Field Evaluations of Zinc for Annual Bluegrass Control in Hybrid Bermudagrass.

Preliminary greenhouse research revealed that application of zinc to annual bluegrass had some efficacy as a pre-emergent herbicide for control of annual bluegrass (Poa annua L.).  The objective of this research was to further evaluate the suitability of zinc to control annual bluegrass in a hybrid bermudagrass (‘Tifway’) fairway.  In two years (2012 and 2013) zinc was applied (as zinc sulfate) every other week at rates of 4.5, 9, 18 or 36 g m^-2 (40, 80, 160 or 320 lbs Zn acre^-1) via a soluble spray application.  Zinc was applied as a one-time application to different plots every-other week from August through December.  Thus, every-other week four replicate plots areas received zinc (a total of 16 application dates).  A zero Zn control was also included, as was a standard herbicide treatment.  Collected data included percent Poa annua control, bermudagrass shoot density, relative color and quality of bermudagrass, and soil zinc (EDTA extractable).   As the rate of Zn increased control of Poa annua increased, but never to the level of that measured in plots to which standard herbicide treatments had been applied.  Bermudagrass shoot density or color was unaffected by application of zinc over the two year period.   Subsequent studies will evaluate if continued Poa annua control is realized via the accumulated, residual soil zinc.