Topography and Sampling Strategy Influence Soil Fertility Parameters of Golf Course Fairways.

Routine soil fertility testing is a commonly used method of estimating fertilizer and/or lime requirements of turfgrass systems. Soil sampling is the critical first step, and the accuracy of nutrient availability prediction increases with number of soil cores collected from each area of interest. Which leads the age-old question; how many sub-samples comprise a robust composite sample? Four- to six-hundred sq. meter sections of three (3) identically-managed Kentucky bluegrass / perennial ryegrass fairways, each situated on a shoulder, footslope, or toeslope landscape position, were intensively grid-sampled in 2017. Thatch was removed and the upper 7-cm soil ground to pass a 0.25-mm sieve before routine fertility analysis by Penn State University’s Ag. Analytical Services Laboratory (AASL). Organic soil carbon fractionation is ongoing and results will be presented. Typical of soils formed in limestone residuum, 1:1 aqueous reaction was predominately neutral. Yet the degree of spatial variability observed within each fairway, comprising as many as two pH-units, was surprising. Generally, Mehlich-3 extractable soil Ca showed direct relation to soil pH and cation exch. capacity (CEC, by summation) levels. Within each fairway, sample elevation related indirectly to Mehlich-3 extractable soil K and S levels. These results show that despite having received identical cultural management inputs for 50 years, nutritional assessment of golf course soil is highly-influenced by both structured and unstructured spatial variabilities. While still in development, guidance on a site-specific method of sampling golf course fairway soil will be presented.