| Object:Xinjiang water shortage,saline-alkali soil widely distributed,soil salinization restricts the development of agriculture,is a problem to be solved.Drip irrigation under film can inhibit salt and pressure salt,and can not discharge salt.The accumulation of salt in successive years is easy to cause soil compaction and secondary salinization.Spring irrigation can effectively reduce soil salinity and provide a good growth environment for crops.Subsurface pipe drainage technology can collect water and salt below the plough layer and discharge salt outside the farmland.At present,there are few studies on how spring irrigation and subsurface pipe drainage technology can produce better drainage and salt washing effect through coupling.Methods:Based on the field experiment and DRAINMOD numerical model of 51 regiment in Tumshuk City,the third division of typical saline-alkali land in southern Xinjiang,three spring irrigation gradients(high irrigation level,3600 m~3/hm~2,G1;medium irrigation level,3150 m~3/hm~2,G2;low irrigation level 2700m~3/hm~2,G3),three subsurface pipe arrangement(buried depth+spacing)modes(0.6 m+12 m,A1;0.8m+16 m,A2;the effects of 1.0 m+20 m,A3)and conventional tillage control treatment(CK)on water and salt transport were studied.The model was calibrated and verified by field test data,and the numerical model of 51 groups of saline-alkali land was established by using the optimized numerical model parameters.Results:The effects of buried depth and irrigation amount on water and salt transport in each soil layer of farmland and the change law of total salt were studied,and the optimal treatment scheme was determined.The main results are as follows:(1)In the range of 0～120 cm soil layer,the soil moisture content during the growth period of cotton showed:after spring irrigation>flowering and boll stage>seedling stage>boll opening stage.The interaction between spring irrigation and subsurface pipe had a significant effect on soil moisture during cotton growth period(P<0.01).Under the combination of spring irrigation and subsurface pipe,the average soil moisture content of G1A3(spring irrigation water 3600 m~3/hm~2,buried depth 1.0 m,spacing 20 m)was the highest.(2)In the range of 0～120 cm soil layer,the soil salt content during the growth period of cotton showed:seedling stage>spring irrigation>flowering stage>boll opening stage.The interaction between spring irrigation and subsurface pipe had a significant effect on soil desalination rate during cotton growth period(P<0.01).Under the combination of spring irrigation and subsurface pipe,the soil desalination rate of G1A1(spring irrigation 3600 m~3/hm~2,buried depth 0.6 m,spacing 12 m)was the highest.(3)The simulated values obtained by DRAINMOD software are in good agreement with the measured values.The maximum RMSE value and the minimum R~2 of the calibrated conductivity are 99.62μs/cm and0.79,respectively.The maximum RMSE value and the minimum R~2 of the verified conductivity are 149.76μs/cm and 0.76,respectively.The soil desalination under different buried depth,spacing,irrigation amount and pipe diameter was simulated by the model after calibration and verification.It was found that the increase of spring irrigation amount was 200 m~3/hm~2,and the increase of desalination rate was 3.21%-15.14%.The buried depth of the subsurface pipe increases by 0.2 m,the desalination rate increases by 0.7%to 5.0%,the spacing of the subsurface pipe increases by 2 m,and the desalination rate decreases by 0.2%to 2.2%.Changing the diameter of the pipe had no significant effect on the soil desalination rate.(4)The interaction between spring irrigation and dark tube had a significant effect on boll weight,dry matter and yield of cotton(P<0.01).The dry matter,cotton yield and boll weight of G1A1(spring irrigation 3600m~3/hm~2,buried depth 0.6 m,spacing 12 m)reached the highest value,which were 94.86 g/plant,5324.52 kg/hm~2 and 4.99 g respectively.The economic benefit of G1A1(spring irrigation 3600 m~3/hm~2,buried depth0.6 m,spacing 12 m)was the highest,which was 24560 RMB/hm~2.The economic benefit of G3A3(spring irrigation 2700 m~3/hm~2,buried depth 1.0 m,spacing 20 m)was the lowest,which was 6510.19 RMB/hm~2,and the economic benefit difference was 3.77 times.Based on the RAGA-PPC model,the economic benefits have the greatest impact on the overall evaluation results,followed by the average desalination rate,cotton yield,and spring irrigation amount.The G1A3(spring irrigation amount 3600 m~3/hm~2,buried depth 1.0 m,spacing 20 m)treatment is the optimal treatment for comprehensive benefits.Conclusion:The combination of spring irrigation and subsurface pipe has a significant effect on soil desalination.The G1A3 treatment(buried depth 1.0 m,spacing 20 m,spring irrigation amount 3600 m~3/hm~2)was the optimal combination of spring irrigation and subsurface pipe layout scheme. |
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