Effects Of Tillage Managements On Soil Organic Carbon,Soil Microbial And Nematodes Communities

Tillage is an important management to improve soil quality of cultivated soil.The fluvo-aquic soil area of the North China Plain is an important food production area in China.The long-term single tillage management in this area tends to aggravate the decline of soil fertility,and it is also easy to cause problems such as soil compaction.Soil aggregates are the foundation of soil structure and are closely related to soil organic carbon,soil microbial and nematodes communities.At present,the researches on the impact of tillage managements on soil organic carbon,soil microbial and nematodes communities have mostly focused on their reactions in soil,while less attention has been paid to that in soil aggregates.For this reason,four tillage treatments were set up in Qihe County,Shandong Province as follows,conventional rotary tillage with straw returned(RT),deep ploughing with straw returned(DP),subsoiling with straw returned(SS)and no-tillage with straw returned(NT).Soil samples were sieved into five particle sizes of aggregates: >5 mm,5–2 mm,2–1 mm,1–0.25 mm and <0.25 mm,so that we colud explore the effects of tillage managements on soil organic carbon,soil microbial and nematodes communities in soil aggregates.This study aims to provide a theoretical reference for seeking suitable tillage managements for wheatcorn rotation system in the fluvo-aquic soil area of the North China Plain.The main conclusions of the study are as follows:1.No-tillage treatment and deep ploughing treatment were conducive to the stability of soil aggregate structure.Compared with traditional rotary tillage,no-tillage significantly showed higher mass fraction of soil large aggregates,higher values of WMD and GMD,and lower value of Dm.Deep ploughing also showed significant higher mass fraction of >5 mm soil aggregates and values of WMD and GMD.2.No-tillage treatment and deep ploughing treatment were conducive to the improvement of soil fertility.Compared with traditional rotary tillage,no-tillage significantly increased the SOC content and labile organic carbon fractions DOC and POC content in soil,especially in large sizes of soil aggregates.In addition,no-tillage treatment increased the stability of organic carbon in large aggregates.Deep ploughing was beneficial to the organic carbon from the straw to enter the large sizes of soil aggregates and increased the content of DOC and POXC in the soil,especially in large sizes of soil aggregates.3.Deep ploughing treatment improved the soil microbial community structure to a certain extent,which is conducive to the improvement of soil carbon sequestration capacity.Compared with traditional rotary tillage,deep ploughing showed significant higher content of fungus and fungus/bacteria ratio in the soil and >5 mm aggregates.It improved the buffering capacity of the soil ecosystem.In each treatment,the microbial communities in large sizes of soil aggregates were mainly affected by the ratio of carbon to nitrogen,water content,p H and aggregate mass fraction,while the microbial communities in small sizes of soil aggregates were mainly affected by soil organic carbon and total nitrogen.4.Deep ploughing treatment and subsoiling treatment showed higher proportion of bacterivores and lower proportion of plant-parasites in large sizes of soil aggregates.The two tillage managements improved the nutrient environment of farmland to a certain extent.And their higher values of WI were beneficial to bacterivores participating in the organic matter and nutrient cycle in the soil food web.In addition,their higher values of NCR than that in rotary tillage treatment indicated the enhancement of the bacterial decomposition pathway of soil organic matter in large sizes of soil aggregates.The total number of soil nematodes and nematodes of feeding groups in each treatment were negatively correlated with the content of soil organic carbon,soil p H and the content of total nitrogen.But there was not significantly correlated with soil water content,carbon to nitrogen ratio,and mass fraction of soil aggregates.5.The structural equation model indicated that soil labile organic carbon affected soil microbial communities,which in turn affected soil nematode communitie,and ultimately affected soil organic carbon content in this study.Specifically,labile organic carbon affected the total amount of PLFAs(path coefficient is 0.37,the same below),fungi/bacteria(-0.19)and Shannon diversity index of microorganisms(-0.10).While the total amount of PLFAs affected the total number of nematodes(-0.02),fungi/bacteria and the Shannon diversity index of microorganisms affected the Shannon diversity index of nematodes(0.11 and 0.05,respectively).The total number of nematodes and the Shannon diversity index of nematodes have significant negative effects on soil organic carbon content(-0.46 and-0.28,respectively).In general,both deep ploughing and no-tillage were conducive to the stability of soil structure and the improvement of soil fertility.In addition,deep ploughing could increase the content of soil fungi and was conducive to the storage of soil organic carbon,while no-tillage improved the soil nutrient environment and was conducive to the turnover of soil nutrients and organic matter which soil nematodes participate in.