Blackgrass (Alopecurus myosuroides Huds.) seed dispersal from a single plant and its consequences on weed infestation

Blackgrass (Alopecurus myosuroides Huds.) seed dispersal from single mother -plants was studied in two experiments. For the first experiment, eight bla ckgrass plants of different heights and number of ears were produced in a g reenhouse with the help of different in sowing densities and nitrogen nutri tion levels. At the beginning of seed shedding, the plants were placed outs ide, and seeds were gathered daily. Daily seed dispersal was analysed by fi tting a Weibull equation to the number of seeds as a function of distance t o the mother-plant. The second experiment was carried out in a field compri sing winter barley and spring barley plots as well as bare soil. In each of these three parts, two isolated blackgrass plants were selected and seeds gathered with the help of small pots located along and across the crop rows at growing distances from the mother-plants. For both experiments, total s eed dispersal was analysed by fitting a sum of two Weibull equations and an alysing the estimated parameters as a function of blackgrass characteristic s (plant height, number of ears per plants), seed characteristics (weight, presence of caryopsis, germination ability), crop cover (winter barley, spr ing barley, no crop) and direction (along or across crop rows). The dispers al equations were then introduced into a weed demography model, and blackgr ass spread in time and in space was simulated for a field cultivated with d ifferent crops, (C) 2001 Elsevier Science B.V. All rights reserved.