Many species of organisms inhabit ricefields. Most of these organisms are not harmful. Most are beneficial or innocent, and include a wide range of predatory and parasitic natural enemies that contribute to keeping the insect pest organisms in check.
Weeds are an almost universal companion of rice in the tropics.
In many situations, weed growth ins prolific and weeds are a major constraint on crop yield. Weeding is a major production cost, with estimates of 50-15o person days per hectare required for manual weeding, depending on the number of weedings and type of rice culture. For many farmers, weeding requires the greatest labor input during the agricultural cycle, labor that is often not available when weeds are most damaging to the crop. Upland rice more than any other crop shows the ravages of lack of proper weeding. Sometimes, when the land is too weedy the crop is abandoned.