Municipal Water Restrictions and Water Conservation

Drought conditions occur on a regular basis throughout the U.S. In 2002, Colorado and most of the western U.S. experienced one of the worst drought years in 110 years of records (see Doesken and Pielke's report). Drought conditions in Georgia have only recently been alleviated by recent rains (see the 3 April 2009 report). Drought conditions often have many economic impacts and the greenhouse and nursery industry is not immune.

Severe droughts often trigger municipal watering bans and plant restrictions. How the greenhouse and nursery industry responds to these regulations requires an integrated approach requiring participating from all involved including growers, landscapers, property owners, water providers, and local government. The Green Industries of Colorado managed to assist growers, retailers, and contractors to survive the 2002 drought through a proactive establishment of Best Management Practices (BMPs) developed in collaboration with all parties.

There are a lot of facts that are often not published when it comes to water use and water consumption. No one likes to see sprinkler systems in poor repair running water everywhere excpet where intended. Landscape irrigation is very visible to the public, but is that where our water goes?

The U.S. Geological Service (USGS) last published an estimate of water use in the United States. The authors determined that the U.S. uses 408,000,000 per day. They estimated that 323,000,000 per day is from surface supplies. The largest single component (48%) of that water use is from the generation of electricity from thermoelectric generating stations (Fig. 1). Second is that from general agriculture (35%), which includes irrigated crops as sell as livestock operations.



Public, domestic, industrial, and mining consume only 16% of the U.S. water. Of that only 46,890,000 gal/day include public and domestic water use. Outdoor water use is estimated to be between 40 and 60% of that use, which ranges from 18,756,000 to 28,134,000 gallons per day or 8.7% of all water used in the U.S.

During times of drought, municipalities often impose watering restrictions. These may range from voluntary restrictions to required watering schedules. Many of these restrictions may be draconian to the point where they may impact the landscape and related green industries.

What is the impact of water restrictions? Do they serve the purpose for which intended? Are those restrictions developed from science or are they developed by bureaucrats operating from a sense of control rather than the impacts of their actions on all effected.

During the late summer of 2002, Colorado was in the midst of coping with a devastating drought and dwindling water supplies. By mid-summer, most municipal water providers implemented some form of watering restrictions and the city of Fort Collins was not different. They implemented an even and odd address irrigation pattern with an attempt to ease water demands.

After receiving a very revealing water bill, a Fort Collins area manufactured home park manager contacted me wondering why the park's water use was so high (Fig. 2).

It is important to note some demographics of this 27 acre park. The park is 100% owner occupied and of those residents, 80% are retired. To maintain a quality environment, the park provides water with an expectation that the residents keep the grass green.

Looking at the months of May and into June 2002, you can see that the water use was on the decrease. During this period water restrictions were voluntary, but on 27 July, mandatory restrictions were enforced. It was at this point that water use increased to a level greater than the year prior.

So why did the water use increase? It is simple human nature. When it is your turn to use a resource, you will use it whether you need it or not. So goes the fallacy of mandatory irrigation scheduling.

The spring planting season is upon us and with any luck, this will be a great year for the green industries. With the economic downturn, many will be staying home and will want to have their own private oasis. Promote good gardening, promote good plants, and recommend proper watering practices.

Xeriscape not zeroscape.

No Leach Irrigation Strategies for Greenhouse Poinsettia Production

For a commercial greenhouse operation to remain sustainable, irrigation practices should be modified to better manage limited water resources as well as manage non-point source pollution issues. We have the technologies to do this in many forms, including waste water capture and recycling water in greenhouses, yet acceptance is low due to the costs of implementation as well as inadequate technical information.

Early in my career at Colorado State University, I worked with Sean Moody, a graduate student who completed a study on growing poinsettias using strategies to reduce leachate and. His study used two cultivars, Eckespoint Freedom Red and Gutbier V- 17 Angelika Red (provided by the Paul Ecke Ranch), which were subjected to three irrigation strategies: 10% leach, ebb-and-flood and no leach or pulse, at two constant liquid feed fertilizer rates, 150 and 300 ppm N from 15-5-15 Cal-Mag Plus from O.M. Scott.

Heavy leaching of water and fertilizer is not an acceptable and sustainable production practice. Most fertilizer recommendations for poinsettias suggest 200 to 400 mg·L^-1 nitrogen (N) applied at every irrigation. Ebb-and-flood (Fig. 1) is one alternative to heavy leaching, but there is a high investment cost in equipment and maintenance. When using ebb-and-flood or pulse irrigation, which is accomplished with small frequent irrigation applications applied to saturate the media with no leaching, fertilizer concentrations must be reduced to avoid high electrical salt build up in the root-zone medium.

Pulse irrigation is a modification of a conventional irrigation system that applies water at reduced volume with little or no leach. Pulse irrigation strategies can be designed using conventional micro-tube irrigation emitters. However, the irrigation controller must be sophisticated enough to provide precision control in fractions of a minute. Additionally, pressure compensated emitters must be used to ensure that each pot receives the exact same volume of irrigation solution from one end of the bench to another.

The study was conducted from week 34 (transplant) through week 47 (anthesis) in a FRP-glazed greenhouse. The plants were grown in 6-inch azalea pots using Premier Pro-Mix HP. All plants on the ebb-and-flood benches were irrigated when approximately 2.5 cm of moist media remained at the bottom of the pot. The irrigation solution was pumped from the holding tank to the containers bench top, held for 10 min., and drained back to the tank for later recirculation. Fertilizer solution was added to the tanks when the level dropped below half to maintain enough solution to sufficiently flood the benches. Pulse and 10% leach strategies were calibrated to where the leachate was equal to zero and 10% of applied solution, respectively. Pulse irrigation was conducted once daily until week 40 and twice daily subsequently at 900 and 1300 MDT study. The 10% leach plants were irrigated daily.

Leaching of containers is a common practice to prevent high salt build-up in the medium of greenhouse crops. The salt levels are typically measured by determining the electrical conductivity (EC) of the root-zone medium. For this study, from three horizontal sections of the media, top, middle and bottom, a saturated paste extract for each irrigation treatment was collected. The EC was then determined from those sections.

'Angelika Red' dry weight, height, and width were greater than 'Freedom Red' as one would expect. Fertilizer rates did affect plant growth in this study, thus those data were pooled. Ebb-and-flood irrigation only slightly reduced plant width of 'Freedom Red' (Fig. 2) and pulse irrigation slightly reduced plant width of 'Angelika Red' (Fig. 3). Other studies have reported that sub-irrigation treatment or no leaching yields poinsettia plants of similar size.

Irrigating to 10% leach resulted in the lowest EC values for poinsettias, followed by pulse, while ebb-and-flood had the highest EC values (Fig. 4). The top medium layer had higher EC values for all three irrigation strategies, which was expected due to the wicking of water to the surface of the medium. The EC value of the top layer from the ebb-and-flood irrigation at 300 mg·L^-1 N resulted in an EC value 1.5 times greater than that normally thought to be injurious to plant growth (>8 mS·cm^-1). Even the middle and bottom layers of the containers from the ebb-and-flood irrigation at 300 mg·L^-1 N had EC values greater than 4 mS·cm^-1, which is considered to be too high, i.e. 4-8 mS·cm^-1. At 150 mg·L^-1 N, the top layer for ebb-and-flood as well as pulse irrigation had a relatively high EC value of approximately 4 mS·cm^-1 or greater (Fig. 4), but all other EC values for the other layers of the container were within acceptable levels, between 2-4 mS·cm^-1. The EC values for the 10% leach irrigation at 150 mg·L^-1 indicated low fertility; whereas, at 300 mg·L^-1 was adequate for good plant growth.

Poinsettias of acceptable quality may be successfully grown using ebb-and-flood or pulse irrigation strategies at constant liquid feed fertilizer rates of 150 mg·L^-1 nitrogen (N). No leach irrigation practices in excess of 300 mg·L^-1 N may result in excessively high EC values resulting in poor plant growth. These practices effectively reduce runoff as and can be adopted to reduce the non-point source pollution risk of a greenhouse.

To see Sean's thesis, click here.
Sean now works for Landscape Designs by Ellison

No Leach Irrigation Strategies for Easter Lily Production

This is a continuation from the previous post on No Leach Irrigation Strategies for Easter Lily Production. In addition to studying no leach irrigation on poinsettia production, Sean Moody also did a follow-up study using 'Nellie White' Easter lilies (provided by the Fred C. Gloeckner & Company, Inc.), which were subjected to three irrigation strategies: 10% leach, ebb-and-flood and no leach or pulse, at two constant liquid feed fertilizer rates, 100 and 200 ppm N from Technigro 17-5-24 plus; Fisons Horticulture Inc.

The study was conducted from week 1 (case-cooled bulbs were transplanted) and spaced at emergence week 4 in a FRP-glazed greenhouse. The plants were grown in 6-inch azalea pots using Premier Pro-Mix HP. The study was terminated week 13.

All plants on the ebb-and-flood benches were irrigated when approximately 2.5 cm of moist media remained at the bottom of the pot. The irrigation solution was pumped from the holding tank to the containers bench top, held for 10 min., and drained back to the tank for later recirculation. Fertilizer solution was added to the tanks when the level dropped below half to maintain enough solution to sufficiently flood the benches. Pulse and 10% leach strategies were calibrated to where the leachate was equal to zero and 10% of applied solution, respectively. Pulse irrigation was conducted once daily until week 40 and twice daily subsequently at 900 and 1300 MDT study. The 10% leach plants were irrigated daily.

Leaching of containers is a common practice to prevent high salt build-up in the medium of greenhouse crops. The salt levels are typically measured by determining the electrical conductivity (EC) of the root-zone medium. For this study, from three horizontal sections of the media, top, middle and bottom, a saturated paste extract for each irrigation treatment was collected. The EC was then determined from those sections.

Easter lily plant growth was not affected by fertilizer rate. Easter lily plants were tallest when grown with ebb-and-flood irrigation and pulse irrigation reduced dry weight, height width and growth indices slightly (Fig. 1). The irrigation practices 10% leach and ebb-and-flood irrigation resulted in the lowest EC values for Easter lilies compared to ebb-and-flood and pulse irrigation (Fig. 2). Higher EC values for all three irrigation strategies were evident in the top layer, which was expected due to the wicking of water to the medium surface as with poinsettias. The EC value of the top layer from the pulse irrigation treatment at 200 mg·L^-1 N resulted in an EC value considered to be potentially dangerous to plant growth (4-8 mS·cm^-1).

Easter lilies of acceptable quality may be successfully grown using ebb-and-flood or pulse irrigation strategies at constant liquid feed fertilizer rates of 100 mg·L^-1 nitrogen (N). No leach irrigation practices in excess of 200 mg·L^-1 N may result in excessively high EC values resulting in poor plant growth. These practices effectively reduce runoff as and can be adopted to reduce the non-point source pollution risk of a greenhouse.

To see Sean's thesis, click here.
Sean now works for Landscape Designs by Ellison