Stubble Height Effect on Winter Wheat in the Northern Great Plains: II. Plant Population and Yield Relations

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Abstract
Partial winterkill of winter wheat (Triticum aestivum L.) is a potential problem each year in the northern Great Plains, reducing plant population and yield potential, and forcing a decision to retain or destroy the crop. The objective was to develop algorithms relating postwinter agronomic characters to potential grain yield. Field trials were conducted 4 yr on Williams loam (fine‐loamy, mixed Typic Argiborolls) to measure the effect of four stubble heights (0, 5, 20, and 36 cm) on postwinter plant populations and agronomic characteristics of three cultivars (Roughrider, Mironovskaya, and Centurk) planted with two drills (disk‐ and hoe‐opener) on an area without and with 50‐mm supplemental water applied 1 to 2 wk before planting. Postwinter, pretilllering plant population, spike population at harvest, and grain yield differed among stubble heights and cultivars each year. Plant populations ranged from < 10 to >220/m2. Average spike/seedling population ratio ranged from about 2.5 to 5.5 with the largest ratio associated with the smallest plant population. Curvilinear relationships of spikes/m2 to plants/m2, grain yield (kg/ha) to spikes/m2, and grain yield (kg/ha) to plants/m2, respectively, were associated with R2 of 0.94, 0.97, and 0.95. The curvilinear function, no intercept option, of grain yield kg/ha (Y) to plants/m2 (X) was Y = 41.04x − 0.18x2 + 0.00021x3. This algorithm is a definitive measure of grain yield potential when postwinter plant population is known.