| Water storage pit irrigation,as one kind of new-type water-saving irrigation model in arid and semi-arid areas of northern China,has researched a lot about the soil nitrogen distribution and soil moisture migration.Those research show that soil microbial diversity has important indicative function on migration and transformation of nitrogen and moisture,and also the evolution of eco-environment,which are caused by irrigation modes change.However,their relationship with micro-ecological environment has not been studied yet.In this research,the spatial distribution characteristics of soil moisture and nitrogen under the condition of different temperature system of water storage pit irrigation,and the spatial distribution characteristics of soil microbial biomass carbon,biomass nitrogen and soil enzyme under hydrothermal coupling effect of water storage pit irrigation were deeply analyzed.The quantity,composition and distribution of microorganism were explored using PLFA method;the DNA of different rhizosphere soil was extracted using Illumina Miseq high throughput sequencing method and biological information analysis process;quantitative analysis was made on the composition,abundance and genetic diversity of different rhizosphere soil microbial community structure under different irrigation treatment at molecular level through PCR amplification;the in-depth study on the microbial community composition and variation,and environmental factors such as nitrate nitrogen,ammonium nitrogen,moisture,microbial carbon,and microbial nitrogen were made by methods of cluster analysis,PCA(Principal Component Analysis),RDA(Redundancy Analysis)and Heatmap Analysis.The main research and findings are as follows:(1)Through the study of the spatial distribution characteristics of soil moisture under different water storage pit irrigation temperature-systems,it conducted that the radial migration rate exceeded far more than vertical rate during the early infiltration,and both of them fell over time.As the temperature rises,soil moisture migration rate increased gradually.The increment of radial migration distance and vertical migration distance present a power function with time.The shape of two-dimensional moisture content was similar to pear shape at different time-points during redistribution phase.The radial migration distance and the vertical migration distance increased gradually under the condition of different temperatures over time;the research show that the soil moisture near the pit walls moved away from the pit walls during redistribution phase,and the moisture content in wet soil was equally distributed gradually.And the rising temperatures can accelerate the speed of soil moisture redistribution,showing that the areas in which the soil moisture content exceed that of soil foundation got wider,and the soil moisture content near the pit walls got lower.(2)Through the study of the spatial distribution characteristics of nitrogen under different water storage pit irrigation temperature-systems,it determined that the rising temperatures could not only accelerate urea hydrolysis reaction rate,but also promote nitration reaction progress and restrain ammonium nitrogen accumulating.When the temperature got 25?~35?,urea hydrolysis reaction progress spend about 15 days,and the rising temperatures had no prominent effect on the radial migration rate of ammonium nitrogen.Soil nitrification was weak at low temperatures,it strengthened when temperatures rose gradually,and the best temperature was 25?~35?.The nitration reaction progress was restrained when soil moisture rate got too high.(3)Studying on the characteristics of soil microbial biomass carbon and nitrogen affected by coupling of water and nitrogen under the condition of water storage pit irrigation,the contents of SMBC and SMBN in the vertical space of water storage pit irrigation decreased with the deepening of soil layer.Compared with surface irrigation,the content of SMBN and SMBC decreased slowly.Under the condition of surface irrigation(G4 treatment),the contents of SMBC and SMBN in radial space were all decreased with the increase of distance from the trunk,the highest value appeared at 20cm;Under the condition of water storage pit irrigation(G1,G2,G3),in the 0-30 cm soil layer all increased with the increase of distance from the tree trunk and then decreased,the highest content of SMBN and SMBC appeared at 35 cm,the least value appeared at 50 cm,in the 30-70 cm and 70-100 cm soil layers it increased with the increase of distance from the trunk,the highest value appeared at 50 cm.(4)Studying on the characteristics of urease,the activity of invertase and phosphatase in soil were affected by coupling of water and nitrogen under the condition of water storage pit irrigation,These results showed that under different irrigation treatments the activities of urease,invertase and phosphatase in the vertical space were gradually decreased with the increase of depth under the surface irrigation(G4),the highest value appeared in the surface layer(0-30cm),under the water storage pit irrigation(G1,G2,G3),activities of urease,invertase and phosphatase increased first with the increase of depth and then decreased,the highest value appears in the deep(30-70cm);Under different treatment,the activities of soil enzymes(urease,invertase,phosphatase)were increased and then decreased with the redistribution time after water and nitrogen irrigation,finally maintainned a stable change characteristics,the activity reached the highest value at 3 days,the activity of Urease and phosphatase increased first and then decreased after irrigation 1-15 days,the activity was maintained at a fixed level after 15 days,the activity of invertase increased first and then decreased after irrigation 1-7days,Its activity after 7 days fluctuated slightly in a stable value;The urease,invertase and phosphatase activities were positively correlated with temperature.Studying on the characteristics of urease,invertase and phosphatase activity in soil affected by coupling of water and nitrogen under the condition of water storage pit irrigation,These results showed that the urease,invertase and phosphatase activities of different irrigation treatments were decreased with the increase of distance from the trunk in the radial space under the condition of surface irrigation(G4 treatment),the highest value appeared at 20cm;Under the water storage pit irrigation(G1,G2,G3),activities of urease,invertase and phosphatase increased first with the increase of distance from the trunk and then decreased,the enzyme activity of 35 cm was the highest and lowest in 50 cm,the 30-70 cm and 70-100 cm soil layers increased with the increase of distance from the trunk,the highest value appeared at 50cm;Surface irrigation in the topsoil(0-30cm)enzyme(urease,invertase,phosphatase)activity was higher than that of water storage pit irrigation,while the activity of water storage pit irrigation was higher than that of surface irrigation in the middle deep(30-70 cm,70-100cm),the roots of apple trees were distributed in the middle deep layers,in the result,the higher activity of urease,invertase and phosphatase in the middle deep layers contributed to the absorption of nitrogen,carbon and phosphorus in soil,which was beneficial to the growth of fruit trees,meanwhile water storage pit irrigation applied water and fertilizer directly to the fruit in the root,which reduced the surface evaporation and ineffective irrigation of surface soil,there was a great water-saving potential,from the point of view of soil enzyme activity and water saving,this paper pointed out the superiority of the new method of water storage pit irrigation.(5)The quantity and species distribution of soil microorganisms under different irrigation methods and years were analyzed by means of PLFA phosphoric acid,The results showed that the water storage pit irrigation changed the soil microbial species,Among them,the PLFA species number of surface irrigation(DM)was 18,the PLFA species number of Water storage pit irrigation for one year(XY)was 17,while the PLFA species number of Water storage pit irrigation for one year(XS)was 19;These results indicated that the water storage pit irrigation changed the living environment of the original microorganisms,because of not adapting to the new environment part of the microbial reduced,dead or even eliminated.After three years of domestication,some adapted to the new environment and multiplied,even new microbes were derived.Based on the analysis of soil microbial community distribution,the results showed that water storage pit irrigation had little effect on Gram negative bacteria(G-),while the content of fungi increased gradually under the condition of water storage pit irrigation;The bacteria showed a tendency to decrease first and then increase,Actinomycetes and Gram-positive bacteria(G)gradually decreased.(6)The genetic diversity of bacterial 16 S rRNA was different in different types of soils,the effects of different irrigation types on the diversity of bacteria and fungi microbial communities in soil rhizosphere were basically the same.The species richness,diversity and uniformity index of bacteria and fungi were in the order of water storage pit irrigation 3 years(XS)> water storage pit irrigation 1 year(XY)> ground irrigation(DM);The dominance index was: ground irrigation(DM)> water storage pit irrigation 1 year(XY)> water storage pit irrigation 3 years(XS).It was mainly due to the construction of the new pit built under water storage pit irrigation 1 year(XY)mode destroyed the original soil structure,which blocked the horizontal capillary transport channel of soil moisture,nutrient and microbial surface.At the same time,the soil water and nutrient migration pathways changed greatly,compared with ground irrigation,which changed the soil microenvironment of soil rhizosphere and induced the change of soil microbial community structure.With the increasing time of water storage pit irrigation,the water and nutrients in the soil under the new irrigation mode gradually migrated obliquely below the storage pits,which accelerated the maturation of the lower soil and formed new transport channel of water,nutrients and microbes,the diversity and abundance of the microbial community structure also increased with the increase of the irrigation years.(7)The microbial soil community in the study area was mainly located in 33 doors,397 genera.Among them,the dominant bacteria of bacteria mainly include: Proteobacteria ? Acidobacteria ? Actinobacteria ? Chloroflexi ?Planctomycetes ? Gemmatimonadetes ? Bacteroidetes and Nitrospirae,Proteobacteria is the most dominant strain.The microbial soil fungal community in the study area were mainly located in 28,86 genera.The dominant species of soil fungi mainly included Ascomycota,Basidiomycota and Zygomycota,the most abundance Fungal door is Ascomycota.(8)The results of PCA analysis in soil samples under different irrigation conditions were consistent with the results of cluster analysis,indicating that long-term water storage pit irrigation will affect the composition of fungi and bacteria in the soil.Compared with the ground irrigation,the water storage pit irrigation changed the soil water and nutrient transportation channel,and induced the micro-organisms to 30-70 cm deep aggregation,which greatly changed micro-ecological environment of the apple rhizosphere soil,resulting in the death of some micro-organisms which failed to adapt to the new environment,and gradually eliminated,while domesticate the micro-organisms which adapt to the new environment,lead to a large number of breeding,resulting in the differences of microbial composition in different groups.(9)The correlation analysis between environmental factors and soil microbial community structure showed that environmental factors such as NO3-N,NH4-N,MC,SMBC and SMBN had an effect on soil microbial community change,the results of RDA redundancy analysis showed that the change of SMBN and NO3-N caused by water storage pit was the main factor causing the change of soil microbial fungi community;Heatmap analysis showed that the accumulation of NO3-N mainly caused the increase of Ascomycota community,and the increase of SMBN caused the increase of Ascomycota and Basidiomycota.The accumulation of NO3-N in the soil was also the main cause of the change of bacterial microbial community,which mainly promoted the growth of bacteria such as Actinobacteria,Gemmatimonadetes,Chloroflexi,Thermotogae and Nitrospirae. |
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