Basics & Beyond: Fundamentals Of Phosphorus Nutrition

One of the most significant research projects influencing greenhouse production in the 1990s was Dr. Paul Nelson, Chen-Young Song and Jin-Sheng Huang’s work on the growth control effects of limiting phosphorus (P) to plugs. Up to that point, plant growth and stretch was primarily attributed to only ammoniacal nitrogen.

Their classical research proved that phosphorus was the element that had the greatest impact on stem stretch and ammoniacal nitrogen had a far greater influence on leaf expansion. This can be seen in Figure 1 where withholding phosphorus significantly controlled plug growth. Most fertilizers high in ammoniacal nitrogen are also high in phosphorus, and it took we North Carolina State University (NC State) researchers some work to decouple these two elements.

Finished Crops Suffered From The No-Phosphorus Principle
Fast forward a few years. That leap in years also resulted in a leap in applying the principle of no phosphorus in finishing crops. This turned out to be disastrous for some growers. In graduate school, the caution of not extending projections beyond the extent of your data was drilled into us. Unfortunately, this concept was forgotten. A concept that worked on a short-term plug crop was applied to the entire growing season.

A few years ago, many poinsettia crops were grown with no added phosphorus. About mid-October, the folly of this recommendation became evident when poinsettia leaves developed lower leaf dark spots along the mid-rib, followed by overall leaf yellowing and finally leaf drop (Figures 2 and 3). The end result was plants with what we called naked knees, which occurred when the bottom half of the leaves abscised. The only option at that point was to purchase taller pot covers.

Reduce, Don’t Restrict, Phosphorus
We forgot that phosphorus is, after all, an essential element. While we can manipulate it by providing only small amounts to control plant growth on short-term plug crops, phosphorus is still needed by the plant. Soilless substrates have very limited holding capacity for phosphorus, so little is held in reserve. With the longer-term crops, they simply ran out of P.

When one considers all the elements that can be modified for controlling plant growth, phosphorus is still one of the best to manipulate. By far, the window between producing smaller plants (Figure 4) and leaf necrosis (Figure 5) and lower leaf purpling (Figure 6) is the widest, so limiting phosphorus is a safe production practice. But there is a point, as we found out with poinsettias, that lower leaf necrosis will occur. We just need to remember that there is a line and to avoid going over it.

  • This means periodical applications of phosphorus still must be done. It can be accomplished:
  • Utilizing low P fertilizers such as 13-2-13 Cal-Mag (what we primarily use in our research at NC State)
  • By adding periodic phosphorous applications (such as potassium phosphate if you mix your own fertilizer) or
  • With monthly applications of 20-10-20 (which when applied at 200 ppm N, provides 44 ppm P).

The target amount of phosphorus in Saturated Media Extract (SME) substrate tests is between 5 and 10 ppm. Values above that will only encourage elongated growth.

Everything In Moderation
There is no doubt that limiting the amount of phosphorus applied to a greenhouse crop is a sound production practice and avoids environmental contamination, too. A little goes a long way, but there is also no doubt we must provide a little phosphorus to still obtain high-quality plants.

The original research cited was published in GPN, January 2002.

Topics: ,

Leave a Reply

One comment on “Basics & Beyond: Fundamentals Of Phosphorus Nutrition

More From Crop Inputs...
Triathlon BA container shot

May 24, 2016

OHP’s Triathlon Biofungicide Now Listed By The Organic Materials Review Institute

Triathlon BA is a broad-spectrum preventative biofungicide that provides control of many foliar and soilborne diseases in ornamentals and herbs.

Read More
Pythium On Chrysanthemum

May 20, 2016

How To Prevent Pythium In Fall Garden Mums

Avoid profit loss in fall garden mums due to pythium root rot with good drainage and integrated pest management practices that reduce risk factors.

Read More
Agro-K

May 19, 2016

Agro-K Expands Distribution In New England Through Partnership With Northeast Agricultural Sales

Agro-K, which manufactures conventional and organic foliar plant nutrients, will distribute its full line of foliar fertilizers and soil biological products through NEAG.

Read More
Latest Stories
Triathlon BA container shot

May 24, 2016

OHP’s Triathlon Biofungicide Now Listed By The Organic …

Triathlon BA is a broad-spectrum preventative biofungicide that provides control of many foliar and soilborne diseases in ornamentals and herbs.

Read More
Two-spotted spider mites, adults and eggs

May 11, 2016

SePRO Launches Summer Insecticide Management Program Fo…

The program is designed to help growers use SePRO’s insect management tools to prevent plant damage from a variety of pests.

Read More
Small Aphid Colony on Calibrachoa

May 2, 2016

How To Stop Aphids In The Greenhouse

When untreated, aphids damage ornamental crops and act as vectors for disease. Integrated Pest Management combined with vigilant scouting can help you stay ahead of the problem.

Read More
Cicada (Greg Hoover, Penn State)

April 26, 2016

Cicadas Set To Emerge In Several Eastern States This Sp…

While there’s no immediate cause for alarm, experts say the cicada’s egg-laying process can damage woody ornamentals and make them vulnerable to diseases.

Read More
Parisitic Wasp Aphidius colemani

April 25, 2016

Plant Growth Regulator Use Can Affect Biological Pest C…

The use of plant growth regulators may negatively influence the outcome of biological control programs, according to researchers at North Carolina State University.

Read More
Beneficial Insectary Orius insidiosus

April 22, 2016

Beneficial Insectary Increasing Production Of Three Bio…

The company is now producing Orius insidiosus, Dalotia coriaria, and Dicyphus hesperus at its California facility, reducing the transit time of perishable biocontrols between producer and grower.

Read More

April 21, 2016

Michigan State University Offers Tips On Greenhouse Soi…

Improper pH and higher than adequate nutrient levels are among the many reasons for regular soil testing.

Read More
Parasitized aphid mummies, ladybird beetle larvae

April 18, 2016

4 Things You Need To Know About Implementing Biological…

Biocontrols are useful alternatives to traditional pesticides that provide effective pest control in the greenhouse. Here are four ways to get started successfully.

Read More
John Wendorf Bayer Ornamentals

April 14, 2016

Bayer’s New Ornamentals Business Manager Aims To Help G…

John Wendorf, who previously managed BFG Supply’s grower division, says when Bayer launches into the ornamentals market this November, growers will have access to a wealth of resources, including a dedicated team focused on ornamentals growers.

Read More
Emerald Ash Borer

March 22, 2016

Canada Implements New Voluntary Biosecurity Standard Fo…

The voluntary standard is designed to protect the greenhouse, nursery, and floriculture industries from invasive plant pests.

Read More

March 22, 2016

EPA Approves Syngenta’s Mainspring GNL Insecticide For …

Featuring the active ingredient cyantraniliprole, Mainspring GNL provides broad-spectrum control of key pests, such as thrips, whiteflies, aphids, caterpillars, leafminers, and leaf-feeding beetles.

Read More
Black Root Rot on Vinca

March 15, 2016

How To Identify Different Root Rots In The Greenhouse

Root rots can cause similar symptoms on hosts. Here are some tips for scouting in your greenhouse.

Read More
One symptom of Botrytis blight is gray, fuzzy sporulation on foliage and flowers, similar to that shown on the flower of this hibiscus

March 11, 2016

Manage Botrytis With These Cultural And Fungicide Contr…

High relative humidity and low temperatures in the greenhouse open the way for Botrytis to develop on plants. A mix of cultural and fungicide control options will help you manage this common disease effectively.

Read More
Biocontrols and beneficials absolutely can be used in outdoor production, with the use of banker plant systems

March 8, 2016

France-Based InVivo Acquiring Bioline, Syngenta’s Bioco…

Bioline, a subsidiary of Syngenta, specializes in the production and marketing of biological control agents, and in particular macroorganisms active against insect pests in fruits, vegetables, and flowers.

Read More

March 5, 2016

Prevent The Spread Of Disease In Irrigation Water

Water-mold pathogens cause significant crop losses and reduce floriculture crop quality. Take measures in your greenhouse to prevent the spread of diseases like Phytophthora and Pythium.

Read More
Bayer Greenhouse Ribbon Cutting

March 1, 2016

Bayer Opens New Greenhouse Research Facility In West Sa…

The $12 million facility will feature two new high-tech greenhouses that will be used in the development of new solutions in vegetable seeds and biologicals.

Read More

February 20, 2016

Hydrogel Technology Means Growers And Their Customers C…

Water and nutrient management are critical elements for quality plant production in the greenhouse. Maintaining the right amounts of available moisture and fertilizer at all times can be pretty labor intensive, but there are tools available to help you keep these inputs at optimum levels as efficiently as possible. Recently, we visited Evonik Industries’ North Carolina production plant for to see how one of these products — Stockosorb — is made, how it works, and learn the benefits of incorporating these tools in your own operation. Learn more about Evonik Industries’ Stockosorb hydrogel product on the Stockosorb website.  

Read More

February 17, 2016

Why It’s Important To Stay One Step Ahead Of Thri…

Keep thrips populations in check and avoid pesticide resistance by using spray and drench products known for their effectiveness.

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