Background

It is welknown that growth dynamics in the early growth stages are important characteristics for the outcome of the competition for light, water and nutrients, resulting in a certain yield loss of the crop due to presence of weeds. If possible, an early and precise prediction of the growth dynamics of both crop and weeds could give a more precise assessment of the need for weed control. This could lead to a better confidence to point out sites in the field, where weed control can be reduced or even eliminated, if the competitive relationship between crop and weeds is in favour to the crop, and the costs to weed control would be less than the potential yield loss. Since weed control is done mechanically under organic growing conditions, often by weed harrowing, there are risks for crop damages by soil coverage or other mechanical damages of the crop leaves. These damages are increasing with increasing weed control intensity, and are resulting in reduced crop growth, and possibly the yield too, immidiately after weed harrowing. Taking this aspect into consideration, a further motivation to optimize the intensity of the weed control is given. Several studies of the competition between crop and weeds have shown that the quota of weed leaf area to the total leaf area (crop+weed) gives a more accurate prediction of the yield reduction caused b