Abstract
Decline in soil organic carbon (SOC) and the associated impacts on crop production under conventional farming raises concerns on how alternative management practices increase SOC sequestration and improve agricultural sustainability. This study aimed to understand SOC mineralization kinetics with different cover crop (CC) residue amendments. Soil samples were collected from a fallow and three CC (pea, oat, and canola) plots. Soil samples from the CC plots were manipulated with zero, five, and 10 Mg ha−1 of the respective CC residues. All soil samples were incubated for eight weeks, SOC mineralization was monitored, and the first order kinetic and parabolic equation models were fitted to the observed data for estimating labile SOC (C0), and the decomposition rate constant (k). Subsequent comparisons of fitted model parameters were based on the first order kinetic model. The C0 varied with the residue amount while k varied with CC type. C0 was 591–858% greater with 10 Mg ha−1 and 289–456% greater with five Mg ha−1 residue additions while k was 122–297% greater with 10 Mg ha−1 and 94–240% greater with five Mg ha−1 residue additions when compared to the fallow treatment. The CC residue stimulated cumulative carbon mineralization (Cmin) irrespective of CC type, suggesting that cover cropping has potential to improve SOC cycling in agroecosystems.
Highlights
Crop residues are the main input in maintaining soil organic carbon (SOC) and nutrients in agricultural soils
The long-term balance between soil carbon inputs through organic residues and losses through mineralization and oxidation determines the SOC storage and nutrient cycling in agroecosystems [1]
The results of this study revealed that amending soil with a higher rate of crop residue increased potential carbon mineralizable, an indicator of labile soil organic matter
Summary
Crop residues are the main input in maintaining soil organic carbon (SOC) and nutrients in agricultural soils. Soil carbon inputs through crop residue and cover crops increase soil microbial biomass and activity, soil water storage, and in the long-term improve SOC sequestration [4]. In disturbed soils such as in conventional agricultural crop fields, the high efflux of CO2 may be associated with organic inputs as well as soil cultivation that breaks aggregates and brings organic residues in contact with soil microorganisms [7]. The latter process may not necessarily increase SOC storage, but may accelerate residue decomposition and nutrient cycling. There are discrepancies in the literature regarding the effects of soil type, amendments, environmental conditions, residue inputs, and tillage practices on SOC mineralization kinetics, which warrants further study [11,12,13,14,15]
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