Effects Of Different Tillage Managements On Soil Carbon And Nitrogen Cycling Microbial Diversity Under Double-cropping Rice Field

Soil microbial biomass is usually by used an index for reflect soil fertility and environmental quality for that it was reflect the change of soil quality.With the rapid development of agriculture,different tillage managements have been applied to in the process of rice(Oryza sativa L.)production,which has a profound impact on the soil microbial activities.In order to explore the effects of different tillage managements on rhizosphere and bulk soil carbon(C)and nitrogen(N)cycling microorganisms under Chinese milk vetch(Astragalus sinicus L.)and double-cropping rice systems in southern of China.The experiment were set up,and including four different tillage treatments:conventional tillage with crop residue incorporation(CT),rotary tillage with crop residue incorporation(RT),no-tillage with crop residue retention(NT),rotary tillage with residue removed as control(RTO).Therefore,the effects of different tillage and crop residue treatments on yield of rice,rhizosphere and bulk soil microbial biomass carbon(SMBC),microbial biomass nitrogen(SMBN),soil C and N cycling microorganisms and emzymes activities,active soil organic carbon(SOC)fractions,carbon pool management index(CPMI),soil microbial diversity at different main growth stages of early and late rice were investigated in the present paper.The results are as follows:(1)At different main growth stages of early and late rice,the average range of SMBC content in rhizosphere and bulk with CT,RT,NT and RTO treatments was 317.2-822.4,276.9-616.8 mg·kg^-1 and 286.8-792.0,281.1-617.8 mg·kg^-1,respectively.The average range of SMBN content in rhizosphere and bulk with CT,RT,NT and RTO treatments was38.6?64.5,33.1?50.6 mg·kg^-1 and 37.8-64.6,33.2-50.6 mg·kg^-1,respectively.At different main growth stages of early rice and late rice,the SMBC,SMBN and(Soil microbial quotient,SMQ)in rhizosphere and bulk with CT,RT,NT and RTO treatments were reached the maximum value at full heading stages of early rice and late rice.Meanwhile,the order of SMBC and SMBN content in rhizosphere and bulk with different tillage treatments decreased in the order CT>RT>NT>RTO.The yield of early and late rice with CT and RT treatments were significantly(P<0.05)higher than that of NT treatment,and yield of rice with different treatments decreased in the order CT>RT>NT>RTO.(2)At different main growth stages of early and late rice,the average range of labile organic carbon(LOC)content in the rhizosphere and bulk with CT,RT,NT and RTO treatments was 4.61-5.38,4.69-5.46 g·kg^-1 and 4.37-5.30,4.60-5.39 g·kg^-1,respectively.The average range of dissolved organic carbon(DOC)content in the rhizosphere and bulk with CT,RT,NT and RTO treatments was 270.12-316.68,268.46-314.35 and 264.37-312.58,260.18-308.64 mg·kg^-1,respectively.The average range of easily oxidized organic carbon(EOC)content in the rhizosphere and bulk with CT,RT,NT and RTO treatments was4.25-7.02,4.12-6.95 g·kg^-1 and 4.06-6.84,4.01-6.63 g·kg^-1,respectively.Compared with CT treatment,RT and NT treatments improved the rhizosphere activity of carbon pool(A)and carbon pool activity index(AI),but Compared with RT and NT treatments,CT treatments improved the carbon pool activity index(CPI)and carbon pool management index(CPMI).(3)At different main growth stages of early rice and late rice,C and N cycling rhizosphere microbe quantity with different tillage treatments showed a trend of increase and then decrease which reached the maximum value at the tillering stages of early rice and late rice.Meanwhile,the order of rhizosphere soil main C and N cycling microbe quantity with different tillage treatments decreased in the order CT>RT>NT>RTO.At different main growth stages of early and late rice,the average range of rhizosphere methane bacteria with different tillage treatments was 4.38-15.94,4.53-17.73(×10³cfu/g),respectively.The average range of rhizosphere abiogenous azotobacter with different tillage treatments was 9.52-26.32,10.08-27.18(×10⁵cfu/g),and the average range of rhizosphere nitrifying bacteria with different tillage treatments was 7.46-17.56,8.73-8.84(×10⁵cfu/g).At maturity stages of early and late rice,the order of rhizosphere and bulk soil main C cycling(methane bacteria,methane oxidizing bacteria,rhizobium)and soil main N cycling(abiogenous azotobacter,ammonifying bacteria,nitrifying bacteria)microbe quantity with different tillage treatments decreased in the order CT>RT>NT>RTO.(4)At different main growth stages of early and late rice,C and N cycling rhizosphere and bulk soil activities with different tillage treatments showed a trend of increase and then decrease.The average range of rhizosphere?-glucosidase activity with different tillage treatments was 7.16-19.82,7.39-15.22?g/(g·h),the average range of urease activity with different tillage treatments was 8.62-52.69,10.12-54.11 mg/(g·h)and the average range of acylamidase activity with different tillage treatments was 10.62-32.15,9.15-28.14 mg/(g·h).At maturity stages of early and late rice,the order of related to C and N cycling rhizosphere and bulk soil activities with different tillage treatments decreased in the order CT>RT>NT>RTO.(5)At maturity stages of early and late rice,the average range of Richness index with different tillage treatments was 15.56-17.15,14.53-16.03,the average range of Shannon index with different tillage treatments was 2.31-2.72,2.17-2.62,the average range of Mc Intosh index with different tillage treatments was 4.93-6.51,4.87-6.49.Amino acids and sugars are the main carbon sources for microbial utilization in rhizosphere soil under combined application of tillage with crop residues conditions.The order of rhizosphere average well color development(AWCD),Richness,Shannon and Mc Intosh indices with different tillage treatments decreased in the order CT>RT>NT>RTO.(6)As a result,it is benefit for increase the rhizosphere and bulk SMBC content,SMBN content,SMQ,C and N cycling rhizosphere and bulk soil microbe quantity and emzymes activities,active soil organic carbon fractions,CPMI,soil microbial diversity and grain yield of rice to taken conventional tillage or rotary tillage with crop residue incorporation practices under double-cropping paddy field in southern China.