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Weed control efficacy with ammonium nonanoate for organic vegetable production

Webber, Charles L. III, Shrefler, James W., Brandenberger, Lynn P., Taylor, Merritt J., Carrier, Lynda K., Shannon, D. Kent
International journal of vegetable science 2010 v.17 no.1 pp. 37-44
weed control, organic production, herbicides, pesticide application, broadleaf weeds, Amaranthus albus, Amaranthus spinosus, Mollugo, Eleusine indica, Digitaria ischaemum
Organic Producers Rank Weed Management Research as their top priority. Organic vegetable producers have many challenges because their weed control tools are mostly limited to cultural methods, with a strong dependence on excessive tillage, cultivation, and hand-hoeing for weed control. Very few chemical weed control options have been approved for organic use. Racer, ammonium nonanoate, is a new contact herbicide labeled for non-food use and under evaluation for registration as a bioherbicide for organically grown food crops. Prior to actual use in crops, new herbicides need thorough evaluations to determine the spectrum of weeds controlled at multiple growth stages as influenced by application methods. The objective of this study was to investigate the weed control efficacy of ammonium nonanoate applied at different rates and application volumes on endemic weed populations. The factorial experiment included two herbicide rates (7.2 and 10.8 kg·ha−1 a.i.) applied at four application volumes (164, 327, 654, and 981 L·ha−1). In general, application of ammonium nonanoate produced greater weed control for broadleaf weeds tumble pigweed (Amaranthus albus L.), spiny pigweed (A. spinosus L.), and carpetweed (Mollugo verticillata L.) than the monocoty weeds goosegrass (Eleusine indica L. Gaertn.) and smooth crabgrass [Digitaria ischaemum (Schreb. ex Schweig Schreb.)]. The best weed control for both pigweed species occurred at the 10.8 kg·ha−1 rate applied at 654 L·ha−1. Carpetweed was very sensitive to ammonium nonanoate, with 66% control at the lowest application rate and volume, and most application rates and volumes produced at least 88% control. Grass weed control ranged from 31% to 54% for goosegrass and 24% to 54% for smooth crabgrass. The lowest ammonium nonanoate rate provided unsatisfactory control for all weed species. Ammonium nonanoate provided consistent control across a large range of application volumes. The results indicate that ammonium nonanoate has excellent potential as an organic herbicide.