WEED INTERFERENCE AS RELATED TO VEGETABLE CROP MANAGEMENT SYSTEMS

Abstract

The ability of an individual plant to obtain the light, water, and nutrients for growth often determines the success of that individual in its environment. Most weed species usually occur in association with other plants, either crops or weeds. It is important to consider the manner in which weeds interact with their neighbors in the agricultural ecosystem because they interact in a number of ways and to varying degrees. Ten biologically possible types of interactions that may occur among plant species growing together have been reported. Seven of them are common enough to have been named as neutralism, commensalism, protocooperation, mutualism, parasitism amensalism, and competition. The three last ones represent the negative effects of common associations in agriculture. It is usual to measure the depressive effect of weeds on crop yield and ignore the effect of crops on weed growth. However, it is also important to understand and exploit the positive effects of weed (as host of beneficial insects) on crops as well as the negative effects of crops on weeds. An overview of weed-crop interference, results of the studies on sorghum allelopathy properties and on weed interference on tomato and on Peruvian carrot is discussed to adequate integrated weed management programs on vegetable crop systems in Brazil.