Research: Reducing the Environmental Footprint of Weed Management

My research has a weed biology and ecology focus and includes studies of susceptibility or tolerance of weedy plants to chemical and nonchemical control methods, the biological and ecological bases of that susceptibility, and sustainable approaches to weed management in conventional and organic horticultural cropping systems.

Methyl bromide alternatives. Since 2005, methyl bromide (a chemical used for soil fumigation) is available only through critical use exemptions. The most difficult pests to control with alternative fumigants are yellow and purple nutsedges ( C. esculentus and C. rotundus ). A formulation of the alternative fumigant can be applied through drip-irrigation systems, a mode of application with the potential to reduce agricultural worker exposure and drift of volatile emissions to adjacent residential communities. Studies were conducted to evaluate the efficacy of nutsedge control with 1,3-dichloropropene + chloropicrin applied by drip-chemigation in Florida 's sandy soils, and the effect of the large volumes of water used on preemergence herbicides and preplant fertilizers.

Cover crops and living mulches for weed suppression. Collaborating on a larger multistate, multidisciplinary project on a biologically-based sustainable tomato production system, studies were undertaken to evaluate the competitiveness of the cover crops Crotalaria juncea (sunn hemp), Mucuna deeringiana (velvetbean), and Vigna unguiculata cv. Iron Clay (cowpea) with the weeds yellow nutsedge and Amaranthus hybridus (smooth amaranth) and to compare the allelopathic potential of the cover crops.

Twelve winter legume and grass cover crops were evaluated for use as living mulches for weed suppression in row middles of organic and sustainable vegetables. Four candidate crops were selected and their effects on weed suppression, and broccoli growth and yield were assessed. Additionally, participation in a multi-state research project, NE-1026 - Weed Management Strategies for Sustainable Cropping Systems involves assessing the effects of planting dates and method of incorporation of buckwheat on weed suppression.

Weed management in organic cropping systems. A multistate on-farm and research farm evaluation of serial integrated crop management systems for the management of nutsedge in organic vegetables is ongoing. With collaborators at Clemson University in South Carolina and at the USDA-Agricultural Research Service (ARS) in Georgia , a systems approach is being used to compare the efficacy of purple and yellow nutsedge suppression with soil solarization, green infrared transmitting film, tillage, flame-weeding, biofumigation, and the cover crop – sunn hemp. Other projects have included a comparison of the efficacy of flaming and non-synthetic herbicides and a study on hydramulch as an alternative to polyethylene mulch. Hydramulch is biodegradable and does not pose the adverse environmental impacts of polyethylene mulches.

A multidisciplinary research team at the University of Florida and the University of the Virgin Islands is conducting a study in which summer cover crops of sunn hemp, velvetbean, pearl millet and sorghum sudangrass in monocultures and mixtures are being grown in sequence with several vegetable crops in monoculture or intercropped in a biannual rotation system. The impact of increasing plant biodiversity on growth and yield of organically produced vegetables, on the population dynamics of weeds, key insect pests and beneficial insects, plant pathogenic nematodes, and soil borne plant pathogens is being assessed.