Effects Of Different Irrigation Strategies On Water And Phosphorus Transport Under Point Source Infiltration In Aeolian Soils

Sandy soils is widely distributed in Xinjiang,but due to its poor water and fertilizer conservation and obvious deep seepage,it has become the biggest obstacle to restrict the agricultural development and ecological environment improvement in this region.In order to explore the effect of different irrigation strategies on water and phosphorus transport in aeolian sandy soil under drip irrigation,the point source infiltration experiment was carried out in the laboratory to study the law and distribution characteristics of phosphorus transport with water under different emitter flow,irrigation amount and irrigation cycle.The main conclusions are as follows.(1)Under different emitter flow conditions,when the emitter flow rate was 0.3 L/h,the soil wetting range gradually narrowed from 0-15 cm depth to 30-45 cm depth,and the peak of available phosphorus concentration was 650 mg/kg at 0-15 cm depth.When the emitter flow rate was 0.9 L/h,the wetting range of 0-15 cm depth,15-30 cm depth and 30-45 cm depth was the same,and the peak of soil available phosphorus concentration was 680 mg/kg at 0-15 cm depth.When the emitter flow rate was 1.2 L/h,the water content decreased obviously,and the peak water content of 15-30 cm and 30-45 cm depth was 7%.The distribution of available phosphorus was concentrated in 0-15 cm soil layer,and the peak concentration of available phosphorus was 600 mg/kg.Through the comparison and analysis of simulation and test results by HYDRUS-1D software,it can be concluded that the accuracy of simulated and measured values of water content and available phosphorus concentration in aeolian sandy soil meets the requirements.The content and distribution range of available phosphorus in soil decreased with the increase of emitter flow,and the distribution of available phosphorus was more concentrated when the emitter flow was small.The larger the emitter flow,the wider the saturated wetting zone formed during irrigation,and it increased rapidly with time.The larger the volume of wetting body,the faster the migration rate of wetting front,and the soil water storage and soil available phosphorus at the same position also increased and accumulated rapidly.On the contrary,the narrower the saturated wetting zone is,the smaller the wetting body is,the slower the migration rate is,and the slower the accumulation of soil water storage and soil available phosphorus is.(2)Under the condition of different irrigation amount,with the increase of irrigation amount,the isoline of soil water content distribution is more dense.The distribution range of available phosphorus gradually decreased and concentrated.When the irrigation amount was 225 m~3/hm~2,the distribution of soil moisture was uniform,and the peak values of soil moisture content in 0-15 cm,15-35 cm and 30-45 cm depth were5.5%,7%and 7.5%;the distribution of soil available phosphorus was disuniform,and the peak concentration was 600 mg/kg.When the irrigation amount was 450 m~3/hm~2,the soil moisture increased from 0-15 cm to 30-45 cm,and the peak value of soil moisture was 7.6%.When the irrigation amount is600 m~3/hm~2,the peak value of soil moisture content in each depth is 9.7%,and the distribution of soil moisture is flaky or banded;the difference of phosphorus content in each depth is small,and the effective phosphorus is comparatively uniform with water infiltration.When the irrigation amount was 750 m~3/hm~2,the peak value of soil moisture content was 10.8%.The higher the irrigation amount was,the easier the fertilizer diffused and meantime the lower the concentration of available phosphorus was.At the same time:the closer to the emitter,the higher the soil available phosphorus concentration was,and vice versa.(3)Under condition of different irrigation periods,when the irrigation period is once every two days and once every four days,the soil moisture content of 20-40 cm depth is greater than that of 0-20 cm depth.When the irrigation period is once every 8 days,the soil water seeps to the deep layer.Three days after irrigation,the soil moisture content in 0-20 cm depth was higher than that in 20-40 cm depth.When the irrigation period is long,the soil is dry,and the wetting process is slow after the irrigation once again;when the irrigation period is short,the distribution of soil available phosphorus is uniform.When the irrigation cycle was once every two days,the peak of available phosphorus concentration in 15-30 cm depth was 95mg/kg.When the irrigation cycle was once every 4 days,the peak of available phosphorus concentration in15-30 cm depth was 80 mg/kg.When the irrigation cycle was once every 8 days,the peak concentration of available phosphorus was 70 mg/kg at the depth of 0-15 cm.Under condition of different irrigation periods,the change of soil available phosphorus concentration in horizontal direction was greatly affected by irrigation period,and the effect gradually decreased with the increase of soil depth.When other factors(irrigation amount and fertilization amount,etc.)are the same,shortening the irrigation cycle length can make the fertilizer infiltration relatively uniform.