Meteorological limits to winter wheat productivity in the U.S. southern Great Plains

Although the U.S. southern Great Plains accounts for approximately 30% of total U.S. wheat (Triticum aestivum L.) production, yields in the region have rarely surpassed 3.0 Mg ha−1 and quantification of the wheat yield gap (YG) and meteorological factors associated with potential wheat productivity are scarce. Our objectives were to identify spatial gradients in key weather variables and to assess the meteorological drivers of wheat productivity and resource-use efficiency, and to quantify the wheat YG across Texas, Oklahoma, Colorado, and Kansas. Water-limited wheat grain yield (Yw) was simulated for 30 consecutive years at 68 locations across the southern Great Plains using Simple Simulation Modeling-Wheat (SSM-Wheat), and actual soil and weather data, sowing date, and population density. Regional gradients in meteorological variables were determined for (i) the entire crop cycle, (ii) pre- and post-anthesis, or (iii) jointing-anthesis interval, and Yw were related back to these variables using linear and stepwise multiple-regression. Boundary function analysis determined water productivity (WP) and transpiration-use efficiency (TE). Strong latitudinal gradients occurred for temperatures and longitudinal gradients for precipitation (P), evapotranspirative demand (ETo), and solar radiation (Rs). Wheat Yw averaged 5.2 Mg ha−1 and followed the longitudinal P gradient increasing from west (3.6 Mg ha−1) to east (6.9 Mg ha−1). Interannual Yw variability was large with coefficient of variation (CV) increasing from 13 to 51% east to west. Meteorological variables accounting for major portions of the Yw variability were water supply (P + PAWs) in the west 82% of regression sums of squares (SS) and cumulative solar radiation (Rs) during the anthesis − physiological maturity in the east (73% of SS). Temperatures during the anthesis-physiological maturity phase negatively affected grain yields across all locations and years (7% of SS). Wheat WP (17.2 kg ha−1 mm−1) and TE (20.8 kg ha−1 mm−1) benchmarks derived in this study align well with values reported for wheat grown in other regions of the world.