Bermudagrass fairway responses to various combinations of a soil surfactant and nitrogen

Surfactants are commonly employed in sand-based turfgrass systems to address soil water repellency, which often results in the formation of preferential flow channels leading to non-uniform wetting patterns. While the influence of soil moisture on nutrient dynamics is well documented, the potential of surfactants to improve N uptake remains poorly understood. A 2-year study was conducted on ‘Celebration’ bermudagrass [Cynodon dactylon (L.)] fairway to better understand the interaction between fertility programs (296 or 586 kg N ha⁻¹ year⁻¹ from ammonium sulfate and 564 kg N ha⁻¹ year⁻¹ primarily from a controlled-release N fertilizer) and surfactant rate and frequency (3.2 L ha⁻¹ every 14 or 28 days, or at 6.4 L ha⁻¹ every 28 days) on turfgrass performance, leaf N content, and soil moisture. Overall, no significant interaction was observed between surfactant treatment and fertility program. During the dry season (November to May), fertility programs influenced turfgrass performance parameters with higher N rates consistently leading to improvements in visual quality, normalized difference vegetation index, percent green cover, and dark green color index; however, no differences were observed during the rainy season (June to October). Surfactants showed no effect on turfgrass performance but led to minimal increase in leaf N content from 3.72% to 3.85%. All surfactant treatments reduced water drop penetration time at 0 cm. Moreover, surfactant treatments applied every 28 days regardless of the rate exhibited a higher volumetric water content compared to those applied every 14 days. Surfactant applications might not be an economically feasible strategy to improve leaf N content in South Florida well-watered bermudagrass fairways.