Use of shoot reduction treatments as a means of simulating hail injury to proso millet

Prose millet, Panicum miliaceum (L.), is a warm-season annual grass well ad apted for grain production in the western Great Plains of the United States , where risk of hail injury is greater than any other region of the United States. Because adjustment procedures and loss equations are not available, prose millet producers in this region have had limited access to crop hail insurance as a risk management tool. Our research was conducted to assess impact of shoot reduction treatments imposed at different crop growth stage s on grain yield loss of proso millet grown under several environments. Our goal was to provide information for development of crop insurance adjustme nt procedures. We also wanted to determine the impact of shoot reduction on various grain yield components. Treatments consisted of a control and thre e levels of shoot reduction (33, 66, and 100% of full stand) applied at fou r growth stages (emergence, 4-leaf, boot, and heading stages). The experime nts were conducted at two locations (Akron, CO and Carrington, ND) during 1 996 and 1997 to assess treatment impact on relative grain yield (RGY), expr essed as percent of control. A significant shoot reduction x growth stage i nteraction was observed for RGY, indicating yield loss from increasing shoo t reduction varied with growth stage. A linear reduction in RGY to increasi ng levels of shoot reduction was observed for the deaf, boot and heading gr owth stages, while RGY displayed a segmented linear response to increasing shoot reduction at emergence. Variation in grain yield, induced by shoot re duction treatments, was more consistently correlated with variation in seed number than seed weight.