| Inner Mongolia Hetao Irrigation District is a typical fragile ecological environment,In recent years,due to the influence of economic benefits,the plant structure has changed a lot,so that some farmers have given up irrigation in autumn(irrigation from October to November each year)in the area,or changed autumn irrigation into spring irrigation,let autumn dry land and spring irrigation had increased significantly.The change of irrigation system will inevitably break the water and salt dynamic balance that have been formed over many years,which will affect the water and salt balance,and cause the degree of salinization of cultivated land increased in Hetao area.According to the soil ecological problems that adjustment of irrigation systems in Hetao region,this study adopted a method that regional survey sample combine with field position experiment to carry out a study that effects of irrigation system adjustment on physicochemical properties and microflora in saline soil.The main progress has achieved as follows:(1)We clarified the effect of different autumn irrigation years on soil chemical properties,bacterial community composition and diversity.According to select five types of typical plots wasteland(CK),always irrigation in autumn(AUI1),2-3 years with autumn irrigation(AUI2),3-4 years without autumn irrigation(AUI3)and 6-7 years without autumn irrigation(AUI4)were known: AUI1 and AUI2 treatment significantly reduced the salt content of 0-30 cm and AUI2 treatment significantly increased the soil microbial biomass carbon and soluble organic carbon content of 0-40 cm;the abundance index between AUI1 and AUI2 treatment(ACE and Chao1)Significantly higher than other treatments;AUI2 and AUI3 treatments are respectively beneficial to increase the abundance of Bacteroides and Acidobacteria.The correlation results showed that Proteobacteria and Campylobacter phylum had a strong negative correlation with soil microbial biomass carbon and soluble organic carbon.Factor analysis showed that soil salinity,pH,microbial biomass carbon and soluble organic carbon were main control factors on the soil bacterial community composition.(2)The effect of straw interlayer combined with spring irrigation on the physicochemical properties of saline-alkali soil and microbial flora without irrigation was clarified.Through the consecutive three years of field micro-area positioning experiment that 2016-2018,we adopt the local conventional irrigation measures "autumn irrigation + spring irrigation"(CK)as a control,set up only spring irrigation without autumn irrigation(I100),and straw combined with local 100% and 90% spring irrigation without autumn irrigation(S100,S90)that total four treatments to study the effect that straw interlayer combine with different spring irrigation treatments on soil water and salt distribution,pH,nutrients,microflora and yield on continuous non-autumn irrigation and under continuous non-autumn irrigation conditions.The results showed that S100 and S90 treatments can significantly increase the crop water content before and after irrigation,reduce soil salinity,and increase the soil pH of 0-40 cm soil layer after crop harvest.S100 and S90 treatments can increase 0-40 cm soil nutrient content,yield and S100 treatment can significantly increase the relative abundance of the five bacterial phylum,S90 treatment can only significantly increase the relative abundance of bacteroides phylum for three consecutive years(except the effective phosphorus content of the 0-20 cm soil layer in 2017).The correlation results showed that the Actinobacteria with relatively high abundance only had a significant positive correlation with the soil alkaline nitrogen content,the Planctomycetes had a significant positive correlation with the soil available phosphorus content,however the Nitrospirae phylum had no significant correlation with the soil salt content,but with other soil Physicochemical properties had a significant or positive or negative correlation.Compared with CK and I100 treatments,S100 increased the average production by 28.03% and 36.01% respectively,and S90 treatments increased the average production by 17.34% and 24.55%.Factor analysis showed that soil moisture and salinity were main control factor on bacterial community composition.In summary,the autumn irrigation every 2-3 years(AUI2)is an optimization measure for the improvement of saline soil and water conservation,and straw interlayer combined with 90% spring irrigation(S90)is a local option program under non-autumn watering conditions. |
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