Competition Between Annual Weeds and Sweet Spanish Onions

Abstract

The competitiveness of annual weeds in irrigated sweet Spanish onions (Allium cepa L.) was studied at North Platte, Nebraska, during 1969 and 1970. Weeds allowed to grow in the row for 2, 4, 6, and 8 weeks after onion emergence reduced onion yields 20, 20, 40, and 65%, respectively. When plots were kept weed-free until onion emergence and 2, 4, 6, 8, 10, and 12 weeks after emergence, onion yields were reduced 100, 99, 87, 75, 46, 25, and 5%, respectively. Redroot pigweed (Amaranthus retroflexus L.), kochia (Kochia scoparia L.), and grass weeds accounted for 54, 21, and 21%, respectively, of the total weed yield.