Effect Evaluation On Subsurface Drainage And Desalination Soda Meadow Alkali Soil In Songnen Plain

Combining with the opportunity of subsurface drainage and desalination soil technology firstly introduction to Songnen plain in northeast China for improving the soda meadow alkali soil and basing on the Da'an rice-planting demonstration plot with subsurface drainage and desalination soil,the thesis researches the soil physical and chemical properties,salt-water movement rules and crop yield about 3 years(2010?2012),and obtains a large amount of data and phenomenon.According to these data and phenomenon,the thesis studies the desalin-alkalization effect,saving water and land effect,improving soil and cultivating fertilizer effect,crop yield effect,eco-environmental effect and economic benefit.All of these can provide an important theoretical basis and technical support for improving land capability and discussing the feasibility of subsurface drainage technology using for amelioration of sodic soil in soda saline-alkali soil region.The main research results showed as follow:(1)The groundwater table of Da' an rice-planting demonstration plot with subsurface drainage and desalination soil fluctuates between 3.05 m and 3.95 m;groundwater pH value,electrical conductivity,total alkalinity and sodium adsorption ratio on the whole presents a decreasing tendency over time;and the subsurface drainage desalin-alkalization quantity is 210 kg/hm2·a which accounting for 40%of the total quantity.And the treatment applying fertilizer and subsurface drainage(TO)can decrease the soil pH,EC,TA,SAR and ESP.In the year of 2012,the contribution made by subsurface drainage to soil TA,SAR and ESP improvement accounts for about 40 percent and while the contribution to rice yield is less than 40%,but all of the contribution indexes are increasing.(2)During the 3 years' experiment,the subsurface drainage could save water 18.3%and land 4.12%.(3)The fertility improvement can improve the soil physical and chemical properties,increase crop yield and improve the environmental quality.Among the treatments of the demonstration plot,the effect of treatment applying fertilizer(CK1)is obvious while the single subsurface drainage treatment shows contrary,but the effect of applying fertilizer and subsurface drainage treatment is best and its effect is significantly higher than single applying fertilizer treatment and single subsurface drainage treatment effect combined.The eco-environment quality changes from "poor" to "good".(4)The investment of the treatment CK1 is 36427 yuan RMB per hectare and the static payback period of investment is 4.7a.The investment of the treatment TO is 66404 yuan RMB per hectare and the static payback period of investment is 6.6a.The investment profit,profit margin,internal rate of return,static payback period and dynamic payback period of treatment CK1 are better than treatment TO.The treatment TO economic benefit is poorer than the CK1.Therefore,the treatment choice depends on the economic capacity.In order to save money at first investment,CK1 is appropriate.And if the target is thoroughly improving soil and getting sustainable economic benefits,with he help of the public subsidies,the subsurface drainage is better than all of them.If the choice is subsurface drainage and desalination soil,according to the comprehensive effects assessment,the optimizable combination of subsurface drainage being buried depth 0.8 m and spacing 10 m with the conditions of soil improvement supporting measures is the best combination.