Studies On Effects And Mechanism Of Saline Soil Conditioners And Simulation Of Water-salt Transportation

Hetao irrigation area in Inner Mongolia is one of the three oversize irrigation areas around China which takes the responsibility of food security for both China and Inner Mongolia.The special natural conditions and human factors have caused severe problems of soil salinization and secondary salinization in the irrigation area,which brought a huge threat to the sustainable development of agriculture.According to the characteristics of saline soil in Hetao irrigation area,four kinds of amendments for saline soil land and three kinds of anti-saline-alkaline-specific fertilizers were used in the improving experiment for medium saline soil and simulation for the water and salt migration laws.The research draws the following conclusions:?1?The seven kinds of improved products used in this research performed well in controlling soil salt by single application and more remarkable effect by combined application.In root layer?0⁴0 cm?,phosphogypsum?T1?combined with ORYKTA?T2?,DS-1997?T3?,Danlu bacterial fertilizer?T5?,and Hezhuang fertilizer?T6?,Nashi Qiqifa?T7?increased the soil desalting rateby 4.93%,2.27%,1.52%,11.10%and 25.94%respectively,compared with various improved products with single application.However the subsoil salt content is higher than the single application caused by the salt migrate down due to the better properties of soil physical improved by phosphogypsum and improved products mixture.Phosphogypsum contains Ca²⁺which can be combined with the alkaline ions OH^-in soil solutions to generate precipitates and decrease pH.This is also why phosphogypsum combined a variety of improved products performed better than improved products with single application in the soil desalination and the reduction of soil pH.?2?Various improved products can also increase the soil nutrient content effectively,by decreased soil salinity and pH,the transformation of soil nutrients to effective form was promoted,and also the growth of sunflower and its yield.Compared to the contrast T8,the increased rate in yield of sunflower from high to low was 51.56%,36.10%,29.12%,13.72%,13.32%,10.91%and 9.80%respectively,which were T5>T1>T6>T2>T3>T>T4>T8.?3?In order to evaluate the improvement effect of various improved products objectively,the original data matrix of 8×11 with soil salinity,soil nutrient and crop index was constructed.The order of the principal component was T1>T5>T6>T2>T7>T3>T4>T8,where T1,T5,T6 stay above the average value.The phosphogypsum,Danlu bacterial fertilizer and Hezhuang fertilizer were chosen as optimum result.?4?The response mechanism of sunflower growth to improved products and soil properties were studied by setting the gradient of the application amount of improved products.The results showed that the indexes were sensitive to the improved products,and the suitable application rate had better effect on soil bulk density,infiltration performance,soil evaporation,ground temperature,salt content and water content,indicating that the appropriate application is an important guarantee in improveing the soil water,heat and salt.The suitable application amount of Hetao irrigation area is about 15000 kg·hm^-2of phosphogypsum,about 1500 kg·hm^-2 of Danlu bacterial fertilizer and about 600 kg·hm^-2 of Hezhuang fertilizer through the comprehensive consideration.?5?In order to understand the Water-Salt transportation and predict its development trend in saline soils.This research established the BP neural network model,and built the PSO-BP model to optimize it by particle swarm optimization in order to master the law of water and salt transportation in saline soil and forecast its development trend.And it took use of the HYDRUS-1D model and PSO-BP model which were rated and good tested for precision comparison.The model of soil water and salt migration is predicted by HYDRUS-1D model under different improved products.The results showed that the three treatments had a certain sustained effect on the soil water and salt of saline soil,and the continuous effect of reducing salt and moisture conservation by phosphogypsum stayed top,DanLu bacteria fertilizer followed and it had a high sustained performance.The improveing effect of Hezhuang fertilizer declined obviously in the next year,slightly better than the contrast treatment.