Soil Salinity Dynamic On Farmland With Long-term Drip Irrigation Under Mulch In Arid Area

Xinjiang is located in the arid area of Northwest China,owing to the unbalance of soil and water resources,saline-alkali land and over exploitation of groundwater,the development of agriculture in arid areas is severely restricted.Therefore,advanced and reasonable drip irrigation under mulch is very important for agriculture in Xinjiang.Based on the experiment data from 2008 to 2015 of the Paotai Soil Improvement Test Station of Eighth Division,Xinjiang Production and Construction Corps,by the drip irrigation under mulch,the characteristics of soil salinity dynamic and some key influencing factors in salt wasteland and different types of soil were analyzed.Combined with the farmland experiment of drip irrigation under mulch for 2016-2017 years in Shihezi reclamation area,the soil salinity dynamic with long-term drip irrigation under mulch.And main conclusions were as follows:(1)After 8 years of drip irrigation under mulch,the soil desalination effect is obvious.According to the classification standard of salty soil,in the salt wasteland experiment,the soil in 121 groups changed from desalinated soil to light desalinated soil,the soil in 144groups changed from strong desalinated soil to light desalinated soil,the soil in 135,142 and145 groups changed from strong saline soil to intermediate desalinated soil,the soil in 149regiments change from medium desalinated soil to non-salinated soil;in the different types of soil experiment,the growth of non-desalinated soil was from 55.6%to 77.8%.(2)The total salinity of soil decreased with the development of cotton during the year.In April,soil finalization occurred in spring before planting,soil salinity decreased rapidly after irrigation;In May,the salt content of 0~30cm soil layer decreased,and the salt content of30~60cm soil layer increased;In July,the trend of soil salt content accumulation in shallow soil were weakened;In August,the salt content of 0~30cm soil layer increased,and the salt content of 60~100cm soil layer decreased;In September the salt content in shallow soil increased.The soil of 0~60cm layer desalination effect is obvious in the whole growth period.(3)In the horizontal direction,the soil salt content is the lowest under drip emitters,the further from emitter,the higher soil salt content was,which reached the maximum at the43cm far away from the drop emitter;The value of soil moisture content is the highest under drip emitters,and soil moisture content is lower and lower around the emitter.According to the distribution characteristics of the soil moisture content and the soil salt content,that soil moisture is significantly correlated with soil salinity.In the vertical direction,the distribution characteristics of soil salinity showed that the effect of shallow layer desalination was better than deep layer,and the farmland soil appeared a stable salt accumulation layer,which was in 60~100cm soil depth;The distribution characteristics of soil moisture increased gradually from the surface to deep layer,reached the maximum value in 30cm soil layer,and then decreased in deep soil gradually.(4)The distribution of soil salinity is influenced by groundwater greatly in Shihezi reclamation area.In the Shihezi reclamation area,the underground water is used to irrigate.At the beginning of irrigation,the groundwater depth decreased,and the soil salt content decreased also;In the middle and later stage of irrigation,with the decrease of groundwater depth and reached the level of stability,the soil salt content increased gradually.At the same time,the dynamic of groundwater salinity between the year and the annual period is opposite to the dynamic of soil salinity.(5)The groups of different types of soil nutrients showed a general increasing trend,but the organic matter is still in lack of level.The cotton emergence rate in salt wasteland increased from the lowest 21.7%(121 group)and the highest 63.2%(145 group)in 2008 to the rate of over 80%in 2012,the average yield of cotton reached 5093-6350kg/hm~2,which is the medium fertility level.We found that drip irrigation under mulch can effectively improve saline alkali soil and increase crop yield effectively.