Simulation Of Potato Growth And Soil Water And Nitrogen Transport Under Different Irrigation Quotas In The Arid Region Of Central Ningxia

Aiming at the problems of water shortage in the arid regions of central Ningxia,irrational use of water and fertilizer,and pollution of groundwater caused by nitrate and nitrogen infiltration in soil,the research on water and nitrogen transport under different irrigation treatments was carried out.In this paper,the field experiment and indoor simulation test are combined.Firstly,the indoor simulation test is carried out.Three irrigation quotas are set,which are 0.71L for F1 treatment,0.99L for F2 treatment and 1.27L for F3 treatment.The fertilization concentration is 500mg/L.The wetting peak,water content and nitrate-nitrogen migration of soil profile under different irrigation treatments were studied,and the relevant fitting model and HYDRUS model were established for simulation verification.Then the field experiment was carried out and the randomized block test method was used.The fertilization amount was 225kg/hm2,irrigation quota is the experimental variable,set three irrigation quotas,namely F1 treatment 900 m3/hm2,F2 treatment 1260m3/hm2 and F3 treatment 1620m3/hm2.The changes of potato growth index(crown width,plant height,stem diameter and leaf area),quality index(reducing sugar,starch and dry matter)and yield were studied,as well as soil moisture content and nitrate state in different soil layers from different roots and the variation of nitrogen as the number of days after irrigation increases.The main conclusions are:(1)The larger the irrigation amount,the longer the migration time of the wet peak and the higher the value.The soil moisture content of different depth soil layers is larger but the fluctuation range is smaller.The vertical measurement values are the highest after 0-40cm irrigation,and the irrigation amount is higher.The higher the value,the more the nitrate nitrogen content increased with the time of irrigation;the F1 treatment after different irrigation days decreased first,next increased and decreased at last,the F2 treatment decreased first,then increased and then stabilized,F3 treatment is reduced first and then increased.(2)Using the five-order polynomial function model between soil water content and nitrate nitrogen content and soil depth to fit soil moisture content and nitrate nitrogen content in different soil layers under different irrigation days,and the model correlation coefficient R2 was higher than 0.95.The relative error between the model fitting value and the measured value is within 5%.The HYDRUS model is used to simulate the soil water content at different depths after each treatment,and the measured value and the simulated value are t-tested.There is no significant difference between the two.The difference(P>0.05),the model can accurately reflect the relationship between soil moisture content and nitrate nitrogen content and soil depth in different treatment days.(3)With the extension of the growth period,the crown width of each treated potato gradually increased,the plant height and stem diameter increased first and then decreased,the leaf area increased first,then decreased and increased at last;with the increase of irrigation amount,the potato crown width,plant height,stem diameter and leaf area keep increasing,potato reducing suger content decreased continuously,starch content,dry matter quality and yield increased first and then decreased;the more irrigation,the negative effect on potato growth and yield.(4)The soil moisture content of each soil layer in the seeding stage and the bud stage increased with the increase of irrigation amount.The soil moisture content of the 20-60cm soil layer decreased gradually during the tuber formation period and tuber expansion period,and the greater the irrigation amount decreased,The soil moisture content decreased gradually in the 20-60cm soil layer during the starch accumulation period;the soil moisture content in the 0-20cm soil layer decreased continuously and there was no significant difference in each treatment,and the soil moisture content in the 60-100cm soil layer increased.As the growth period progresses,the moisture content of the soil layer increases first and then decreases.(5)When the distance from the root is the same under different irrigation conditions,the soil moisture content in different depths of indoor and field shows a downward trend with time,but the deep soil moisture content in the indoor test is increasing,and the deep soil moisture content in the field test is under high irrigation condition increase;indoor 20-40cm nitrate nitrogen content gradually increased,the more irrigation water,the more likely to cause the accumulation of nitrate nitrogen in deep soil,while the nitrate content of 20-40cm soil layer in Datian gradually decreased,nitrate nitrogen in 60-100cm soil layer the content tends to be stable.Considering the growth index,quality index and yield of potato in the field and the law of soil water and nitrogen transport in the presence or absence of crops,the optimal treatment is F2,that isthe irrigation amount is 1260m3/hm2,which is a suitable irrigation scheme for the field.