Scientifically, irrigation should occur based on plant response to environmental demand. Thus, irrigation frequency and amount will be defined by the environmental demand (i.e., evapotranspiration, ET), soil water-holding capacity, and plant root zone depth. Irrigation should be applied such that the soil water reservoir is filled and gravity drainage and runoff do not occur. This approach is detailed in an EDIS publication, Basic Irrigation Scheduling in Florida, (Smajstrla et al. 2006), which provides summary information from internationally recognized publications such as Crop Evapotranspiration: Guidelines for Computing Crop Water Requirements (Allen et al. 1998). This scientifically accepted approach aims to result in "well-watered" conditions where no stress is allowed. In addition, an irrigation system must be well-designed and in good repair to apply irrigation efficiently to plants (i.e., without losses due to runoff and deep percolation).In practice, irrigation is often limited to specific days of the week by water management districts through most of Florida. Thus, landscape plants may undergo varying levels of stress depending on specific site conditions and plant type.PLANTSIn the case of newly planted trees and shrubs, water should be applied to the root ball and perhaps the soil just beyond the root ball. In all of the studies over the past twenty-two years on trees in Florida, the area beyond the root ball has not been irrigated. Trees and shrubs establish decently without broad, landscape-wide (i.e., sprinkler) irrigation. For example, live oak and southern magnolia tree root systems extend to about 14–20 feet in diameter one year after planting in a non-compacted soil without interference from curbs, sidewalks, and other soil obstructions.TURFGuidelines for turf irrigation include an irrigation system that is well designed and in good repair. Generally, UF/IFAS irrigation guidelines recommend irrigation of ½–¾ inches when 30–50 percent of turfgrass shows signs of wilt during the day. However, if an automatic irrigation system is used under day-of-the-week water restrictions, program run time recommendations are given in Operation of Residential Irrigation Controllers. The recommendations in this publication have been further refined into user-friendly guidelines and posted as the FAWN urban irrigation scheduler.Generally, these irrigation schedules developed for turfgrass will over-irrigate ornamental plantings. As indicated in this section, the most efficient way to irrigate trees and shrubs is using microirrigation. Ongoing research projects using these schedules have shown that 60 percent replacement in Operation of Residential Irrigation Controllers (https://edis.ifas.ufl.edu/ae220) and "maximum conservation" in the FAWN urban irrigation scheduler, http://fawn.ifas.ufl.edu/tools/urban_irrigation/, provide adequate water for St. Augustinegrass during drought with well-designed irrigation systems in good repair. Technologies such as soil moisture sensor irrigation controllers have been shown to reduce irrigation 70–90 percent over a range of irrigation schedules and controller brands (Cardenas-Lailhacar et al. 2008).Many homeowners set irrigation amounts and do not readjust properly for seasonal changes. This tendency is reinforced by water restrictions which mandate specific day-of-the-week schedules. Day-of-the-week water restrictions have been shown to reduce municipal water use 15% to 20% in SFWMD during the spring and summer of 2007 (data not shown), but this amount is far below the 50% reduction expected from a 2 day/week to a 1 day/week transition. Recommendations, such as SWFMD's winter "Skip a Week" campaign, encourage users to adjust their time clocks. However, the challenge with such recommendations is getting homeowners to follow through on them.​​