Soluble Salts: Don’t Get Burned

Soluble Salts: Don't Get Burned

As discussed in our previous article last month, high soluble salts can accumulate in the root zone when there is poor quality (high salt) irrigation water or excessive fertilizer input. Understanding which bedding plants are most sensitive can aid in crop selection and in management practices such as leaching.

At Cornell University we conducted an experiment to determine the response of 14 common bedding plants to increasing levels of high soluble salts. In this article we detail the growth effects on the studied species, provide a classification grouping for response to extreme salt stress and list corrective actions for high salts.

Bedding Plants For Salt Sensitivity

Table 1 ranks the bedding plants we studied for growth and height response to high soluble salt levels (PourThru EC 7.1). The irrigation water used for this treatment contained table salt (460 ppm Na + 710 ppm Cl) and had an EC of 2.4. This is roughly equivalent to the highest salt levels we have seen in New York state wells.

In one case, the high EC came from road deicing salts. In the other case, well water was in contact with a salt deposit. All plants examined except for fuchsia and snapdragon showed a significant reduction in plant biomass (measured as shoot dry weight). Coleus, Elatior begonia and zinnia were half the size of their control counterparts. Most affected were zonal geranium and euphorbia hybrid, which were both two-thirds to three-quarters smaller than control plants.

It is interesting to note that only seven species showed a significant reduction in height. For begonia, fuchsia, marigold, petunia, snapdragon, verbena and vinca there was not a significant reduction in height, whereas dry weight was significantly reduced at high EC. In a practical sense, this means a grower observing a crop purely from the standpoint of plant height may not detect a problem with high soluble salts (Figure 1). An astute grower of these crops may notice the problem appears first as sparser growth and a reduced leaf area.

The highest salt treatment in our experiment (1840 ppm Na + 2840 ppm Cl) was designed to look at plant response to extreme salt stress (PourThru EC averaged 14.5). Under these conditions all plants exhibited tell-tale signs of high salts: marginal necrosis (brown edges) on lower leaves and reduced plant size.

Of the 14 species, snapdragon (Figure 2) and petunia were the most salt-tolerant plants. Pansy and Zinnia angustifolia were the most sensitive. All plants were dead after five-week exposure to extreme salts.

From another experiment at Cornell, we also found New Guinea impatiens, sanvitalia and fibrous begonia are also very salt sensitive. All plants died in response to five-week exposure to extreme salts. While we’re not advocating growers use irrigation water anywhere close to this extreme treatment, it is amazing to note many of the bedding plants could grow (albeit slowly) and stay alive (at least in the short term) under these conditions.

Correcting High Soluble Salt Levels

Once root-zone salts have been determined to be too high, effort should be taken to determine the source of high salts. Test the irrigation water EC and the fertilizer solution EC. Compare the solution EC to the fertilizer label to make sure the correct rate of fertilizer is being applied. An error indicates improper fertilizer mixing or the injector ratio was not dialed in correctly. A New York grower reported discovering their plants got a 10-fold higher fertilizer rate than should have been received. Unfortunately, this wasn’t noted early on by checking the stock solution EC–it was noticed when leaf edges began turning blue from the fertilizer coloring agent.

Immediate action is required if there are visible salt damage symptoms on the plant or if root salt levels test in the high to very high range. In this case, clear water leaching is required. Irrigate each plant so about 50 percent of the applied water leaches out the bottom of the container (e.g. leaching fraction of 50 percent). Then recheck substrate EC values. If values are still too high, you can repeat the leaching procedure until EC is in the acceptable range.

Should you leach and re-leach if containers are already saturated with water? Yes! Waiting for them to dry out before leaching will compound the salt problem. Salt levels will become more concentrated as pots dry out, causing increased damage to roots. The best thing to do is to leach out the excess salts right away, then let the roots begin to recover in an environment with the proper EC.

Perhaps through periodic monitoring of the substrate you’ll find EC is just starting to become borderline high. The most probable cause of this is fertilizer salts being applied at a greater rate than the plant can absorb. In this case, leaching may not be required. Instead, take action to decrease the fertilizer rate. This can be done by switching to a lower concentration of fertilizer for plants on constant liquid feed or reducing the frequency of fertilization. For example, if you were previously fertilizing every time you water, switch so that clear water is used every second or third time you water the plants.

Coping With Poor Quality Water

When deciding where to site a greenhouse or nursery operation, the first consideration should be given to water availability and quality. What is the water source? What volume of water can be economically used per day? What is the water quality in terms of EC and alkalinity?
When a greenhouse operation faces poor quality irrigation water, there are essentially three choices: 1) filter the water; 2) seek a higher quality water source or 3) follow close management and plant selection decisions to minimize salt damage.

Several methods are available to filter the existing water. Reverse osmosis (RO) is most commonly used, as it tends to be the most cost effective. Reserve osmosis uses pressure to force water through a semi-permeable membrane that excludes most ions. With reverse osmosis, one consideration is disposal of the waste water containing the unfiltered ions. Depending on the RO unit and water source, 25 to 75 percent of water will not pass through the membrane and, thus, will need to be disposed of.

It may be more economical to find a different water source rather than filter existing water. Rainwater is of high quality for greenhouse plants (low salts, alkalinity) and is relatively straightforward and cheap to capture and use from gutter-connected greenhouses. A pond or large tank will be required to hold the water, and debris should be filtered before it enters the tank. This may be done using a device that diverts the first flush of rainwater and associated debris from entering the tank. If river or pond water is used, it should first be filtered (to remove debris suspended solids) and then disinfected (to remove pathogenic organisms) before being applied to plants.

Most operations that filter water or collect rainwater blend this with their original water. Some proportion of RO water or rainwater is added to their original water source to achieve a set EC set point (e.g. 0.7 or 1.0 mS/cm). Alternatively, pure water may be applied periodically to flush salts from containers. Caution: When switching water sources, you will likely need to change your fertilization/acidification practices. Consult with your Extension educator or commercial testing laboratory to determine what changes should be made. For example, if the original irrigation water is high in alkalinity and salts, an acidic fertilizer that doesn’t include calcium and magnesium may be appropriate. But if rainwater is used, calcium and magnesium may need to be added and the fertilizer should be less acidic.

Getting Creative

If operations do not have the ability to change their water source or filter high salt water, they must be both diligent and creative in their plant selection and care. These operations may need to follow one or several of the following suggestions:

– Grow only plants that can tolerate elevated salts.

– Grow plants with a quick production cycle.

– Minimize salt buildup by leaching frequently and using a porous, well-drained substrate.

– Irrigate frequently and keep substrate moist (so EC doesn’t rise as soil dries down).

– Avoid excessive inputs of fertilizer salts. Consider controlled-release fertilizers.

In summary, periodic monitoring of substrate EC is the best way to keep salt problems in check. Early detection and corrective action will go a long way toward keeping your plants and your pocketbook full of green.

Leave a Reply

More From Annuals Production...
Great Lakes Expo

November 30, 2015

6 Reasons You Should Attend The Michigan Greenhouse Growers Expo

The Michigan Greenhouse Growers Expo, held Dec. 8-10 in conjunction with the Great Lakes Fruit, Vegetable and Farm Market Expo, will feature an expansive trade show and several educational sessions aimed at greenhouse growers.

Read More
Colorado State University 2015 Container Field Trials

November 29, 2015

2015 Colorado State University (Fort Collins, Colo.) Field Trials Results

See the 2015 field trials results (includes photo gallery) for Colorado State University in Fort Collins, Colo.

Read More
Coleus 'Colorblaze Velveteen' (2015 University of Tennessee Field Trials)

November 28, 2015

2015 University of Tennessee Gardens (Knoxville and Jackson, Tenn.) Field Trials Results

See the 2015 field trials results (includes photo gallery) for University of Tennessee Gardens in Knoxville and Jackson, Tenn.

Read More
Latest Stories
Vivero International_Endisch

September 8, 2015

Vivero Internacional Continues To Expand Unrooted Cutti…

The tenth largest cuttings farm in the world, Vivero Internacional was founded in 1991 and began exporting unrooted cuttings in 1993. Based in Tepoztlan, Morelos, just outside of Mexico City, Mexico, the operation opened with 2 hectares or 5 acres. With time and new customers, the farm has experienced rapid growth, now spanning 40 hectares or 99 acres, says Vivero’s Dennis Hitzigrath. “The first 10 years, production was doubling every season,” Hitzigrath says. “In the last three years, it’s been about 20 percent.”     The independent operation grows 100 million cuttings annually for several breeders, serving the North American market. Hitzigrath says consolidation among breeders has brought more of a focus on Vivero Internacional from third-party breeders in recent years. This growing interest is spurring even more growth. “We are planning for a minimum growth of 20 percent,” Hitzigrath says. “We are adding more production space and hope to be […]

Read More

August 19, 2015

Greenhouse Growing Recommendations For Lobularia

Modern-day Lobularias are garden classics with good vigor and long bloom times. These growing recommendations will help keep your crop in prime condition.

Read More

September 16, 2014

Ball FloraPlant’s Las Limas Facility Provides Gro…

Ball FloraPlant’s Las Limas farm in Esteli, Nicaragua, is one year away from full production, but sales and quality from the two-year-old facility are right on track.

Read More

December 31, 2013

Successfully Propagating Yellow Petunias

Finicky yellow petunias require ample nutrition through aggressive fertilizer use during propagation.

Read More

November 19, 2013

Suntory Flowers Releases Its New Grower’s Guide A…

Just in time for spring production, Suntory Flowers introduces the Grower’s Guide app – the first greenhouse production app developed by a flower breeder. Designed for iPad tablets, the fully integrated tool provides complete cultural information for the entire Suntory catalog of varieties. With the portable and user-friendly app, growers can sort crops by temperature, light and fertility requirements and view crop times at a glance. In-depth cultural information is provided for each crop. It’s easy to see how many plants per pot are recommended for 4-inch and 6-inch pots and hanging baskets, along with number of weeks to finish. Growers can customize their Grower’s Guide by selecting the varieties they plan to grow and sell. Award ribbons indicate which varieties have been recognized for landscape performance at leading university trials. Once the Grower’s Guide app is downloaded, all of this vital information is available without access to the internet. […]

Read More

October 17, 2013

Next Generation Coleus Offers Production Advantages

Coleus has been reinvented so many times over the past 50 years that it is often hard to remember what the plants used to be like. Even the scientific name has been reinvented multiple times in just the last five years. What was once known as Coleus blumei became Solenostemon scutellarioides, which then became Plectranthus scutellarioides, where it rests for now. Originally, coleus was a seed-produced crop used primarily as a houseplant. It was also used as an herbal remedy in tea to help folks sleep. That has all changed in the last 20 years with the infusion of sun-tolerant varieties, late-flowering varieties (to avoid deadheading and extend season of performance), new colors and new forms. In the past 10 years, there has been some very nice breeding for landscape performance and heat tolerance. Over and over, this plant has changed until what we grow today is so superior to […]

Read More

May 8, 2013

Tips For Growing Otomeria O’Premiera

by CHANOCHI ZAKS When it comes to standing up to summer’s worst, nothing’s better than the Otomeria O’Premiera series. This hot plant choice — native to East Africa — doesn’t just survive but thrives in the most intense sun and the hottest heat that nature can provide.O’Premiera, the only commercially produced Otomeria series, includes four colors: Baby Pink, Pink, Ruby and White. All are hardy to Zone 11.Growing 14 to 18 inches tall and 12 to 14 inches wide, they are ideal for containers and landscape plantings alike. With an upright, well-branched habit, these sun lovers stay a pleasing, compact size. O’Premiera varieties flower continuously in warm weather and high light, typically through summer. General CultureFor a 5-inch (12 cm) pot, use one plant per pot. Plants will be ready for sales (from rooted cutting) within six to eight weeks. For 6-inch (15 cm) pots, use one to two plants […]

Read More

November 8, 2012

How To Decide What Varieties To Grow

Every fall, growers throughout our industry devote a great deal of time and effort to creating their production plans for the upcoming spring. This is after sifting through the new varieties shown at the California Spring Trials, the OFA Short Course and various other grower meetings, as well as from the stack of catalogs collected from various suppliers. When developing a production plan, what should a grower consider when selecting new varieties? Three key points to consider are: can I grow a quality plant, can I sell the finished product and can I make money on the finished product? Questioning your ability to grow a quality plant is not a criticism of your growing talents. But it is important to know the amount of knowledge you have about the growing requirements for the given plant. Over the course of many years there are often new genera or “resurrected” genera from […]

Read More

October 30, 2012

New Programs Require Staff Support

When we started the annuals program this year, we had 180,000 square feet and started growing bedding plants. We just decided to do it. An important part of getting started on a new program is to have the customer base. You have to have someone that is going to buy your bedding plants. And, of course, you have to have the buildings to grow the plants. Manpower is also very important in terms of having someone who knows how to do it. In this case, the staff here knows how to do woody ornamentals, perennials and so on, but they did not know much about bedding plants. That’s where I came in. As head grower, I like to teach people. Explain The Why When Training When I started with the annuals program, I was already here for a year. This gave me enough time to start learning who at this […]

Read More

April 2, 2012

Lantana Finished Production Tips

Grow Time (From Rooted Cutting) Lantanas in a quart container with one plant per pot take seven to eight weeks, in a gallon container with two plants per pot and also in a 12-inch baskets with four to five plants per pot, 11 to 12 weeks of grow time. Pinching Only one pinch is needed for compact lantanas like Bandana, either late in propagation or after transplant. Try to leave two or more sets of nodes when pinching. For more vigorous varieties like ‘Bandana Trailing Gold,’ two pinches are best. Growing Media High quality media with good porosity is critical for best growth. Peat-based mixes, like Fafard 2 Mix or 1P Mix, or bark-based mixes, like Fafard 4P Mix or 3B Mix work well. Fertilizer Rate Apply 200 to 250 parts per million (ppm) nitrogen, using Cal-Mag fertilizers (i.e. 13-2-13,15-5-15,14-4-14, etc.) for more compact growth and neutral pH. Use high […]

Read More

April 2, 2012

Lantana Propagation Tips

Upon arrival Lantanas should be stuck immediately. Do not store cuttings at a temperature below 48°F. Rooting Time Unrooted cuttings typically take four and a half to five weeks to root in a 105-sized plug. Dipping the base of the stem into 1,000 parts per million (ppm) IBA (indole-3-butyric-acid) can be beneficial, especially during early stick weeks. Growing Media High-porosity media like Fafard 1P Mix is ideal. Fertiss and Ellepot are also common choices. Keep pH at 5.6 – 6.2, test media E.C. and pH about three weeks after sticking and adjust as needed. Pinching Pinching is optional for compact varieties like Bandana but recommended for more vigorous varieties, like Bandana Trailing Gold. Make sure cuttings are well-rooted before pinching. Temperature Media temperatures of 72–74°F are ideal. Misting Spray CapSil one day after sticking to reduce wilting. Apply at a rate of 2 to 4 ounces per 100 gallons. Lantanas […]

Read More

March 7, 2012

Lobelia: Finished Production Tips

Grow Time (From Rooted Cutting) A lobelia in a quart container with one pinch per plant (ppp) takes six to seven weeks of grow time. In a gallon container with two ppp, grow time is estimated at eight to nine weeks. Lobelias in 12-inch baskets with four to five ppp take 10 to 11 weeks of grow time. PinchOne pinch, ideally done in propagation, is enough for small and midsize pots. Trailing types will benefit from a second pinch a few weeks after transplant.  The second pinch is not as crucial for Techno Heat Upright types. When pinching, use excellent sanitation, including viricides like Virkon-S, RelyOn or Trisodium phosphate (TSP). Growing Media High quality media with good porosity is critical for best growth. Peat-based mixes, like Fafard 2 Mix or 1P Mix, or bark-based mixes, like Fafard 4P Mix or 3B Mix work well. Fertilizer Rate Apply200 parts per million […]

Read More

March 6, 2012

7 Steps To Create Great Combos

The numbers and range of combination baskets and containers grown for spring sales have increased tremendously in in the past 10 to 15 years. An explosion of new genera and improved genetics from breeders and suppliers over the same timeframe contributed to this trend, and consumers have reacted positively. Although single variety baskets and containers are still produced in large numbers, combinations are now the primary focus at retail. With the continuing realignment of production into combination plantings, a number of factors need to be considered when planning, planting and growing these crops. Such factors include color combinations, plant vigor, plant habit, planting design, container size, cultural requirements and flowering time. Follow these seven tips to ensure success with each factor. 1. Get Color Combinations Right Color combination refers to the designing and blending of a certain mix of colors in the finished container. This combination can be as simple […]

Read More

March 5, 2012

Lobelia: Propagation Tips

Upon Arrival Stick relatively quickly and get cuttings hydrated as soon as possible. Only store unrooted cuttings overnight in a cooler if necessary. Cuttings can easily dehydrate. Rooting Time Unrooted cuttings typically take about three and a half to four weeks to root in a 105-sized plug. The “heat” type lobelias (i.e. Techno Heat varieties) root faster than most traditional “non-heat” types (i.e. Techno Blue). Growing Media High-porosity media like Fafard 1P Mix is ideal. Fertiss and EllePot are also common choices. Keep pH at 5.6 – 6.2, test media E.C. and pH about three weeks after sticking and adjust as needed. Pinching Lobelias do need to be pinched. Be sure to use good sanitation. Cuttings should be well-rooted before pinching. Temperature Media temperatures of 72–74°F are ideal. Once the cuttings are fully rooted, the temperatures can be lowered to control growth. Misting Spray CapSil one day after sticking to […]

Read More

October 12, 2011

Late-Season Combination Containers

Nearly 15 years ago as a retail grower I was troubled by the fierce competition among retailers for the standard fall offerings. Garden mums, flowering cabbage and kales, and pansies were the only crops we grew. As a perennial grower we offered quarts for early spring sales, gallons for spring and a small number of 2-gallons for late spring and summer sales. We were almost always finished with perennials by July 4. Yes, we may have had some sedums and ornamental grasses, or perhaps a crop of late-planted rudbeckia ‘Goldsturm,’ but that was it. That scenario worked great for production and the space the mums needed to be planted. Starting around Memorial Day my first rooted cuttings for poinsettias had to be planted, but was there opportunity to have other offerings in the fall? How about a nice-looking container with fantastic-looking foliage and blooms that would last through late fall […]

Read More

October 11, 2011

How To Overcome Downy Mildew Spread On Impatiens

The town of Saratoga, N.Y., has observed downy mildew on Impatiens walleriana in public and private gardens for about three years. So it was only a matter of time, Margery Daughtrey thought, before downy mildew arrived about 250 miles southeast in Riverhead, N.Y. Downy mildew on impatiens officially arrived late this summer, around mid-September, when leaf yellowing and leaf drop on impatiens occurred, as well as the appearance of white spores on the undersides of leaves. Three weeks after those symptoms, stems collapsed onto the ground while nearby flower beds were still flowering and looking healthy. “They look very strange in this ‘stems-only’ stage,” says Daughtrey, senior extension associate at Cornell University. “We haven’t had any frost so this is purely a matter of downy mildew and conducive weather conditions.” Daughtrey describes the Northeast’s weather late summer as cooler than usual and constantly rainy. Those conditions helped spread the disease. […]

Read More

August 3, 2011

Using ABA To Reduce Water Loss In Chrysanthemum & A…

Greenhouse crop production often employs the use of plant hormones and growth-regulating chemicals to control growth such as plant height, rooting and flowering. Abscisic acid (ABA) is a natural plant hormone produced in roots in response to drought conditions. ABA is moved to the leaves, where it stimulates the closure of stomata, reduces water loss and halts photosynthesis. Until recently, ABA has not been used in greenhouse crop production because there have been no products registered for commercial use. However, Valent BioSciences Corporation is planning to release ConTego Pro, a new plant growth regulator utilizing S-abscisic acid (S-ABA), the biologically active form of ABA. ConTego Pro has already received EPA registration. To delay wilting, S-ABA is best applied as a foliar spray. An application causes the stomata to close, and therefore, reduces water loss from the leaves. Treated plants exposed to water-limiting conditions can therefore tolerate a longer period of […]

Read More

July 25, 2011

Making Water Work For Growing

Many articles have been written over the past few years on water quality and the need for growers to adapt to their individual water supply. Most of these articles have been written by university or industry experts, and they have done a tremendous job explaining the scientific aspects of various water types and how the chemistry of these water types affect the pH of the soil, nutrient availability and overall plant quality. My favorite reference source on this subject is a book titled “Understanding pH Management,” by Bill Argo and Paul Fisher published by Greenhouse Grower. Many frequently asked questions by our grower customers have focused on soil pH and plant nutrition. Countless callers have a question like this: “I grow in soil brand X, my salesman says the pH is 5.8 to 6.2 straight from the bag, I feed with 20-10-20, and my water pH is 6.0. So why […]

Read More
[gravityform id="35" title="false" description="false"]