Fertility Expert: Good Time To Apply Phosphorus And Potassium

By Jennifer Shike, College of Agricultural, Consumer and Environmental Sciences, University of Illinois

With a promising harvest under way, it’s a good time to replenish fields with phosphorus and potassium, says Fabian Fernandez, University of Illinois Extension specialist in soil fertility and plant nutrition.

“High fertilizer prices for a few years were followed by a wet fall and late harvest last year,” Fernandez says. “This resulted in many fields not receiving all the phosphorus and potassium needed to maintain optimum test levels. Since many fields have already been harvested and soil conditions are ideal for tillage or to drive equipment over the field, now’s a great time to plan for phosphorus and potassium applications.”

Fernandez said how phosphorus and potassium are applied does not matter as long as you apply it so test levels are adequate for crop production.

For farmers interested in strip-till this fall, Fernandez recommends waiting until at least the middle of October to avoid heavy rains that can flatten the berm created during the tillage operation.

Applying phosphorus and potassium annually or biennially is debatable. U of I research indicates that as long as needed fertilizer is applied, there is no yield benefit hinging on whether the application is done every year or every other year.

“However, we have seen that for biennial applications it is better to apply fertilizer before the corn crop and have soybean as a residual feeder,” he says. “Research has shown that having corn in the second year after fertilization can cause yield reductions, especially in no-till systems. Conversely, soybean yields were not affected in response to the time of fertilization. Even if a biennial application results in time saving and one less pass over the field, if your experience tells you that your soil does not build up, I would suggest always applying on an annual basis.”

Both fall and spring applications have proven to be effective alternatives to provide nutrients to the crop and there is no agronomic difference in terms of one timing being better at increasing nutrient availability relative to the other.

“Fall is normally the preferred time since typically there is more time and equipment available in the fall than during the planting season in the spring,” Fernandez says. “Also, soil compaction is less of a concern when driving heavy equipment loaded with fertilizer in the fall because soil is typically drier than in the spring, and phosphorus and potassium applications combined with tillage operations are more feasible in the fall.”

One potential drawback for fall applications is the fact that the nitrogen accompanying phosphorus in di-ammonium phosphate (DAP, 18-46-0) and mono-ammonium phosphate (MAP, 11-52-0) is more susceptible to loss even if applied late in the fall. However, the amount of nitrogen present in these applications is not very high and the benefits of a fall application typically outweigh the potential for any small nitrogen losses.

If phosphorus and potassium are at adequate levels, there is no need to make any significant change in the short term when going into a rotation with more corn.

For farmers planning to make a long-term commitment to more corn, remember that overall corn can remove more phosphorus and less potassium than soybean. Thus, fertilization plans should be adjusted accordingly.

Finally, Fernandez said that before deciding placement method and when and how much to apply, the single most important thing to know is the test level of the soil. To find out, there is no substitute to a regular (every four years) soil sampling program.

For more information, check out The Bulletin, an online publication written by U of I Extension specialists in crop science.

(Source: College of Agricultural, Consumer and Environmental Sciences, University of Illinois)

Leave a Reply

Fertilizer Stories

FertilizerKoch Agronomic Services Launches N-TEGRATION Technology
July 27, 2015
Koch Agronomic Services, LLC (KAS) has launched  N-TEGRATION Technology, a process technology platform designed to enable production of enhanced efficiency fertilizers at Read More
FertilizerWSJ: Cf Industries Exploring Merger With Dutch Chemical Company
July 23, 2015
U.S. fertilizer maker CF Industries is in advanced merger talks with Amsterdam-listed chemical company OCI NV, the Wall Street Journal Read More
Crop InputsH.J. Baker Launches Fall Sulphur Campaign
July 22, 2015
H.J. Baker has launched their “Keep Your Future Green – Use Tiger This Fall and Win Big” campaign. The campaign Read More
FertilizerNew Research Could Lead To Less Reliance On Nitrogen, Eliminate Runoff
July 21, 2015
Farmers often are required to apply nitrogen fertilizers to their crops to maintain quality and improve yields. Worldwide, farmers used Read More
Top 100 Articles
CropLife 100Southern States Coop Hosting Drone Flight This Friday
August 3, 2015
Southern States Cooperative — No. 9 on the CropLife 100 — is hosting an FAA-approved drone demonstration at Grandview Farms Read More
CropLife 100Allied Ag Distributors Adds Four New Owners
July 30, 2015
Aligned Ag Distributors LLC has announced the addition of four new customer/owners to Franklin Holding Co. LLC. They are: The Read More
CropLife 100Pinnacle Purchases California-Based Specialty Crops Retailer
July 20, 2015
Pinnacle Agriculture Holdings has successfully acquired California-based NH3 Service Co.  Operating as part of Pinnacle’s Performance Agriculture brand, the new locations Read More
Asmus Farm Supply liquid fertilizer facility features 20,000 square feet
CropLife 100Slideshow: Asmus Farm Supply Shows Off Its New Liquid Fertilizer Facility
July 15, 2015
Asmus Farm Supply, Rake, IA, recently added a new liquid fertilizer facility to its company operations. The new liquid fertilizer Read More
CropLife 100Wilbur-Ellis Feed Division Facilities Receive Safe Feed/Safe Food Certification
July 13, 2015
Wilbur-Ellis Co.’s Feed Division, a marketer and distributor of value-added feed ingredients for the aquaculture, livestock and pet food industries Read More
CropLife 100BRANDT Expands To Brazil With Acquisition
July 8, 2015
BRANDT has acquired a majority interest in Target Brasil Fertilizantes Ltda. through its Brazilian subsidiary. Target Brasil manufactures, distributes and Read More
Latest News
Young corn plants
Crop InputsNufarm Reorganizing Ag, Industrial Vegetation Managemen…
August 3, 2015
Today Nufarm announced a reorganization of its Agriculture and Industrial Vegetation Management sales and marketing organizations effective August 1, 2015. Read More
StewardshipExcellence Through Stewardship Reaches 30 Members
August 3, 2015
Excellence Through Stewardship, a non-profit that promotes the adoption of best practices and stewardship in agricultural technology, reached the milestone Read More
CropLife 100Southern States Coop Hosting Drone Flight This Friday
August 3, 2015
Southern States Cooperative — No. 9 on the CropLife 100 — is hosting an FAA-approved drone demonstration at Grandview Farms Read More
CropLife 100Allied Ag Distributors Adds Four New Owners
July 30, 2015
Aligned Ag Distributors LLC has announced the addition of four new customer/owners to Franklin Holding Co. LLC. They are: The Read More
FungicidesReport: Sudden Death Syndrome Symptoms Appearing In Soy…
July 30, 2015
Last week, symptoms of sudden death syndrome (SDS) began to appear in April 15-planted soybeans at the University of Illinois’s Read More
Seed/BiotechAdvanta Seeds Adds New Phoenix Corn Hybrids
July 30, 2015
Corn growers in the High Plains and Western states have new options available for the 2016 growing season from Advanta Read More
ManagementTechnology and agriculture: a Futurist’s Perspective
July 30, 2015
Futurist David Zach, speaking at this week’s InfoAg Conference in St. Louis, shared thoughts on the benefits and limitations of Read More
Biofuels Plant in Lousiana
Industry NewsIdle Biofuels Plant In Louisiana To Reopen As Ammonia F…
July 30, 2015
A Lithuania-based company plans to spend $265 million to reopen an idle biofuels refinery in Grant Parish as an ammonia Read More
FFA at Monsanto Booth at the 2015 National Farm Machinery Show
Industry NewsFive Students Receive The 2015 Monty’s Plant Food Compa…
July 29, 2015
This fall, five college-bound students will have financial support through the Monty’s Plant Food Company FFA Scholarship. All five scholarship Read More
GYPSOIL Blendable Pellets
Crop InputsBeneficial Reuse Management Launches Pelletized Gypsum …
July 29, 2015
Beneficial Reuse Management (BRM) announced this week at Ag Media Summit that its GYPSOIL Pelletized Products Division will open a Read More
StewardshipOhio Water Quality Project To Determine How Much Phosph…
July 27, 2015
Researchers with the College of Food, Agricultural, and Environmental Sciences at The Ohio State University are looking for farmers in Read More
FertilizerKoch Agronomic Services Launches N-TEGRATION Technology
July 27, 2015
Koch Agronomic Services, LLC (KAS) has launched  N-TEGRATION Technology, a process technology platform designed to enable production of enhanced efficiency fertilizers at Read More
HerbicidesExpert: IARC Herbicide Classifications Leading To Confu…
July 24, 2015
Few people in the crop protection industry had heard of the International Agency for Research on Cancer (IARC) before this Read More
ManagementFCI Trade Summit Update & Precision Tank Turns 50
July 23, 2015
Editors Dave Frabotta and Eric Sfiligoj discuss the upcoming FCI Trade Summit in Las Vegas, NV, and how Precision Tank Read More
Palmer pigweed seedhead in cotton
HerbicidesUSDA Deregulates Dow AgroSciences’ Enlist Cotton Trait
July 23, 2015
The USDA today issued its decision deregulating Dow AgroSciences’ Enlist cotton trait in the U.S. The USDA has now completed its Read More
Industry NewsVerdesian Life Sciences Showcases Versatile Product Por…
July 23, 2015
Technology has revolutionized agriculture by bringing farmers, retailers and distributors to the forefront of the digital age. To meet the Read More
FertilizerWSJ: Cf Industries Exploring Merger With Dutch Chemical…
July 23, 2015
U.S. fertilizer maker CF Industries is in advanced merger talks with Amsterdam-listed chemical company OCI NV, the Wall Street Journal Read More
HerbicidesNufarm Releases New Panther SC Herbicide
July 23, 2015
Nufarm has announced the availability of new Panther SC herbicide. Panther SC is the first liquid formulation of flumioxazin available Read More