Mycorrhizal Applications was founded twenty-five years ago in an effort to solve a problem foresters had faced for decades: How do you improve transplant success of conifer seedlings when replanting a forest that had been clear-cut or ravaged by wildfire?
The history: By the early 1990s, U.S. Forest Service Researcher Dr. Mike Amaranthus had conducted many years of field trials and research demonstrating the value of mycorrhizal inoculation of forestry seedlings and the resulting increase in transplant survival. However, when Dr. Amaranthus began recommending the use of mycorrhizae to forestry nurseries, it became apparent that mycorrhizal inoculum were not readily available commercially. To meet that demand, Dr. Amaranthus left his position with the USFS and founded Mycorrhizal Applications in Southern Oregon in 1995. Mycorrhizal Applications has since branched out well beyond forestry, and developed the MycoApply® brand of professional mycorrhizal inoculants in order to promote sustainability and expand the commercial access to mycorrhizae in all industries involving soils, plants, and people.
How it works: The benefits of mycorrhizae can be explained quite simply: “The better the roots, the better the plant.” Mycorrhizal fungi live in symbiosis with plants, directly providing the root system with what the plant needs (water and nutrients), while the plant provides what the mycorrhizal fungi need (excess sugars from photosynthesis). The mycorrhizae establish this relationship when a growing plant’s roots come into contact with a mycorrhizal propagule (the “seed” of the fungi). Once established, mycorrhizae expand the root mass by sending out ultra-fine mycelium filaments (hyphae) into the soil which act as a living extension of the plant’s roots, and increase the efficiency and effectiveness of nutrient and water utilization by the plant.
How nurseries can benefit: Approximately 95% of all plants on earth are mycorrhizal and rely on this symbiosis to thrive. Plants and mycorrhizae have developed this mutually beneficial relationship over the past 450+ millions years as a mechanism for increased survival. If you go out into nature on a hike in any undisturbed area like a forest or a meadow, the plants all around you are relying on this symbiotic relationship to survive in the absence of inputs. However, in horticulture, the mycorrhizal propagules that kick off this relationship are generally absent from soil or artificial growing media, and must be introduced through inoculation. Mycorrhizal Applications’ MycoApply® mycorrhizal inoculant products can be easily added to a professional grower’s production protocol by several means: horticulture injection systems, soil/media incorporation, drench, or plug/liner/bare root dip, or by any means a grower can position the inoculum in direct contact with growing or emerging roots.
Why MycoApply®? As the leader in the field of commercial mycorrhizal inoculant products, the team at Mycorrhizal Applications collectively has decades of experience helping professional growers adopt this crucial biological technology. Growers can work with Mycorrhizal Applications to determine the best blend of mycorrhizal species to utilize for the particular crops that they grow, discuss which inoculation methods to consider, and plan for the ideal timing in the production process for inoculation in order to ensure the lowest cost and maximum return on investment.
The Bayer Ornamentals business operates on the principle that scientific innovations can help build a better life for our customers. At Bayer, our customer’s success is our success, which is why Bayer is not only dedicated in providing the best customer service, but also in providing innovative products that you can count on for the visible results you need in order to be successful.
The Bayer experience begins with our team of ornamental experts. With almost 150 years of collective market experience, the experts on the Bayer ornamentals team have a vast knowledge base that spans from managing a greenhouse as a professional grower and working as a major distributor, to serving as an acclaimed extension specialist and publishing the latest research on plant pathology. Experts such as Aaron Palmateer (aaron.palmateer@bayer.com ) are just an email away the moment you need them.
Our science is backed by world-class research and development which has allowed Bayer to offer several products including Altus, Marengo and Broadform which has become the standard in the ornamentals industry.
Altus insecticide is our most novel chemistry, providing selective, broad-spectrum systemic control of insects, making it an excellent option for integrated pest management programs. Altus also has no application timing restrictions – labeled for use before, during and after bloom. Giving you the flexibility you want, with the control you need. Now maximizing your investment and comparing insecticide costs is easier. Head to es.bayer.us/altus-calculator to see side-by-side numbers for any insecticide you choose.
Our comprehensive herbicide portfolio includes Marengo, the longest-lasting preemergence herbicide for nurseries providing effective control that lasts up to eight months on over 70 different types of weeds. Its active ingredient, indaziflam, is unlike any other preemergence herbicide active ingredient currently on the market. You can now see if Marengo is right for you by comparing different herbicide costs and planning for the future live at es.bayer.us/Marengo-calculator. See the savings for yourself.
Broadform ornamentals fungicide consistently demonstrates strong control of Botrytis and other major diseases including, leaf spot, powdery mildew, and black spot of rose. The dual modes of action in Broadform, provided by the combination of Fluopyram an SDHI, and trifloxystrobin, a Qol, deliver long-lasting disease management and act quickly to control disease preventatively.
With our knowledgeable, experienced ornamentals experts and myriad of products and solutions, all you have to do is focus on cultivating your business; we’ll handle the science. Together, we’ll grow something beautiful.
Learn more about our ornamental products, find your Bayer representative, and read up on our latest expert ornamentals solutions, Ornamental Insights at our website.
In November, Dave Wilson Nursery acquired Fredrik’s Nursery (inset), adding 13 acres of greenhouse production for controlled-environment tree farming.
AC&C Marketing
California’s Central Valley is an agricultural powerhouse, home to many field growers of everything from carrots and tomatoes to nectarine orchards and almond groves. Dave Wilson Nursery started there in 1938 on a rented patch of ground near Modesto, California. Since then, the company grew into one of the largest growers of deciduous fruit, nut and shade trees in the U.S.
About five years ago, Dave Wilson Nursery was producing around 500 acres of bareroot trees. Over the last five years, the company’s customers in the commercial grower space started to demand more potted trees and fewer bareroot trees. Almonds are Dave Wilson’s biggest seller in that market, and five years ago, 80% of almond production was bareroot trees and about 20% was potted. Now, those numbers have completely flipped.
Dave Wilson president and CEO Bill Reid, who joined the company in 2017, says the company now delivers 80% of its almond trees in pots using hybrid rootstocks. Reid has made a commitment to grow more potted trees.
“We've seen a really strong surge in the need from our customer base on a potted tree,” Reid says. “That's where this whole thing kicks off and it's our desire to make sure we meet the demands of the marketplace.”
Dave Wilson Nursery is split into three divisions and maintains separate sales departments.
The wholesale department sells to retail nurseries, garden centers, wholesale container growers and mail order companies which, combined, provide DWN trees and plants to home gardeners in all 50 states. The production department is charged with growing quality nursery stock, from planting seed, liners and cuttings, to budding and grafting, cutting back, suckering, staking and grading. The commercial orchard division makes up the largest part of the business, and those customers have forced a change in the way Dave Wilson Nursery grows its trees.
Behind the move
There are two reasons behind the push for potted trees. No. 1 is convenience. Commercial growers that buy Dave Wilson’s trees to eventually harvest the fruit and nuts appreciate the ability to plant a potted tree whenever they want, depending on their needs.
“With a dormant bareroot tree, you have a fairly small window of opportunity to get that tree in the ground,” Reid says. “But any month of the year is a good month to plant a potted almond tree. They don't have to do it just during the bareroot season.”
Weather conditions also impact bareroot planting schedules. Potted trees offer greater planting flexibility.
The second reason commercial growers have been pushing for more potted trees is the surge in demand for hybrid rootstocks in the marketplace. Most fruit trees are a combination of two plants that have been grafted together. One plant is selected for its roots and is called the rootstock. The other plant is selected for its fruit, flavor, ripening time, and chill hour requirements and is called the scion. Hybrid rootstocks have several advantages over conventional rootstocks, but the main one is the ability to better fit the customer’s growing situation. For instance, some hybrid rootstocks have been bred for certain soil types. If a grower has saltier ground, or wet soil, or if their field-grown trees will need to stand up to high winds, Dave Wilson Nursery is able to tailor an offering to that customer that meets their specific needs.
However, despite those advantages, the hybrid rootstocks do not excel in a bareroot growing environment.
“The hybrid rootstocks can't really thrive in exposure to the sun and the wind that your conventional rootstocks typically go through when they're dug,” Reid says. “They like to stay out of the sun, out of the wind as we process them and as we grow them.”
The four big hybrid rootstocks currently available in potted trees through Dave Wilson Nursery are Viking (used for almonds, apricots, nectarines, peaches, plums), Atlas (mainly almonds), RootPac-R (almonds, nectarines, peaches) and Hansen (almonds).
L-R standing: Tim Morris, Steve Huffman, Dale McHaley, Rob Alamo, Stacy Anderson Sitting: Bill Reid, Jereme Fromm, Harbir Singh
Space and control
Those are the two reasons commercial tree growers increasingly want potted trees. But there are reasons Dave Wilson Nursery has been eager to expand its potted tree production, as well. More effective use of space is one. The acreage requirements to grow a potted tree are drastically smaller than it takes to grow a bare-root tree. Reid says at Dave Wilson Nursery, his team can grow 200,000 trees in the same space they grow 18,000 bareroot trees. They didn't have much greenhouse space, so they were growing their potted trees outdoors. However, the production department came to the realization that they could grow a more consistent quality plant if they could control their environment.
“Consistent quality is what we want to produce,” Reid says. “And the more control we have, the better a job we can do. A controlled environment is a big deal and a game changer for Dave Wilson.”
Potted trees grown outdoors are still subject to the same environmental issues that a bareroot tree must handle. Temperature, in particular, presents a tricky challenge.
“If we're not getting warm enough days, we don't get a good kickoff,” Reid says. “On the other hand, if it gets too hot, our trees can grow too rapidly.”
In addition to offering advanced environmental controls, growing under cover allows Dave Wilson to incorporate production line and manufacturing processes and take advantage of the resulting efficiencies. Labor is an issue in California, just as it is all over the U.S. The difficulty in finding labor is another reason the increased focus on potted trees has gained traction.
Compounding the issue, many of the steps in Dave Wilson’s production of tree nursery stock are done the old-fashioned way, by hand.
The nursery does its own rooted production and buys rooted cuttings from some outside sources. The container itself isn’t groundbreaking. Reid says Dave Wilson’s potted trees are grown in a nursery tree pot similar to everyone else's, a 4-by-4-by-9 inch container. However, they can be run through a flat filler or popped onto a production line.
“One thing I believe is being able to manage your labor so that you can bring your plants to the people and not have your people spread out over 500 acres to try to do your production,” Reid says. “Not that there aren't opportunities in both segments, but common sense tells you if you have a smaller, confined space to do your work in, you can be more efficient.”
With the ability to run their potted trees on a production line and with automatic flat fillers, DWN got the opportunity grow their trees like how greenhouse operations grow annuals and perennials.
Going undercover
Reid had been exploring his options for building greenhouse space on Dave Wilson Nursery’s Hickman, California, location. As part of the process, Reid visited Fredriks Nursery, another Central Valley grower 40 miles away in Ripon. He wanted to see their greenhouse structures in person, because they were the same type he was considering building in Hickman. During the visit, David Fredrik approached Reid and the DWN team with an intriguing possibility: would they be interested in purchasing his facility?
This turn of events was fortuitous, as Dave Wilson Nursery was looking to buy exactly what Fredriks Nursery was selling.
"When the opportunity to sell to a fellow Central Valley family-owned business presented itself, it made sense for our family to sell at this time in our life,” Fredriks president David Fredrik said in a statement. “We believe that Dave Wilson Nursery will be a good partner here in Ripon and we're pleased by the local leadership.”
The opportunity to buy an existing space was advantageous because DWN was still in the phase of scouting locations, planning a build and applying for permits. The Fredriks Nursery acquisition meant DWN could accelerate its greenhouse production timeline.
“We didn't have to go through any environmental and timing issues that we would've had to do here in Hickman,” Reid says. “It was already up and running.”
Currently used for flower production, the greenhouses will undergo some technological enhancements to adhere to Dave Wilson Nursery's stringent quality requirements for growing almond, walnut and stone fruit varieties and rootstock. Reid expects only minor retrofits.
Fredriks Nursery presently employs approximately 20 full-time staff and 140 seasonal employees. Reid says all Fredriks employees will have the opportunity to apply at DWN.
The deal was scheduled to close in January 2020, with crop conversion goals set for this winter and early spring. Additional production from the new facility should be delivered to customers as soon as fall 2020.
Bareroot isn’t dead
Despite losing favor with the commercial grower market, there are still plenty of customers out there who prefer bareroot trees. Bareroot offers some specific advantages, especially for the consumer market. Phil Pursel is a sales representative for Dave Wilson’s wholesale business, which produces about 2 million trees a year. They are sold and shipped to retail nurseries and garden centers all over the country. It’s a small part of the business compared to the 10 million almond trees the company grows for the commercial market. And it’s very seasonal, with most of the shipping being done from mid-December to mid-February. Pursel says 1.5 million trees ship in about a two-month period, shortly after the trees are dug in December. Bareroot, field-grown trees cost less to ship than potted trees because of the additional weight that comes with shipping the pot and soil. Pursel says Dave Wilson Nursery has shipped 15,000 trees on a 53-foot truck.
The wholesale division provides additional diversity in the business’ revenue streams.
“When the commercial side is down, we support the nursery and vice versa,” Pursel says.
Whichever way the trends turn next, Dave Wilson Nursery aims to keep innovating as its customers needs change.
“I don't think any business can just sit back and take it easy,” Reid says. “We have to earn our business every single day.”
Peter Kolster, owner of Kolster, B.V. in Boskoop, Holland
Nursery Management: Why do global consumers continue to buy and plant hydrangea?
Peter Kolster: Our nursery has been growing hydrangeas since I was 16 years old. We started with garden plants, then got into cut flower breeding. Gardeners love the large flowers and the flower colors. We found that consumers really loved the antique colors (we call them classic colors in Europe) and the hard flowers. We started working with another breeder, Horteve Breeding, who was breeding gift plants. And that’s a market the European consumer really loved. In the U.S. we launched the Everlasting Series of hydrangea. The flowers change colors throughout the growing season and can be shades of many colors, depending on the cultivar. These flowers can also be cut and brought inside and last for a long time.
Revolution XXL
Photo by Plants Nouveau
Everlasting Revolution is a short plant, growing to about 2 or 3 feet high. Consumers can use it in the garden or in a container outdoors or put it in a pot and place it indoors in spring and it still looks good in November. We also found that the Revolution varieties are sterile. Another plus for consumers and growers is that the Revolution plants can grow with less water because of their waxy leaves and flowers.
NM: Which characteristics do you require when breeding hydrangea?
(L-R) Linda Guy (Plants Nouveau) Peter Kolster and Angela Treadwell-Palmer (Plants Nouveau) take a closer look at Everlasting Crimson.
Photo by Plants Nouveau
PK: Before we introduce a plant to the market, we focus on certain traits. The plant must not need support to stay upright, it must have a strong root system and it must have hard flowers. Our hydrangeas are good for the consumer for their looks and garden performance; for the grower because of their root system; and for the retailer because of the long shelf life — with proper watering, of course.
NM: What’s your next breeding goal?
PK: We’re looking at breeding for red leaves, which will make a lovely and unique plant. And we’re looking at hydrangeas that will be suitable in hanging baskets.
Michael A. Dirr, horticulturist, breeder and author
NM: What’s the next big thing in hydrangea breeding?
Seaside Serenade Fire Island
Photo courtesy of Monrovia
Michael A. Dirr: I’ll talk about the next big thing in hydrangeas to anyone who will listen. Remontancy/reblooming opened the floodgates of enthusiasm for H. macrophylla. Every breeder/introducer played the same tune with varying degrees of success. The Endless Summer brand dominates and will for the foreseeable future. Many of the H. macrophylla imports from Europe and Japan were promoted as remontant and have already disappeared from the market. I believe a cold hardy (Zone 4/5) macrophylla that flowers reliably every year would be transformational, whether remontant or not. I know this is possible based on H. serrata genotypes that have flowered with no stem dieback after exposure to -35°F. The two species are easily hybridized, and this was already a goal of our former company, Plant Introductions, Inc. Jeff Beasley, Mark Griffith and I have started a new PII, Premier Introductions, Inc., with the goal of cold-hardy macrophyllas looming large.
H. macrophylla
Photo by Mike Dirr
NM: Why do hydrangeas resonate with the consumer?
MD: Everyone recognizes the brilliant orbs of blue and pink. I posit the question to growers, gardeners and people on the street: When you hear the word hydrangea, what does the mind conjure? Almost always, heavenly blue spheres. Ask the same question about a viburnum and there is no answer.
NM: Can growers continue to capitalize on this crop?
Photo by Carol Reese
MD: Absolutely. At the recent Georgia Green Industry Association trade show, I was told that a major retailer ordered one million Summer Crush for 2021. At present, there is greater focus on hydrangea breeding/procurement in the U.S. than at any time in history. The major nurseries like Bailey and Spring Meadow support hydrangea breeding programs. Monrovia, under the leadership of Jonathan Pedersen, acquire hydrangea genetics from other breeders and build new brands such as the Seaside Serenade series. Southern Living added several H. paniculata selections to the brand. These were developed by Buddy Lee, who has worked almost exclusively with PDSI and Flowerwood Nursery. I am in contact with a private breeder in Virginia who has a boat load of pretty H. paniculata hybrids. There is demand and the breeders are trying to accommodate. The industry has benefited mightily from the advances in hydrangea breeding. There will be introductions never dreamed possible. In fact, scientists in China successfully produced interspecific hybrids of H. macrophylla x H. arborescens with fertile offspring.
Tim Wood, breeder, author and new plant development manager at Spring Meadow Nursery
NM: What breeding breakthroughs should we expect in the near future?
Tim Wood: In my opinion, the next step is moving beyond reblooming Hydrangea macrophylla onto continuous blooming H. serrata hybrids. They have greater stem and bud hardiness so they’re more likely to flower in late spring and summer. This breeding has also brought us plants like Let’s Dance Cancan hydrangea, which seems to flower even without vernalization. Growers can shift up a trimmed quart liner into a 2 gallon and sell it in bloom in about 10-12 weeks. These types of plants should be big winners for growers and consumers alike.
Little Quick Fire
Photo by Spring Meadow
NM: Why does this crop continue to woo both growers and consumers?
TW: The breeding keeps getting better and better. When Bailey introduced Endless Summer, it was a game changer. There were about 100 non-reblooming bigleaf hydrangea varieties on the market, but Endless Summer was just the beginning and now every form and color needs to be transformed into a rebloomer, or better yet a continuous bloomer. Hydrangea arborescens ‘Annabelle’ has been reinvented with the introduction of the Invincibelle series, and now we have five different flower colors and a choice of smaller, dwarf varieties. Who could have imagined this 20 years ago? H. paniculata keeps getting better with the introduction of earlier blooming dwarfs such as Bobo and Little Quick Fire. The new pink and the red flowered varieties are getting better, too. They color up earlier, with richer colors and have improved, stronger habits. Growers will especially appreciate how good these new varieties present and hold up their blooms in a container at retail. Everything keeps getting better.
Let’s Dance Cancan
Photo by Spring Meadow
NM: How can growers continue to capitalize on the crop’s popularity?
TW: Breeders are creating outstanding plants with increased value. Growers and retailers can capitalize on these new plants by embracing change. We can sit around and complain about the pace of new plants, or we can make money selling them. To do that we must have the fortitude to drop the older and weaker growing, less profitable varieties. We do this in the perennial world, and we need to do it in the shrub world, too.
Irrigation system checkup
Features - Irrigation
Proper use of these tools will increase water use efficiency at your operation.
Even if you only grow succulents and cacti, irrigation is an essential part of your operation — but could your operation’s irrigation system be optimized? In the previous article in this series, we looked at three tools that could help you better understand your water reservoir (pond) resources. In this article, we focus on your irrigation system with three additional tools: 1) interception efficiency, 2) coefficient of uniformity, and 3) leaching fraction for salt reduction. You can access these tools and many others for free through the www.cleanwater3.org website under the “Tools” section.
Figure 1. The web interface for the interception efficiency calculator you can use to determine the efficiency of overhead irrigation.
Interception efficiency calculator
Interception efficiency measures how much of the irrigation water applied overhead (mainly impact head and wobbler-type sprinklers) makes it into the container. Drip and spray stakes should irrigate the container surface directly and have 100% interception efficiency. As any grower knows, round containers placed tightly together still have empty area where applied irrigation will land between pots instead of in them. Figure 1 shows the information needed to calculate your interception efficiency using the interception efficiency tool, while Figure 2 provides an explanation of the terms. As the distance between containers increases, your interception efficiency decreases exponentially. For example, an 8-inch container with 8-inch spacing within and 8-inch between rows (8 x 8-inch) has an 79% interception efficiency, while a 9 x 9-inch spacing is 62%, 10 x 10-inch spacing is 50%, and 12 x 12-inch spacing is 35%. A 35% interception efficiency means that if you apply 1,000 gallons of water, only 350 gallons actually makes it into your containers.
As you shift material into larger containers you increase your substrate surface area that can intercept water, but you also typically increase spacing to give larger plants more room to grow. At container sizes of 5 gallons or larger consider switching from overhead irrigation to either spray stake or drip to increase interception efficiency and conserve water. Even though setup and maintenance can be more difficult with micro-irrigation systems, you will save large volumes of water due to higher interception efficiencies.
Some plants have a canopy structure that will more naturally funnel water to the container surface, increasing interception efficiency, while other plant canopies will shed water making it more difficult to get water to the = substrate surface. Canopy structure is not included in these calculations, but regardless of structure or container size, wider spaced plants will have a lower interception efficiency than closer spaced plants.
Figure 2. Interception efficiency calculations for round containers. (A) is the diameter of the container, (B) is the distance from one container middle to the next within a row, and (C) is the distance from one container middle to the next between rows.
Coefficient of uniformity
Do some plants within an irrigation zone receive too much water, while others get too little? As we are typically irrigating to sufficiently irrigate the driest plants. Poor irrigation uniformity results in some plants getting too much water, which unnecessarily leaches nutrients and may lead to plants growing at different rates. Testing coefficient of uniformity can help you know exactly how evenly you are applying irrigation in a given irrigation block and decide if you need to make improvements. To measure irrigation uniformity, you need the following items:
24 or more of the same size containers (plastic sandwich containers are best but large plastic cups will also work)
1 measuring device (graduated cylinder, preferred, or measuring cup)
An empty irrigation block
A calm, non-windy day (wind speed < 5 mph)
Set up the empty containers in a grid pattern similar to the one in Figure 3 (pg. 24) making sure to evenly cover the irrigation block you are testing. To keep your containers from moving due to minor wind, you can put a rock in each container to hold it in place but remember to remove the rock before you measure the volume. After the containers are laid out, turn on the irrigation system for a set amount of time (for example 20 minutes). Run the irrigation long enough to collect a volume of water that can be easily measured. It is easiest to run irrigation long enough to half-fill the containers but be careful to not let water overflow any container.
Label each container and note their locations on a map (we recommend numbering the irrigation block and sketching the layout so that you can determine where issues occur). As you collect each container, pour the collected water into the graduated cylinder or other measuring device. Measure and record the water volume in each container (remember to empty the measuring device between containers). If labor is available, have one-person measure and one-person record water volume. The more accurate your measurements, the better your results will be. You can write the volume of each container into the tool directly, on a piece of paper or as a note on your phone etc. Once you have collected and recorded all of the samples you can enter them into the tool, entering one on each line or separating them by commas (Figure 4, pg. 20). If you input both the length of time the irrigation system was run for the test and the surface area of the container, the tool will also calculate your irrigation rate (inches per hour).
Figure 4. Coefficient of uniformity tool interface to help you determine how evenly irrigation water is applied in a given block at your operation.
Once you enter the volume from each container, irrigation duration, and the diameter or length x width of your collection container press the “Recompute” button and your results will be calculated. Ideally, overhead irrigation uniformity should be at least 85%, while drip irrigation uniformity should be over 90%. Measuring and correcting your distribution uniformity is a critical first step if you want to introduce automation, increase irrigation efficiency, or save water. If you want to apply 1 inch of water, at 90% efficiency you need to apply 1.11 inches to achieve 1 inch everywhere or for 80% efficiency, 1.25 inches needs to be applied. If you are irrigating 50 acres at 80% efficiency, you are applying an extra acre-foot of water every irrigation cycle.
Improving your irrigation uniformity can save significant amounts of water as well as disinfection costs and equipment maintenance costs.
If uniformity is below the recommended level, it is important to determine why. Some places to start include:
Checking nozzle orifice sizes (are they old and worn?) and replacing as needed.
Determining if all of the sprinklers in each irrigation block have the same flow rate.
Determining if all risers are plumb and the same height.
Ensuring system pressure matches the pressure recommended for the heads.
Wind can also reduce distribution uniformity. When possible, minimizing irrigation when conditions are windy will help to maintain irrigation distribution uniformity.
Figure 3. Example of an irrigation block layout for measuring your coefficient of uniformity. In this example, the same size containers are laid out in a grid pattern.
Leaching fraction
A leaching fraction, in general, tells you how much of the water that was applied to your container drains out of the bottom. If you add a liter (1,000 ml) of water to the top of a container, and 150 ml comes out the bottom, 15% of the water left (leached out of) the container. Ideally, when irrigating with high-quality, low-salt content water, leaching fractions should be low (below 10%) since water coming out of the bottom of the container also carries dissolved nutrients (which means money).
Application of most commercial fertilizers results in a build-up of salts in the growing media over time. This salt build up occurs more quickly when irrigation water has a higher salt content, like recycled irrigation runoff water. Source irrigation water with higher electrical conductivity (EC) values are more common in the southwestern and western U.S., where water is taken out, used, and then put back into the same river or lake repeatedly, increasing the salt content. Common water treatment processes do not remove salts before water is discharged back to the water body. Although high EC source water may be more common in the western U.S., any grower recycling irrigation runoff water will experience higher salt content in recycled water versus source water. As water EC increases, plants have to work harder to absorb the water from soil while leaving the salt behind. Some species of plants tolerate the presence of salt in water better than others, salt tolerance is species and cultivar specific. As plants absorb water, some salts are left behind in the substrate making it increasingly more difficult for the plants to remove the water with each additional irrigation cycle. The easiest solution to managing salt buildup within substrates is to regularly slightly over-irrigate plants, so that salts dissolve into the water and leach out of the bottom of the container.
Figure 5. Leaching fraction calculator interface. This tool can help you determine how much irrigation water to apply to remove excess salts from your containers.
You can use the leaching fraction calculator (Figure 5, pg. 25) to help determine how long to run your irrigation system to prevent substrate salt concentrations from becoming too high and damaging your plants. First, you need to know the EC of your irrigation water, which can easily be determined with a handheld EC meter. In the leaching fraction tool: enter the EC of your irrigation water, and then select the plant you are interested in from the dropdown list. They are listed alphabetically by common name. You can also search for a plant or select a generic plant sensitivity. Then you enter EITHER your irrigation amount (inches per day) and application rate (inches per hour of your irrigation system), OR the length of time your irrigation system is run for that species. The “Compute Irrigation Time” button will calculate how long you need to irrigate to accommodate the proper leaching fraction (normal irrigation time + additional time for leaching accumulated salts). Generally, your irrigation time will increase as the EC levels in your irrigation water increase or the plant’s salt tolerance decreases.
These three tools give you some of the information you need to help you determine which components of your irrigation system need attention. When you integrate information from these tools with your practical knowledge, you can help your operation save water, energy, money, and grow plants more efficiently and uniformly. Give them a try and get a little more efficient today.