Evaluating biological thatch control on Zoysia matrella (L.) Merr. golf greens

Thatch is a layer of living and dead plant material (stems and roots) between turfgrass leaf tissue and the soil surface. If excessive, thatch can decrease turf playability, increase scalping and disease pressure, reduce pesticide efficacy and water infiltration, and harbor insects. In golf putting greens, disruptive mechanical practices such as vertical mowing, core cultivation, grooming, and topdressing are traditional agronomic methods for managing thatch/organic matter. Non‐disruptive biological thatch reducers have been used as an alternative. Field studies were conducted to evaluate two commercial biostimulant products, a liquid vermicompost extract marketed as Worm Power ® Turf and a liquid humate derivative marketed as EarthMAX, and their ability to reduce thatch on a Zoysia matrella (L.) Merr. ‘Diamond’ putting green; rooting depth and weight were also evaluated. EarthMAX ® was applied at two rates/frequencies, EarthMAX (1) and EarthMAX (2). In addition, two industry standards were included: blackstrap molasses and sand topdressing. In Year 2, untreated resulted in ≥42% thicker thatch than EarthMAX (2) and blackstrap molasses, no other treatment was statistically different to untreated for both years. All treatments provided lower (≥48%) thatch thickness than the industry standard sand topdressing for both years. No treatment performed differently to the untreated for thatch weight. Blackstrap molasses provided greatest root weight for both years (≥133% and ≥184% than all other treatments); however, it also provided amongst the lowest root length. Inconsistent results make it difficult to recommend biostimulants for thatch reduction. Improvements amongst some treatments over untreated and sand topdressing indicate potential benefits of their use.