Offering detailed information on the production of 162 flower, herb, and vegetable crops, this essential resource for growers includes techniques and advice that work in real-life production, not just in the lab or trial greenhouses. Information is offered on how to decide what to grow, as well as tips on temperature, media, plant nutrition, irrigation, water quality, light, crop scheduling, and growth regulators. Details about propagation, growing, pest and disease control, troubleshooting, and postharvest care are presented and arranged by genus name. The plants represented in this compendium include annuals, perennials, flowering potted plants, herbs, and some vegetable bedding plants.
|Edition description:||Eighteenth Edition, 18th edition|
|Product dimensions:||7.30(w) x 10.10(h) x 1.80(d)|
About the Author
Jim Nau is the greenhouses and gardens manager at Ball Horticultural Company, a recipient of the Perennial Plant Association’s Garden Media Award, and a speaker at gardening conferences across the nation. He is the author of The Ball Culture Guide and The Ball Perennial Manual. He lives in West Chicago, Illinois.
Read an Excerpt
Volume 2 Crop Production
By Jim Nau, Jayne VanderVelde
Ball PublishingCopyright © 2011 Ball Publishing
All rights reserved.
John M. Dole, Paul Fisher, and Brian E. Whipker
Poor quality water — whether it is high in electrical conductivity (EC), alkalinity, or waterborne pathogens — can make a grower's life difficult. Water with a high EC can reduce seed germination, inhibit rooting of cuttings, and increase the likelihood of root and crown diseases. Water with an excessively high pH and alkalinity increases the likelihood of nutrient deficiency problems. The presence of waterborne pathogens in the water can eventually result in diseased plants. These problems are greatly magnified if you grow plugs and cuttings, because young plants are particularly sensitive to water quality.
Before we address water quality considerations, however, we need to discuss the practice of watering. For most crops the best plant growth is obtained when plants are irrigated just prior to wilting. Water stress reduces photosynthesis and slows growth. In addition, the cells of drought-stressed plants do not expand to their full potential, resulting in shorter, more compact plants. While limited drought stress can be beneficial for bedding plants such as bedding impatiens or tomatoes, plant quality is reduced on a majority of crops. Excessive drought stress can cause lower-leaf yellowing and damage roots, leading to disease. Excess water can lead to anaerobic conditions in substrate, also encouraging root diseases, nutrient deficiencies resulting from poor root function, and reduced root growth.
Generally the substrate should be watered thoroughly to the point that at least a small amount of water can be seen coming out of the bottom of the containers or beds. Insufficient watering can mean that part of the root-ball remains dry, or that salts such as sodium and chloride accumulate in the substrate. Irrigating with an excessively high volume of water will leach fertilizers from the growing substrate and increase the potential for runoff into the environment.
When hand watering, be sure to use a nozzle that breaks up the flow of the water and reduces the force of the water hitting the plants and the substrate. Using hoses without breakers at high volume will flush substrate out of the containers or cause compaction, resulting in reduced soil aeration. Automated irrigation systems are covered in volume 1 of the RedBook.
What Is High-Quality Water?
A variety of measures are used to determine chemical water quality (table 1–1).
One of the most important factors is the electrical conductivity (EC), a measure of total soluble salts. Water with a low EC (0.0 to 0.5 mS/cm) is advantageous because high soluble-salt levels are less likely to accumulate in the root substrate, and leaching is not necessary. Plant species vary in their tolerance to high EC, which can stunt plant growth, induce wilting even though the substrate is moist, and cause marginal leaf burn especially in sensitive crops such as New Guinea impatiens, pentas, and ferns. High substrate EC levels can be managed by periodic leaching. See chapter 3 for more information on EC management. Reverse osmosis (discussed in High Soluble Salts) can be used when water EC is too high.
Other equally important measures are pH and alkalinity. The ideal water pH is in the range of 5.4 to 7.0, and alkalinity between 0.8 to 1.3 meq (40 to 65 ppm HCO3-), although a broader range in levels can be successfully managed. Water pH is important for dissolution and efficacy of chemicals and pesticides. Check the ideal solution pH range of agrichemicals from the pesticide label or manufacturer. Water that is high in alkalinity (which can be considered as dissolved liming content) results in higher pH of the growing substrate (the "substrate pH") over time, resulting in deficiencies in micronutrients such as iron. Conversely, water with low alkalinity is often also low in dissolved calcium and magnesium (which therefore need to be incorporated in fertilizer) and increases the likelihood that iron and manganese toxicity will result from excessive uptake of those elements when the substrate pH is low. Treatment options for alkalinity are discussed in the Alkalinity section.
The content of individual nutrients (i.e., N, P, K, Ca, Mg, S, B, Cu, Fe, Mn, Mo, and Zn) of the water should also be checked, along with non-nutrient ions such as Na, Cl, Al, and F. When fertigating with water-soluble fertilizers, the nutrient solution is a blend of ions in the water plus the ions added in the injected fertilizers and/or acid. Therefore, while low levels of some nutrients can be beneficial, high levels of one or more nutrients may require adjustments in the fertilizer program. If the water has high levels of nitrogen, calcium, or magnesium, less of those nutrients can be added as fertilizers. High nitrogen levels can be especially prevalent in areas with sandy soil, shallow wells, or intensive agriculture. Unfortunately, high levels of calcium, magnesium, and iron can be antagonistic to other nutrients, such as manganese or boron, and can reduce their uptake. Water that is specifically high in calcium and magnesium is known as hard water. Most plant species are tolerant of high calcium and magnesium levels, but overhead irrigation with hard water can leave unsightly white salt deposits on the foliage, especially with mist propagation. High micronutrient levels (particularly boron) can be phytotoxic. Sodium and chloride increase the water EC and can disrupt nutrient uptake, without contributing to plant growth. Ions such as aluminum and fluoride are not nutrients but can be toxic to plant growth above threshold concentrations. Treatments for preventing problems with specific ions are listed below.
Testing your water: Commercial labs
A number of commercial labs conduct water analysis for alkalinity and micronutrients. A partial listing is in table 1–2.
Testing your water: In-house
In-house testing of your water sample is an economical and easy way to monitor your pH, EC, and alkalinity levels. To determine the water pH, a quality pH meter is required. Combination pH and EC meters are an excellent choice. Expect to pay $150 or more for a combination meter, and be sure to follow instructions on storage, calibration, and use. To determine the water alkalinity level, a colormetric alkalinity test kit is required. Expect to pay $30 or more for a kit.
Remember that EC is a measure of the combination of all ions including nutrients such as N, P, K, Ca, and Mg, plus other ions, such as sodium and chloride, which are not needed for growth. Nutrient-specific tests are available for ions such as potassium. However, generally pH, EC, and alkalinity are the main onsite tests, and for detailed analysis of other elements it is more cost effective and accurate to send samples to a commercial laboratory.
A major factor increasing substrate pH over time is the amount of alkalinity in the irrigation water. High substrate pH (discussed in chapter 4) results in micronutrient deficiencies in crop plants. The relative concentration of carbonate types — carbonates (CO32-), bicarbonates (HCO3-), and carbonic acid (H2CO3) — is the main buffering system controlling irrigation water pH and substrate solution pH. If the irrigation water contains a high concentration of carbonates and bicarbonates, the substrate pH can rise to undesirable levels during plant production.
High alkalinity levels in irrigation water can limit plant growth and cause losses for producers of container-grown nursery and greenhouse crops. High alkalinity typically occurs in coastal areas or in locations with limestone bedrock. Much of the well water in the Midwest and Great Plains of the United States, Florida, southern Ontario, and the prairie provinces of Canada contain high levels of alkalinity.
The level of alkalinity in irrigation water can vary with well location, well depth, and time of year. A standard water analysis usually includes pH, EC, and alkalinity. Growers may also want to test for macro-and micronutrients in their water. Water tests are recommended for each well and should be done annually. Because plugs contain a small volume of substrate with little buffering capacity, plug producers should consider monthly water tests.
Evaluating and neutralizing your alkalinity level
As alkalinity increases, the appropriate management options change in terms of the desirability of acid injection to neutralize alkalinity, nitrate versus ammonium fertilizer selection, and blending with more pure water sources (table 1–3). Regardless of the method you select to manage alkalinity, neutralizing alkalinity is required for operations that have water alkalinity levels above 2 meq. Select a method that best suits your operation. Conduct a routine analysis of root substrate to monitor pH and nutrient levels and to ensure that fertility and alkalinity neutralization programs are on target.
A number of methods can be used to overcome high alkalinity in irrigation water: acid injection, fertilizer modification, or blending with another water source low in alkalinity (such as captured rainfall or reverse osmosis — treated water). Every greenhouse varies in water quality, root substrate type, fertilizer type (i.e., acidic or basic), watering practices, container size, and length of time a crop is grown. Therefore, because alkalinity is the main component influencing the production system, neutralize alkalinity first and then determine a fertilizer strategy. Excessive alkalinity levels will need to be neutralized by adding acid, which is discussed below, or fertilizer, as discussed in chapter 4.
Acid is injected into the irrigation water to neutralize the alkalinity. The amount of acid to use depends on the starting pH, the alkalinity level of the irrigation water, and the target endpoint alkalinity level desired. In general, a target endpoint alkalinity of around 2 meq is recommended for most crops. This should result in an endpoint water pH of 6.0–6.2. This target endpoint allows for seasonal variations of alkalinity that naturally occurs in wells, limits the potential problem of plants that naturally acidify the root substrate (for example, geraniums, dianthus, Celosia, begonias, and others), and allows for errors in measuring acids. Operations that produce plugs and are willing to monitor their alkalinity level weekly may desire to neutralize to 1 meq of alkalinity (resulting in a water pH near 5.7) to have greater control of their substrate pH.
Deciding which acid to use
The common acids used for alkalinity control are phosphoric (H3PO4) (75 and 85%), sulfuric (H2SO4) (35 and 93%), and nitric (HNO3) (61.4 and 67%). Each acid supplies nutrients to the plants. For instance, one ounce of each acid added per 1,000 gal. (7.4 mg/l) of water would supply: 2.92 ppm phosphorus (P) with 75% phosphoric acid, 1.14 ppm sulfur (S) with 35% sulfuric acid, or 1.47 ppm nitrogen (N) with 61.4% nitric acid. The fertility regime may need to be altered to accommodate the added nutrients. All acids are dangerous because of their caustic characteristics, with the most relatively safe being phosphoric, then sulfuric, then nitric. Citric acid can also be used but is the most costly.
The most commonly used chemical is battery acid, which is 35% sulfuric acid. It is the least expensive, is moderately safe, and provides sulfur. Phosphoric acid is suited for operations needing to neutralize up to 1 meq of alkalinity. When higher amounts of alkalinity must be neutralized, the amount of P provided far exceeds the requirements of the plants. High levels of P can result in excessive plant stretch, especially for plugs. Alternatively, some growers use phosphoric acid to provide their plants with sufficient levels of P and neutralize the remaining alkalinity with sulfuric or nitric acid. Some growers select nitric acid because it supplies N and allows them to decrease the amount of N fertilizer applied. After adding acid, retest the water after one day and again after two to three weeks to double-check the water pH and alkalinity levels.
Determining the amount of acid to add
An online tool that calculates the amount of acid to add to your irrigation water is available from the University of New Hampshire website: http://extension.unh.edu/Agric/AGGHFL/Alkcalc.cfm.
Water Treatments for Ions
A number of options are available to treat your water if water quality is poor. The first option is to locate a high-quality water source (such as municipal water, well water, or surface water from a river or other source) to blend with poor-quality water. If using poor-quality well water, check with a hydrologist to see if another well could be drilled, as water quality can vary with the depth of the well. Often it is difficult and expensive to find another water source, and water treatments will need to be considered.
High soluble salts
Reverse osmosis (RO) is the most common method to remove ions from water and reduce EC. Reverse osmosis forces water through a semipermeable membrane, leaving 90 to 99% of the soluble salts behind. One drawback to RO is the large quantity of wastewater produced (30 to 60% of original volume), which contains high amounts of salts. Disposal of this brine should be handled carefully due to environmental and regulatory concerns. Proper filtration and maintenance are essential in order to keep an RO unit operating smoothly.
Other water treatment systems (i.e., deionization, distillation, and electrodialysis) are available for treating water with a high ion content but are currently more expensive than RO or do not produce the volume of water needed during production. With deionization, water flows over ion-exchange resins that remove the ions. The resins are usually solid beads with either positive or negative charges. Deionization is most feasible when highly pure water is required and the water has a low initial EC. In distillation, the water is boiled and the resulting steam is condensed into pure water, which leaves behind the salts, particulates, and nonvolatile compounds. In electrodialysis, water is passed between cation- and anion-permeable membranes. When an electrical current is applied, ions migrate through the membranes, leaving pure water. Neither distillation nor electrodialysis is used on a large commercial scale in the greenhouse, but advances in technology may make them more feasible in the future.
If water treatment is not an option for handling water with a high EC, cultural practices can be used to reduce the problem. Increased leaching rates will prevent soluble salts from building up in the substrate and will prevent plant damage. High EC water is particularly challenging for the production of seedlings and cuttings. Buying in plugs and rooted cuttings instead of propagating your own and using high-quality water for propagation are options. For growers using recirculating irrigation water, controlled-release fertilizers can also be used to reduce the nutrient content of water. Generally, proper use of controlled-release fertilizers will allow the plants to take up a greater percentage of the nutrients applied. Consequently, less fertilizer is leached out of the pots with controlled-release fertilizers, which helps to keep the EC of the recirculated water low.
Water can occasionally be high in individual ions without having a high overall salt content. With some of these ions, specific treatments or cultural practices are required.
Iron and manganese
Subsurface water can be high in a reduced, soluble form of iron and manganese which oxidizes upon contact with air into a less soluble, rust-colored form. The oxidized form is responsible for the brown- to rust-colored stains on plants and equipment. The iron and manganese can be removed by instigating the oxidation process prior to using the water. The water is sprayed into a tank or pond, which rapidly oxidizes the iron and manganese into insoluble forms that are allowed to settle to the bottom of the tank or pond. The tanks or ponds must be large enough to treat sufficient water to allow the iron and manganese to settle before the water is used.
Calcium and magnesium
The calcium and magnesium in hard water can be replaced by potassium in a process known as water softening. The total salt content is not reduced, but the potassium can act as a fertilizer and the amount of potassium can be reduced or eliminated in the fertilizer solution. Note: Water softening should not be confused with home water softening, which replaces the calcium and magnesium with sodium, which can be damaging to plants.
Carbonates and bicarbonates
Carbonates and bicarbonates can be eliminated by acid injection, as described earlier.
Excerpted from Ball Redbook by Jim Nau, Jayne VanderVelde. Copyright © 2011 Ball Publishing. Excerpted by permission of Ball Publishing.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.
Table of Contents
Water, Media and Nutrition,
1. Water Quality,
3. Plant Nutrition,
4. Managing pH for Container Media,
5. Water, Media and Nutrition Testing,
8. Growth Regulators,
9. Managing Insects and Mites,
10. Managing Diseases,
11. Controlling Soilborne Pests,
12. Managing Resistance,
13. Propagating Seed Crops,
14. Propagating Vegetative Crops,
15. Indexing for Disease,
16. Postharvest Care and Handling of Flowering Potted Plants,
Part 2: Crop Culture A-Z,
Appendix: USDA Hardiness Zone Map,