Carbon saturation deficit and litter quality drive the stabilization of litter-derived C in mineral-associated organic matter in long-term no-till soil

Author(s)

Rodrigues, Lucas Antonio Telles ; Giacomini, Sandro J. ; Dieckow, Jeferson ; Cherubin, Mauricio R. ; Ottonelli, Anai Sangiovo ; Bayer, Cimelio

• Document type: Journal article
• Source: CATENA; v. 219, p. 11-pg., 2022-08-27.

Abstract

Long-term no-till cropping systems can induce significant differences in the mineral associated organic matter (MAOM) saturation levels but little is known on the effect of MAOM saturation on "new " C stabilization from added litter in different fractions of soil organic matter (SOM). We assessed the effect of C saturation deficit (Csd) in the MAOM on C stabilization in different SOM fractions in the surface layers of a sandy clay loam Acrisol under five no-till cropping systems adopted over 36 years in a field experiment. The cropping systems with varying C inputs led to a range of C content and Csd in the MAOM (< 20 mu m) in a thin soil layer (0-5 cm). In each field plot with different Csd levels,C- 13-labeled litter from shoot biomass of black oat (grass) and vetch (legume) was added at a rate equivalent to 4.5 Mg ha(-1)C in PVC collars. After 15-month field incubation, soil was sampled and physically fractionated. Higher C stabilization in MAOM was observed for legume than grass-derived C in the top 0-2.5 cm layer, but only for soils with higher C stabilization capacity. When litter-derived C stabilization in MAOM was limited by its previous C level close to saturation, C incorporation was greater in the intra-and inter -aggregate SOM fractions. Our findings revealed that Csd and litter quality affect C stabilization in surface soil layers of no-till soils, and when C stabilization in MAOM is low due to saturation of the MAOM fraction, the C accrual occurs preferentially in labile and intra-aggregate fractions in long-term no-till soils. Therefore, sus-tainable management practices that promote continuous and diversified C inputs involving legume cover crops are crucial to sustain C incorporation in relatively stable forms in long-term no-till soils. (AU)

• FAPESP's process: 20/15230-5 - Research Centre for Greenhouse Gas Innovation - RCG2I
• Grantee: Julio Romano Meneghini
• Support Opportunities: Research Grants - Research Centers in Engineering Program