Air-Propelled Abrasive Grit for Selective Postemergence Weed Control.

No single form of weed control is sustainable. Consequently, long-term weed management is challenging not just in conventional broad-acre farms, but also in fruit and vegetable crops, orchards, vineyards, parks, gardens, lawns, roadsides, and even city sidewalks. Synthetic herbicides eased these challenges for the past seven decades and will continue to do so for many years to come. However, where herbicides are not permitted, or where they have lost efficacy, new concepts are needed for short-term weed control, and these novel approaches must be combined for long-term management to be successful. One new technique involves the postemergence application of abrasive grits under high air pressures, which shreds leaves and often severs stems of weed seedlings. The technique can be selective given appropriate size differences between crop plants and the weeds. Abrasive agents can include any number of crop residues, agricultural and food wastes, and fertilizers that can be formulated into materials with a gritty texture (i.e., pellets about 0.5 mm diameter). Machinery has been and is being designed to apply these grits to agronomic and horticultural crops. The technique, generally, and the machinery to apply grit, specifically, still are in their infancies. Nevertheless, preliminary results have been encouraging, with end-of-season weed control often being 70 to 90% with no loss of crop yield after two to three successive applications of grit during the early part of the crop growth cycle. Costs are not well-documented yet, but likely will be more expensive than traditional herbicide applications, but equivalent to repeated tillage and flaming operations in organic crops. Air-propelled grit is not a panacea for weed management; it is one option among many that are needed.