ABSTRACT
Research was conducted to assess the suitability of using multispcctral scanner data to evaluate turfgrass stress associated with irrigation management. Tall fescue (Festuca arundinacea Schreb) was irrigated under three different leaching fractions (LF = 0.05, 0.15, 0.25) and three different application uniformity coefficients (UC = 0.65, 0.75, 0.85). Each research plot was equipped with a lysimeter that allowed maintenance of a complete hydrologic balance for quantifying evapotranspiration (ETa) and scheduling irrigations based on established LF'S. Canopy temperatures (solar noon) and tissue moisture contents were measured on a 5 × 5 grid within each plot to coincide with remote sensing data acquired on July 28, 1994. Biomass was estimated from a weekly cutting (5.08 cm cutting height) taken on both the lysimeter and whole plots. A two way ANOVA indicated that average NDVI (normalized difference vegetation index) values varied by UC based on the low UC (low UC = 1.4675, med UC = 1.5475, high UC = 1.5447, df = 2, p = 0.022). Average NDVI values did not vary by LF (p = 0.081) but a significant interaction between UC and LF on average NDVI values was observed based on separation of the low UC value at both the low and medium LF (df = 4, p = 0.045). Average NDVI values for each plot were cross correlated with biomass (r2 = 0.37**), canopy temperature (r2 = 0.29*), tissue moisture content (r2 = 0.90***), and ETa/ETo (r2 = 0.81***). Kriging was performed on 5 × 5 data sets of NDVI, canopy temperature, soil matric potential and tissue moisture content, for the most stressed turfgrass plot, to determine similarities in spatial structure as influenced by low uniformity and low leaching. The resulting isopleths indicated a similar shape for all four parameters. Our results thus suggest that high spatial resolution (1 m) multispectral data could provide NDVI values to assess turfgrass health on a microscale within large irrigated areas as influenced by the irrigation system and management practices.
