Adapting an Agroecosystem Model to Account for Cover Crop Management in the Midwest USA

Abstract

Agroecosystem modeling tools can provide insights into cover crop performance under varying environmental and management combinations. This study aims to (1) simulate winter cereal rye cover crops in Agro-IBIS, a process-based terrestrial ecosystem model and (2) evaluate Agro-IBIS performance in predicting aboveground biomass (AGB) of winter cereal rye cover crops. To achieve this, the winter wheat plant functional type (PFT) in Agro-IBIS was adapted to represent winter cereal rye as a cool-season winter annual grass cover crop. We adjusted the specific leaf area (SLA), maximum Rubisco activity at 15 oC (Vc­,max), growing degree days (GDD) base temperature, GDD upper threshold, and planting and termination dates as indicated by observed data. Model performance was evaluated using observed data from continuous maize and maize-soybean rotation systems in southern Wisconsin. The model effectively represented interannual variability of winter cereal rye cover crop AGB that was measured in southern Wisconsin in continuous maize and maize-soybean rotation systems. This demonstrated the efficacy of Agro-IBIS in representing establishment success, cold-hardening, spring green-up, and AGB accumulation of winter cereal rye cover crops in conventional annual grain cropping systems. Environmental drivers like growing season length, accumulated GDDs, precipitation amount, and solar radiation were key drivers of cover crop AGB production, which is generally represented by Agro-IBIS. This suggests the model would be an accurate tool to use when investigating the impact of climate change or increased weather variability on the success of cover crops across the Midwest and beyond.

Keywords: winter cereal cover crops, biomass, cropping systems, agroecosystem modeling, Agro-IBIS, model validation, Simulation