Nursery - Improving Irrigation Efficiency in Container Production

The following is information on an upcoming training being held in Maryland on improving irrigation efficiency in container nursery production.

Irrigation Uniformity = Irrigation Efficiency
Andrew Ristvey, Exension Nursery Crop Specialist, University of Maryland.

Irrigation management is the key to nutrient management for above ground or containerized nursery operations. Efficient irrigation systems can apply water uniformly throughout the growing bed area. An irrigation manager will determine the amount of time plants should be under irrigation based on the plant that gets the least amount of water. If an irrigation system does not apply water uniformly over the plants, then some plants will be under-irrigated, while others are over-irrigated. The over irrigated plants will leach nutrients, and the under irrigated plants will lose growth potential. Uniform application depends on many factors including operating pressure, equipment age and wear, the number of irrigation nozzles per unit distance, the overlap of irrigation water, etc. All these factors can be difficult to keep track of, but each is important for increasing efficiency.

On Wednesday October 15 an Advanced Nutrient Applicator Training will be held at the Conard-Pyle Nurseries in Centreville, MD. This program is hands-on. You will be able to interact with the instructors and experience the latest techniques in improving irrigation efficiency of container-grown crops. Not only is this program for those who need to renew their applicator voucher credits, some of which expire next year, but also for anyone managing an irrigation system. Learn to evaluate irrigation systems and how to perform an Irrigation Audit, a practical methods for achieving irrigation uniformity. Also, learn about how to evaluate your substrate’s physical properties and more... Attendance at this workshop awards 3 continuing education hours for Nutrient Applicator Voucher renewal or Maryland Nutrient Management Certification. This is one program that you do not want to miss. The program is free, but advanced registration is required; call University of Maryland Extension at the Wye Research and Education Center at 410-827-8056.

Landscape - Watering Trees and Shrubs

With the current drought in mid-state it is critical to water trees and shrubs to prevent premature defoliation

While many homeowners are diligent to keep their lawns watered and green, trees and shrubs often get ignored. Reducing stress to trees and shrubs this time of year is critical. As we go into the fall, trees are shifting internal resources and undergoing physiological changes that will enable them to withstand the rigors of the winter to come. If plants are subjected to severe stresses now, they will be more predisposed to various winter injuries. With this in mind, irrigating trees and shrubs is important in landscapes.

Give good, long soakings rather than frequent light waterings. A typical rule of thumb is to provide at least one inch of irrigation per week. How many gallons of water this translates into depends on the size of the tree. If we measure the width of crown spread of a tree we can calculate the area under the drip line. We can then figure the volume of water needed to cover this area with one inch of water.

Increase the irrigation amount as temperature soar. The one inch per week is a good rough guide but peak evaporative demand can approach three inches per week in Delaware during extremely hot summer weather.

Apply mulch properly. Mulching is the best way to conserve precious soil moisture in the landscape.

Use irrigation bags on newly established trees. Gator bags are designed to provide about 15 gallons of water over several hours, providing an easy way to ensure a slow steady watering. Gallons of water needed to provide 1 inch of irrigation under the dripline of trees of various sizes

Don’t allow water to run-off. Water that runs off is wasted water. If you’re watering by hand and notice water running off, move from tree to tree to allow water to soak in before resuming watering.

Wilting leaves, leaf scorch, dropping leaves and drooping leaders in conifers are signs of water stress. If using overhead sprinklers, some experts argue against watering late in the evening due to possible disease problems associated with wet foliage. Morning is the best time to water.

Adapted from the Michigan State University Landscape Alert Newsletter.

Landscape and Turf - Proper Irrigation

With the hot, dry weather, irrigation systems are being used in landscapes throughout the state. The following is an article on factors to consider to reduce water waste and irrigate plants properly.

Improper irrigation can lead to wasted water and potential plant problems with over or under watering. Take time to inspect irrigation systems for broken heads, leaks, clogged drip emitters, obstructed sprinklers, and sprinklers that are malfunctioning. Make sure that sprinklers in turf areas have head to head coverage/proper overlaps. Replace or repair malfunctioning sprinklers with the same types that have the same application characteristics. Don’t put different types of sprinklers in the same zone. Operate at the pressure levels sprinklers or emitters were designed for. Excessive pressure will cause misapplication and potential water waste due to misting or pressure induced leaks; low pressure will lead to poor coverage. Avoid daily watering. Water 1 to 3 times a week to wet the root zone thoroughly but without drainage loss. Cut grass on the high side and maintain mulch layers to reduce surface evaporation losses. Do not water in the middle of the day – night and early morning applications will conserve water. Avoid overspray onto impervious surfaces such as sidewalks or roads and onto areas without plants such as fence lines and pathways as this wastes water. Use a soil probe to check irrigation depth and alter irrigation timings if too shallow or deep. Avoid over-irrigation of landscape beds with overspray from turf areas - landscape beds should be irrigated separately.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Landscape and Turf - Avoid Irrigation Overspray

Irrigation systems are being used daily with the hot, dry weather. One concern is irrigation overspray. Irrigation overspray is a waste of water resources and contributes to runoff. Turf and landscape managers should make efforts to design and operate irrigation systems to avoid overspray. The following is an article on the subject.

Irrigation overspray damages pavement, contributes to stormwater pollution, and is an unsightly waste of a valuable resource. It is called nuisance water and it can be prevented.

Nuisance water is chronic running water in gutters and street crossings, standing water where it doesn’t belong, wet areas that never dry and is a common eyesore. The vast majority of nuisance water could be eliminated if managers would follow proper watering schedules, adjust sprinkler timers, and maintain irrigation systems. Overspray is a major culprit. Overspray is water from a sprinkler that lands outside the planted area on a sidewalk or roadway. This is caused by poor sprinkler maintenance and/or design.

Another common cause of nuisance water, although less easy to remedy, is poor landscape design, such as grass planted on a sloping bank along the roadway.

To locate possible nuisance water, look for runoff from an irrigated area when the sprinklers are on. This indicates that all the water is not entering the soil and could be a sign of overwatering, a malfunctioning sprinkler, a broken waterline, or improper landscape design. If the problem is not remedied, sidewalks, gutters, and streets can become slippery with algae. It can also lead to deterioration of asphalt pavement and can contribute to the creation of potholes in the street.

Irrigation overspray also contributes to stormwater pollution by causing fertilizers applied to the landscape areas to be washed away and flow into the gutter. This enters our storm drain system and eventually flows our waters (bays) which can result in reduced water quality. If you are responsible for the maintenance of landscape or turf areas, inspect your irrigation system to ensure that it is operating properly.

Adapted from information from the City of Cypress, CA.

Turf - Proper Irrigation

Hot, dry weather is upon us. For those property owners with lawns receiving irrigation, it is important to know how to irrigate properly. Turf and landscape professionals installing irrigation systems should take time to educate their clients on proper irrigation. The following is and article on the subject.

Water is essential for turf growth. It is required for germination, photosynthesis and as a part of the turf. Most of the water absorbed by turf is transpired through the leaves into the atmosphere. This water moves nutrients from the soil into the plant, but equally important, it eliminates heat buildup from solar radiation.

The water applied by an irrigation system will evaporate from the soil and be transpired from plant surfaces. Evaporation and transpiration (evapotranspiration) depend mostly on the climate around the plant, thus, the amount of water used by turf changes with the seasons. Because of this, for a well-managed turf, irrigation frequency should change with the time of year.

Only water that is in contact with the roots can be absorbed by the plant. The volume of soil where water can be stored is as deep as the roots are. Root depth is affected by mowing, fertilizing and irrigation practices. A well-managed turf system will develop most of its roots in the first 12 inches of the soil. Another important property of the soil reservoir is that soils have a limited ability to store water. The larger the pores in the soil the less water the soil will hold. Sandy soil hold much less water than loam soils.

Two questions must be answered when scheduling irrigation:

WHEN DO I IRRIGATE?

Water should be applied to turf only when soil-water in the root system has been depleted to an unacceptable level, usually by 1/2 to 2/3 of the stored soil-water. There are several ways to determine when the soil-water reservoir has been depleted beyond an acceptable level. These are:

Visual inspection of the turf . Becoming familiar with the way that turf reacts when water is becoming scarce in the soil is a common method of deciding when to apply irrigation. Common symptoms of water stress include leaf color changes to a bluish-gray tint, footprints that linger long after being made, and curled or folded leaf blades.

Estimations based on climatic records . Past history of climate can be used to estimate how often irrigation should be applied to turf. Tables are available that show the expected number of days that soil water will last for a certain texture of soil.

Direct measurement of soil moisture . Using sensors for measuring the amount of available water in the soil is another way to determine when to irrigate. One such sensor is the tensiometer. As the soil dries, water moves out of the tensiometer through the ceramic, causing a suction that is measured by the vacuum guage. Other moisture sensors are also available and systems can be automated using these sensors.

HOW MUCH WATER SHOULD I APPLY?

The quantity of water applied to turf should not exceed the amount required to refill the soil occupied by the root system (poor quality water may require higher volumes for leaching). Regardless of the time of year, for an established turf the quantity of water applied at each irrigation should always be the same. Irrigation will not be required as often during low demand periods. Typical Delaware soils will be able to hold at least 1 inch of water per foot of soil. The amount of water to apply to a one-foot-deep soil water reservoir, which has been depleted to 50 percent and has a water holding capacity of one inch per foot (1"/ft), is 2/3 of an inch of water.
This assumes an irrigation efficiency of 75 percent. The total volume required will depend on the size of the area being irrigated and the soil-water holding capacity. It takes 620 gallons of water to apply one inch of water to 1000 square feet of an area.

APPLYING IRRIGATION

In order for irrigation to be successful and efficient, the volume of water applied must be measured. There are several ways to measure irrigation volumes of water.

Using a water meter . In a permanently installed system a water meter should be included as part of the irrigation system. In systems that are connected to an urban water supply, the meter installed by the service company can be used. The time required to apply the necessary water can be easily determined by observing the water meter to measure how much water is applied by the irrigation system in a minute. For example, a system that requires 1200 gallons is turned on, and from the meter it is observed that 12 gallons per minute are being used. Thus, the time that the irrigation system should be turned on is 100 minutes (1200 gallons divided by 12 gallons per minute).

Measuring the depth of water applied . When a water meter is not available place five wide- mouth, flat-bottom cans spaced equally along the diagonal of four sprinklers. After 20 minutes of irrigation, turn the system off and use a ruler to measure how deep the water is in each can. Average the five measurements and use the average to determine the time required to apply 2/3 of an inch of water. For example, if a 20-minute can test resulted in an average water depth of 1/2 of an inch, the time that irrigation system should be turned on in order to apply 2/3 of an inch of water is obtained from is 27 minutes. Any water applied after 27 minutes will be wasted as deep percolation.

If a hose and sprinkler is used with this method, set the sprinkler pattern to 1/4 of a circle before carrying out the test. Move the sprinkler to each corner of the irrigated area and irrigate for five minutes from each corner for a total of 20 minutes. When irrigating the turf, apply water for the irrigation duration when the hose-and-sprinkler is used in full circle; for 1/2 the irrigation duration when the hose-and-sprinkler is used in half circle; and for 1/4 the irrigation duration when the hose- and-sprinkler is used in quarter circle. Also, if possible, carry out the test in the early morning hours and under no-wind conditions.

Using automatic shut-off values . A variety of automatic shut-off valves are available that are especially suited for irrigating with a hose and sprinkler. These allow the user to set a time period or volume to apply. These are inexpensive and convenient and reduce water waste due to lack of attention to hose-and-sprinkler systems.

Using soil-moisture sensors . When permanently installed irrigation systems are run using timers, sensors can be used to control these systems. The timer should be set to irrigate every day to apply about 1/3-1/2 of an inch of water during early morning hours for best efficiency. The moisture sensor will allow irrigation only if water is required.

Adapted from "Turf Irrigation for the Home" by F.S. Zazueta, A. Brockway, L. Landrum and B. McCarty, University of Florida.

Turf and Landscape - Overirrigation

With the recent hot weather, irrigation systems have been running in turf areas and landscapes. However, there is potential for over-irrigation and this can cause many problems. The following is an article on the subject.

One common problem that I routinely see is over-irrigation in the landscape. This occurs with improper use of manual irrigation systems, automated irrigation systems with design flaws such as improper overlaps, and irrigation systems with maintenance problems such as broken sprinkler heads or missing drip emitters. It also occurs where irrigation scheduling is improperly done so that excess water is applied or is applied incorrectly.

Excessive irrigation can lead to many problems. Frequent, light irrigation can lead to shallow rooting, especially in turf, making plants more susceptible to stress. Excessive watering can increase foliar disease pressure in turf and root and crown rots (Phytophthora, Pythium) in susceptible ornamentals such as Taxus (yew), junipers, azaleas, rhododendrons, Japanese hollies, hemlock, dogwood, Camellia japonica, Pieris, deodar cedar, mountain laurel, heather, high-bush blueberries, white pine, leucothoe, boxwood, and others. Many perennials and annuals such as geraniums and chrysanthemums are also susceptible to these root rots in wet conditions. Over-irrigation also results in nitrogen leaching and runoff. Excess water can lead to increased weed pressure from nutsedge, nimblewill, bent grass, crabgrass and moss and will decrease the longevity of preemergence herbicides. Weed growth on top of mulch is encouraged in landscape beds that stay wet. Drainage ways, low areas, shaded areas, and areas with restrictive soil layers are the most at risk for overwatering.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Turf - Irrigating Lawns

A frequently publicized rule of thumb for irrigating lawn turf is to apply 1 to 2 inches of water per week. Although this may keep turf green during most of the summer, it may be wasteful or ineffective, particularly where thick thatch layers, heavy clay soils, or "hard pans" exist. In general, it is much more effective to water turf by need and not by rule.

The best time to irrigate the lawn is when turf just begins to show signs of wilt. This of course is not always easy to determine. However, there are two prominent symptoms exhibited by turf as it begins to wilt: (1) foot printing, and (2) turf develops a blue-green or blue-gray leaf color. After walking across drought stressed turf, leaves of the walked upon plants remain depressed for several minutes, providing the "foot printing" effect. When turf exhibits foot printing or develops a blue-gray color, it is very important that the turf be irrigated to avoid permanent wilting of leaves, and induction of summer dormancy (i.e. browning of the turf). During periods of extreme heat and drought stress dormant plants may die. Some professional managers use instruments that measure soil moisture levels, but most rely on the visual symptoms expressed by drought stressed turf, and frequent soil probing to determine moisture levels.

The lawn should be deeply watered as soon as it has been determined that turf is under drought stress. The duration and quantity of water applied should be sufficient to wet the soil to a depth of 4 to 6 inches. Deep watering encourages the roots of grass plants to grow deeper into soil. This indirectly enhances the drought resistance of turfgrasses by providing a greater reservoir of soil water for plants to draw upon.

The duration and quantity of water needed depends greatly upon soil texture and structure, and thickness of the thatch. In many housing developments, lawns are grown on sub-soils deposited during excavation that have higher clay content. This type of soil resists water penetration and the downward movement of water (percolation) through the soil. In many situations, it is extremely difficult to get water percolation to a 4 to 6 inch depth. Hence, on heavy, clay soils or where hard pans and dense layers of thatch exist, water must be applied slowly. If the rate of water applied exceeds the rate at which water infiltrates soil, water will run off and be wasted.

Sprinklers will have to be moved as water begins to run off onto sidewalks or the driveway. The sprinkler must be continually moved back and forth on rapid run-off areas at 30 to 90 minute intervals or as needed until water has penetrated to the desired depth. Installed underground systems will require zoning, turning one zone on, the turning it of and turning another zone on, back and forth until fully watered. The same principles and practices apply when irrigating turf on slopes or other rapid run-off areas. Probing the soil will enable an individual to determine soil moisture depth. This is best achieved using a probe that removes soil plugs. Probing with a screwdriver also may provide a good indication of depth of soil wetness.

Night irrigation is discouraged because it may encourage diseases, particularly when night temperatures exceed 68 F. Night irrigation, however, is a standard practice on golf courses and other large recreational turfs. Night irrigation is preferred in the aforementioned situations because it does not interfere with daily management operations or recreational activities, and it reduces the potential for soil compaction in turf areas with heavy traffic. The best time to irrigate is during the coolest part of the day when there is no wind. These conditions usually occur during early morning or late afternoon, and help conserve water by reducing evaporation. Conversely, mid-day irrigation during hot, sunny or windy days should be avoided because of increased evaporative losses of water. Furthermore, water that collects in low areas and inundates the turf for an extended period may cause scald injury during sunny, hot periods. Contrary to a popular misconception, scald will not occur if water is applied properly on hot days when turf is under heat and drought stress. Scald will only occur when turf has been inundated by water for an extended period of time on sunny and hot days.

Excessive or frequent irrigation can be just as detrimental to turf as inadequate watering. Turfgrass plants that are subjected to frequent irrigation become lush and succulent. These lush plant tissues are more susceptible to injury from heat, drought, and wear stress, and are more prone to disease injury. Frequent irrigation also discourages roots from growing deeper into soil thereby limiting the soil volume from which plants obtain water and nutrients. Excessively irrigated turf is more prone to invasion by moss and algae, and wet soils are more easily compacted by traffic. Soil compaction is common on homelawns, particularly those lawns where children play frequently. Turf growing in compacted areas will have restricted root systems, and lose vigor as a result of poor aeration. Because of the harmful effects of compaction, turf growing in these areas has a tendency to wilt more rapidly during dry periods, and normally thins-out allowing crabgrass, knotweed and other weeds to invade the area. Compaction can be minimized by not subjecting turf to traffic, and other heavy uses when soil is wet. Compaction can be alleviated by aeration, but only rototilling, adding soil amendments (if necessary), and reseeding or sodding the area will cure the problem.

Light and frequent irrigation also restricts rooting, reduces stress tolerance, enhances germination of weed seed (especially crabgrass, goosegrass and white clover seed), and encourages diseases. Many homeowners get into the habit of applying small amounts of water to their lawns on a frequent basis. These homeowners often return to a brown lawn after taking a one or two week vacation during hot, summer months. Grasses in these brown lawns are usually not dead, but in a state of dormancy. However, in extreme cases of drought coupled with a past history of light and frequent irrigations, large areas of the lawn may die. Homeowners who are likely to take vacations longer than one week in the summer are best advised to begin restrictive, deep and infrequent irrigation several weeks in advance of their vacation. Light and frequent, or excessive watering prior to leaving on vacation is likely to cause more severe injury than not applying any water at all. This is particularly true where Kentucky bluegrass or perennial ryegrass are the predominant turf species.

Adapted from "Irrigation and Water Conservation on Home Lawns", Agronomy Memo 88, from the University of Maryland

Greenhouse - Overhead Irrigation Reduces Mite Populations

The following is a report of research on the effect of overhead irrigation on mite populations in greenhouses.

Irrigation and Twospotted Spider Mites.

Research update by George Opit, USDA-ARS GMPRC, Manhattan, KS

For many years the literature has stated that overhead irrigation of greenhouse crops can reduce insect/mite pest populations. Unfortunately, it also can be labor intensive if done by hand, may increase disease incidence, and typically increases water usage. Therefore, does the increased switch away from overhead irrigation by production greenhouse growers also result in potentially higher insect/mite pest pressures? The USDA, in cooperation with the Kansas State Cooperative Research and Extension, recently conducted a study to determine impacts of overhead irrigation vs. systems that do not wet foliage (e.g. drip tubes, flood floor, & ebb & flow benches) on insect/mite pests. Their research specifically compared hand watering vs. drip tube irrigation methods on twospotted spider mite (TSSM) pest populations and beneficial predacious mites (P. persimilis). The crop selected for this study was impatiens ‘Impulse Orange’.

Two studies were conducted to test the effect of the different irrigation strategies, hand-watering and drip-tube, on the populations of TSSM and predacious mites (P. persimilis). The first study the crop was watered 2 times every 3 days, and the second study tested two frequencies – ‘wet’ (the crop was watered 2 times every 2 days) and ‘dry’ (the crop was watered 3 times every 4 days). The environmental conditions were controlled within narrow ranges – the temperatures were maintained at 23-26? C, and the relative humidity was maintained between 34-46%. The number and release of adult female twospotted spider mites and adult female P. persimilis predacious mites on the crop was also tightly controlled.

The first study, in which the crop was watered 2 times every 3 days, indicated that the hand watered plants had far fewer pest mite populations than those plants that were irrigated with drip tubes. In fact, the experiments showed that the hand-watered plants had a 98% reduction in pest mite populations compared to the drip tube irrigated plants. The impact of the irrigation types on the beneficial mite (P. persimilis) populations was also very dramatic. The predatory mite numbers were much lower on the handwatered plants compared to those irrigated with drip tubes. Similar to the twospotted mites, their populations were reduced by greater than 97%. The different irrigation frequencies, ‘wet’ and ‘dry’, applied in the second study had no effect on either the TSSM populations or the P. persimilis mite populations. Each of the frequencies applied provided similar reductions.

The use of both hand watering and the release of P. persimilis mites significantly lowered TSSM pest numbers. The P. persimilis mite was capable of multiplying rapidly under drip tube irrigation. However, hand watering was even more effective than the predatory mites at reducing TSSM. Furthermore, hand watering reduced spider mite related crop damage more successfully than P. persimilis on drip tube irrigated plants. Although the role of P. persimilis as a control for spider mites in hand watered crops is small, they do provide a major contribution for reductions with drip tube irrigated plants. In general, however, greenhouse production areas not using overhead irrigation will typically be more susceptible to spider mite infestation problems.

Greenhouse production sites that normally use drip tube, flood floor, or ebb & flow bench irrigation methods could incorporate overhead watering to suppress local hot spots of twospotted spider mites preceding the release of P. persimilis. Such a strategy would epitomize the true meaning of integrated crop management (ICM).

Reprinted from the Winter 2006 edition of Greenhouse IPM Notes a joint newletter from the Cooperative Extension Services of Rutger and Cornell.