Conservation Tillage Impact on Topsoil and Deep Soil Aggregation and Aggregate Associated Carbon Fractions and Microbial Community Composition in Subtropical India: A Review

Soil macro-aggregate turnover and micro-aggregate formation: A mechanism for C sequestration under notillage agriculture had its genesis in attempts to identify and isolate soil organic matter (SOM) fractions that reflect the impacts of climate, soil physiochemical properties and physical disturbance on the soil organic carbon balance.Soil tillage can affect the formation and stability of soil aggregates.The disruption of soil structure weakens soil aggregates to be susceptible to the external forces of water, wind, and traffic instantaneously, and over time.The application of chemical fertilizers (NP) alone did not alter labile C fractions, soil microbial communities and SOC mineralization rate from those observed in the CK treatment.Whereas the use of straw in conjunction with chemical fertilizers (NPS) became an additional labile substrate supply that decreased C limitation, stimulated growth of all PLFA-related microbial communities, and resulted in 53% higher cumulative mineralization of C compared to that of CK.The SOC and its labile fractions explained 78.7% of the variance of microbial community structure.The degree of soil disturbance and the use of crop residues influence the availability of organic compounds and minerals for the soil biota.This conglomerate of elements can affect population, diversity and activity of the different soil organisms.Besides, soil communities also have an impact on soil physical and chemical conditions.From macro-fauna to micro-fauna, all parts interact and therefore play a role in nutrient cycling and organic matter decomposition.Soil microbial community compositions were changed with straw return.Crop straw return significantly increased total phospholipid fatty acid (PLFA), bacterial biomass and actinomycete biomass by 52, 75 and 56% but had no significant effects on PLFAs as compared to N treatment.MBC and TOC were the two main factors affecting microbial communities under short-term crop straw return.The labile part of organic carbon has been suggested as a sensitive indicator of changes in soil organic matter.Conservation tillage (NT and S) increased microbial metabolic activities and microbial index in >0.25 and <0.25 mm aggregates in the 0-5 cm soil layer.