Impact of corn gluten meal on direct-seeded vegetable seedling establishment

Authors: Webber Iii, Charles; SHREFLER, JAMES - OSU, LANE, OK

Submitted to: International Journal of Vegetable Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2007
Publication Date: 9/15/2007
Citation: Webber III, C.L., Shrefler, J.W. 2007. Impact of corn gluten meal on direct-seeded vegetable seedling establishment. International Journal of Vegetable Science. 13(3):5-15.

Interpretive Summary: Corn gluten meal (CGM) is an organic preemergent or preplant-incorporated herbicide; unfortunately, CGM can also adversely affect seedling survival of certain direct-seeded vegetable crops. Research has not yet determined the impact of CGM applications on direct-seeded cucurbit crops or dry beans. Field research was conducted in southeast Oklahoma (Lane, OK) to determine the phytotoxic impact of CGM application and incorporation methods on seedling establishment of four vegetable crops: black bean (Phaseolus vulgaris L.), pinto bean, cantaloupe (Cucumis melo) and watermelon (Citrullus lanatus). A factorial experiment was repeated twice during the 2001 growing season with 5 CGM application rates, 3 incorporation methods, 4 crops, and 4 replications. CGM was applied by hand at 5 rates (0, 1000, 2000, 4000, and 8000 kg/ha). Certified 'Black Knight' black bean, 'Apache' pinto bean, 'Magnum 45'cantaloupe, and 'Allsweet' watermelon were direct-seeded in 2 rows on raised beds at a rate of 1 plant/15.2 cm within rows (20 plants/3 m). Stand data were collected 14, 20, and 31 days after planting (DAP) and converted to percentage seedling survival based on planting rate. CGM applications adversely affected seedling establishment of all 4 direct-seeded vegetable crops. Injury and morality occurred prior to seedling emergence. In all but 2 isolated instances the lowest CGM rate, 1000 kg/ha, significantly decreased seedling establishment. Seedling mortality percentages at 1000 kg/ha were 66% (black bean), 58% (pinto bean), 50% (cantaloupe), and 58% (watermelon). Seedling establishment also significantly decreased as the CGM application rate increased. Although all of the CGM applications rates significantly decreased seedling survival for these crops, the potential usefulness of CGM as a preemergent or preplant-incorporated herbicide for organic production should encourage additional research to develop safer application methods for CGM. These results also indicate that once the seedlings of these crops are established, as transplants or emerged direct-seeded plants, CGM should be safe to use. Further research should investigate the impact of application rates below 1000 kg/ha on these direct-seeded vegetables, CGM applications on other cucurbit crops, different application methods, and weed control efficacy of CGM when used with these vegetable crops.

Technical 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 research has not yet determined the impact of CGM applications on direct-seeded cucurbit crops or dry beans. It is also unknown how the incorporation method may impact these direct-seeded vegetable crops. Field research was conducted in southeast Oklahoma (Lane, OK) to determine the phytotoxic impact of CGM application and incorporation methods on seedling establishment of the following four vegetable crops: black bean (Phaseolus vulgaris L.), pinto bean, cantaloupe (Cucumis melo) and watermelon (Citrullus lanatus). 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 soil [Bernow fine sandy loam, 0-3% slope (fine-loamy, siliceous, thermic Glossic Paleudalf)] was prepared for planting by plowing, fertilizing, and forming raised beds. CGM was applied by hand at 5 rates (0, 1000, 2000, 4000, and 8000 kg/ha). The 3 incorporation methods included tilling the prepared beds to a depth of 2.5 to 5.0 cm either before or after applying the CGM, or leaving the beds undisturbed. Certified 'Black Knight' black bean, 'Apache' pinto bean, 'Magnum 45' cantaloupe, and 'Allsweet' watermelon were direct-seeded on raised. Stand data were collected 14, 20, and 31 days after planting (DAP) and converted to percentage seedling survival based on planting rate. CGM applications adversely affected seedling establishment of all 4 direct-seeded vegetable crops. Injury and morality occurred prior to seedling emergence. In all but 2 isolated instances the lowest CGM rate, 1000 kg/ha, significantly decreased seedling establishment. Seedling mortality percentages at 1000 kg/ha, when averaged across evaluation dates and incorporation methods, were 66% (black bean), 58% (pinto bean), 50% (cantaloupe), and 58% (watermelon). Seedling establishment also significantly decreased as the CGM application rate increased. CGM, applied at these rates, has significant phytotoxicity and potential as an organic herbicide if the crop safety of direct-seeded vegetables can be enhanced. Although all of the CGM applications rates significantly decreased seedling survival for these crops, the potential usefulness of CGM as an organic should encourage additional research to develop safer application methods for CGM. These results also indicate that once the seedlings of these crops are established, as transplants or emerged direct-seeded plants, CGM should be safe to use. Further research should investigate the impact of application rates below 1000 kg/ha on these direct-seeded vegetables, CGM applications on other cucurbit crops, different application methods, and weed control efficacy of CGM when used with these vegetable crops.