Temporal And Spatial Stability Of Weeds

Patch spraying in an important weed control measure aiming to reduce herbicide application. The feasibility of implementing patch spraying depends on how often it is necessary to make weed assessments and on the number of samples needed for making precise weed maps. It has been suggested that weed maps from the previous seasons can be used to make decisions on patch spraying in a field. However, knowledge of the temporal stability and dispersion of patches are scarce, especially for broad-leaved species. The dispersion of weeds on a whole field scale have been surveyed for 3 years. The temporal correlation between years is analyzed using plant densities and data of the presence-absence of species. For most of the species and for the total number of weeds the best correlation was found between 1993 and 1995. I both years the field was grown with spring sown crops, indicating that weed phenology influences the correlation. The results suggest that a weed map made from assessments in a spring sown crop can be used to support future maps for spring sown crops to reduce the sampling effort.