ABSTRACT
Competition between weeds and a crop is of major importance in determining the economics of weed control, thus affecting directly the income of the farmer. Weed competition at the early stages of growth results in severe yield losses. Weed competition adversely affects both total yield and the marketable share of the yield, namely the percentage of large or medium sized bulbs. Late infestation with weeds may not directly affect the yield, but may interfere with mechanical harvesting. Allium crops, due to their slow germination, morphology, and slow growth rate are very sensitive to early-season weed competition. Weed population density is likely to affect the time at which irreversible effects of competition become apparent. Under strong competition, bulbing occurs in the season and at a younger physiological age, as compared to weed-free conditions. Pre-emergence application of herbicides can be done at any time between sowing and crop emergence.
