Effects of moisture and temperature on C and N mineralization from surface-applied cover crop residues

Cover crop (CC) decomposition and subsequent release of nitrogen (N) are highly influenced by residue water potential (psi) and temperature (T). To evaluate how carbon (C) and N mineralization from surface-applied CC residues responds to changes in psi and T, a controlled microcosm experiment was conducted for 150 days with three CC residues (early-killed cereal rye (Secale cereale L.), late-killed cereal rye, late-killed crimson clover (Trifolium incarnatum L.), and a soil-alone control) under different psi (-0.03, -1.5, -5, and -10 MPa) and T (15, 25, and 35 degrees C) conditions. Headspace gas was sampled periodically to determine carbon dioxide (CO2) and nitrous oxide (N2O) emissions. Soil inorganic N was determined by destructive sampling at 15, 30, 60, 100, and 150 days. Temporal dynamics in C and N mineralization from surface-applied CC residues were adequately described by first-order rate kinetic models. Early-killed rye and crimson clover (low C:N) residues decomposed quickly and mineralized N, whereas, late-killed rye residue (high fiber content and C:N) immobilized N. The normalized values of C and N mineralized from surface-applied CC residues increased exponentially with increasing psi from -10.0 to -0.03 MPa. Increasing T from 15 to 35 degrees C further amplified the effect of psi, suggesting a strong interactive effect of psi and T on C and N mineralization from CC residues. Mathematical equations were developed to describe these interactive effects. Existing computer simulation models (e.g., CERES-N) could be improved by integrating these equations to simulate the effect of environmental conditions on surface-applied CC residue decomposition and N mineralization.

Automated summary

The decomposition and N release from cover crop residues are influenced by residue water potential and temperature. Different cover crop residues respond differently to changes in water potential and temperature, with early-killed residues decomposing quickly and mineralizing N, and late-killed residues immobilizing N. The interactive effects of water potential and temperature on C and N mineralization from cover crop residues can be described by mathematical equations.