Nitrogen application timing influences winter color of ‘Empire’ zoysiagrass ( Zoysia japonica Steud.) in South Florida

Abstract

Winter nitrogen (N) fertilization for zoysiagrass ( Zoysia spp.) in South Florida is not well defined, yet maintaining a green canopy during this season is crucial for both aesthetic purposes and plant health. A 2‐year study was conducted at the University of Florida's Ft. Lauderdale Research and Education Center to evaluate the performance of ‘Empire’ ( Z. japonica Steud.) during winter under four N‐fertilization programs that varied in total rate and frequency. Treatments evaluated against an unfertilized control consisted of a total of 0.50 lb N 1000 ft ⁻² split in one or two applications and a total of 1.0 lb N 1000 ft ⁻² split in two or four applications throughout the winter. Visual quality rating (QR), Normalized Difference Vegetation Index (NDVI), percentage green cover (PC), and Dark Green Color Index (DGCI) were assessed every 2 weeks. All fertilized plots outperformed the control by the end of winter. However, 1.0 lb N 1000 ft ⁻² split into four applications produced the highest values of QR, NDVI, PC, and DGCI at the end of the evaluation period, with performance comparable with 1.0 lb N 1000 ft ⁻² applied twice throughout the winter. The lower rates maintained turfgrass performance near the acceptable threshold values. These findings indicate that “spoon‐feeding” zoysiagrass through the winter in subtropical environments can preserve winter color. Moreover, a low‐rate (0.50 lb N 1000 ft ⁻² ) of N applied through the winter can also maintain acceptable visual quality of ‘Empire’ zoysiagrass in South Florida.