EFFECT OF APPLICATION METHOD AND RATE OF METAM SODIUM ON GERMINATION OF YELLOW NUTSEDGE

Mike Thornton*¹, Brad Geary², Deron Beck¹, and Dennis Atkinson¹.

University of Idaho¹ and Brigham Young University². * 29603 U of I Lane, Parma, ID 83660. Office: (208) 722-6701, Ext 211, Fax: (208) 722-6708, E-mail: miket@uidaho.edu

Yellow nutsedge has become one of the most difficult to control weed pests in Western Idaho cropping systems. Onions are especially sensitive to yield reduction under heavy nutsedge pressure because they emerge and develop a full canopy at such a slow rate. The objective of this study was to determine which application method and rate of metam sodium provides the best level of nutsedge control. Nutsedge tuber populations were determined in soil cores prior to and after fumigation. Twelve inch soil cores were divided into three sections to determine the location of tubers within the soil profile. Tubers recovered were tested for viability. Metam sodium was incorporated by the standard method (shank injection at two depths) or with a plow. A third treatment consisted of applying half the fumigant with the plow, followed by the other half by shank injection. Metam sodium was evaluated at rates of 0, 50, 60 and 75 gallons/acre. Populations of viable nutsedge tubers were reduced by all fumigation treatments. The plow plus shank combination was the only incorporation treatment that significantly reduced nutsedge populations near the soil surface (0-4 inch depth). Even under the best treatments the reduction in nutsedge germination by fumigation was in the range of 40 to 50%. Due to this weeds ability to spread rapidly from a single tuber, this level of control is not adequate to allow fumigation to be used as a stand alone practice for control of yellow nutsedge.

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