Validation of an agroecosystem process model (AGRO-BGC) on annual and perennial bioenergy feedstocks

We also estimated long-term implications of varying residue removal rates on SOC. Model estimates compared to field data tested the hypothesis that long-term increased residue removal decreases SOC. Field observations showed 0.17, 0.09, and a −0.17 t C ha−1 yr−1 change for control, harvest, and bare grass residue removal treatments, respectively. Simulated SOC loss was greatest for the most intensive residue removal scenarios (−0.48 and −0.68 t C ha−1 yr−1 for corn and grass, respectively), compared to no-harvest scenarios that increased SOC by 0.05 t C ha−1 yr−1 for both corn and grass. AGRO-BGC estimated a 0.07 t C ha−1 yr−1 loss under corn residue harvest, while estimating 0.09 t C ha−1 yr−1 loss for grass. Results suggest long-term increased corn and grass residue harvest (beyond grain) for biofuel feedstock will decrease SOC and soil productivity by approximately 15% in corn and 21% in grass systems over 47 years.