Modeling Perennial Groundcover Effects On Annual Maize Grain Crop Growth With The Agricultural Production Systems Simulator

The inclusion of perennial groundcover (PGC) in maize (Zea mays L.) production offers a tenable solution to natural resources-related concerns associated with conventional maize; however, insight into system management and key information gaps is needed to guide future research. We therefore extended the Agricultural Production Systems sIMulator (APSIM) to an annual and perennial intercrop by integrating annual and perennial APSIM modules. These were parameterized for Kentucky bluegrass (Poa pratensis L.) or creeping red fescue (Festuca rubra L.) as PGC using a 3-yr dataset. Our objectives for this intercropping modeling study were to: (a) simultaneously model a PGC and annual cash crop using APSIM software; (b) utilize APSIM to understand interactive processes in the maize-PGC system; and (c) utilize the calibrated model to explore both production and environmental benefits via scenario modeling. For the first objective, the integrated model successfully predicted maize total aboveground biomass (relative root mean square error [RRMSE] of 13-27%) and PGC above- and belowground tissue N concentration (RRMSE of 11-18%). The calibrated model captured observed trends in PGC biomass accumulation and soil nitrate. For the second objective, model analysis showed that competition for light was the primary PGC-related maize yield-penalty factor, while water and N affected maize yield later in the growing season. In the third objective, we concluded that effective PGC suppression produces minimal maize-yield loss and significant environmental benefits; conversely, poor groundcover suppression may produce unfavorable environmental consequences and decrease maize grain yield. Effective PGC suppression is key for long-term system success.