Seedling emergence of tall fescue and wheatgrass under different climate conditions in Iran

Seedling emergence is one of the most important processes determining yield and the probability of crop failure. The ability to predict seedling emergence could enhance crop management by facilitating the implementation of more effective weed control strategies by optimizing the timing of weed control. The objective of the study was to select a seedling emergence thermal time model by comparing five different equations for tall fescue and wheatgrass in two sites with different climate conditions (semiarid- temperate and humid-warm) in Iran. In addition, seedling emergence between two target species were studied. Among the five models compared, the Gompertz and Weibull models gave more succesful results. In humid-warm conditions, the total emergence of wheatgrass was higher than observed in tall fescue. In contrast, emergence was faster in tall fescue than wheatgrass in both study sites.Given that early-emerging plants have been described as contributing more to crop yield than later-emerging ones, tall fescue is proposed as a more suitable specie for semiarid- temperate conditions in Iran.