Simulating long-term soil carbon storage, greenhouse gas balance, and crop yields in semi-arid cropping systems using DayCent model

Authors: BISTA, PRAKRITI - New Mexico State University; HARTMAN, MELANNIE - Colorado State University; Del Grosso, Stephen - Steve; THAPA, VESH - New Mexico State University; GHIMIRE, RAJAN - New Mexico State University

Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2023
Publication Date: 1/17/2024
Citation: Bista, P., Hartman, M., Del Grosso, S.J., Thapa, V., Ghimire, R. 2024. Simulating long-term soil carbon storage, greenhouse gas balance, and crop yields in semi-arid cropping systems using DayCent model. Nutrient Cycling in Agroecosystems. https://doi.org/10.1007/s10705-023-10335-4.
DOI: https://doi.org/10.1007/s10705-023-10335-4

Interpretive Summary: Crop-fallow systems are common in dry regions of the Southwestern USA, but long fallow periods promote erosion of bare soil and losses of soil carbon. Cover crops offer an opportunity to address concerns associated with fallow. University and government scientists used the DayCent ecosystem model to estimate carbon sequestration and greenhouse gas emissions under no-till winter wheat - sorghum -fallow rotations with and without cover cropping. They predicted about 40% more soil carbon storage and decreases in net greenhouse gas emissions of 6-12% with cover cropping compared to conventional fallow. Cover cropping could improve soil health and sustainability of limited irrigation cropping systems while maintaining cash crop production.

Technical Abstract: Crop-fallow systems are common in the arid and semi-arid Southwestern USA. Long fallow periods between crops hinder biomass production and soil organic carbon (SOC) accumulation. Increasing weather variability, decreasing precipitation, and declining water resources have led to the rapid transition of croplands from irrigated to limited irrigation or dryland cropping, which further poses a challenge to residue production. Cover cropping can reduce the fallow period, increase residue returned to the soil and increase SOC. Despite the multiple benefits of cover cropping, there is uncertainty in their role in greenhouse gas (GHG) mitigation and subsequent cash crop yield in arid and semi-arid regions. This study aimed to calibrate and validate the DayCent ecosystem model for croplands transitioning to limited irrigation and predict the long-term changes in soil organic carbon (SOC) and GHG emissions. We estimated SOC sequestration, nitrous oxide (N2O) emissions, and methane (CH4) uptake in no-till winter wheat (Triticum aestivum L.)-sorghum (Sorghum bicolor L. Moench)-fallow rotations with and without cover cropping. The cover crops considered were pea (Pisum sativum L.) and oat (Avena sativa L.). DayCent was verified with five years of observations and achieved R2 values of 0.81, and 0.24, for wheat and sorghum total yield (grain and biomass). Observed cover crop biomass was highly variable (R2 = 0.11) but DayCent captured the observed trend and treatment difference with no significant model bias. The simulations conducted for three decades investigated long-term net GHG balance. The model predicted 39.2% to 42.7% more SOC sequestration with cover cropping and no-tillage together compared to no-tillage fallow alone despite the limited-irrigation management in the study agroecosystem. In addition, cover crops increased the potential of no-tillage fallow to reduce net GHG balance by 6.6% to 11.9% while maintaining comparable cash crop yield among all the treatments. Cover cropping could improve soil health and sustainability of limited irrigation cropping systems while maintaining crop production.