| In order to explore the soil ecological effect of maize straw returning to the field and its influence on maize yield formation in arid region of Ningxia,and to rationally develop and utilize maize straw resources.In this paper,the farmland under the management of continuous maize straw returning was taken as the experimental object,five treatments were designed according to the method of single factor randomized block design,and no straw returning to the field(TO)was selected as the control,with the straw returning amount of 3000kg·hm-2(T1),6000kg·hm-2(T2),9000kg·hm-2(T3)and 12000kg·hm-2(T4).The change rules of soil chemical and biological characters and physical structure were analyzed,and the structure and function of soil microbial community were studied and predicted by phospholipid fatty acids and metagenomic sequencing technology,and the relationship among soil physicochemical and biological characters,soil microbial community,and maize yield were discussed.The results were as follows;(1)Compared with no straw returning,the contents of total carbon,available potassium and available nitrogen in the soil were significantly increased in T2,T3 and T4 in 2018(P<0.05),while the contents of total phosphorus and pH in the soil were significantly increased in T3 and T4,respectively(P<0.05).The contents of soil available nitrogen in T2 was significantly higher than that in TO in 2020(P<0.05).However,compared with 2018,the contents of total carbon,total nitrogen and available potassium contents in the soil were significantly increased in 2020,while C/N decreased(P<0.05).(2)Soil enzyme activities were changed by soil chemical traits.Catalase activity in T2 in 2018 and 2020 was significantly lower than that in TO(P<0.05),alkaline phosphatase activity in T4 in 2018 and 2020 was significantly higher than that in TO(P<0.05),urease activity in T3 and T4 in 2018 was significantly higher than that in TO(P<0.05),but had no significant change in 2020.With the increase of straw returning years,the activities of catalase and alkaline phosphatase in soil increased,and the activities of urease decreased.(3)Compared with no straw returning,clay grains in the soil in T1,T2 and.T3 in 2018 were significantly increased(P<0.05),while silt grains,very fine sand grains and fine sand grains were significantly decreased(P<0.05).In 2020,only T1 significantly increased clay grains(P<0.05),and decreased silt and very fine sand grains(P<0.05).Moreover,with the increase of straw returning years,clay grains in the soil continued to increase,while silt grains,very fine sand grains and fine sand grains continued to decrease.Pearson correlation analysis showed that the fractal dimension of soil was also significantly increased(P<0.05)driven by soil clay particles.(4)Compared with T0,bacteria and gram-positive bacteria in T1,T2,T3 and T4 and fungi under T3 were significantly decreased in 2018(P<0.05),while bacteria,fungi,actinomycetes,gram-positive bacteria and gram-negative bacteria were significantly increased in T3 compared with TO in 2020(P<0.05).In T2 and T3,the total phospholipid fatty acids(PLFAs)of microorganisms in soil in 2020 were significantly increased compared with that in 2018(P<0.01).Under continuous straw returning,F/B was increased and G+/G-was decreased.(5)The results of metagenomic sequencing showed that the number of microbial community genes in soil increased with the increase of straw returning amount.Bacteria accounted for the largest proportion of soil microbial community species,Proteobacteria and Acidobacteria were the dominant phyla in each treatment,while Sphingomonas,Pedosphaera and Gemmatimonas were the dominant phyla;T4 significantly increased the relative abundance of Acidobacteria(P<0.05),and significantly decreased the relative abundance of Pedosphaera and Gemmatimonas(P<0.05).With the increase of straw returning amount,the similarity of soil microbial community species composition increased,and the relative abundance of beneficial bacteria increased.The results of functional prediction showed that straw returning increased the soil microbial groups involved in CAZy,and T1 significantly increased the soil microbial groups involved in Polysaccharide Lyases and Glycoside Hydrolases(P<0.05),and T4 significantly increased the soil microbial groups involved in Auxiliary Activities and Carbohydrate Esterases(P<0.05);T4 also significantly decreased the microbial groups involved in the translation function of genetic information in the secondary functional layer of KEGG(P<0.05),and significantly increased the microbial groups involved in the transport and metabolism of carbohydrates and inorganic ions in eggNOG(P<0.05).(6)Pearson correlation analysis showed that soil F/B were the main factor affecting maize yield.Grain number per ear,100-grain weight,ear number per mu and maize yield had no significant changes after continuous maize straw returning,but the average yield in T4 was significantly increased by 7.81%compared with TO(P<0.05).And with the increase of straw returning years,the more straw returning amount,the more obvious trend of maize yield increase. |
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