Effects of Nozzle Selection and Ground Speed on Efficacy of Liberty and Engenia Applications and Their Implication on Commercial Field Applications

摘要

Sprayer applicator-controlled variables, such as nozzle selection and ground speed, will become increasingly important for making labeled POST applications of dicamba in next-generation cropping systems. Typically, nozzle orifice sizes and ground speeds differ greatly between small-plot research applications, from which efficacy recommendations are made, and commercial field applications. However, little research has been conducted to compare applications made with backpack sprayers and tractor sprayers. Thus, a field experiment was conducted in 2013 and 2014 at the Northeast Research and Extension Center in Keiser, AR. Tank mixtures of Engenia (TM) (N, N-Bis-(aminopropyl) methylamine form of dicamba), Liberty (glufosinate-ammonium), and Liberty + Engenia were applied with TeeJet XR, TT, AIXR, AI, and TTI nozzles at 5 km h(-1) and 20 km h(-1). Two nozzle sizes (110015 and 11006 rated at 0.58 L min(-1) and 2.27 L min(-1) at 276 kPa, respectively) were used to keep spray volume constant at 141 L ha(-1), whereas ground speed was varied. Weed control ratings were typically lower at 5 km h(-1) than at 20 km h(-1). For example, Palmer amaranth control 4 WAT in 2013 with glufosinate and the TTI nozzle was 89 at 5 km h(-1) and 96 at 20 km h(-1). More differences between speeds were observed for the coarser nozzles, such as the TTI and AI, as opposed to finer nozzles, such as the XR and TT. Results from this research suggest increasing orifice size increases droplet size and that other factors related to applications at faster speeds (e.g., higher droplet velocity, disruption of the crop canopy) may influence the efficacy of herbicide applications. However, increasing ground speed is not a recommended means for increasing efficacy of herbicide applications.