Root/Shoot Response of Penn A-4 Creeping Bentgrass to Rootzone Acidification by Elemental Sulfur.

The optimal pH range for creeping bentgrass is generally considered to be 5.5–6.5. Rootzone pH highly influences nutrient availability and root growth during both establishment and maintenance of 'Penn A-4' creeping bentgrass putting greens (PGs). Rootzones prepared with modest calcareous sand inclusions are often buffered to higher pH values. Furthermore, topdressing sand and/or irrigation water are common sources of alkalinity to PGs. Supraoptimal pH levels have been shown to increase turfgrass disease susceptibility while limiting nutrient availability, root growth, and stress tolerance. Our research objective was to quantify Penn A-4 shoot/root growth response to applications of elemental sulfur (So) to maintained PGs. Pelletized So was broadcast over an internally-drained, calcareous sand PG at rates of 0, 6, 12, or 18 lbs So/1000ft2. Of the two plots assigned to receive any So rate, one was randomly core-aerified immediately prior to application. Response variables measured include: clipping yield, canopy color and density, soil pH (by 3 depth segments), Mehlich-3 extractable nutrients, leaf nutrient content, and root length density. Due to resultant degrees of PG canopy desiccation, one-time applications ≥12 lbs So/1000ft2 are not recommended. One year following broadcast applications, marginal soil pH reductions were primarily-confined to the surface 5-cm soil layers, yet correlated to So rate. Despite frequent visual inspection of the sand rootzone in the months following applications, no evidence of black layer (precipitated manganous- or ferrous-sulfide) was observed. Leaf nutrient content and shoot/root growth of the Penn A-4 PG showed significant response to the 6 lbs So/1000ft2 rate.