at the end of experiment. The soil desalinization rates of the treatment Ⅰ,treatment Ⅱ,treatment Ⅲ and treatment Ⅳ were 2.5%,7.7%,9.7% and 15.8% respectively. Compared with the soil salinity in soil layer of 0-40 cm in depth,the average soil salt contents for all the treatments were increased in soil layer of 0-100 cm at the end of experiment,they were increased by 0.4 dS/m,0.3 dS/m,0.3 dS/m and 0.1 dS/m for the treatment Ⅰ,treatment Ⅱ,treatment Ⅲ and treatment Ⅳ,and their salinization rates were 9.3%,6.8%,6.7% and 2.6%,respectively. Therefore,high drip irrigation volume of 4 800 m3/hm2 could be the most suitable drip irrigation regime for leaching soil salinity under drip irrigation in silt loam soil in arid regions.