Metribuzin Injury in Soybeans as Influenced by Application Timing and Cultivation
1981
Moshier, L. J. | Russ, O. G.
Kansas growers wish to improve broadleaf weed control in soybeans [Glycine max (L.) Merr.] grown in sandy soils with high pH or low organic matter content. Metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5 (4H)-one] applications would effectively control broadleaf weeds on such soils; however, crop injury risk would also be present. Thus, a field experiment was initiated to determne if a 3-week interval between herbicide application and planting or cultivation after soybean emergence improved tolerance of soybeans grown on a soil with a high pH and low organic matter content. Metribuzin was applied at 0.6 or 1.1 kg/ha and incorporated prior to soybean planting in a Haynie very fine sandy loam (coarse-silty, mixed, calcareous, mesic Typic Udifluvent) with pH of 7.9 and 0.7% organic matter content in 1978 and 1979. Visual injury of 4-week-old plants was less in 1978 but more in 1979 when metribuzin was applied 3 weeks before planting rather than immediately before planting. Injury in 7-week-old plants was not significantly affected by time of metribuzin applications in 1978 but was greater from applications immediately before planting compared to applications 3 weeks prior to planting in 1979. Injury differences were attributed to rainfall quantity and pattern. The meribuzin applications at 0.6 or 1.1 kg/ha 3 weeks prior to planting did not affect soybean yields either year even though the higher rate reduced plant stand and plant height. Yields were reduced only when metribuzin was applied at the higher rate immediately before planting. Cultivation at 3 and 7 weeks after soybean planting did not significantly affect soybean tolerance either year.
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