Leaching of Sodium and Potassium Azide Sources Applied to Native Soils On Established Turf.

Formulations of sodium and potassium azide were impregnated on/into granular carriers consisting of Profile^® and Biodac^® and evaluated for their nematicidal efficacy in established turf.  Previous research had shown the need to wash the azide sources out of the turf canopy and into the soil in order to minimize phytotoxicity.  Therefore, studies were conducted with the objective to determine depth of leaching with selected amounts of irrigation water in native soils.  Previous studies had been conducted on a Mini-Verde bermudagrass putting green consisting of a 90/10 sand/peatmoss mixture to determine depth of leaching with selected amounts of irrigation water.  Data from these studies clearly showed that sodium and potassium azide readily leached through the sand/peatmoss profile as water was applied.  Some golf courses have ‘push-up’ putting greens constructed of native soils. Therefore, a need to determine leaching of sodium and potassium azide sources exists in native soils.  Tests were conducted in 2007 at the Auburn University Turfgrass Unit on a Marvyn series fine-loamy sand.  One study was conducted on Crenshaw creeping bentgrass and one on Tifway hybrid bermudagrass.  Treatments included sodium and potassium azide on both carriers at 33.6 kg ai/ha rate.  Soil samples were collected after 1.45 centimeter irrigation plus rainfall and after 3.35 centimeters of irrigation plus rainfall. Soil samples were collected at 0-7.62, 7.62-15.24, 15.24-22.86 and 22.86-30.48 centimeter depths. There were occasional leaching differences between and among carriers and the two azide salts.  However, practically speaking, averaging leaching over both carriers and salts in the bentgrass study showed after 3.35 cm irrigation plus rainfall more sodium azide/Biodac was detected for the 22.86-30.48 cm depth.  Like data for the bermudagrass study more potassium azide/Biodac was detected.  These studies showed that formulations of sodium and potassium azide on both carriers leach through native soils.