Effect of Longterm Tillage Management on Soil Organic Carbon Fractions and Enzyme Activities in Bulk and Rhizosphere Soils

ABSTRACT The biogeochemical cycling of carbon (C) and its associated enzyme activities are vital for maintaining crop productivity and play a crucial role in soil C sequestration. However, distinguishing the specific effects on the rhizosphere and bulk soils soil organic C (SOC), labile organic C (LOC) and enzyme activities presents a significant knowledge gap that needs to be addressed. The objective of this study is to explore the effects of various tillage management practices on soil C fractions and enzyme activities, while examining their interrelationships in both the rhizosphere and bulk soil. We measured SOC and LOC fractions, including microbial biomass C (MBC), dissolved organic C (DOC), particulate organic C (POC), easily oxidizable C (EOC) and light‐fraction organic C (LFOC), as well as soil enzyme activities, including cellobiohydrolase (CBH), β‐glucosidase (BG) and xylosidase (BXYL) after 10 years of different tillage management practice. The tillage management included no‐tillage with straw return (NTS), mouldboard ploughing with straw incorporated into the 0–20 cm soil layer (MPS) and conventional tillage practice (CT). The results demonstrated that NTS and MPS significantly increased both rhizosphere and bulk SOC contents, LOC fractions and enzyme activities compared to the CT treatment. Moreover, the rhizosphere exhibited higher SOC, LOC and enzyme activity levels than the bulk soil. Redundancy (RDA) analysis unveiled that tillage practices boost soil enzyme activities through the modulation of SOC and LOC levels. RDA analysis also indicated significant impacts of tillage management techniques and soil type on SOC, LOC components (including MBC, DOC, POC, EOC, LFOC) and C‐cycle enzyme activities (CBH, BG, BXYL). Notably, soil CBH activity exhibited positive associations with MBC, DOC and LFOC, while no significant correlations were observed between CBH and SOC, POC or EOC. Furthermore, it highlights the differential responses of SOC, LOC and enzyme activity to tillage management in both the rhizosphere and bulk soil. These findings contribute to a deeper understanding of the interactions between the rhizosphere and tillage management, offering valuable implications for assessing the ecological dynamics of rhizosphere soil. Such insights can guide the development of plant‐focused strategies aimed at enhancing productivity and promoting sustainability within agroecosystems.