| The scarcity of freshwater in Ningxia is one of the important reasons for restricting the development of facility vegetable agriculture.How to adjust the utilization rate of irrigation water,and make full use of slightly brackish water and brackish water mixed fresh water,has become an important means to solve the problem of low utilization of water.This paper mainly expounds the using of three kinds of irrigation water:freshwater,brackish water,and brackish water mixed with freshwater.The soil is restored by earthworm compost and desulfurization gypsum,so that the soil salt concentration reaches a relative balance.In order to explore the changes of soil salt concentration under different treatments and the changes of soil enzyme activities under salt stress conditions,a soil salt leaching method with irrigation water was selected.The test was a two-factor design:factor 1 was the soil improvement treatment in the root zone,including:?untreated compared soil(S),?root layers(0-25 cm),increased application of compost(W),and ?root layers(0-25 cm).Add desulfurization gypsum(DG)to the soil,?root layers(0-25cm),soil application,composting and desulfurization gypsum(W+DG);factor 2 is the irrigation system,including:?single freshwater irrigation(FW),?brackish water Mixed irrigation(SFW)and ?single brackish water irrigation(SW).The study results show that:The results showed that:(1)Changes in soil water content and water content:In the soil layer 20-30cm,the soil moisture content under the slightly brackish water irrigation treatment reaches 30%at the maximum;with the combined application of the worm compost and desulfurization gypsum above plus brackish water mixed with freshwater.Under the treatment,the soil moisture content reached a maximum of 43%.Uunder the untreated soil,freshwater with brackish water mixed irigation on the day of irrigation(d)respectively have 6.1%and 5.2%water content;by using freshwater,and brackish water mixed with fresh water,the two things above used in the irrigation reached 6.7%and 6.2%water content(d),indicating that the manure can play a certain role in water retention.(2)Changes in soil nutrients:Compared with freshwater irrigation,the total nitrogen and organic matter content of the soil under slightly brackish water irrigation decreased by 11.1%and 8.3%respectively.At 20-40 cm;under the treatment of manure and desulfurization gypsum plus brackish water with freshwater,the total nitrogen content of soil reached 1.89g·kg-1.Under the treatment of manure,the soil organic matter content in brackish water mixed irrigation was 11.3%,which was higher than that in freshwater irrigation and than that of untreated soil.23.3%;In the 0-20cm soil layer,with the application of manure and desulfurization gypsum plus slightly brackish water irrigation,the soil available phosphorus content was 98.84mg·kg-1,which was 4.5%higher than that of untreated soil;Under the condition of brackish water mixed with freshwater,the effective potassium content of the treated manure and desulfurization gypsum was 112.2mg·kg·-1 and 112mg·kg-1,which was 64.7%and 25.8%higher than that of the untreated soil,indicating that the manure can increase the soil.Organic matter content improves soil.(3)Changes in the content of soil Na and K in soil:In the untreated soil at the depth of 50-60cm,the soil Na content under salt water freshwater irrigation and brackish water irrigation was 17.1mmol/L and 25mmol/L respectively,which was 46.1%higher than freshwater irrigation;In the 0-20cm soil layer,the sorghum compost and the two materials were applied together.The Na content in the soil under fresh and brackish water irrigation was respectively 9mmol/L and 18mmol/L,which was 40%a 10%lower than the untreated soil.In the untreated soil,brackish water irrigation in the soil layer 20-30cm has a K content reaching a maximum of 28.1mmol/L,and freshwater mixed with brackish water in the soil layer 40-50cm reached the soil K+ content to the maximum of 27mmol/L;In the 30-40cm soil layer,the content of K in the soil under the method of alfalfa compost plus freshwater irrigation and alfalfa compost plus brackish water was 26mmol/L,indicating that the Na content in soil can be appropriately reduced by using manure and desulfunzation gypsum.(4)Changes in the quantity of soil microbial:in untreated soil,the number of fungi and bacteria in freshwater-irrigated soil was 2.45 log10/g and 3.44 log10/g respectively,and the number of fungi and bacteria lived in the slightly brackish water decreased by 46%and 61%compared with freshwater irrigation.Under the conditions of freshwater mixed with brackish water,the amount of soil fungi applied by these two kinds of water was 3.42 log10/g;under the condition of slightly brackish water and brackish water mixed with fresh water,the number of bacteria used for composting was 1.96 log10/g and 4.12 log10/g,and the amount of bacteria in the freshwater irrigation increased by 19.8%compared with the soil irrigated with freshwater,and the amount of microorganisms could be increased by applying earthworm compost and desulfurization gypsum under brackish water mixed with fresh water.(5)Changes in soil microbial carbon and nitrogen:at 0-20 cm soil layer,under the combined application of two materials,the soil microbial biomass carbon content of freshwater irrigation and brackish water mixed with fresh water irrigation was 138.9mg/kg and 176.9mg/kg respectively.Irrigation increased by 27.3%compared with fresh water.Soil microbial nitrogen content was 44.7 mg/kg and 58.2 mg/kg,which was 23.2%lower than freshwater irrigation.(6)Changes in soil enzyme activity:in the 0-20 cm soil layer,the combined using of three methods,the brackish water irrigation,worm compost,and desulfurization gypsum,have a effect on the average content of soil CAT,phosphatase and urease activities,and they were 14.7 ?g·g-1,2.12 ?g·g-1 and 78.23?g·g-1.The activity of phosphatase and urease increased by 1.26 times and 1.28 times compared with untreated soil.(7)Changes in cucumber quality and yield:In untreated soil,the vitamin C content of cucumber fruit under freshwater and brackish water mixed with freshwater was 11.36 mg/g and 13.69 mg/g respectively,which was 20.5%higher than that of freshwater irrigation;With the freshwater and slightly brackish water plus worm compost,the vitamin C content of cucumber fruit was 21.36mg/g and 19.63 mg/g respectively.In the untreated soil,the titratable acid content of cucumber fruits by using fresh and brackish water irrigation was 21.33 mg/g and 18.32 mg/g respectively,which was 14.1%lower than freshwater irrigation.With the application of the two things,the titratable acid content of the irrigated fruit was 12.5%higher than that of freshwater irrigation.In the untreated soil,the nitrate content in the cucumber fruit was reduced by 9.6%under the brackish water treatment.Under the treatment of desulfurization gypsum,the cucumber fruit was irrigated by fresh water and brackish water.The nitrate content was 0.61 mg/g and 0.58 mg/g respectively,which was 4.9%lower than freshwater irrigation.The yields of application of desulfurization gypsum,worm compost were 5284kg/667m2,5626kg/667m2 and 5508kg/667m2 respectively,which increased by 7.5%,14.5%and 12.1%respectively compared with untreated soil,indicating that the brackish water mixed with freshwater.Under the application of manure,desulfurization gypsum and the combination of previous materials can improve the quality of cucumber. |
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