Effects of integrating grass‐clover leys with livestock into arable crop rotations on soil carbon stocks and particulate and mineral‐associated soil organic matter fractions in conventional and organic systems

International audienceOrganic systems, integrated crop-livestock systems (ICL) and leys are posited as strategies to increase soil carbon (C) stocks. However, previous studies have: i) only considered one driver of change; ii) evaluated soil C content instead of stocks; iii) been limited to the 0.20 m depth; iv) used short-term leys; and v) rarely assessed the distribution of C among soil organic matter (SOM) fractions, which relates to C stabilisation. The aim of this study was to investigate the impact of conventional vs. organic agricultural systems, grazing regimes (non-grazed vs. grazed) and different proportions of temporary grass-clover leys in crop rotations (ley time proportion-LTP) on soil C stocks and C distribution among SOM fractions down to 0.60 m soil depth. SOM fractions assessed were particulate organic matter (POM>53 μm), heavy fraction (HF>53 μm) and mineral-associated silt and clay fraction (SC