Media pH, EC & Water Quality: The Basics Of Monitoring

Media pH, EC & Water Quality: The Basics Of Monitoring

The cover of an environmental monitoring company catalog contains a quote: “To measure is to know.”

Monitoring is an attempt to quantify the invisible, to know before you see. We have become accustomed to this practice in human health and wellness and have our temperature and blood pressure taken. We understand the importance of the resulting values and what they mean, based on a scale resulting from scientific data.

Monitoring, as a tool in greenhouse production, has the same end. It can be an instructive learning tool, focusing attention on details that can otherwise go easily ignored until there is a “wellness” issue that commands your full attention and your wallet. Of benefit to greenhouse production over field production is greater environmental and cultural control of temperature, light, substrate, water and fertilizer.

Published recommendations for these inputs are available for many of the crops commonly grown, and monitoring is the tool by which we assess our successful manipulation of the environment and cultural inputs and make adjustments accordingly.

This third article in the Basics of Monitoring Series will focus on monitoring irrigation water quality and substrate pH and electrical conductivity (EC).

First Steps
The very first step in monitoring would be to submit an approximately 500-milliliter (16-ounce) sample of your irrigation water to a professional laboratory. This will cost approximately $75 and would be a good annual investment, as water quality can change over time depending on your water source. To submit a water sample, fill a clean plastic container to the top and secure a tight-fitting lid to avoid room for air. Mail early in the week so the sample arrives at the lab and analysis is performed with as little delay as possible for accuracy.

Aside from pH (values affect nutrient availability), EC (values indicate dissolved salt concentration) and alkalinity (values indicate buffering capacity), the analysis will include quantities of other important nutrients that affect plant growth and development (Figure 1, scroll down). In addition, the presence of some elements can create maintenance issues in your system (calcium, magnesium and iron deposits), and high irrigation water pH and alkalinity of water can potentially decrease the effectiveness of the pesticides and plant growth regulators you depend on to control crop quality.

The resulting information will help you make decisions as to whether acidification is necessary, as well as enable you to choose a fertilizer formulation and prepare it at the right concentration. For example, here at Purdue University our irrigation water has a pH of 7.2 and 298 ppm alkalinity due to the presence of naturally occurring calcium and magnesium carbonates. We must either acidify the irrigation water with sulfuric or other acid to neutralize the alkalinity or use an acidifying fertilizer to maintain substrate pH in the suitable range (5.4 to 6.2) for most floricultural crops.

Remember substrate pH affects the availability of those expensive nutrients you are providing through fertilization, especially micronutrients. Do not be intimidated by all of the generated values on the analysis. Guidelines for high quality irrigation water are available to compare with your test results (Figure 2, scroll down).

There are also published charts of suggested pH and EC ranges for specific greenhouse crops (www.ces.ncsu.edu/depts/hort/floriculture/hils/HIL590.pdf), and the values will be helpful to your consultant, fertilizer representative or Extension specialist.

Keep Monitoring
The irrigation water analysis gets you started. However, the ongoing monitoring of your substrate finishes the job. This is especially important for long-term crops like poinsettias, Easter lilies and stock plants, as the substrate lime charge will become exhausted and substrate solution pH will change. Monitoring substrate pH and EC on a weekly or biweekly basis allows you to see an upward or downward trend in these values, allowing corrections before nutrient deficiencies or high soluble salt issues affect your crop’s growth and development.

As with irrigation water samples, you can collect substrate samples to submit to a professional testing lab, which can cost $25 for a pH and EC analysis and have a three- to four-day turnaround time, depending on location. Alternatively, an in-house substrate solution test (PourThru) has been developed to achieve same-day results (Figure 3, scroll down).

There are other accurate ways to obtain a sample of the substrate solution in order to assess the pH and EC of the root zone. The PourThru method was developed for greenhouse and field use. Instruments are reasonably priced and it is not costly (Figure 4, scroll down). However, it is a time commitment and the person performing the analysis must know how to maintain and calibrate the pH/EC meter and perform this task with consistency. The basics of the PourThru consist of fertigation or irrigation as usual and waiting 30 to 60 minutes for substrate solution equilibration. A saucer is then placed under the pot, and a predetermined volume of distilled water is poured on the substrate surface to displace the solution in the root zone for pH and EC measurement.

Test values obtained from the test are then compared to those in the acceptable range for a given crop and informed production decisions can be made. For more information, the Purdue Extension bulletin (English and Spanish versions available) pH and Electrical Conductivity Measurements in Soilless Substrates (www.extension.purdue.edu/extmedia/HO/HO-237-W.pdf) includes details on how to perform this test and equipment needed.

Time must be allocated to obtain random samples, collect data and make an assessment of values. Each substrate, fertilizer and plant species requires separate sampling. Again, there are published values that tell you what the numbers you generate mean. Electrical conductivity measurement values do not tell you how much of a specific nutrient (i.e. nitrogen) is available, but it does indicate whether too much or too little fertilizer is being supplied. Plant tissue analysis is an additional tool that can provide this kind of detail and is often complimentary to the results of substrate analysis when trying to diagnose nutrient disorders.

Additionally, an EC measurement of your fertilized irrigation water can indicate whether you have mixed stock solutions correctly or if injectors are properly functioning. A chart on the fertilizer bag includes the target concentration (ppm N) after dilution and the resulting EC by injector rate. By comparing the EC value you obtain with the target listed on the fertilizer bag, you can know rather than assume how much nitrogen you are providing when you fertigate.

Takeaways
There is no way to sugar coat monitoring irrigation water and substrate pH and EC to the extent that it does not sound like work. Instead, we attempted to entice you with the low hanging fruit of the benefits, which is basically a “well check” on your crop. Think of the associated expense as an investment in your horticultural education, and like all education, an investment that pays you back.

A working knowledge of the important principles associated with plant irrigation and fertilization will make you a better grower and enhance your ability to be competitive in an industry that requires a high level of brain as well as brawn.

Leave a Reply

More From Special Series...
Aquaponics At Brogue Hydroponics

March 30, 2015

10 Things You Need To Know About Aquaponics

Are you curious about expanding into aquaponics? From pest control to equipment, Bob and Jesse Kilgore of Brogue Hydroponics offer 10 factors you need to consider.

Read More
Aquaponics At Brogue Hydroponics

March 30, 2015

Aquaponics Is Making A Splash At Brogue Hydroponics

The owners of Brogue Hydroponics explain why they expanded into aquaponics, and how the shift has helped them uncover a new market opportunity.

Read More
Hendriks-Half-Open-Roof_GGS

March 26, 2015

10 Greenhouse Products For First-Rate Growing Environments

From coverings to fork-lifts, greenhouse suppliers offer a variety of products to make growing easier. Check out the slideshow to learn more about these, plus several other products that can offer you value, versatility and durability.

Read More
Latest Stories

January 29, 2014

Growing Seedlings Under LEDs: Part Two

In the second part of a two-part series, Michigan State University researchers share their findings in germinating seedlings with LED lights.

Read More

December 4, 2013

Plant Breeder Yasuko Isobe: Consumer Lifestyles Will De…

People are more conscientious about living healthy lives and protecting the environment, says this Suntory Flowers breeder.

Read More

December 2, 2013

Plant Breeder Troy Thorup: If Consumers’ Needs Ar…

Troy Thorup breeds various seed and vegetative annual bedding plants for PanAmerican Seed. He has been a breeder for 13 years and holds a Ph.D. in plant genetics and breeding GG: What crops do you feel will be relevant and important over the next 30 years? Thorup: Anything that can balance the combination of beautiful and hard to kill. GG: Will the fervor for all new varieties continue in the industry? Will breeders begin to focus on filling consumers’ needs? Thorup: In my breeding, I don’t view these two things as separate issues. My goal in creating new varieties is largely driven to fulfill consumers’ needs. At the end of the day, if the consumers’ needs aren’t met, they will not buy the product. GG: How will breeders address needs to reduce chemicals by increasing crop resistance to pests and diseases? Thorup: This is a tough question to answer concisely […]

Read More

December 2, 2013

Plant Breeder Jason Jandrew: Multifunctional Plants Are…

This young breeder for Ball Horticultural Co. says breeders can take a cue from cell phones: keep adding features.

Read More

December 2, 2013

Plant Breeder Hans Hansen: The Future’s Plants Wi…

Hans Hansen is the director of new plant development, heading up the hybridizing department for Walters Gardens Inc. in Zeeland, Mich. A graduate of the University of Minnesota, Hansen has been hybridizing plants since he was in high school. At Walter’s Gardens, he manages perennial crops including hemerocallis, hostas, monardas, digitalis, baptisias, leucanthemums and ferns, among others. What direction do you feel breeding is headed? We are living in an absolutely incredible time to be a plant breeder. Recent advancements in science and technology are opening an entirely new direction and present fascinating new opportunities for hybridizers. These include new species recently being discovered, mutagenic plant breeding, new classifications of plants based on scientific studies and new tools not available previously. The internet has turned the world into a very small place. What crops do you feel will be relevant and important over the next 30 years? With the general […]

Read More

December 2, 2013

Plant Breeder Brent Horvath: Grasses Are A Breeding Foc…

Brent Horvath is the owner of Intrinsic Perennial Gardens, Inc., headquartered in Hebron, Ill. Horvath grew up in the industry, working at his parents’ garden center and florist shop. He holds a degree in ornamental horticulture from Oregon State University and today, he grows a wide range of perennials and ornamental grasses. GG: How long have you been a breeder or studying to be a breeder? Horvath: I started in the mid ’90s. After I read Alan Bloom’s Hardy Perennials book, where he talked about how many of his introductions came about, I really started becoming more interested in selecting and breeding. GG: What direction is your breeding career taking? Horvath: As a perennial grower with ornamental grasses being a big part of our production and sales, I focus on those plants that sell well for me. Half of my business is to landscapers and around 20 percent to retailers. […]

Read More

December 2, 2013

Plant Breeder Amanda Hershberger: Pest And Disease Resi…

Amanda Hershberger is a plant breeder for Syngenta. She holds a B.S. in horticulture from Purdue University and an M.S. and Ph.D. in horticulture from the University of Georgia. GG: How will breeders address needs to reduce chemicals by increasing crop resistance to pests and diseases? How far away is this technology? Hershberger: Resistance breeding is vital to the success of many crops and reduces the need for chemical control, as well as reducing the pest’s development of resistance to a chemical control. My personal work experience involves resistance of vinca to Phytophthora. Breeding for pest and disease resistance in ornamental plants has primarily utilized traditional breeding methods. Resistance breeding has also included molecular methods for problems such as black spot in rose and Fusarium in carnation. Agronomic crops have really paved the way for resistance development using molecular markers. I foresee a greater use of molecular techniques to achieve resistance […]

Read More

December 2, 2013

Plant Breeder Joseph Tychonievich: Rock Gardening Will …

Take a look at the other trends Tychonievich says he sees shaping the next 30 years of the greenhouse industry.

Read More

December 2, 2013

Plant Breeder Kelly Norris: Breeders Must Be Champions …

Kelly Norris is currently the horticulture director at the Greater Des Moines Botanical Garden and he holds two degrees (B.S., M.S.) in horticulture from Iowa State University. Norris has been part of the industry since age 15, when he talked his parents into buying a nursery and moving it from Texas to their family farm in Iowa. As the owner of Rainbow Iris Farm, he started breeding irises 12 years ago and continues to focus on breeding independently, as well as in the new breeding program at the botanical garden. GG: As a young breeder, what direction do you feel breeding is headed? Norris: I feel there are two kinds of plant breeders entering the market today. There are those coming of out graduate school looking for jobs in the industry (which aren’t plentiful) and end up toiling away with petunias and commodity crops. I feel for them. Then there […]

Read More

December 2, 2013

Plant Breeder Ockert Greyvenstein: Minimal Inputs Are A…

Greyvenstein also says edible landscapes and hardy grasses will become more relevant floriculture crops.

Read More

December 2, 2013

Plant Breeder Ping Ren: Breeding Must Meet Consumer And…

Jianping (Ping) Ren breeds various seed and vegetatively propagated annuals and perennials for PanAmerican Seed, where she has worked for 13 years. Ren received a Ph.D. in plant breeding in 1998 at Cornell University. Before coming to the floriculture industry, Ren was a vegetable breeder in China with a focus on Brassica vegetables. GG: Will the fervor for all new varieties continue in the industry?  Ren: There are so many new varieties each year. It can be confusing and sometimes difficult for growers and consumers to keep up. But we are all looking for “new” things all the time. There has to be something “new” each year. Of course, some new varieties are new for certain improved traits, which are necessary and can benefit breeding companies (high yield, reduced cost), growers (high germ, more uniform) and consumers (better color and garden performance). The more exciting new for the industry is “true” new […]

Read More

December 2, 2013

Today’s Breeders On Tomorrow’s Plants

One of the future challenges is the continuing need for new and improved crops for the consumer. Make no mistake about it, new crops — and new breeders — are the lifeblood of this industry.

Read More

November 14, 2013

The Basics & Beyond: Understanding The Differences …

As I talk to growers around the country, I often find that there is confusion between (1) photoperiodic lighting used to create a long day for flower induction of long-day plants and (2) supplemental lighting used to increase the total quantity of photosynthetic light received over the course of the day, which is referred to as daily light integral (DLI) in the greenhouse. For more information on DLI, please visit http://bit.ly/11x79eK To add to the confusion, supplemental lighting is sometimes referred to as photosynthetic or assimilation lighting. In this article, I will attempt to clarify the differences to assist you in selecting the appropriate lighting strategy for your greenhouse crops. Understanding Photoperiodic Lighting The number of hours of light in a 24-hour period (photoperiod) controls flowering of both short-day and long-day crops. It is actually the uninterrupted period of darkness that controls flowering responses. Long-day plants are those that only flower […]

Read More

November 14, 2013

Comparing LED Lighting To HPS Lamps For Plug Production

Research at Purdue University is determining how LEDs, providing light of different wavelengths, compare to traditional high-pressure sodium lamps.

Read More

August 6, 2012

Capillary Mats Are Back

Thirty years ago, capillary mats were used for production of floricultural pot crops like Easter lilies. The advantage was that plants could be grown practically pot-to-pot, thus maximizing plants per square foot. Also, since Easter lilies grow best when fertigated with tempered water delivered on a uniform schedule, the capillary mat was ideal. During the 1990s, capillary mats for growing plants fell out of favor as a fertigation method when compared to drip irrigation and other sub-irrigation methods. However, recent advances in electronic controls, mat composition and the use of a drip tape to deliver water directly to the mat at even locations, make cap-mat watering worthy of another look. Combine this with concerns about groundwater contamination, quantity, quality and costs associated with water usage, cap mats and their low-water requirements will certainly come back into the greenhouse growing picture. There are a number of capillary mat types available, each […]

Read More

July 9, 2012

Save Water With Automation And Sensors

Automating irrigation is a great way to save water. One of the latest innovations in irrigation automation is the use of substrate moisture sensors to trigger irrigation. These sensors are relatively inexpensive and, when used, can conserve water and, consequently, reduce pollution and the amount of money spent on electricity for pumps in wells. A wide variety of annual and perennial plants may be irrigated with as little as 0.3 to 1.3 gallons of water for the entire cropping cycle using substrate moisture sensors. Sensors Ensure Proper Substrate Moisture For High-Quality Plants Most substrate moisture sensors literally measure the amount of water in soils. This is usually expressed by volume, as the ratio of the volume of water to the volume of substrate in a pot (substrate moisture content percent = (volume of water xvolume of substrate) / 100). In peat-based substrates, the substrate moisture content of 45 to 50 […]

Read More

April 26, 2012

Subirrigation: Watering From The Ground Up

The goal for any irrigation system is to deliver water to the growing medium as effectively and efficiently as possible. Effectively means getting the right amount of water into the growing medium. Efficiently means minimizing the amount of water that is lost from the system.  In order to irrigate effectively, an irrigation system must deliver water uniformly to every pot in an irrigation zone. An efficient irrigation system will either deliver water with minimal leaching and runoff or capture and reuse all the water that is not retained in the growing medium. Sub-irrigation systems are generally both more effective and efficient than top-down systems. These systems include capillary mats, troughs, flood and drain trays and flood floors. Capillary Mats The simplest form of sub-irrigation, in these systems water is delivered to a porous mat that is in contact with the bottom of the container. This allows water to move from […]

Read More

April 24, 2012

Hand Watering, Booms, Sprinklers Or Drip?

The amount of water that can be held by the substrate in a given container with a specific irrigation method is the effective water-holding capacity (EWHC). It may be desirable to maintain the moisture content of the medium below EWHC in order to regulate plant growth or reduce the risk of soil-borne diseases. Overall, it is important to irrigate thoroughly. The amount of water applied must be sufficient to re-wet the entire volume of growing medium. If the medium is dry and not enough water is applied, only part of the mix will be re-wetted. In irrigating thoroughly, the method of delivery plays an important role. With top-down irrigation, water will be pulled downward by the force of gravity. As it moves downward, some will be held by the growing medium. Usually, some water will escape from the bottom of the pot before the medium is thoroughly wet. At the […]

Read More