A degree-day model ofCirsium arvenseshoot emergence from adventitious root buds in spring

Abstract

Abstract If decision-aid software models of weed emergence and growth are ever to help producers better time weed management, these models must be able to predict perennial weed shoot emergence from vegetative propagules. In this research, Cirsium arvense shoot emergence from adventitious root buds in spring was modeled using degree-day heat sums. Fractional C. arvense shoot emergence was best modeled as a logistic dose–response function of degree-day heat sum as follows: Y = 1.108/(1+[X/488.344]−5.161) where Y = fractional C. arvense shoot emergence (0 to 1) and X = heat sum in degree-days above 0 C after day 91 of the year (April 1) with an upper limit of 800 degree (C) days (r2 = 0.83). This empirical model was validated by graphing observed vs. model-predicted C. arvense shoot emergence using two independently gathered data sets, one of C. arvense emergence in autumn chisel-plowed Triticum aestivum (r2 = 0.82) and the other in no-till fallow (r2 = 0.63). The model slightly overestimated emergence at l...