Plant growth regulator and nitrogen fertilizer effects on soil organic carbon sequestration in creeping bentgrass fairway turf

The objective of this study was to determine the effects of plant growth regulator (PGR) (no PGR, trinexapac-ethyl, and paclobutrazol) and N fertilizer (zero N, an average of 37 kg N ha⁻¹ month⁻¹, 6 and 12 kg N ha⁻¹ week⁻¹) on soil organic C (SOC) and soil N in creeping bentgrass (Agrostis stolonifera L.) fairway turf. After 4 years of field experiments soil samples were obtained from soil depths of 0-2.5, 2.5-5, 5-7.5, 7.5-10, 10-15, 15-20, and 20-30 cm. Soil bulk density, SOC, total N, NO ₃ ⁻ -N, and NH ₄ ⁺ -N concentrations were determined. Paclobutrazol and trinexapac-ethyl application increased SOC. The 37 kg N ha⁻¹ month⁻¹ application increased SOC at the 0-2.5 cm depth with both PGRs. When paclobutrazol was used, N fertilizer always increased SOC; however, the greatest increase was observed with the 12 kg N ha⁻¹ week⁻¹ application when compared to other rates, inversely related to the NH ₄ ⁺ -N concentration. Nitrogen application increased soil total N and NO ₃ ⁻ -N in the upper three depths. The application of PGRs and N fertilizer to creeping bentgrass fairway turf is an effective strategy for promoting C sequestration.