IRRIGATION FCHP Chapter 6 — part 1 HOS

IRRIGATION FCHP Chapter 6 - part 1 HOS 1010 C - Introduction to Horticulture

INTRODUCTION TO IRRIGATION CHAPTER • Florida growers depend on the ability to irrigate daily during production cycles (sometimes every few minutes). • Florida receives 50 -60 inches of rainfall each year. • This is enough to maintain any landscape EXCEPT it is not distributed evenly. • The timing, frequency and amount supplemental irrigation is often determined without proper knowledge/understanding of plants’ water needs. Irrigation management is arguably one of the most important and most over-looked aspects of a landscape.

6. 1 Define “irrigation”. Irrigation is the application of supplemental water to a soil for the purpose of supplying the appropriate moisture for plant growth. • Supplying irrigation to satisfy pant needs the at correct time is the key to water conservation. • Over or under irrigating leads to a litany of problems: decline, disease, death, leaching/run-off of nutrients and pesticides, wasted time and money.

6. 2 Describe ways to avoid excess irrigation. • Adjust timers to meet changing plant needs. • Use flow meters to determine how much water has been applied and automatically turn off the irrigation system. • Use tensiometer (electronic moisture sensor) below the rooting zone to measure water tension and cut-off irrigation system. • Use rain gauges or collection cans to measure how much water (rain) has been applied.

6. 3 Describe and compare 2 methods of deciding when to water. 1. Use site specific conditions determined by measurement (automated ET controllers, tensiometers, soil moisture probes, rain gauges). 2. Use “Potential Evapotranspiration” (ETp) available for regions of Florida from the Florida Automated Weather Network (FAWN). ETp should only be used as a general guideline when local site-specific data is not available.

6. 4 Describe how much water should be applied at each application. An irrigation event should apply enough water to penetrate the average rooting depth of the root system of plants in the ground, or to the bottom of the container for container-grown plants. • An “inch” of water is the amount that, if it remained on top of the ground, would cover the entire area to a depth of 1 -inch. • 1 inch of water in a sandy soil penetrates to a depth of 12 inches in an hour ( 6 inches for a loam soil). • To prevent leaching of fertilizers/pesticides and to promote root development, a rule-of-thumb is to apply no more than 1/2 inch to 3/4 -inch for a single irrigation event.

6. 5 List visual indicators of water need in plants. • Grass has a dull, bluish-gray coloring. • Foot tracks remain in the grass. • Turf leaf blades are folded in half on at least one-third of the site. • Soil samples from the root zone arae dry and crumbly. • Indicator landscape plants have droopy leaves.

6. 6 Identify the best time periods to apply water when using overhead irrigation. • Irrigation should be timed to reduce loss due to ET. • Avoid times of high temperature, low humidity and high wind. • Best time is usually early morning hours. On a typical summer afternoon, it is not unusual to lose 40% to 50% of overhead irrigation to ET. There are times. During plant establishment, irrigating at these times may be necessary. The main point is to use some logical method to irrigate other than just setting a timer and never adjusting it.

6. 7 Identify times when overhead irrigation should be avoided. • daily high temperatures (mid-morning through the afternoon) • low humidity (increased plant transpiration) • when there are highest winds (increased evaporation)

6. 8 List factors that cause poor uniformity in irrigation applications. • poor spacing (coverage). Should be head-to-head coverage • unmatched nozzles sizes (gpm) Poor uniformity leads to areas of over watering and areas of under watering at the same time. This leads to leaching, brown spots, waste of water and money