| Inner Mongolia Hetao Irrigation District is located in the inland of northwestern China.This area has low rainfall and high evapotranspiration.For a long time,it relied mainly on the irrigation of the Yellow River to develop agriculture.The groundwater level remains high for many years.The problem of secondary salinization of soil is very serious.This is not only an obstacle to agricultural production and development in the region,but also a major ecological and environmental problem.Previous studies on soil salinization in this area have focused more on improved techniques and single-component improvers,while the development of compound conditioners is relatively weak.The traditional improver has the problems of single component,large application amount,large water demand,high cost,inconvenient application,and potential environmental pollution.Therefore,this study applied salt-controlling materials,acid-fertilizing materials,water-retaining and salt-inhibiting materials to form saline-alkaline soil compound conditioner in different proportions.By exploring the compound conditioner to improve the soil salt,alkali,water,nutrients and microorganism in the root zone of crop growth,it creates an ideal environment of "low salt,low alkali,high water and high fertilizer" within the range of crop root growth.The purpose of this study is to develop the compound ecological conditioning products with strong pertinence,convenient application,low water demand,low cost and low environmental pollution for saline-alkali land in Hetao area.In this study,polymer adsorption resin,calcium silicate,FGD gypsum and bentonite were separately mixed with humic acid and super absorbent polymer in different proportions to form saline-alkali soil compound conditioners.Through pot experiments,field experiments and field demonstration,the effects of different types of compound conditioner application on pH,exchangeable sodium percentage,salt,water-soluble salt ions,nutrients,moisture,hardness,microbial community structure,microbial diversity,enzyme activity and sunflower growth of saline-alkali soil were compared and analyzed.The main findings are as follows:1.Main results of the pot experiments:(1)After applying polymer adsorption compound conditioner,calcium silicate compound conditioner,FGD gypsum compound conditioner and bentonite compound conditioner at different levels,the soil pH decreased significantly by 0.23?0.50,0.18?0.39,0.45?0.79 and 0.41?0.78,respectively.The total salt content of soil decreased after the application of polymer adsorption compound conditioner and calcium silicate compound conditioner,while the total salt content of soil increased after the application of FGD gypsum compound conditioner and bentonite compound conditioner.Polymer adsorption compound conditioner had a certain adsorption effect on K+,Na+and Cl-in soil.The contents of Na+Mg2+ and Cl-in soil decreased after the application of calcium silicate compound conditioner.After the application of FGD gypsum compound conditioner,the contents of Na+ and HCO3-decreased,while the contents of Na+,Ca2+,Mg2+and SO42-increased.After the application of bentonite compound conditioner,the contents of K+,Na+,Ca2+and Mg2+increased.(2)The contents of organic matter and available nitrogen in soil increased after four kinds of compound conditioner were applied at different levels.The content of available phosphorus in soil increased after calcium silicate compound conditioner was applied,while the content of available potassium in soil increased after bentonite compound conditioner was applied.The soil moisture increased after four kinds of compound conditioner were applied at different levels.Among them,the calcium silicate compound conditioner has better water retention effect than the other three compound conditioners.After applying calcium silicate compound conditioner and FGD gypsum compound conditioner at different levels,the soil hardness was significantly reduced by 36.7%?58.4%and 13.4%?51.7%,respectively.(3)The addition of bacillus gigas,bacillus subtilis and EM compound microbial agent in four kinds of compound conditioner had little effect on the improvement of saline-alkali soil.2.Main results of field experiments:(1)At different growth stages of sunflower,soil pH and exchangeable sodium percentage were significantly reduced after applying FGD gypsum compound conditioner at medium and high levels.At the seedling stage of sunflower,the salt of soil was significantly reduced by 39.3%?60.2%after applying calcium silicate compound conditioner at different levels by small hole fertilization.At the seedling and flowering stages of sunflower,the salt of soil significantly reduced by 33.3%?52.3%and 35.9%?37.8%,respectively in the two growth stages after applying calcium silicate compound conditioner at different levels by big hole fertilization.At different growth stages of sunflower,the salt of soil significantly increased after after applying FGD gypsum compound conditioner at medium and high levels.(2)Polymer adsorption compound conditioner had a certain adsorption effect on Na+and Cl-in soil.The contents of Na+and Cl-in soil also decreased after the application of calcium silicate compound conditioner.After the application of FGD gypsum compound conditioner,the contents of CO32-and HCO3-decreased,while the contents of K+,Ca2+,Mg2+and SO42-increased.After the application of bentonite compound conditioner,the content of Na+increased.(3)The contents of organic matter,available nitrogen and available potassium in soil increased after the application of four kinds of compound conditioner at different levels,and basically increased with the increase of the application level of each compound conditioner.The content of available phosphorus in soil increased after calcium silicate compound conditioner and bentonite compound conditioner were applied.(4)The microbial diversity of soil fungi decreased significantly after the application of four compound conditioners at high level.However,the microbial diversity of soil bacteria increased significantly after the application of calcium silicate compound conditioner at a high level.The microbial richness of soil bacteria increased significantly after the application of calcium silicate compound conditioner and bentonite compound conditioner at a low level and the application of calcium silicate compound conditioner and FGD gypsum compound conditioner at a high level.The dominant groups of soil fungi and bacteria were not changed by applying various compound conditioners at different levels.The fungi with relatively high abundance in control and each treatment were ascomycota,chytridiomycota,zygomycota and basidiomycota.The bacterial with relatively high abundance in the control and each treatment were proteobacteria,actinobacteria,chloroflexi,acidobacteria and gemmatimonadetes.(5)During the whole growth period of sunflower,soil urease activity increased significantly after the application of FGD gypsum compound conditioner at different levels.At the seedling and flowering stages of sunflower,soil invertase activity increased significantly after the application of polymer adsorption compound conditioner,calcium silicate compound conditioner and bentonite compound conditioner at different levels.At the flowering and mature stages of sunflower,soil phosphatase activity increased significantly after applying calcium silicate compound conditioner at different levels and bentonite compound conditioner at medium and high levels.During the whole growth period of sunflower,the application of polymer adsorption compound conditioner,calcium silicate compound conditioner and bentonite compound conditioner at different levels had no significant effect on soil catalase activity.In general,it is more economic and effective to apply compound conditioner to improve saline-alkali soil by small hole fertilization.The seedling survival rate of sunflower increased significantly after four kinds of compound conditioner were applied at medium and high levels.Among them,high level application of polymer adsorption compound conditioner,FGD gypsum compound conditioner and medium level application of calcium silicate compound conditioner had obvious effects on increasing yield and soil improvement.3.Main results of the field demonstration:(1)High level application of polymer adsorption compound conditioner(MB-10 resin 1147.5 kg hm-2,humic acid 344.3 kg hm-2,super absorbent polymer 91.8 kg hm-2)and FGD gypsum compound conditioner(FGD gypsum 1147.5 kg hm-2,humic acid 344.3 kg hm-2,super absorbent polymer 91.8 kg hm-2)had obvious effects on increasing yield,which increased by 31.8%and 36.8%respectively compared with the control in the field demonstration.(2)In the field demonstration,the application of FGD gypsum compound conditioner had simultaneously increased the yield and income,with an increase of 5512.7 yuan per hectare,which can be considered for popularization.Due to the high cost of the resin,after the application polymer adsorption compound conditioner had increased the yield but not increased the income.In the future,if the price of adsorbent resin declines,it can also be considered for promotion. |
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