Labile soil carbon and nitrogen fractions under short and long-term integrated crop–livestock agroecosystems

Abstract

Context Labile soil C and N fractions are strongly influenced by agricultural management practices. Aims This study was conducted on three long-term (≥30 years) on-farm sites (sites 1–3), and one short-term (3 years) experimental site (site 4) to evaluate the impacts of integrated crop–livestock system (ICLS) on labile C and N fractions and β-glucosidase enzyme activity for the 0–5 cm soil depth. Methods Long-term management systems (ICLS, corn (Zea mays L.)/grazing–soybean (Glycine max (L.) Merr.)/grazing–cover crop/grazing), control (CNT, corn–soybean with no cover crop and no grazing), and a grazed pasture (GP) at sites 1–3 were compared. At site 4, the treatments included: ICLS (corn/grazing–soybean/grazing–oat (Avena sativa L.)–cover crop/grazing); CC (corn–soybean–oat–cover crop with no grazing); CNT (corn–soybean–oat–fallow with no grazing); and GP. Key results ICLS had higher hot water extractable organic carbon (HWC), cold water extractable organic carbon (CWC), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), potential carbon mineralisation (PCM) and potassium permanganate oxidisable carbon (POXC) than CNT under long-term management system. Long-term ICLS also enhanced β-glucosidase activity compared to CNT. ICLS had 72%, 214% and 60% higher glucosidase activity than the CNT at sites 1, 2 and 3, respectively. However, the C and N fractions and β-glucosidase activity were not affected by short-term ICLS (site 4). GP always had higher C and N fractions than ICLS and the CNT. There was a significantly positive relationship between SOC and labile C and N fractions, except POXC. Conclusions and implications Long-term inclusion of cover crops and livestock grazing in corn–soybean system was effective in enhancing labile soil C and N fractions.