Using Elemental Sulfur to Optimize/Lower Soil pH of Bentgrass Putting Greens.

Soil pH highly influences nutrient availability and root growth during both establishment and maintenance of creeping bentgrass (Agrostis stolonifera L.) putting greens (PGs). The optimal 1:1 soil pH range for creeping bentgrass is 5.5–6.5, yet PG rootzones containing even modest amounts of calcareous sand are often buffered to higher pH values. Furthermore, common cultural practices often serve as sources of added alkalinity. Supraoptimal pH levels have been shown to increase disease susceptibility while limiting nutrient availability, root growth, and stress tolerance of creeping bentgrass. Our objectives were to quantify growth and nutritional response of bentgrass PGs to method and/or rate of a single elemental sulfur (S_o) application, and to develop safe and effective rate recommendations. In Sept. 2012, pelletized or flowable S_o was applied to two internally-drained Penn A-series PGs at rates of 0, 195, 390, 586 kg S_o ha^–1 (0, 4, 8, or 12 lbs S_o /M). Response variables measured over the 2013 season were: clipping yield, canopy color and density, soil pH (by 3 rootzone depth segments), soil extractable nutrients, leaf nutrient content, specific root length, and root length density. Soil pH reductions observed within the surface 5-cm and 5 to 15-cm rootzone depths were highly correlated to S_o rate. While other experimental variables collected proved statistically significant, observed differences were marginal. Nutrient levels of all treated and untreated plots remained within the sufficiency range of creeping bentgrass. The most notable effect of S_o on plant nutrition was a 20 to 40% increase in leaf Mn content. Frequent visual inspection of the sand rootzone following application showed no evidence of black layer formation. Specific considerations will be presented in greater detail; yet the authors generally recommend that fall S_o application to bentgrass PGs be limited to 195 kg ha^–1 (4 lbs /M).