Agronomic Optimum Seeding Rate for Irrigated Maize in Texas is Concomitant to Growing Season Mean Daily Minimum Temperature

Our study was conducted to determine agronomic optimum seeding rates ( AOSR ) for irrigated maize under a range of agroecological conditions in T exas. Environmental factors that affect irrigated maize production vary considerably across T exas. This variability imposes region‐specific limitations on statewide maize seeding rate recommendations. Our research examined the efficiency of varying seeding rates on irrigated maize grain yields in five USEPA L evel IV E coregions that comprise most of the irrigated maize‐producing area of T exas. The selected sites span a distance of 1200 km from south to north T exas and elevations from 20 to 1218 m above mean sea level. We conducted the study over three growing seasons from 2005 through 2007 in two L evel IV E coregions of the H igh P lains of N orth T exas ( N ), one in the E ast C entral P lains ( E ), one in the S outhern P lains and one in W estern G ulf C oastal P lains of S outh T exas ( S ). We observed that maximum grain yields and AOSR to achieve maximum maize grain yields vary considerably among ecoregions. In S outh T exas, we observed grain yield response rates of 125–129, 151 kg 1000 seeds −1 in E and 163–199 kg 1000 seeds −1 in N . We show that growing season average daily minimum air temperature ( T MIN ) explains most of this variation (r 2  = 0.98, P‐value < 0.01) and conclude that seeding rate efficiency is concomitant to T MIN . Maximum grain yields ( GY MAX ) determined with seeding rate response analysis also varied among ecoregions and with T MIN from south to north T exas, from a low of 8.3 Mg ha −1 in S to a high of 18.4 Mg ha −1 in N (r 2  = 0.59, P‐value < 0.01). We conclude that development of agronomic management models by L evel IV E coregions of T exas combined with site‐specific T MIN climatological data serve as a valid template for delivering robust and agroecozone‐specific irrigated maize seeding rate recommendations in T exas.