Incorporation Depth and Rainfall on Wed Control in Soybeans with Metribuzin1
- L. M. Wax2
Metribuzin [4.amino-6-tert-butyl-3-(methylthlo)-as-triazin-5)4H) one] controls several species of annual broadleaf weeds in soybeans [Glyclne max (L.) Merr.]; however, inconsistent weed control and excessive crop injury sometimes result from the use of metribuzin. To determine the extent to which rate of application, rainfall, and depth of incorporation influence weed control and crop injury with metribuzin, microplot and large plot field experiments were conducted in 1973 and 1974. In microplot studies, metribuzin provided 67 to 100% control of comon ragweed (Ambrosia artemisiifolia L.), prickly sida (Sida spinosa L.), velvetleaf (Abutilon theophrasti Medic.), and jimsonweed (Datura stramonlum L.). Degree of weed control increased with a corresponding increase in herbicide rate from 0.56 to 0.84 kg/ha. Increased control of these species (and slightly greater soybean injury) resulted from increasing depth of soil-incorporation from 0 to 7.6 cm. Control of common cocklebur (Xanthlum pensylvanicum Wallr.) and ivyleaf morningglory [Ipomoea hederacea (L.) Jacq.] was only 35 to 75% but control did improve with increased herbicide rate and depth of incorporation. Abundant rainfall within 10 days after treatment resulted in 88 to 99% control of velvetleaf and 85 to 95% control of jimsonweed. However, control of these two weeds was poor under limited rainfall, unless metribuzin was incorporated to a depth of at least 5.1 cm. Ivyleaf morningglory was not controlled well with metribuzin in the microplots (12 to 62%) regardless of rate, rainfall, or depth of incorporation. In the large plot studies, metribuzin, under moderate-to-abundant rainfall conditions, controlled several annual broadleaf weed species, whether applied preemergence to the soil surface or used as a preplant soil-incorporated treatment. Metribuzin injured soybeans and caused significant yield reduction when soil-incorporated at 1.12 kg/ha.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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