Critical overwintering plant population for the successful production of winter wheat in Montana

Winterkill and injury has long been detrimental to the production of winter wheat (Triticum aestivum) in Montana.Three cultivars differing in winterhardiness were grown in five Montana environments with a control and six reduced plant populations to simulate winterkill.The objectives of this study were to measure the compensation ability of several cultivars over a range of reduced plant populations, determine the threshold plant population at which a significant yield reduction occurs, and to measure secondary plant variable responses to reduced plant populations.Compensation by surviving plants for those lost to winterkill was accomplished by means of increased tillering, larger spikes, and/or increased kernel weight.Yield component compensation often resulted in final yield equivalent to that of the target plant density.With a seeding rate of 67.2 kg/ha, critical plant population to achieve control level yields ranged from 25 percent survival (54 plants/m^2) to 63 percent survival (136 plants/m^2) .Over all five environments, the critical plant population averaged 43 percent (93 IV ACKNOWLEDGMENTS I would like to express my sincere appreciation to the f o l l o w i n g : ■ To my major advisor Dr.