This research aims to subsidize decision making for weed control based on crop yield threshold. Field experiment was conducted in Botucatu (São Paulo, Brazil), with the objective of evaluating the utilization of soybean and weed parameters for monitoring weed interference on soybean yield. The experiment was delineated in a randomized block design. The crop was kept weedy or weed-free for different periods. Total weed dry matter and soybean parameters, such as number of leaves, leaf area, leaf dry matter and total dry matter, can be used for monitoring weed interference on soybean yield. Dry matter of each species separately, had no importance as a competitive element.
Weeds; interference; monitoring; soybean; threshold