Correlation and calibration of Mehlich-3 sulfur for Kentucky bluegrass

Abstract

Sulfur (S) is a crucial macronutrient for turfgrass growth, and declining atmospheric deposition has increased the risk of S deficiency. Reliable Mehlich-3 soil test interpretations for S are lacking for turfgrass. This study aimed to correlate and calibrate Mehlich-3 S with the visual quality and yield of Kentucky bluegrass (Poa pratensis L.) through four field trials conducted over 2 years in Lexington, KY. Results indicated that critical Mehlich-3 soil S concentrations for acceptable turfgrass quality ranged from 3.1 to 5.7 mg kg⁻¹ varying by seasons, and for maximum yield ranged from 6.1 to 8.1 mg kg⁻¹. Applying S at a rate of 8.2 kg ha⁻¹ alleviated visual S deficiency symptoms and resulted in acceptable turfgrass quality when soil S was limiting. Tissue S content was more variable than extractable soil S but tissue S also correlated well with turfgrass response. When antecedent Mehlich-3 S levels were ≥8.4 mg kg⁻¹, S application did not improve turfgrass parameters. This research demonstrates the Mehlich-3 extract can be used to predict soil S deficiencies for Kentucky bluegrass, with concentrations ≤5.7 mg kg⁻¹ suggesting a high risk of turfgrass quality reduction, and soil with >8.4 mg kg⁻¹ unlikely to be associated with S-deficient Kentucky bluegrass.