Simulating Winter Wheat Forage Production in the Southern United States Using a Forage Wheat Model

Abstract

Core Ideas Winter wheat biomass had one‐phase exponential association with N application rate. A finer, more fertile soil produced more biomass than a coarser, less fertile soil. Biomass significantly decreased with a delay in planting for N rates ≥135 kg ha–1. The effect of the initial drought on biomass was higher with an increase in N rate. The reduction in biomass due to the terminal drought was greatest at 135 kg N ha–1. ABSTRACTWinter wheat (Triticum aestivum L.) is an important component of pastures in the southern United States. This study examined winter wheat biomass responses to N application rate as influenced by soil type, planting date, drought, and El Niño‐Southern Oscillation (ENSO) for the Pineywoods region of Texas using a new forage wheat model that had been incorporated into the Decision Support System for Agrotechnology Transfer suite of crop models. Biomass was simulated for various scenarios comprising two soils, three planting dates, seven N rates, and 74 yr of weather data. The biomass response to N rate was represented by a one‐phase exponential association. Biomass generally peaked at 135 kg N ha−1 on the finer, more fertile Lilbert soil and at 269 kg N ha−1 on the coarser, less fertile Darco soil. Biomass decreased with a delay in planting date at N rates ≥135 kg N ha−1 for Lilbert and ≥202 kg N ha−1 for Darco. The effect of drought during September to October was greater for a higher N rate, the Darco soil, and an earlier planting date. The effect of drought during March to April was greatest at 135 kg N ha−1 and greater on Darco, with up to 45% reduction in biomass compared with 35% on Lilbert. Biomass reduction was up to 45% for the mid‐October planting and 32% for the mid‐September planting. Winter wheat biomass yield was not significantly affected by ENSO. These findings might assist winter wheat forage growers in this region in identifying soil type–, planting date–, and weather‐specific N rates to optimize forage production.