Study On Soil Fauna Communities In Sugarcane Field Under Different Irrigation Modes In Chongzuo,Guangxi

Water saving irrigation could enhance the water storage capacity of soil,combinn-ing with the improvement ofsoil nutrient conditions and soil micro-environment in sugarcane filed.In order to investigate the effect of different irrigation modes on soil fauna community structure in sugarcane field in Guangxi,we set five kinds of irrigati of irrigation modes,including subsurface drip irrigation,surface drip irrigation,tube-well irrigation,sprinkler irrigation and micro-sprinkler irrigation,and also one control without any irrigation in sugarcane field.We investigated soil fauna communities and soil physicochemical properties at five growth stages of sugarcane(tillering,early period of elongation,boom growth,last period of elongation and the maturing stage)from May to November in 2015.The main results are as follows:(1)In this study,a total of 3526 soil fauna individuals were caught,and they belonged to 2 phyla,10 classes,26 orders and 48 families,repectively.The dominant species were Hymenoptera,Collembola and Acarina,respectively.And common species were Diptera,Isoptera,Diptera larvae and Coleoptera,respectively.(2)The group number and density of macro-soil fauna were highest at maturing stage,while the group number of meso-and micro-soil fauna was highest at the maturing stage,and the density was highest at the boom growth stage of sugarcane.There were significant differences of soil fauna density among different irrigation modes(P<0.05),but no significant differences of the group number(P>0.05).The soil fauna density,Shannon-Wiener diversity index(H'),Pielou evenness index(E),and Margalef richness index(D)were significantly higher compared with those in irrigated plots.The subsurface drip irrigation and sprinkler irrigation were significantly higher than those of other plots(P<0.05).However,the trend of Simpson dominance index(C)was opposite.(3)The density of meso-and micro-soil fauna was 25012 ind.m12 in 0-5 cm soil,which Was alinostl.3-times than that in 5-10 cm soil and almost 2.3 times than that in 10-15 cm soil.The difference of soil fauna density was obvious among different soil depths.The results showed that the different irrigation modes did not alter the soil surface-aggregation.However,there were significant differences of group number and density of species under different irrigation modes(P<0.05).And the significant effect of different irrigation modes on soil vertical structure was mainly manifested in the significant increases of soil fauna and density at each soil depth.(4)The growth stages of the macro-soil fauna in different irrigation modes changed a little.In the subsurface drip irrigation and sprinkler irrigation which had the highest density,the macro-soil fauna showed the maximum density during the maturing stage and the minimum density during the tillering stage.While in other irrigation modes,different degrees of changes have taken place in the growth stages of the macro-soil fauna,which indicated that the subsurface drip irrigation and sprinkler irrigation were helpful to enhance the community structures' stabilities of the macro-soil fauna.Under different irrigation modes,the dynamic changes of meso-and micro-soil fauna fluctuated significantly.The density of meso-and micro-soil fauna showed different dynamic changes during different growth periods,and the rather low density appeared during the tillering stage.(5)The effects of different irrigation modes on soil physicochemical properties in sugarcane fields were significant(P<0.05).Soil water content,organic matter,available nitrogen,available phosphorus and available potassium were higher in subsurface drip irrigation,surface drip irrigation,tube-well irrigation,sprinkler irrigation and micro-sprinkler irrigation plots than those inirrigation plots With the highest level under subsurface drip irrigation and sprinkler irrigation.Soil water content and organic matter significantly affected the macro-soil fauna density and its dominant group(Hymenoptera)(P<0.05).The effects of soil water content on the density,group number,dominant group of Hymenoptera and Acarina were significant(P<0.05),and the effects of soil organic matter on the density of small and meso-and micro-soil fauna,the group number,the dominant group of Hymenoptera and the Acarina were significant(P<0.05).