simulation of emergence pattern of weeds species in corn (zea mays l.) field based on sigmoidal models

the application time of weed control methods due to population dynamics of this species is one of the most important aspects of weed management. in this study tried to use four sigmoidal functions (logistic, gompertz, richards and weibull) and to select the best fit by using r2adj , rmse and aicc. our results showed that the seedling models of every weed are different from one another and the majority of all weeds emerge in 20 days after maize planting. after fitting the models and their calculated parameters, richard 4 paramete model was excluded from comparisons.results showed that logistic, gompertz and weibull models were the best model to show the pattern of emergence for amaranthus retroflexus and echinochloa crus-galli, chenopodium album and solanum nigrum and portulaca oleracea respectively. in this species the start of germination process occurred after planting the desired crop immediately. 50% germination in the 175 to 318 degree days (2 to 4 weeks after planting) occurred.