Effect of Diuron and Fluometuron on Grain Sorghum and Soybean as Replacement Crops Following a Cotton Stand Failure

Abstract

Preemergence herbicides are widely used in cotton (Gossypium hirsutum L.) to control glyphosate-resistant weeds. If a stand failure occurs after the acceptable replanting date for cotton, the most likely replacement crops are grain sorghum [Sorghum bicolor (L.) Moench.] and soybean [Glycine max (L.) Merr.]. When replanting to another crop, one must consider the potential impact of previously applied cotton herbicides on the replacement crop. The objective of this study was to determine the potential for sorghum and soybean as replacement crops following diuron- and fluometuron-treated cotton on coarse-textured, low organic matter soils. Specific objectives were to determine effects of tillage and time between herbicide application and replacement crop planting. Treatments consisted of a factorial arrangement of no herbicide, 1120 g ai ha-1 of fluometuron, or 840 g ai ha-1 of diuron, replant delays of three, six or nine wk after cotton herbicide application, and no tillage or disking prior to replacement crop planting. Soybean response to cotton herbicides was noted primarily with the three-wk replant delay, and greater response was noted with fluometuron. Soybean planted three wk after diuron and fluometuron application was injured 1 to 15% and 6 to 33%, respectively, depending upon location. Disking prior to soybean planting generally increased injury. Regardless of replant delay, diuron did not reduce soybean yield. Soybean yield was reduced at two of three locations by fluometuron in a three-wk replant delay but not with six- or nine-wk replant delays. No visible injury was noted on grain sorghum and yield was not reduced at any of four locations regardless of replant delay or cotton herbicide.