A Wheat Grazing Model for Simulating Grain and Beef Production: Part I—Model Development

Abstract

It is a common practice to grow winter wheat (Triticum aestivum L.) as a dual-purpose crop in the U.S. Southern Great Plains to decrease production risk and to increase profit margin through cattle (Bos taurus) production. Crop management of the dual-purpose wheat is complex because of the tradeoffs between beef production and wheat grain yield. A wheat grazing model helps in making optimal decision. The objective of this study was to develop and incorporate a grazing and metabolizable energy-based cattle growth module into the Decision Support Systems for Agrotechnology Transfer (DSSAT) to simulate beef and wheat grain production. The wheat grazing model was comprised of wheat growth, wheat-cattle interaction, and cattle growth components. Wheat growth was simulated by the cropping system model (CSM) of DSSAT.For the wheat-cattle interface, removals of canopy biomass and leaf area by grazing were estimated daily. Predicted grain yield was also reduced by 50 kg ha -1 per day for each day of grazing past the first hollow stem stage. Cattle growth rate was based on a metabolizable energy intake. Maximum voluntary daily intake was estimated based on stocker body weight and forage quality, and is further adjusted for actual forage availability, temperature, and adaptation status during the first two week of grazing to estimate the actual daily intake. Changes in wheat growth processes brought about by grazing, including a grazing effect on the delay of plant phenological development, are not simulated in the model. Field experiments to characterize any such effects are needed to help fine-tune the model.

Optimal Grazing Termination Date for Dual-Purpose Winter Wheat Production

“…In a typical year 12 million acres are planted to winter wheat in New Mexico, Oklahoma, and Texas. It is likely that more than half, 6 million acres, are managed to produce dual-purpose wheat and provide fallwinter forage for 3 million stocker cattle (Brorsen et al 1983;Coulibaly, Bernardo, and Horn, 1996;Epplin, Hossain, and Krenzer, 2000;Fieser et al, 2006;Hossain, Epplin, and Krenzer, 2003;Kaitibie et al, 2003a;Ralston et al, 1990;Redmon et al, 1995;Rodríguez et al, 1990;Whitson et al, 1973;Zhang et al, 2008). Dual-purpose wheat is also an important crop in Argentina (Arzadún et al, 2006), Australia, Morocco, Pakistan, Syria, and Uruguay (Rodriguez et al, 1990).…”

Systems approaches to beef cattle production systems using modeling and simulation

“…1991). In a recent study, Zhang et al . (2008) reported a wheat grazing model for simulating grain and beef production.…”

Variable Environment and Market Affect Optimal Nitrogen Management in Wheat and Cattle Production Systems

“…The DSSAT‐Cropping System Model (CSM)‐CERES‐Wheat module was a restructured and slightly modified version of the original CERES‐Wheat model of Ritchie and Otter (1985) (Hoogenboom et al, 2003). Zhang et al (2008b) developed a wheat grazing model by coupling the DSSAT‐CMS‐CERES‐Wheat module (v4.02) and a cattle growth module based on a metabolizable energy balance. The wheat grazing model simulated wheat and cattle growth interactively and dynamically (in a daily time step), and thus was capable of simulating the tradeoffs between livestock and grain production.…”