Q&A On Controlled-Release

Pilon: What are the methods controlled-release fertilizers (CRF) are applied?

Passchier: The two most common methods of applying controlled-release fertilizers in greenhouses and nurseries is to incorporate them into growing mixes prior to planting (incorporation) or placing the fertilizer on top of the potting substrate (topdressing).

Topdressing entails placing a predetermined amount of fertilizer on top of the growing medium of each container. Generally, topdressing is reserved for second-season crops, but there are some growers who topdress crops just after planting new liners. Care should be taken with this practice to make sure you have a first-season fertilizer and not a second-season topdress fertilizer.

The first method I was exposed to 15 years ago was the "big hand" method. The grower/owner would show the hired help how much fertilizer to put in their hands and then place it on the surface of the container. Needless to say, the size of the hand seemed to make an optical illusion of what was the correct amount. There were very inconsistent amounts applied using this method, even when only one person was making the application.

The spoon method entails using plastic spoons with pre-measured (numbered) quantities depicting how many grams each spoon size contains. This method works pretty well with smaller containers, but becomes less effective on larger containers where multiple spoons per pot are necessary and it is easy for applicators to lose count.

For large containers, many growers use PVC pipes capped at one end that have been cut to hold a specific amount of fertilizer for the desired container size. The PVC pipe is filled with fertilizer and poured over the top of the container. This method ensures the delivery of the proper amount of nutrients without the worry of improper applications due to miscounting when small measuring devices are used.

There have been a number of portable and backpack applicators engineered over the years to help make topdressing more efficient and practical for growers. Some of the most popular applicators include the original Fertil Pak by Great Western Bag Company of St. Louis, Mo., Select-a-Feed and Perfect-a-Feed dispensers available from a number of distributors, the Fertil Dispenser from Simeoni Tecnogreen out of Italy (www.simeonitecnogreen.com) distributed by Agrinomix of Oberlin, Ohio, (www.agrinomix.com) and the GreenElf applicator out of Australia (www.greenelfworks.com).

Some growers use the drop spreader method for topdressing their crops. This method is usually performed over young, small plants or over-wintered crops that are in pot-to-pot space configurations. Several growers have retrofitted various types of drop spreaders or used a Nursery Special Spreader with high clearance from the Gandy Company (www.gandy.net/nursery_sprdr.php3). 

Pilon: When producing plants inside greenhouses and in outside production sites, how do I pick an effective rate to use?

Passchier: Understanding CRFs and determining the optimal rates to use is very challenging for most growers.

Many growers find the easiest method is to use the medium rate recommended on the fertilizer’s technical sheet. This strategy gets them through most growing conditions, but may lead to excessive or inadequate fertility under certain circumstances.

From my observations, greenhouse growers are most familiar with using parts per million (ppm) of Nitrogen when referring to fertility rates while outdoor producers seem most comfortable with rates of CRFs expressed in pounds of Nitrogen per cubic yard. Each type of grower can produce awesome crops, but each has different cultural practices and their rates of fertility are highly affected by differing cultural practices.

Greenhouse growers tend to utilize growing mixes with a high percentage of peat moss, which holds more water. Their irrigation practices are well managed, reducing the amount of leaching compared to many outside growers. They often have had mixed experiences with CRFs in the past. Why do many greenhouse growers obtain less than favorable results? The answer is simple and painful: the nutrient release was less than or greater than the grower was able to control.

From my observations, the most successful growers are using approximately 1 pound of elemental Nitrogen incorporated per cubic yard. They typically use a NPK ratio of 2:1:2 or 3:1:1, such as the ratios found in Diffusion 17-6-17 GH and Scott’s 15-9-12. At 1 pound of elemental Nitrogen per cubic yard, growers need to incorporate 6 pounds of Diffusion 17-6-17 GH or 6.8 pounds of Scott’s 15-9-12 per cubic yard. At these rates, many crops will perform very well in greenhouse situations and it still leaves room for tweaking the crop with their water-soluble sources. If the same crops were produced in outside ranges, growers would likely increase the rate up to 1.25 to 1.5 pounds of Nitrogen per cubic yard.

Why the difference in rate between indoor and outdoor production? As stated earlier, temperature determines the release and leaching determines what is left to feed the plant. In the greenhouse, there is often greater control of temperature and leaching than in outside facilities. Generally, outside ranges have greater fluctuations in temperatures and are irrigated more frequently or subject to heavy rainfalls. These temperature fluctuations often result in a lower average temperature, which reduces the release from CRFs. Using slightly higher rates will help compensate for these reduced temperatures. With more irrigation and leaching, it requires more volume of nutrients in the container to keep up with the amount of nutrients that are leached out.

Additionally, the growing mixes used for outside production typically contain a high percentage of bark and little peat moss compared to greenhouse blends. Consequently, these substrates are more open and porous. When a substrate is more open, there is a tendency to hold less water and leach more. With a higher leach fraction, more nutrients are required for sufficient plant growth. If growers could reduce the amount of leaching that occurs, they could reduce the rate of fertilizers needed. Leaching less may sound easy, but it takes exceptional water management to keep the nutrients available to the plant in outdoor sites. I estimate that only 20 out of 100 growers manage their water to the maximum ability. As an industry, we have many opportunities with new innovations and techniques to manage our water and nutrients better.

In the final installment in this series, we will continue our discussion of how the formulation, application method and irrigation practice affect the release of controlled release fertilizers.

Leave a Reply

More From Fertilization...
Capsicum 'Basket of Fire' (2015 University of Georgia Field Trials)

November 25, 2015

2015 University Of Georgia (Athens, Ga.) Field Trials Results

See the 2015 field trials results (includes photo gallery) for the University of Georgia in Athens, Ga.

Read More

November 25, 2015

Everything You Need To Know About the New England GROWS Conference

Held In Boston December 2-4, New England GROWS includes a comprehensive conference program, a trade show, and with six special programs that teach new skills and provide opportunities to network with colleagues.

Read More
Giving Tuesday

November 24, 2015

Giving Tuesday On December 1 Is An Opportunity For The Industry To Make Charitable Tax-Deductible Donations

Organizations such as American Floral Endowment and others are encouraging industry members to participate in the generous spirit of the holiday season.

Read More
Latest Stories
Fertilizer Rates Feature Image

August 12, 2015

Selecting Fertilizer Rates For Several Spring Bedding P…

Fertilizing bedding plants can be difficult due to the differing needs of the large variety of plants that we grow. Many operations do not grow enough of any one crop to cater the fertilizer specifically for each crop. Therefore, grouping crops with similar fertilizer requirements and having two to three fertilizer strengths available is a practical way to ensure plants are getting the fertilizer they need. With many new plant varieties on the market, we wanted to conduct a trial at Cornell University to determine best fertilizer rates for several common bedding plant crops. 22 Bedding Plants Studied To Establish Fertilizer Rates Plugs and rooted liners of 22 crops (Table 1) were transplanted into 4-inch (500 mL volume) round pots with a commercial peat/perlite based substrate. The plants were grown in a glass greenhouse at Cornell University during the spring season at a spacing of one plant per square foot. Heating set […]

Read More

June 13, 2015

UMASS Fertilizer Trials Recommend Nature’s Source Organ…

In a recent online fact-sheet at its Extension website, the UMass Amherst Center for Agriculture, Food and the Environment lists Nature’s Source Organic Plant Food 3-1-1 as “the best liquid organic fertilizer,” according to Dr. Douglas Cox, Stockbridge School of Agriculture. It is called-out by the Extension after a number of years of studying the use of organic fertilizers for growing commercial greenhouse crops. The trials evaluated traditional water soluble and granular slow-release chemical fertilizers. Dr. Cox recommends Nature’s Source Organic Plant Food 3-1-1 as a liquid fertilizer that is readily available, cost effective, OMRI-listed and with good label directions for greenhouses. He also mentions the ease-of-use in how it mixes well with water and can pass fertilizer injectors. “Nature’s Source is currently the best liquid organic fertilizer,” Cox wrote in his article “Organic Fertilizers – Thoughts on Using Liquid Organic Fertilizers for Greenhouse Plants,” “I have seen no foliar chlorosis yet with this fertilizer. Nature’s source is widely available and a great […]

Read More

January 9, 2015

6 New Fertilizer Products For Healthy Plants

These five products add even more options for delivering nutrients to the root zone.

Read More

January 7, 2015

Fertilizers And The Future

As growers look for new ways to cut costs and conserve resources, fertilizer and equipment companies are offering products that strive to save water, reduce toxic runoff and keep chemicals out of the equation.

Read More

December 31, 2014

Gain Greater Control Of Fertilizer With Automated Ferti…

University researchers look at integrating irrigation and fertilization with the help of water sensors to reduce fertilizer treatments and improve application timing.

Read More

October 30, 2014

Basics & Beyond: Comparing Substrate Fertilizer Ame…

Cornell University researcher determines if substrate-incorporated slow-release fertilizers can be used to replace or reduce the need for liquid fertilizer for four spring crops.

Read More

July 24, 2014

Using Controlled Release Fertilizers To Produce Garden …

Researchers determined whether or not garden mums can be grown with controlled-release fertilizer, and if it reduces fertilizer leaching, as compared with water-soluble fertilizers.

Read More

March 14, 2014

New Foliage Pro Fertilizer Offers Complete Nutrition Pl…

Dyna-Gro Nutrition Solutions has developed a process it says is capable of keeping all 16 essential plant nutrients in solution form.

Read More

January 30, 2014

OASIS Grower Solutions Introduces New One-Bag Hydroponi…

The new 16-4-17 Hydroponic Fertilizer from OASIS Grower Solutions (OGS) is a one-bag solution that replaces two-part systems traditionally used by commercial hydroponic growers. It is specifically formulated for commercial hydroponic production of lettuce, herbs and vegetables.

Read More

December 30, 2013

Fertilizer Changes Growing Mix pH

When considering a fertilizer's influence on media pH, you need to know its acid or basic reaction.

Read More

December 30, 2013

Basics & Beyond: Fundamentals Of Phosphorus Nutriti…

Phosphorus is an essential element, after all.

Read More
Everris Liquid S.T.E.M.

December 30, 2013

New Fertilizers For 2014

New fertilizer products not only deliver optimum nutrition, they also provide for easier application and increased efficiency. Check out these new products to help your operation produce a healthy crop in 2014. Click through on the pages below.

Read More

December 18, 2013

Focus On Fertilizer: Micronutrients And Organics

New fertilizer products are focusing on micronutrients and providing efficient options for organic production.

Read More

August 27, 2013

BioWorks Adds EcoVita To The Verdanta Family Of Biofert…

EcoVita, a homogeneous granular organic fertilizer, has been added to Bioworks Inc.’s Verdanta biofertilizers product family. This fertilizer will be manufactured and supplied to BioWorks by DCM Corporation of Belgium, a producer of natural and organic-based fertilizers in Western Europe. EcoVita is suitable for a wide variety of crops with its gentle release curve including:• Organic fertilization as a base nutrition in potting mixes• Leafy vegetables• Fruiting vegetables (s a top dressing) • Roses and other ornamentals The new fertilizer offers long-lasting and continuous action for 75 to 100 days and contains organic phosphorus (5 percent P2O5) for fast rooting. Nutrients in EcoVita are gradually released by the soil microbes, in addition to producing humus for better rooting and less leaching. EcoVita is OMRI Listed, making it suitable for use in organic production. “We’re pleased to introduce EcoVita 7-5-10 as our organic NPK product to complement our organic products: K-Vita 2-0-20 […]

Read More

April 29, 2013

Rockwell Farms Introduces Ready-To-Pour Container Ferti…

Rockwell Farms has introduced Rockwell Farms Plant Food, a bottled liquid fertilizer that does not need to be diluted before use. Always looking for ways to help the consumer succeeed, Jason Roseman of Rockwell Farms says the operation is also always looking for ways to get consumers to come back and buy more plants and flowers. “We feel like fertilization is one of those things that can be very confusing,” Roseman says. “Not everyone does it, and not everyone knows what they’re supposed to do.” The solution: Rockwell Farms Plant Food. The formulation is 150 ppm of a 20-10-20 fertilizer and is sold in 24-ounce bottles. Rockwell recommends that one bottle be used to fertilize 1.5- to 3-gallon outdoor plant and flower containers every 21 days. The product’s signage shows a young patio gardener pouring the bottled fertilizer on a windowbox with the tagline, “Just pour on your way out […]

Read More

April 29, 2013

Plant Products To Be Purchased By MGS Horticultural And…

MGS Horticultural Inc., a full-service supplier of fertilizers, pest control products, seeds and substrates in North America, together with Haifa Chemicals, a global supplier of potassium nitrate for agriculture and industry, specialty plant nutrients and food phosphates, today announced a plan to purchase Canadian fertilizer and pesticides supplier Plant Products Co. Ltd. The deal is anticipated to close by the end of June 2013. MGS will acquire Plant Products’ Canadian distribution business, sales force and name. MGS plans to use both names (MGS Horticultural and Plant Products) in all communications going forward. MGS will maintain locations in Leamington, ON; Brampton, ON; Laval, QC; St. Hyacinthe, QC; and Detroit, Mich. As part of the deal, MGS has signed multi-year agreements with Haifa to maintain exclusive distribution of Plant-Prod Soluble Fertilizers, Acer Controlled Release Fertilizer, Stim-Root and potting soil premix fertilizers for distribution in Saskatchewan, Manitoba and Eastern Canada. “MGS is excited […]

Read More

March 19, 2013

Irrigation And Fertilizer Tips For New Vegetable Grower…

Compared to other variable costs, fertilizers are not the largest part of the budget in conventional greenhouse production. Nevertheless, over the course of the season, mistakes in fertilizer use can lead to significant damages or crop losses. That makes this an important topic for ornamental growers who are experimenting with growing vegetable crops. This article will emphasize major differences between fertilizers used in vegetable production and in ornamentals production. The different nutrition strategies, monitoring and water volume per plant will also be explained. Fertilizer In ornamental production, nutrients are delivered using various water-soluble fertilizers through a fertilizer injector, through the use of controlled-release fertilizers, or a combination of the two. There are numerous fertilizer mixes available with all the needed nutrients already included. The fertilization rate is often given in parts per million (ppm) of nitrogen (N), which is a way of expressing the fertilizer concentration. At younger stages, plants will […]

Read More

March 11, 2013

Daniels Plant Food Rebranded As Nature’s Source

Ball DPF has announced the launch of Nature’s Source, a rebranding in name and packaging for its seed extract-based plant fertilizer product Daniels Plant Food. The new brand will make its industry debut at California Spring Trials. “While we are proud of our heritage, we made this bold decision because we’re expanding sales to our existing market segments and entering new ones. It was a good opportunity to start with a fresh name and a modern look for all our products and packaging,” says Chance Finch, general manager for Ball DPF. “We wanted to make it obvious, beginning with our Nature’s Source brand name, to know our products are sourced from nature. Growers, contractors and gardeners can be confident that our effective and unique formulations remain unchanged. We’re excited about launching updated packaging for all our products, and especially the new ready-to-spray plant food for home gardeners.” The Nature’s Source brand […]

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