Alfalfa Tolerance to Norflurazon (Zorial 5G) on Coarse Textured Soils in Central Arizona

Abstract

The tolerance of seedling alfalfa to norflurazon applied at various times after planting was evaluated at the University of Arizona Maricopa Agricultural Center (MAC) and in Glendale, AZ during 1998 and 1999. At each application date, rates of 0, 1, 1.5, 2, 3, or 4 lbs a.i./A of norflurazon formulated as a 5% sand granule (Zorial 5G) were applied using a ground driven Valmar granule applicator. Zorial 5G at rates ranging from 1.5 to 4.0 lbs a.i./acre applied as early as 25 days after planting (DAP) had no effect on alfalfa seedling emergence and stand establishment at (MAC). Significant alfalfa height reductions were observed as Zorial 5G rate was increased when Zorial was applied at 25 and 62 DAP (MAC) and 64 DAP (Glendale). Alfalfa fresh weight yield for the MAC location was reduced at the second cutting after application as Zorial 5G rate increased for the at planting and 25 DAP treatments. Alfalfa yields approximately one year after planting were not affected by applications of Zorial 5G at 25 DAP or later. Results suggest that Zorial applications at rates of 1 to 2 lbs a.i./A applied at the 3 to 4 trifoliate leaf stage (approximately 2 months after planting) have little effect on yield at first and second cuttings of alfalfa.