Pre-Emergence Herbicide and Fertilizer Selection Influence Re-Establishment of Zoysiagrass Sod Fields.

Triazine herbicides have become heavily relied upon for sod production throughout Texas and across the southern U.S. for their effective pre- and post-emergence weed control and low cost.  However, triazines have been identified by the EPA as an herbicide family of significant concern for groundwater contamination and are considered to be systemic toxicants that can potentially cause a variety of acute health effects.  The potential elimination of triazines from the U.S. market would force sod growers to explore other pre-emergence options, many of which may have the potential to injure or delay development of re-establishing sod production fields.  Experiments were conducted to determine the relative influence of pre-emergence herbicides and fertilizer on re-growth following harvest of ‘Palisades’ zoysiagrass (Zoysia japonica Steud.).  Following sod harvest, pre-emergence herbicide and fertilizer treatments were applied to plots in all possible combinations.  Herbicide treatments included simazine, prodiamine, dithiopyr, metolachlor, and oxadiazon.  Fertilizer, either replete with (7-7-7) or lacking (7-0-14) phosphorus was applied to plots at rates of 36.8 kg N ha^-1 during the first and fourth weeks.  Over the course of the following five months, percent zoysiagrass cover was determined within plots.  The most rapid re-growth occurred in simazine- and oxadiazon-treated plots, while prodiamine noticeably delayed zoysiagrass re-growth.  Fertilizer addition significantly improved establishment density, however, phosphorus provided no additional benefit.