The utilization of mathematical models in order to predict grain yield losses due to weed infestations, which use leaf area measures, depends on the rapid and precise evaluation of this variable. This way, leaf cover, defined as the proportion of soil area accupied by the vertical projection of the foliage of a species, can be a viable alternative. The purpose of this research was to compare the efficiency of methods to evaluate leaf cover in quantifying soybean grain yield losses due to Bidens spp. (beggarticks) and Sida rhombifolia L. (arrowleaf sida). Weeds and crop leaf covers were evaluated 20 days after soybean emergency. It was proved that photographic methods of evaluating leaf cover, integrated to computing aids, are promising alternatives in quantifying this variable although visual evaluation was more practical and rapid to be performed.
Bidens spp.; Sida rhombifolia L.; soil cover; yield loss prediction
