EFFECT OF VOLUNTEER POTATO DENSITY ON DRY BULB ONION YIELD AND QUALITY

Authors: Williams, Martin; RANSOM, COREY - OREGON STATE UNIV; THOMPSON, W - UNIV OF IDAHO

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2004
Publication Date: 9/28/2004
Citation: Williams, M.M. II, Ransom, C.V., Thompson, W.M. 2004. Effect of volunteer potato density on bulb onion yield and quality. Weed Science. 52:754-758.

Interpretive Summary: Potatoes and onions are important horticultural crops in the United States and are often grown in the same field over time. However, not all tubers are recovered from potato harvest, resulting in 'volunteer potatoes' that infest rotation crops including onions. The purpose of this study was to determine the effect of volunteer potato density on onion yield loss, onion bulb characteristics, and volunteer potato tuber production. Onion is highly susceptible to volunteer potato and significant yield loss can occur in the presence of 1 volunteer potato per 31.3 m2. In addition to total yield loss, volunteer potato also reduces individual bulb size of onion, resulting in a less valuable crop. The impact of this research is several fold, including: 1) relationships between onion yield loss and weed density have been empirically quantified for the first time, 2) this research improves the fundamental understanding of interactions of weeds with onions, and 3) integrated weed management systems can be improved by using new knowledge of economic thresholds for onion.

Technical Abstract: Dry bulb onions are poor competitors and volunteer potato is commonly observed in the western U.S. and difficult to manage in the crop. In order to improve the understanding of onion and weed interactions, relationships were quantified among volunteer potato density, onion yield, and volunteer potato tuber production using hyperbolic or linear models. Onion yield losses due to volunteer potato interference occur at densities commonly observed in the field. Percent crop yield loss as weed density approaches zero (I parameter) was 165 and initial volunteer potato density as low as 1 plant per 14.9 m-2 resulted in 10% crop yield loss. Asymptotic yield loss (A) was 100% and achieved with some 4 volunteer potato plants m-2. Volunteer potato competition limits onion bulb size, resulting in a lower quality, less valuable crop. Volunteer potato tuber density and biomass increased linearly with initial weed density as high as 8 volunteer potatoes m-2. Onion yield loss from volunteer potato competition occurs to a greater extent and at a lower weed density than demonstrated in previous research on small seeded annual weed species.