Natural Mulches Are Not Very Effective for Weed Control in Onions

This study was undertaken to evaluate natural mulches for weed control in organic onion ( Allium cepa ) production where current practices rely on hand-weeding or plastic mulch. Three experiments were conducted over 2 years, with two experiments conducted on-farm in different years and one experiment conducted on-station. Treatments consisted of hand-weeding or mulches of wheat ( Triticum aestivum ) or oat ( Avena sativa ) straw, bermudagrass hay ( Cynodon dactylon ), compost, and needles of slash pine ( Pinus elliottii ) and longleaf pine ( P. palustris ). All of the mulches with the exception of compost tended to lodge in the onion tops due to their close spacing. Wheat straw and bermudagrass hay reduced plant stand and yield. Compost settled well around the onion plants and initially smothered weeds, but over time the compost treatment became very weedy. Pine needle mulch (referred to as pine straw in the southeastern U.S.) showed the most promise with less stand loss or yield reduction, but did tend to lodge in the tops. None of these mulches were acceptable compared to hand-weeding.