Physiological Response of St. Augustinegrass to Irrigation Scheduling

Abstract

AbstractIrrigation is an integral part of a turfgrass management program and accounts for a large part of the energy inputs on a turf area. As potable water supplies decrease, use of limited water will impose stress on turfgrass areas which may result in reduced quality. Research on irrigation practices should help to minimize the effects of water stress resulting from reduced irrigation frequency. Response of St. Augustinegrass [Stenotaphrum secundatum(Walt.) Kuntze] to irrigation scheduling was studied during the summers of 1980 and 1981 on a loamy, siliceous, hyperthermic Grossarenic Palendult soil. An irrigation schedule of 2‐, 3‐, 4‐, and 6‐day intervals simulated conditions ranging from grass being under no water stress to severe water stress. Field plots were constructed to maintain an undisturbed soil profile that horizontally isolated adjacent plots to prevent lateral water movement. Irrigation treatments were implemented by irrigating with evapotranspiration estimates of 0.64 cm day−1in 1980 and 0.38 cm day−1in 1981 at either 2‐,3‐,4‐, or 6‐day intervals. Plots received equal volumes of water, only irrigation timing was varied. Turfgrass swards were evaluated on 12‐day cycles under water stress prior to irrigation and after 24 h of recovery following irrigation. Measured parameters included turfgrass quality, carbon exchange rates (CER), evapotranspiration rates (ET), plant water potential component changes, and leaf diffusive resistance, and transpiration. Irrigation scheduling affected many of the parameters studied. The 6‐day irrigation schedule caused a reduction in CER and ET and concurrent increase in stomatal resistance and a loss of turgor pressure prior to irrigation. Following irrigation, CER and ET increased, turgor pressure increased, and diffusive resistance decreased during each 12‐day cycle. When averaged over the entire study period preirrigation values of CER, ET, leaf water potential components, and transpiration were lowest and diffusive resistance highest for the 6‐day schedule, and these increased or decreased during recovery following irrigation. Even under the most severe conditions of 0.38 cm of water day−1applied every 6 days, the sward remained in positive carbon balance. Turfgrass quality and percent cover were not affected by irrigation treatments. Scheduling irrigation every 6 days with 2.3 cm of water will not affect St. Augustinegrass turf quality if adequate mowing height is maintained.