Impact of Corn Gluten Meal on Direct-Seeded Vegetable Seedling Establishment

Abstract

Corn gluten meal (CGM) may be used as a preemergent or preplant-incorporated herbicide for organic weed control of young developing or emerging weed seedlings. Unfortunately, CGM can also adversely impact seedling survival of certain direct-seeded vegetable crops. Various vegetable crop seedlings respond differently to CGM applications, and the impact of CGM applications on direct-seeded cucurbit crops or dry beans has not yet been determined. Field research was conducted in southeast Oklahoma (Lane, OK) to determine the phyto-toxic impact of CGM application and incorporation methods on seedling establishment of black and pinto bean (both Phaseolus vulgaris L.), cantaloupe (Cucumis melo L.) and watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai]. A factorial experiment was repeated twice during the 2001 growing season with 5 CGM application rates, 3 incorporation methods, 4 crops, and 4 replications. The Bernow fine-loamy, siliceous, thermic Glossic Paleudalf soil was prepared for planting by plowing, fertilizing, and forming raised beds. CGM was applied by hand at 1,000, 2,000, 4,000, and 8,000 kg·ha−1. An untreated control was included. Three incorporation methods included tilling prepared beds to a depth of 2.5 to 5.0 cm either before or after application of CGM, or leaving the beds undisturbed. ‘Black Knight’ black bean, ‘Apache’ pinto bean, ‘Magnum 45’ cantaloupe, and ‘Allsweet’ watermelon were direct-seeded on raised beds. Stand data were collected 14,20, and 31 days after planting. CGM applications adversely affected seedling establishment of all direct-seeded vegetable crops. Injury and morality occurred prior to seedling emergence. In all but 2 isolated instances the lowest CGM rate significantly decreased seedling establishment. Seedling mortality percentages at 1,000 kg·ha−1, averaged across evaluation dates and incorporation methods, were 66% (black bean), 58% (pinto bean), 50% (cantaloupe), and 58% (watermelon) increased as CGM application rate increased. Although all of the CGM applications rates significantly decreased seedling survival for these crops, the potential usefulness of CGM as an organic herbicide should encourage additional research to develop safer application methods for CGM. Once seedlings of these crops are established, as transplants or emerged direct-seeded plants, CGM may be safe to use. Research should investigate the impact of application rates below 1000 kg·ha−1 on direct-seeded vegetables, CGM applications on other cucurbit crops, different application methods, and weed control efficacy of CGM when used with these vegetable crops.