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Project description

Trifluralin Application at Varying Rates Across the Bed for Layby Weeds. (95CC021)
Program UC IPM competitive research grants program
W.T. Lanini, Vegetable Crops, UC Davis
T.S. Prather, UC IPM, Kearney Agricultural Center
Host/habitat Tomatoes
Pest Unspecified Weeds
Discipline Weed Science
Cultural Controls
Start year (duration)  1995 (Two Years)
Objectives Evaluate reduced rates of trifluralin applied at layby, relative to standard constant rate applications in processing tomatoes, and their impact on weed control, weed seed production, tomato yield, tomato quality, and economics.
Final report In processing tomatoes, layby herbicide treatments are soil-incorporated. Incorporation of the layby herbicide dislodges emerged weeds, thus weeds emerging this operation come from seed or perennial propagules. Tomato growth is rapid after layby herbicide treatment, responding to the sidedress fertilizer application (applied 1 to 7 days before layby). The rapid expansion of the tomato canopy helps to block light and prevents or reduces weed growth, and thus reducing the need for herbicide near the crop. The farther from the tomato row, the less the competitive effect. Herbicide rates can be varied on a spray boom by changing the nozzle size. In this study, variable rate applications were made using a boom with the center nozzles positioned over the furrow and outside nozzles near the crop; the center nozzles applied full rate, while nozzles near the crop were one-half the size and applied half rate. Variable rate treatments reduced herbicide the amount of herbicide applied by 40% compared constant rate. Variable rate treatments were compared to constant rate treatments at eleven locations throughout California. Trifluralin was used in all studies with 0.85 lb/a applied as the standard rate. An untreated control was also included with no herbicide, but was cultivated by the incorporator. Tomato yield and quality were not affected by layby treatment. Weed density and cover were generally greater on untreated plots compared to other treatments, but did not differ at any location between varying rate and constant rate treatments, regardless of the weed species present on a site. Weed seed production also did not differ between varying rate and constant rate treatments. Implementation of variable rate layby treatments requires a simple nozzle change on the layby application equipment, using a nozzle size smaller (1/2) than that used in the furrow area.

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