THESIS

PULSE IRRIGATION STRATEGIES FOR GREENHOUSE PRODUCTION

Submitted by D. Sean Moody Department of Horticulture and Landscape Architecture

In partial fidfillment of the requirements for the Degree of Master of Science Colorado State University Fort Collins, Colorado December 1996

COLORADO STATE UNIVERSITY

November 12. 1996

WE HEREBY RECOMMEND THAT THE THESIS PREPARED UNDER OUR

SUPERVISION BY D. SEAN MOODY ENTITLED PULSE STRATEGIES

FOR

GREENHOUSE

PRODUCTION

BE

IRRIGATION

ACCEPTED

AS

FULFILLING IN PART REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE.

Committee on Graduate Work

Advisor

Department Head

ABSTRACT OF THESIS PULSE IRRIGATION STRATEGIES FOR GREENHOUSE PRODUCTION

The purpose of the study is to reduce the amount of water and nutrients applied, and with this, reduce the amount of groundwater contamination that results in over watering and over fertilizing. The study is an irrigation study to observe the effects of eliminating runoff fiom irrigations and lowering fertilizer concentrations. Three irrigation strategies [lo% leaching, no leaching (pulse), and ebb-and-tlood] and two constant liquid feed fertilizer treatments, [I50 and 300 mg.L-' nitrogen (N)], were applied to two poinsettia cultivars, [Eckespoint Freedom Red and Gutbier V- 17 Angelika Red], with expected anthesis date of 25 November 1995. Height was measured twice weekly, from the pinch date through anthesis, and growth rate was tracked by the Greenhouse CAREm System (Michigan State University). Height and width data were collected on all plants in the experiment at anthesis. At 300 mg.L-' N, 10% leaching irrigation grew plants with the greatest dry weights, followed by the ebb-and-flood treatment and the pulse treatment, respectively. The 10% leaching and ebb-and-flood plants had the greatest growth index, while the pulse treatment growth index was lower. Growth index was greatest for the 10% leaching for cultivar Eckespoint Freedom Red, while ebb-and-flood had the lowest index. The growth

index was greater at 150 mgL-' N for 'Eckespoint Freedom Red' compared to 300 mgL-' N. Pulse irrigation grew marketable poinsettia plants at lower fertility levels. Three irrigation strategies [40% leaching, no leaching (pulse), and ebb-and-flood], two media types, and two constant liquid feed fertilizer treatments, 100 and 200 r n g . ~ "N, were applied to Easter lilies, cutting geraniums, and New Guinea impatiens. height and width data were collected on all plants in the experiment at time of bloom. Plants in the BX media (peat, pearlite, and vermiculite) produced more flowers compared to HP media (peat and pearlite) for geranium cultivar Sarah and Easter lily cultivar Nellie White. The top media layer had the highest EC (electrical conductivity) values for all three irrigation strategies compared to the middle and bottom media layers and the lower fertilizer levels produced lower EC values for all three media layers than did the higher fertilizer levels for all species of plants in the study. Easter lily plants receiving 40% irrigation strategy along with ebb-and-flood irrigation had the largest dry weight. The BX and HP media with the 100 m g K 1 N had a higher pH than the 200 mg.L-' N. AU three irrigation strategies with 100 mg.L-' N had higher pH values than did 200 mg.L-' N for all three media layers. Both geranium cultivars, Dark Red Sassy and Sarah, produced plants with larger dry weights for pulse irrigation receiving 100 mg.L-' N than did 200 mgL" N. Overall, plants receiving 40% leaching or ebb-and-flood irrigation with 200 mg.L-' N produced the

largest dry weights. Plants receiving pulse irrigation produced a greater index at 100 mg.L-' N compared to plants receiving 200 mg.L-' N for both cultivars. All three irrigation strategies produced plants that had greater growth indices with BX media compared to HP media. New Guinea Impatiens plants receiving 100 mg.L-' N grown in BX medium had larger growth indices compared to the HP medium. Plants receiving 100 mg.L-' N grown in BX media produced larger growth indices compared to 200 m g . ~ ' 'N. Pulse and 40% leaching irrigated plants grown in BX media produced larger growth indices compared to plants receiving ebb-and-flood for 'Anaea'. All three irrigation strategies grown in BX media had lower pH values compared to HP media.

D. Sean Moody Department of Horticulture and Landscape Architecture Colorado State University Fort Collins, CO 80523- 1 173 December 1996

ACKNOWLEDGEMENTS

I sincerely thank Dr. Douglas A Hopper for his guidance, concern, and motivational assistance throughout my M.S. studies, allowing me to complete this body of work. I also thank the members of my graduate committee, Dr. Steven E. Newman, and Dr. Dwayne Westfall, for guidance and criticism. Thanks to Elizabeth Succop, Amy Briggs, Meaghan Matthews, and Danielle Heath, and for assistance in data acquisition and general plant care. Special thanks to the Colorado Floriculture Fondation for their continued support throughout the program. I would also like to thank Paul Ecke Ranch, Busch Greenhouses, and The Fred C. Gloekner & Co., Inc. for supplying the plants for this study. Facilities for conducting t b research were provided by the Department of Horticulture and Landscape Architecture, Colorado State University. Finally, I would like to thank my h c k , Amanda Yule for all the moral support and help setting up the experiments, without her, achieving t b goal would not have been possible.

"All there is left to do is smile, smile, smile."

By The Greatful Dead

TABLE OF CONTENTS

ABSTRACT

... .....................................................................................................................111

LIST OF TABLES .................................................................................................................. x INTRODUCTION ......................... . .................................................................................... 1 Literature Cited ........................................................................................................ 13 CHAPTER 1 PULSE IRRIGATION FOR POINSETTIAS ........................................ 17 Summary .................................................................................................................. 17 Introduction ............................................................................................................. 19 Materials and Methods ............................................................................................. 20 Results and Discussion ............................................................................................ 23 26 Literature Cited ....................................................................................................... Tables ..................................................................................................................... 28 CHAPTER 2 PULSE IRRIGATION FOR EASTER LILIES. GERANIUMS. AND NEW GUINEA IMPATIENS .......................................................................37 Summary .................................................................................................................. 37 Introduction .............................................................................................................. 39 Materials and Methods ............................................................................................. 42 Results and Discussion ............................................................................................ 47 Literature Cited ....................................................................................................... 58 Tables .................................................................................................................... 61 CHAPTER 3 CONCLUSIONS ........................................................................................... 91 APPENDICES ..................................................................................................................... 93 94 Appendix A: Poinsettia Growing Log ................................................................... Appendix B: Easter Lily Growing Log ................................................................. 98 Appendix C: Geranium Growing Log .................................................................. 104

viii

TABLE OF CONTENTS CONTINUED Appendix D: New Guinea Impatiens Growing Log ............................................108 Appendix E: Experimental Designs .................................................................... 112

LIST OF TABLES

Table 1.

The effect of two nitrogen levels on dry weight of poinsettia cultivars 'Eckespoint Freedom Red' and 'Gutbier V-17 Angelika Red' ..................... 28

Table 2.

The effect of two poinsettia cultivars, 'Eckespoint Freedom Red' and 'Gutbier V- 17 Angelika Red' on dry weight .................................................. 29

Table 3.

The effect of three irrigation strategies on height, width, and growth index of poinsettia cultivars 'Eckespoint Freedom Red' and 'Gutbier V-17 Angelika Red' .......................................................................... 30

Table 4.

The effect of two nitrogen levels on height, width, and growth index of poinsettia cultivars 'Eckespoint Freedom Red' and 'Gutbier V- 17 Angelika Red' ................................................................................................... 31

Table 5.

The effect of three irrigation strategies on height, width, and growth index of two poinsettia cultivars 'Eckespoint Freedom Red' and 'Gutbier V-17 Angelika Red' .......................................................................... 32

Table 6.

The effect of two nitrogen levels on pH for combined samples from poinsettia cultivars 'Eckespoint Freedom Red' and 'Gutbier V-17 Angelika Red' ...................................................................................................33

Table 7.

The effect of three irrigation strategies and two nitrogen levels on electrical conductivity (EC) for combined samples from poinsettia cultivars 'Eckespoint Freedom Red' and 'Gutbier V- 17 Angelika Red' .....................34

Table 8.

The effect of three irrigation strategies and three media layers on electrical conductivity (EC) for combined samples from poinsettia cultivars 'Eckespoint Freedom Red' and 'Gutbier V-17 Angelika Red' .....................35

Table 9.

The effect of two nitrogen levels and three media layers on electrical conductivity (EC) for combined samples from poinsettia cultivars 'Eckespoint Freedom Red' and 'Gutbier V-17 Angelika Red' ..................... 36

Table 10.

The effect of two medium on number of flowers of Easter Lily 'Nellie White' .................................................................................................... 6 1

Table 11. The effect of three different irrigation strategies on dry weights of 62 Easter Lily 'Nellie White' ................................................................................. Table 12. The effect of three irrigation strategies on height, width, and growth index of Easter Lily 'Nellie White' .................................................................. 63 Table 13. The effect of two nitrogen levels on height, width, and growth 64 index of Easter Lily 'Nellie White' ................................................................. Table 14. The effect of three irrigation strategies and three media layers on electrical conductivity (EC) (m~.cm")of Easter Lily 'Nellie White' ............................65 Table 15. The effect of two nitrogen levels and three media layers on electrical conductivity (EC) (m~.cm")of Easter Lily Nellie White' ............................ 66 Table 16. The effect of two medium and two nitrogen levels on pH for Easter 67 Lily 'Nellie White' ............................................................................................ Table 11. The effect of three irrigation strategies, two nitrogen levels and three media layers on pH of Easter Lily 'Nellie Whlte' ........................................ 68 Table 18. The effect of three irrigation strategies and two nitrogen levels on dry weights of cutting geraniums 'Dark Red Sassy' and 'Sarah' ........................ 69 Table 19. The effect of two medium and two nitrogen levels on dry weights of 70 cutting geranium 'Sarah' .................................................................................. Table 20.

The effect of three irrigation strategies and two medium on dry weights of cutting geraniums 'Dark Red Sassy' and 'Sarah' ...................................... 71

Table 2 1. The effect of three irrigation strategies and two nitrogen levels on heights, widths, and growth index of cutting geranium 'Dark Red Sassy' .................72 Table 22.

The effect of three irrigation strategies and two nitrogen levels on heights, widths, and growth index of cutting geranium 'Sarah' .................................. 73

Table 23.

The effect of two medium and two nitrogen levels on height, width, and growth index of cutting geranium 'Dark Red Sassy' .............................. 74

Table 24.

The effect of two medium and two nitrogen levels on height, width, and growth index of cutting geranium 'Sarah' ............................................... 75

Table 25.

The effect of three irrigation strategies and two medium on height, width, and growth index of cutting geranium 'Sarah' ............................................... 76 xi

Table 26.

The effect of two nitrogen levels on number of flower buds of cutting geranium 'Dark Red Sassy' .............................................................................. 77

Table 27.

. The effect of two medium on number of flower buds of cutting

geranium 'Sara................................................................................................ 78 Table 28.

The effect of three irrigation strategies, two nitrogen levels and two media layers on pH and electrical conductivity (EC) of cutting geraniums 'Dark Red Sassy' and 'Sarah' and New Guinea Impatiens 'Anaea' and 'Martinique' ................................................................................. 79

Table 29.

The effect of two nitrogen levels, two medium, and two media layers on pH and electrical conductivity (EC) of cutting geraniums 'Dark Red Sassy' and 'Sarah' and New Guinea Impatiens 'Anaea' and 'Martinique' ..................... 80

Table 30.

The effect of three different irrigation strategies on dry weights of New Guinea Impatiens 'Anaea' and 'Martinique' ..................................................8 1

Table 3 1.

The effect of two medium and two nitrogen levels on dry weights of New Guinea Impatiens 'Anaea' ............................................................................... 82

Table 32.

The effect of two medium and two nitrogen levels on height, width, and growth index of New Guinea Impatiens 'Anaea' .................................... 83

Table 33.

The effect of two medium and two nitrogen levels on height, width, and growth index of New Guinea Impatiens 'Martinique' ............................ 84

Table 34.

The effect of three irrigation strategies and two medium on height, width, and growth index of New Guinea Impatiens 'Anaea' .................................... 85

Table 35.

The effect of three irrigation strategies and two medium on height, width, and growth index of New Guinea Impatiens 'Martinique' ............................ 86

Table 36.

The effect of three irrigation strategies and two medium on pH and electrical conductivity (EC) of New Guinea Impatiens 'Anaea' and 'Martinique' ...............................................................................................87

Table 37.

The effect of three irrigation strategies and two media layers on pH and electrical conductivity (EC) of New Guinea Impatiens 'Anaea' and 'Martinique' ............................................................................................... 88

xii

Table 38.

The effect of two nitrogen levels and two media layers on pH and electrical conductivity (EC) of New Guinea Impatiens 'Anaea' and 'Martinique' .............................................................................................89

Table 39.

The effect of two medium and two media layers on pH and electrical conductivity (EC) of New Guinea Impatiens 'Anaea' and 'Martinique' ......90

xiii

INTRODUCTION Justification The United States Department of Agriculture (USDA) established floriculture research priorities as recommended by scientists, growers, environmentalists, and consumer groups to rank fourth behind Pest Management Strategies, Resource Management, and Post Production Practices. Of the three top ranked topics, Resource Management is of direct concern to the Colorado greenhouse industry, and can be described as the system that integrates the environment with the internal chemicaVphysica1 factors that control plant growth. Research is fundamental to facilitating advancements towards more effective resource management of water, media, nutrients, and site preparation The greenhouse industry is in need of information that will aid in wise management of limited water resources. Research should develop efficient and innovative methods to analyze the minimum amount of water required to produce a plant to a marketable stage. Technologies and practices should be developed and further evaluated to retain and recycle water in greenhouses. Consideration also should be taken for how these practices affect the nutrient status of a plant, and what media modifications will be required. Greenhouse growers in Colorado use either near pure water sources resulting from snow melt or highly alkaline water sources from shallow wells.

Those with high

quality water are concerned that their source may be limited in the future. Those coping with poor quality water are in need of additional and alternate management strategies. Managers must consider the path of water once it has served its purpose in the greenhouse. The Environmental Protection Agency (EPA) enforces the Clean Water Act of 1965 (and revisions) to dictate the runoff of all irrigation water.

The Colorado

legislature has recently granted greater power to the state agency to regulate groundwater pollution with the 1990 revision of the 1966 Colorado Water Quality Control Act by Senate Bill 90-126 (Norton et al., 1990). The act addresses agriculture chemical use, from the producer through the end user.

Agricultural chemicals are defined as any

commercial pesticide or fertilizer applied to agricultural product. The act also addresses the management of potential contamination of groundwater with an agricultural chemical by an applicator. This is pertinent to any person who applies pesticides and fertilizers. This act has already affected several growers in Colorado, and has the potential to affect more who may be neglecting to take responsibility for the runoff, which the facility may produces. It is pertinent for growers to begin to evaluate and adapt alternative methods for reducing runoff. Reducing leachate volume from irrigations is one way to reduce the runoff. Many growers continue to use manual watering techniques and often this job is delegated to a junior staff member (Larson, 1994). This person may not have the experience to perform this task correctly or may not be aware of any potential problems. With the advent of new irrigation technologies, water management can become a less expensive task. With the new automatic irrigation systems, (ebb-and-flood, capillary mats,

microtube, and pulse) irrigation requires less labor. Other benefits of these new systems are:

1. Uniform plants. All plants get very similar amounts of water. 2. Nutrient solution is recirculated or leachate eliminated. Potential for groundwater pollution is eliminated.

Growers who are using the system change the nutrient

solution every few months. Therefore, less water is needed to grow a crop.

3. Flexibility. Pot sizes and spacing can be varied. 4. Adaptability. Systems can be used in most existing greenhouses and work well with fixed or movable benches.

5. Lower humidity. Leaves remain dry. The dry bench surface also results in a lower humidity and increased temperature in the crop area (Bartok, 1989). Aside from the obvious physical characteristics of the new irrigation systems, there are many more advantages to these systems. Ebb-and-flood irrigation reduces water and fertilizer use by about 40% when compared to overhead hand-watering with a hose (Holcomb, et al., 1992). One reason for wanting to reduce runoff is the increasing cost and decreasing availability of high quality irrigation water. Yet, no matter what system is used, water quality is always a primary consideration (Dole, 1994). Heavy leaching of water and fertilizer is no longer acceptable, and methods of irrigation and fertilization based on zero runoff must be implemented (Biernbaum, 1992). Most fertilizer recommendations for poinsettias call for 200 to 400 mgL-' nitrogen (N) applied at every watering. Biernbaum et al. (1992) maintained the same media nutrient level for 15 cm poinsettias having 400 mg.L-' N applied with 40% to 60% leaching, and having 200 r n g . ~ -N' applied with 10% to 15% leaching. Biernbaum and Yelanich (1994)

had plants receiving 200 mg.L" N applied with 40% leaching fraction, while another treatment received 100 mg.L-' N with a 0% leaching fraction. The nitrogen concentration in the media of the 200 mg.L-' N with a 40% leaching fraction and the 100 m g . ~ -N' with a 0% leaching fraction were similar. This shows that it is possible to achieve the same media nutrient concentration by a variety of methods. They also commented, "Multiple crops of corn and wheat could be produced with what is leached from a 15 cm poinsettia crop." Ebb-and-flood is one of the most water-efficient irrigation systems (Dole, 1993). Using ebb-and-flood or pulse irrigation (small frequent irrigation applications applied to saturate the media while reduce leaching and run-off), fertilizer amounts must be reduced to avoid high electrical conductivity (EC) build up in the media due to reduced or no leaching. However, leaching is recommended from time to time to avoid salt buildup and crop damage. Leaching should be based on the EC measurements of the soil solution, and not be performed indiscriminately with every irrigation (Lieth, 1994). A 15 cm pot has varying EC and pH ranges. Biernbaum (1993) divided a 15 cm pot into five different layers for pH and EC measurements. The pH readings in an ebb-and-tlood system (from top to bottom, respectively) were 5.5, 5.9, 6.2, 7.3, 7.3 and EC were 7.8, 1.1, 0.4, 0.4, 0.6. The pH values rise from top to bottom, and the EC value drops dramatically from the first two layers. Due to the increase of soluble salts from the fertilizing and no leaching of the media, the EC rises over time when using an ebb-and-tlood irrigation system. Each different type of irrigation strategy available to greenhouse growers requires a different degree of sophistication and technology. Ebb-and-flood systems, where plants are placed on a watertight bench surface or floor and periodically flooded, require

considerable bench or floor moditication.

Alternatively, microtube systems can be

conveniently placed on most any bench. Therefore, a grower must determine the level of sophistication desired to improve water management. Ebb-and-flood There are two main methods of ebb-and-flood irrigation used today (Biernbaum, 1993). The first is a bench designed to hold water, sometimes called flood benches (Ball, 1985; Bartok, 1989). The benches are usually made of watertight aluminum or ridged plastic (SAF, 1992) and fdled up to 2.5 cm with water or nutrient solution. It is left just long enough for the plants to absorb the irrigation solution through the holes in the bottom of the pot. The water or solution then can be drained back into a reservoir for recirculation. The second system is a concrete floor that floods. The principle is the same as for the bench system. These are most common in The Netherlands (Biernbaum, 1993; SAF, 1992). Floor flooding is becoming more popular in the United States because it is less expensive than benches and more space efficient. Heating pipes can also be installed in the concrete. The floors are sloped with grooves in them to aid in drainage. These systems have not been as popular in the past due to the expertise it takes to properly install the concrete floor to provide both uniform flooding and adequate drainage. The reservoir must be large enough to store the amount of solution needed to flood the bench or tloor area. A rule of thumb is that 20 liters of solution are needed to fdl a square meter of bench area. At this rate, about 20% of the solution used to fdl the area is taken up by the plants (Biernbaum, 1993; SAF, 1992).

Reservoirs have many different designs. Growers in The Netherlands tend to have large outside reservoirs for holding storm runoff, but most recirculating nutrient solution are held in small cement tanks in the floor of the greenhouse (Biernbaum, 1993). In the United States, some producers also use concrete tanks, but other common tanks are made of rigid plastic, which are common to farming and ranching communities. These tanks usually range from 1,000 to 4,000 L (Biembaum, 1993). Some of the advantages of ebb-and-flood systems are savings in resources, including water, fertilizer, and labor (SAF, 1992). The elimination of runoff reduces the waste of water and fertilizer, and reduces potential groundwater contamination. Reduced hand watering, reduced crop handling, and ease of spacing are the major factors that provide labor savings. Cultural practices must be considered when using ebb-and-flood systems. Physical properties of the media, scheduling and timing of irrigations, and disease prevention are three main areas must also be addressed (Biernbaum, 1993; SAF, 1992). Media that does not move water via capillary action is not acceptable for this irrigation strategy. Peat- or bark-based media have a mixture of small capillary pore spaces (rnicropores) that hold water and larger capillary spaces (macropores) that hold air (Biernbaum, 1993). If a media contains a poor balance of pore sizes, waterlogging (small pores) or excessive drying (large pores) can occur. Peat-based media has also been known to decompose over time, thus limiting water available to the plants. Michiels and Hartmann (1993), established that certain types of peat had higher pore space and had less readily available water. They recommended

using a coarse textured substrate over a fine textured substrate since the loss of readily avadable water is compensated for the gain in water buffer capacity. Container size also has a role in selection of media type. Plugs and small pots tend to be susceptible to overwatering because they are shallow. Pots that are deeper, such as 15 cm standard pots, may be difficult to wet all the way to the top of the pot (Biernbaum, 1993; SAF, 1992). Smaller containers should have a much coarser media to provide more

air space, and deeper pots should have a finer textured media to facilitate capillary action. As with most peat-based media, rewetting is diffcult, especially with subirrigation. Peatbased media should not be allowed to dry out, and wetting agents provide more umform moistening (SAF, 1992). One of the most precise ways to determine irrigation timing is to weigh a potted plant before and after irrigations. This can be done by a small electronic kitchen scale. By weighing the pots, growers can then determine the usable container capacity (volume of water available to the plant) the media can retain. Biernbaum and Argo (1995) define usable container capacity as the difference between the saturated weight and the wilted weight. Many growers irrigate by the 'Growers Eye" approach. They either irrigate by lifting up the pot and feeling how heavy it is compared to how heavy the pot is after irrigation, or irrigate when the bottom third of the pot is still moist. These methods are not as precise as the weighing method, but many argue that it is just as effective. Regardless of how the timing of the irrigations are achieved, the key is not to waterlog the plants for extended periods or let them dry excessively before the next irrigation.

The last cultural consideration is diseases prevention. This topic has been studied for years due to the potential spread of many pathogens through the recirculated solution. The keys to the prevention of diseases are maintaining a healthy plant, applying good sanitary practices, and recognizing initial symptoms.

A healthy root system provides a barrier to prevent pathogens from entering the plant (SAF, 1992). Good sanitary practices should always be a priority to attain the healthiest plants possible. A greenhouse should be disinfected after each crop. Sodium hyporchloride can be used to treat irrigation water for prevention of algae, bacteria, and fungi (SAF, 1992).

Discard weakened plants, since they are more susceptible to

pathogens (Nelson, 1985). Plant parts should always be removed from the greenhouse, never tossed under a bench or where pathogens can grow. Being able to recognize beginning symptoms of a pathogen allows a grower to initialize preventative measures to keep the pathogen from becoming a disease. Sanogo and Moorman stated (1993) that the movement of Pythium from infested pots to other pots within the ebb-and-flood system does not appear to pose any greater threat to production in operations where recirculating systems are not used. No matter what type of irrigation strategy is used, it is essential to keep a clean greenhouse with healthy plants in it. Disease prevention is much easier than eradication of a disease. When using the ebb-and-flood system, monitoring salt levels is critical. Sanogo and Moorman (1993) have hypothesized that high levels of nutrients can predispose plants to Pythium root rot.

Microtu be The microtube system (drip system) is less expensive, more portable, and more flexible than ebb-and-flood (Dole, 1993). However, higher fertilizer rates are required and the amount of water used and runoff produced are greater with the microtubes compared to ebb-and-flood (Dole et al., 1994).

Drip irrigation improves water application

efficiency, precision placement of solution, and minimizes nitrate-N leaching (Hartz, 1993). The major disadvantage of the microtube system is that it is not as efficient as the ebb-and-flood system.

Water and fertilizer consumption increas along with greater

leaching resulting in possible groundwater contamination. Another disadvantage of the microtube system, if used incorrectly, or too frequently, depletion of oxygen in the media to potentially damaging levels can occur (Meek et al., 1983). The microtube system is much cheaper and is easier to install than an ebb-andflood system. If the irrigation system needs to be moved, it is more convenient to move than the ebb-and-flood system. Benches do not have to be leveled and reservoirs are not needed. A grower is able to grow a larger variety of container sizes and shapes with the microtube system compared to an ebb-and-flood system. Clear water can be applied to crops that are irrigated with the microtube system and still have nutrients move through the root zone. This movement does not occur with ebb-and-flood, so constant application of nutrients is more important with ebb-and-flood (Biernbaum et al., 1995). Microtube is not as efficient as ebb-and-flood, but is many times more efficient than hand-watering.

Greater umformity of irrigation with the microtube system can

increase crop production. After the system is in place, labor is greatly reduced, as there is

not an employee hand watering every plant. This also gives the control of the crop back to the growerlmanager A grower from Florida stated that he had a water savings of as much as 80%, increased crop growth by 20 to 30%, and saved $50,000 in labor alone after he switched from hand watering to drip imgation (Thomas, 1994). Using the microtube system a grower can produce a crop that duplicates a crop produced by an ebb-and-flood system. George (1989) found no differences in the bract diameter, dry weight, and height of poinsettias grown with hand-watering, microtube, or ebb-and-flood. Dole et al. (1994) stated that top irrigated plants (hand watering and ' greater leaf, stem and total dry weights than those microtube) with 250 mg ~ l i t e i had grown with 175 mg

m liter-'.

Consequently, the two subirrigated systems (ebb-and-flood

and capillary mat) produced plants that were taller and had greater leaf, stem, and total dry weights when grown with 175 than with 250 mg ~ . l i t e i ' .This shows that when using different irrigation strategies, fertilizer concentrations can be manipulated to produce the highest quality crop possible. When using the microtube irrigation strategy, one can maintain nutrient levels of a pot several different ways depending on the fertilizer rate and the amount of leaching received. Biernbaum et al. (1992) maintained the same media nutrient level of an 15 cm poinsettia having 400 mg.L-' N applied with 40% to 60% leaching by application of 200 mg.L-' N applied with 10%-15% leaching. Similar roo t-media nutrient concentrations could be maintained when 28 m0l.m" N (ppm) was applied with a 50% leaching fraction, or 14 m0l.m" N with a 15% leaching fraction (Yelanich and Biernbaum, 1993). The grower has a great deal of latitude applying nutrient solution to a crop. A grower that leaches heavily when irrigating needs to use a higher fertilizer rate.

Alternatively a grower that does not leach as heavily will need to reduce the fertilizer rate. The microtube strategy can accommodate many fertilizer rates while still maintaining appropriate soil nutrition. This suggests that higher leaching (40% to 60%) is not needed to grow quality crops. Pulse Pulse watering is a recent concept where small frequent irrigation applications are applied to a plant to reduce leaching and run-off (Dole, 1994). There are two methods of pulsing (Dole, 1993). The objective for pulse irrigation is to allow no leaching by applying small amounts of water by microtube. T h also can be done with ebb-and-tlood or capillary mat. The second is to place containers under the pots so any leachate that does occur will be captured and reabsorbed later. Research with pulse watering and lower fertilizer rates may allow microtubes to be more water efficient and produce less runoff (Yelanich and Biernbaum, 1990). The advantages of pulsing are that plant growth is generally greater than with standard irrigation and lower fertilizer rates can be used (Dole, 1994). Greater plant growth can be achieved compared to traditional irrigation, but it must be conducted with high quality water and low fertility rates (Dole, 1994). Beeson (1992) also stated that total canopy dry weight was greater with pulse irrigation for Elaeagnus pungens,

Ligustrum japonica, and Photinia X fraseri. Pulsing can be used with microtube and ebband-flood. With ebb-and-flood, most nutrient solution uptake was completed within the first 5 to 10 minutes of flooding (Biernbaum, 1993).

Subirrigation treatments were

compared to no leaching treatments. Growing medium nutrient levels, plant fresh and dry weight, height, and leaf area were similar. Pulse subirrigation treatments received only

five more irrigations than did pulse with no leaching top-watered plants over the entire crop cycle (Yelanich and Biernbaum, 1994). Beeson (1992) stated that pulse-irrigated plants tended to accumulate less daily water stress. With less water stress, plants grew faster and remained healthier than plants that were stressed on a daily basis. Another benefit is that disease prevention is less difficult. Just as with ebb-andflood and microtube strategies, foliage stays dry. Photina leaf spot was shown to spread in the overhead irrigation system, while absent in the pulse-irrigated treatment (Beeson, 1992). Alternatively the major drawback with pulsing, as with ebb-and-flood, is the possible increase of soluble salts. To prevent this, low levels of fertilizer in solution keep soluble salts from building up rapidly in the media and reduce the need for leaching (Dole, 1993). Regular soil samples should be analyzed to track the soluble salt level. When using the pulse strategy, salt levels must be maintained at low levels especially for crops sensitive to high soluble salts such as vinca or New Guinea impatiens (Dole, 1993). As more and more greenhouse operations are impacted by state and federal

regulations, an economical strategy is prudent. One greenhouse operation in California was faced with this dilemma: state and regional environmental and water-quality agencies identified this company for contaminating a yacht harbor (Neal, 1996). Part of the solution was to incorporate pulse irrigation to limit runoff. The owner stated that they also had big savings in labor and reduced fertilizer cost (Neal, 1996). Pulse irrigation offers one of the most economical alternatives when it comes to limiting runoff. In the future, more pulse irrigation research is needed to develop fertilizer recommendations and to investigate media-fertilizer interactions relevant to crop production (Elliott, 1992).

LITERATURE CITED Ball, V. 1985. Ebb and flow irrigation. Grower Talks 49:70. Bartok, J.W. 1989. Ebb and flow: new technology provides efficient irrigation alternatives. Greenhouse Manager August. 8(4): 157- 160. Bartok, J.W. 1989. Ebb and flow from an engineers viewpoint. Conn. GH Newsletter 150 June:11-12. Beeson, R.C., Jr. 1992. Restricting overhead irrigation to dawn limits growth in container-grown ornamentals. HortScience 27:996-999. Biernbaum, J.A. 1993. Subirrigation could make environmental and economical sense for your greenhouse. PPGA News. April:2- 14. Biernbaum, J. A. 1992. Root-zone management of greenhouse container-grown crops to control water and fertilizer use. Hort. Tech. 2: 127- 132. Biernbaum, J. A. and W.R. Argo. 1995. Peat based media physical properties and water holding capacity. Oral Presentation, Rocky Mountain Hort Expo. Biernbaum, J. A., W.R. Argo, and M. V. Yelanich. 1995. Steps to better nutrition. Greenhouse Grower 13(8):52-58. Biernbaum, J. A., M. V. Yelanich, and W.R. Argo. 1992. Are you overfertilizing your poinsettias? Greenhouse Grower 10(8):37-38. Dole, J. M. 1994. Comparing poinsettia irrigation methods. The Poinsettia 10:4-9. Dole, J. M. 1993. Water and fertilizer rate reduction. Greenhouse Grower 11(13):24-28.

Dole, J. M., J. C. Cole and S. L. von Broembsen. 1994. Growth of poinsettias, nutrient leaching, and water-use efficiency respond to irrigation methods. HonScience 29:858864. Elliott, G.C. 1992. A pulsed subirrigation system for small pots. HonScience 27:71-72. George, R.K. 1989. Flood subirrigation systems for greenhouse production and the potential for disease spread. M.S. Thesis, Michigan State Univ., East Lansing. Hartz, T. K. 1993. Drip-irrigation scheduling for fresh-market tomato production. HortScience 28:35-37. Holcomb, J.E., S. Gamez, and D. Beattie. 1992. Efficiencies of fertigation programs for Baltic ivy and Asiatic lily. Hon. Tech. 2:43-46. Larson, R.A. 1994. What's wrong with hose watering. The Poinsettia 10:2-4. Lieth, J.H. 1994. Controlling poinsettia irrigation based on moisture tension. The Poinse~iia10:2-4. Lieth, J.H. and D.W. Burger. 1989. Growth of chrysanthemum using an irrigation system controlled by soil moisture tension. J. Amer. Soc. Hort. Sci. 114:387-392. Meek, B.D., C.F. Ehlig, L.H. Stolzy, and L.E. Grahm. 1983. Furrow and trickle irrigation: Effects on soil oxygen and ethylene and tomato yield. Soil Sci. Soc. Arner. J. 47:63 1-635. Michiels, P. and R. Hartmann. 1993. Physical properties of peat substrates in an ebblflood irrigation system. Acta Hort. 342:205-214. Neal, K. 1996. Why should you consider automated controls. Greenhouse Management & Production l5(lO):33-35.

Nelson, P. V. 1985. Greenhouse operation and management third edition. Reston Publishing Company, Inc. New York:373. Norton, Bishop, Powers, Wattenberg, Hopper, and Winkler, Senators and Williams, Masson, DeHerrera, Entz, Fish, Grant, Johnson, Knox, Kopel, Owen, Pankey, Rupert, and Webb, Representatives. 1990. An Act concerning the regulation of substances from manufactured agricultural chemicals of this state, and making an appropriation in connection therewith. Senate Bill 90- 126. General Assembly of the State of Colorado. Sanogo, S. and G.W. Moorman. 1993. Transmission and control of Pythium

aphanidermatum in and ebb-and-flow subirrigation system. Plant Disease 27:287290. Society of American Florists. 1992. Clean and Green water Quality Action Manual for Greenhouse and Nursery Growers. Horticultural Water Quality Alliance:65-72. Stanley, C.D. and B.K. Harbaugh. 1984. Estimating daily water use for potted chrysanthemums using pan evaporation and plant height. HortScience 19:287-288. Stanley, C.D. and B.K. Harbaugh. 1982. The use of leaf water potential for estimation the effect of seasonal water stress on yields of chrysanthemums. HortScience l7:8 12813. Thomas, S. H. 1994. Decreased runoff, faster turnaround result from automated irrigation. Greenhouse Manager 13(12):66-69. White, J.W. 1993. Geraniums IV. Ball Publishing, Geneva, Illinois.

Yelanich M.V. and J. A. Biernbaum. 1990. Effect of fertilizer concentration and method of application on media nutrient concentration, nitrogen runoff and growth of

Euphorbia pulcherrima 'V-17 Glory'. Acta Hort. 272: 185- 189. Yelanich M.V. and J. A. Biernbaurn. 1993. Root-media nutrient concentration and growth of poinsettias at three fertilizer concentrations and four leaching fractions. J. Arner. Soc. Hort. Sci. 1l8:V 1-776. Yelanich M.V. and J. A. Biernbaum. 1994. Using leaching and fertilizer concentration to manage the nutrients in the root zone environment. Ohio Florists' Assoc. Bulletin 779: 1-4.

CHAPTER 1 PULSE IRRIGATION FOR POINSETTIAS

SUMMARY The purpose of the study is to reduce the amount of water and nutrients applied, and with this, reduce the amount of groundwater contamination that results in over fertilizing and over watering. The study is an imgation study to observe the effects of eliminating runoff from irrigations and lowering fertilizer concentrations. Three irrigation strategies [lo% leaching, no leaching (pulse), and ebb-and-flood] and two constant liquid feed fertilizer treatments, 150 and 300 mgLm'N, were applied to two poinsettia cultivars, Eckespoint Freedom Red and Gutbier V-17 Angelika Red, with expected anthesis date of 25 November 1995. Height was measured twice weekly, from the pinch date through anthesis and growth rate was tracked by the Greenhouse

CARE'^

System (Michigan State University). Height and width data were collected, on all plants in the experiment, at time of anthesis. There were no differences in plant dry weight among the three irrigation strategies at the 150 mgL" N treatment. At 300 mgL-' N, 10% leaching irrigation grew plants with the greatest dry weight, followed by the ebb-and-flood treatment and the pulse treatment, respectively. Dry weight for the lowest level treatment 150 mgL-' N (26.6 g) was larger than that for the higher 300 mg.L" N.

18

The 10% leaching and ebb-and-flood plants had the greatest growth index (growth index equals the height added to the average of the two widths, divided by two), while the pulse treatment growth index was lower.

Growth index was greatest for the 10%

leaching strategy for 'Eckespoint Freedom Red', while ebb-and-flood had the lowest index. The growth index was greater at 150 mg.L-' N for 'Eckespoint Freedom Red' compared to 300 m g . ~ "N. Growth index of 'Gutbier V-17 Angelika Red' was not influenced by fertility level. Applying 300 mg.L" N produced a lower pH media value than did 150 mg.L-' N. All irrigation strategies had lower EC values with 150 mgL-' N than with 300 mg L-' N. At 150 and 300 mg.L-' N, media irrigated with 10% leaching had the lowest EC values. followed by pulse, and ebb-and-flood had the highest EC values. The top media layer had higher EC values for all three irrigation strategies. Ebb-and-flood irrigation resulted in the highest EC values, followed by pulse, and 10% leaching had the lowest EC values for the top layer.

At 150 mgL" N the EC values were lower in all three media layers

than at 300 mgL" N. Pulse irrigation grew marketable poinsettia plants at lower fertility levels. Pulse irrigation grew marketable plants at lower fertility levels and the quality of pulse irrigated plants were similar to that of 10% leaching and ebb-and-flood irrigated plants. This enables growers to efficiently use water resources and apply lower fertilizer concentrations while reducing potential groundwater contamination. My recommendation for using the pulse irrigation strategy and lower fertility rates are to learn how to use this new system properly. Growers can not use high rates of

fertilizer with the pulse irrigation strategy due to the rapid increase of soluble salts (EC). Once growers learn how to grow with this new system, a marketable crop can be produced that is similar to the quality they produced before using the pulse strategy.

rNTRODUCTION Poinsettia, Euphorbia pulcherrima Willd., (Ecke et al., 1990) was first introduced to the United States in 1825 by Joel Robert Poinsett, the first United States ambassador to Mexico. Poinsettias are now the number one flowering potted crop grown in the U.S. with over 57.4 million pots grown annually (Agr. Stats. Board, 1996). With the llarge number of poinsettias being grown annually, developing new and more economical ways of producing them is essential. Producing a quality crop while using less water and fertilizer will return more profit to the growers as well as benefit the environment. Poinsettias are often recommended to be grown at 250 mg'L'l N for constant fertigation (Ecke et al., 1990).

However, they can be grown with moderate

concentrations (150 to 200 mg.LelN) of fertilizer (Biernbaum, 1995). They can tolerate wide ranges of soluble salts (Schuch et al., 1995), and are more tolerant of high levels than New Guinea impatiens.

Poinsettias fertilized with 300 mgL-l having leaching

fractions ranging from 0% to 40% showed no differences in growth, but accumulated high EC levels in the media (Ku and Hershey, 1991). Poinsettias require large amounts of water and should not be allowed to totally wilt between waterings. Wilting can lead to excessive leaf drop. Care should be taken not to overwater newly planted cuttings, as root loss can occur.

The objective of this study was to develop efficient and innovative methods reducing the amount of water and nutrients required to produce a marketable crop while reducing the potential of groundwater contamination.

MATERIALS AND METHODS

The experiment was conducted as a completely randomized design (CRD) having two blocks with two cultivars, two fertilizer concentrations, three irrigation strategies, and 12 single plant replications per irrigation strategy for a total of 384 plants. Data were analyzed using the general linear model (GLM) procedures of SAS (Statistical Analysis System Inc., Cary, North Carolina). Two poinsettia cultivars were used in this experiment, Eckespoint Freedom Red and Gutbier V-17 Angelika Red (Paul Ecke Ranch, Encinitas, Calif.). Rooted cuttings were transplanted into a commercial peatlite media (Premier Pro-Mix HP, Professional High Porosity, Premier Peat Moss Ltd., Canada) 23 Aug. 1995 into 12-cm tall X 15-cm wide (1.36 L) plastic pots. The media contained a complete proprietary fertilizer charge with all the essential macro and micro elements. The experiment was conducted at the Colorado State University W.D. Holley Plant Environment Research Center (PERC), in a well-ventilated fiberglass greenhouse oriented east-west. There were four ebb-and-flood benches (1.6 X 4.2 m) and ten wooden benches (0.74 X 4.3 m bench top) in the greenhouse. The benches were modified to provide microtube, ebb-and-flood, and pulse irrigation strategies.

On 7 Sept. 95, plants were spaced on 0.40 X 0.40 m on wooden or ebb-and-flood benches, and were grown with one of three irrigation systems: 1) ebb-and-flood [1.6 X 4.2 m bench top, 418 liter tank, pump, and drain], 2:) pulse with microtube [2.5 cm main line, 1.9 mm diameter leader, leader being 0.46 m long with plastic emitters (Chapin Watermatics, Watertown, New York)], and 3) traditional microtube (same size as treatment 2). The temperature averaged 25.2/15.1°C (daylnight). A 50% shade cloth was added at transplant to acclimate the cuttings to the environment and then removed 8 Sept. 95. Plants were pinched to six nodes above the medium line 6 Sept. 95. Incandescent lamps (60 watts, spaced at 0.60 m) provided illumination from 2100 to 0400 HR daily. Lamps were used from 1 Sept. 95 to 4 Oct. 95. Standard disease and insect control procedures were followed according to need (Ecke et al., 1990). Plants were fertilized at two fertilizer rates, 150 and

300 mg.L" N from a

commercial 15N-2.19P-12.X water soluble fertilizer (Peters Exel Cal-Mag Plus, O.M. Scott Co., Marysville, Ohio.). As the nitrogen level increased from 150 to 300 mgL-', other nutrients in the fertilizer mix increased proportionately. Two injectors (Dosatron model DI-16, Dosatron International Inc., Clearwater Fl.) dispensed the two fertilizer solutions. The injectors were calibrated by using the EC value on the label of the ' fertilizer bag and an EC meter. The critical EC values on the label were 0.99 m ~ c m -and 1.98 m ~ . c m -for ' 150 and 300 mg.L-' N, respectively. The tap water EC (0.1 1 m ~ c m " ) , was added to the 150 and 300 mg.L-' N bag values to ascertain the overall EC value. The 150 mg.L" concentration was 1.O8 ms'cm" and the 300 mg.L-' concentration was 2.10 rn.~crn-I.

All plants were fertilized initially with 150 m g ~ -N' 7 Sept. 95. After 10 Sept. 95, each irrigation strategy and fertilizer rate was applied independently. The pulse and 10% leaching strategies were controlled by a time clock (TC-2400 LX 11, James Hardie Irrigation, El Paso, TX). 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 containerized bench top, held for 10 minutes, 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% leaching strategies were irrigated until the leachate was equal to zero and 10% of applied solution, respectively. The pulse plants were irrigated daily 28 Sept. 95 and twice daily 6 Oct. 95 (9:OO am and 1 :00 PM MDT) until the remainder of the study. The 10% leaching plants were irrigated daily until the remainder of the study. Height was measured twice weekly, from the pinch date through anthesis and growth rate was tracked by the Greenhouse CARE'"' System (Michigan State University). Height and width data were collected on all plants in the experiment at time of anthesis. Height was measured from the bench surface to the highest growing point. Width was determined as the average of the widest portion and one perpendicular. The growth index was then calculated by adding the height to the width mean and divided by two. Observations for Pythium (present or not) were taken on 10 plants randomly selected from each treatment and recorded at the termination of the study. Dry weight data were determined from five randomly selected plants from each treatment and recorded at the

termination of the study. Plants were cut off at the media surface, placed in paper bags, and dried for 48 hr at 70C. Electrical conductivity (EC) and pH were determined for three sections of the media. The sections were equal portions of top, middle, and bottom fiom five randomly selected plants. A saturated paste extract was formed from mixing 150 ml of media with 90 ml of deionized water. This mixture was stirred in 250 ml beakers and allowed to equilibrate overnight (Page et al., 1982). The paste was filtered through Whatman No. 5 filter paper in a buchner funnel and collected in an erlenmeyer flask. The filter paper was subsequently rinsed with deionized water, then was used for the media filtering process. A vacuum pulled the liquid from the media into a 500 ml erlenmeyer flask. The extract was put into a 10 ml beaker for testing. The pH of the extract was determined (Model 720A, Orion Research Inc., Boston, Mass.), as were soluble salts [electrical conductivity (EC)] of each irrigation treatment using the same solution (YSI Model 35 Conductance Meter, Yellow Springs Instrument Co., Inc. Yellow Springs, Ohio).

RESULTS AND DISCUSSION Dry weight for the lowest fertility level, 150 mg.L-' N (26.60 g), was larger than that for 300 mg.L-' N (23.26 g) (Table 1). The dry weight for cultivar 'V-17' (26.67 g) was larger than for 'Freedom'(23.19 g) (Table 2). Schuch (1995) also determined that 'Freedom Red' was the shortest of six cultivars studied, which would in turn result in lower dry weight. Dole et al. (1 994) noted the fertilizer interacted with irrigation systems such that plants grown with 175 mgL-' N had higher dry weights for subirrigated

systems than plants grown with 250 mgL-' N. The same interaction in this study was not significant at P10.05, but did show a similar trend. These study results are in agreement with Yelanich and Biernbaum, (1994) indicating that subirrigation treatments and zero leaching had similar dry weight results. The tallest plants were produced by the ebb-and-flood irrigation strategy (32.3 cm) and 10% leaching (3 1.5 cm). Pulse irrigated plants were significantly shorter (30.5 cm) than ebb-and-flood treated ones, but similar to plants receiving 10% leaching (Table 3). Applying 150 mg.L" N produced wider and larger growth index (growth index equals the height added to the average of the two widths, divided by two) values than did 300 mg.Lm1 N (Table 4). There was no difference between cultivars for width or growth index for plants receiving 10% leaching and pulse irrigation strategies. The 'V-17' plants produced a wider and larger growth index than 'Freedom' plants with the ebb-and-flood irrigation strategy.

The growth index for 'Freedom' did not show any differences

between irrigation strategies. The 'V-17' plants were wider and had a larger growth index with ebb-and-flood than pulse treatments, results were similar to plants receiving 10% leaching. Pulse and 10% leaching plants were similar in width and growth index (Table 5). Dole et al. (1994) stated that plants that were subirrigated with 250 mg.L-' N were shorter than those receiving 175 mgL-' N, the results of this study were not significantly different (P

Growth indexz

10% leaching Eb b-and-flood Pulse 'Growth index equals plant height added to plant width. divided by 2. YMeanseparation within columns determined by Fisher's protected LSD Pc0.05.

Table 4. The effect of two nitrogen levels on height, width, and growth index of poinsettia cultivars Eckespoint Freedom Red and Gutbier V- 17 Angelika Red.

Nitrogen" (mg.~-')

Plant height (cm>

Plant width (cm>

Growth indexY

"Nitrogen is total soluble nitrogen in irrigation solution and standardized by measured electrical conductivity. 'Growth index equals plant height added to plant width, divided by 2. "Mean separation within columns determined by Fisher's protected LSD Pc0.05.

Table 5. The effect of three irrigation strategies on height, width, and growth index of two poinsettia cultivars Eckespoint Freedom Red and Gutbier V-17 Angelika Red.

............................................... ...............................................

Irrigation strategies 10% leaching 10% leaching Eb b-and-flood Eb b-and-flood Pulse Pulse

Cultivar Eckespoint Freedom Red Gutbier V-17 Angelika Red Eckespoint Freedom Red Gutbier V-17 Angelika Red Eckespoint Freedom Red Gutbier V- 17 Angelika Red

Plant height (cm>

Plant width (cm>

Growth indexz

31.6 aY 31.4 a 31.5 a 33.1 a 31.0 a 29.9 a

47.4 ab 47.6 ab 44.3 c 48.5 a 45.8 bc 45.2 bc

39.5 ab 39.5 ab 37.9 b 40.8 a 38.4 b 37.6 b

"Growth index equals plant height added to plant width, divided by 2. YMeanseparation within columns determined by Fisher's protected LSD Pc0.05.

Table 6. The effect of two nitrogen levels on pH for combined samples from poinsettia cultivars Eckespoint Freedom Red and Gutbier V-17 Angelika Red. Nitrogen' (mg.~-')

"Nitrogen is total soluble nitrogen in irrigation solution and standardized by measured electrical conductivity. YMeanseparation within columns determined by Fisher's protected LSD P

Growth indexY

100 200 100 200 100 200

Nitrogen is total soluble nitrogen in irrigation solution and standardized by measured electrical conductivity. YGrowthindex equals plant height added to plant width, divided by 2. "Mean separation within columns determined by Fisher's protected LSD P