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

FertilizerThe Fertilizer Institute: New President, Renewed Energy
February 3, 2014
Chris Jahn relishes the opportunity to lead the organization through the challenging times ahead. Read More
FertilizerA New Cycle For Fertilizer Demand
January 2, 2014
Changes in the corn market could have a major impact on the crop nutrients sector in 2014, say experts. Read More
FertilizerOSHA Hammers West Fertilizer With Over $100K In Fines For April Explosion
October 10, 2013
The Occupational Safety and Health Administration is fining the parent company of the West Fertilizer plant, Adair Grain Inc., $118,300 for 24 violations. Read More
FertilizerTFI Appeals Chesapeake Bay TMDL Ruling
October 10, 2013
The Fertilizer Institute joined a coalition appealing a U.S. District Court ruling on the Chesapeake Bay Total Maximum Daily Load (TMDL) for nitrogen and phosphorus. Read More

Trending Articles

Green Valley Ag facility
Retail FacilitiesGreen Valley Ag Adopts A.J. Sackett’s Precision Fertilizer Blending® Technology At New Facility
July 8, 2014
Sackett's Precision Fertilizer Blending® Technology is making huge strides around the world. Green Valley Ag adopts the technology at its new facility to support its advancing agronomic needs. Read More
Retail FacilitiesWaconia Manufacturing Builds Facility Designed For Speed, Efficiency
July 7, 2014
To make its new hub facility more efficient, Cooperative Elevator enlisted the aid of Waconia Manufacturing. Read More
EquipmentSummer Show Preview 2014: Superior Sprayers Take The Field
July 3, 2014
In this final installment of our coverage of the major categories of Big IRON that retailers can expect to test-drive at this summer’s events, here is a look at 19 sprayers. Read More
Scouting a soybean patch at Green Valley Ag.
EmployeesCropLife Compensation Survey: Battling Talent Drain
July 2, 2014
Retailers too often lose employees to companies outside of agriculture, while recruiting efforts are most often limited to competitors and other ag-focused organizations. Read More
HerbicidesDow AgroSciences Introduces SureStart II Herbicide
June 16, 2014
The enhanced formulation has improved viscosity and increased stability under heat and controls more than 60 high-anxiety grasses and broadleaf weeds found in corn fields. Read More
HerbicidesBASF Investing $270 Million To Expand U.S. Herbicide Production
June 11, 2014
BASF has invested more than $270 million to expand herbicide production capacities in the U.S., including more than 20 new products to be launched over next two years. Read More

Latest News

StewardshipMonsanto Joins Panel Of Innovators To Advance Research …
July 30, 2014
Monsanto Co. and The Climate Corp., its division, recently joined a roundtable of experts at the White House to share ideas and research approaches to help the world’s farmers manage and adapt to the impact of climate change on the global food supply. Read More
Crop InputsSoybean Checkoff Produces Big ROI
July 30, 2014
Under the soy checkoff program, all U.S. soybean farmers contribute a small percentage of their gross soybean sales for research and marketing projects that maximize their profit potential. Read More
CropLife 100Learfield Sports, CHS Agree To Football-Centric, Colleg…
July 30, 2014
CHS Inc. will embark on a highly integrated collegiate sports sponsorship platform with 24 Division I universities in 19 states designed to reach the farmer-owned cooperative's rural owners and customers. Read More
LegislationUSDA Implements Key Farm Bill Crop Insurance Provision
July 30, 2014
The new Supplemental Coverage Option, available through the federal crop insurance program and set to begin with the 2015 crop year, is designed to help protect producers from yield and market volatility. Read More
CropLife 100Wilbur-Ellis Forms New Organizational Structure For Its…
July 30, 2014
The new structure will provide more responsive internal support and will allow regional vice presidents and area managers to spend more time with customers, on talent development and on operational excellence across branches. Read More
Palmer pigweed in cotton
HerbicidesNew Training Modules On Herbicide Resistance Now Availa…
July 30, 2014
The Weed Science Society of America has announced the availability of three new education modules on herbicide resistance in weeds. Read More
HerbicidesWillowood To Market Glufosinate
July 28, 2014
Willowood USA recently announced that Federal EPA has approved its technical registration for glufosinate. Read More
InsecticidesHow To Scout For Corn Earworms In Corn
July 28, 2014
In her weekly report, University of Missouri Agronomy Specialist Jill Scheidt discusses what to look for when scouting for corn earworm. Read More
Crop InputsDuPont Pioneer, Weyerhaeuser Enter Technology License A…
July 28, 2014
The agreement brings together agricultural and forestry know-how to sustainably improve crop productivity for corn growers around the world. Read More
EquipmentAGCO Launches Global iPad App
July 28, 2014
The free AGCO Global iPad App can be downloaded from the Apple iTunes Store and features the full family of RoGator self-propelled sprayers and TerraGator high-floatation spreaders. Read More
Eric SfiligojYuma Centennial Ag Supply Earns 2014 National Environme…
July 28, 2014
Colorado-based ag retailer receives top trophy in 24th annual DuPont Crop Protection/CropLife ceremony. Read More
CropLife 100Pinnacle Forms Alliance With Wildlife Managment, Seed O…
July 25, 2014
The strategic alliance will provide Tecomate with key wildlife products, processing facilities, distribution centers and sales through Pinnacle’s ever-growing retail network. Read More
ManagementFranken Presses White House On RFS Support
July 25, 2014
Al Franken and a group of Senate democrats recently met with senior White House official John Podesta to urge the administration to change its position on an EPA proposal. Read More
ManagementASA, FarmLink To Launch ‘Operation Benchmark̵…
July 25, 2014
The American Soybean Association (ASA) and FarmLink are teaming up to help farmers close the $11 billion gap between what they harvested in 2013 and what they could harvest annually. Read More
StewardshipNorthey: Farmers Commit $1.4 Million to Try New Water Q…
July 25, 2014
The practices that are eligible for funding include cover crops, no-till or strip till and using a nitrification inhibitor when applying fall fertilizer. Read More
Precision AgFarmers Learn How Changing World Will Impact Iowa
July 24, 2014
Technology and understanding global consumer demand for Iowa farm products brought hundreds of farmers and agribusiness leaders to Ames recently for the annual Iowa Farm Bureau Federation Economic Summit. Read More
HerbicidesPurdue: Late Season Weeds May Require Manual Removal
July 24, 2014
Hand-rouging and pulling late season weeds by hand may be the best way to remove them, more so than using a herbicide, a Purdue Extension weed scientist says. Read More
Soybean Field
InsecticidesTransform WG, Closer SC Insecticides Receive R&D 10…
July 23, 2014
Dow AgroSciences has received the award from R&D Magazine for Transform WG insecticide and Closer SC insecticide with Isoclast active. Read More