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

FertilizerNutrient Management, Conservation Among Topics Covered At Indiana CCA Conference
November 23, 2016
Certified crop advisers, consultants, farmers, agribusiness professionals and students will learn more about nutrient management, soil and water conservation, pest Read More
NutriSphere-N Application
Crop InputsVerdesian: NutriSphere-N Making A Water Quality Difference In Midwest
November 18, 2016
Farmers sitting on the largest aquifer in the United States have learned a thing or two about managing nitrogen (N) Read More
FertilizerThe Fertilizer Institute Issues Statement On The U.S. Elections
November 10, 2016
The Fertilizer Institute (TFI) President Chris Jahn has issued the following statement on the results of the 2016 elections: “TFI Read More
Fertilizer Storage
FertilizerThe Fertilizer Institute Hires New Director Of Agronomy
November 4, 2016
The Fertilizer Institute (TFI) has hired Dr. Sally Flis as its director of agronomy, a new position created to support Read More
Trending Articles
R4023 Sprayer, John Deere
CropLife 100Ag Retail Equipment Report: The Green Party Continues
December 7, 2016
In the annual race for sales in the ag retail equipment marketplace, the color schemes for participants are a little Read More
Mike Stern
Precision AgClimate Corp. CEO Talks Retailer Support For Digital Ag
December 1, 2016
CropLife Magazine’s sister publication, AgriBusiness Global, recently sat down with Mike Stern, CEO of The Climate Corp., following the Monsanto subsidiary’s Read More
Precision AgTrimble Debuts End-to-End FMIS Platform
November 28, 2016
October’s inaugural PrecisionAg Vision Conference left this author with many thoughts and things to ponder in the coming months. Probably Read More
CHS Primeland
CropLife 100The 2016 CropLife 100 Report: Reviewing The Many Bulls And Bears Impacting This Year’s Marketplace
November 28, 2016
For virtually all of 2016, the nation was wholly focused on the big Presidential election. Some folks aligned themselves with Read More
Monsanto sign
Crop InputsMissouri Governor Meets With Bayer CEO To Discuss Monsanto Merger
November 21, 2016
Missouri Gov. Jay Nixon visited Bayer AG global headquarters in Leverkusen, Germany, on November 18 to discuss the proposed Bayer-Monsanto Read More
STS16 2017
SprayersHagie Manufacturing Releases 2017 STS16 Sprayer To Market
November 16, 2016
Hagie Manufacturing LLC’s largest full season applicator is now available with enhancements for the 2017 model year. Hagie is officially Read More
Latest News
AgriSync
Matt Hopkins17 Agriculture Apps That Will Help You Farm Smarter In …
December 9, 2016
Ag professionals are working smarter, not harder, than ever before. Smart farming technologies have enabled them to reduce costs, maximize Read More
Ryan Bartlett
Crop InputsCompass Minerals Appoints Vice President, Innovation An…
December 8, 2016
Ryan Bartlett, Ph.D., has joined Compass Minerals as vice president, innovation and product development. Dr. Bartlett will be responsible for Read More
HerbicidesHerbicides 2017: New Cropping Systems Set For Debut
December 7, 2016
Herbicide-resistant weed are inching ever-closer to a potentially frightening saturation point here in the U.S. Heading into 2016, USDA planting Read More
CropLife 100Wilbur-Ellis Acquires Michigan Ag Retailer
December 7, 2016
Wilbur-Ellis’ Agribusiness, a recognized leader in precision agriculture technology and the distribution and marketing of plant protection, seed and nutritional Read More
Fertilizer storage The Andersons
CropLife 1002016 Fertilizer Report: Another Really Rough Year For A…
December 7, 2016
In many ways, the fertilizer category cannot seem to catch a break. During the early part of the 2010s decade, Read More
R4023 Sprayer, John Deere
CropLife 100Ag Retail Equipment Report: The Green Party Continues
December 7, 2016
In the annual race for sales in the ag retail equipment marketplace, the color schemes for participants are a little Read More
Winter wheat
HerbicidesTalinor Herbicide Approved For Wheat And Barley
December 7, 2016
Talinor herbicide from Syngenta has received federal registration from the U.S. EPA, giving wheat and barley growers a new option Read More
Forage Sorghum
UncategorizedMilestone Achievement Continues For Dow AgroSciences, A…
December 7, 2016
New and innovative forage products are on the horizon driven by continued collaboration between Dow AgroSciences, a wholly owned subsidiary Read More
Palmer pigweed seedhead in cotton
HerbicidesNew WSSA Factsheet Explores Weed Seeds And Their Longev…
December 7, 2016
Did you know some weed seeds can lie dormant in the soil for more than a century and then sprout Read More
Crop InputsARA 2016: 5 Developments Worth Monitoring Into 2017
December 6, 2016
You can pretty much set your watch to it (do people even still wear watches? I know I do…but I’m Read More
Tim McCardle, ARA Chairman
CropLife 100BRANDT COO Named ARA Chairman
December 5, 2016
BRANDT EVP and Chief Operating Officer Tim McArdle has been named chairman of the Agricultural Retailers Association (ARA) during a Read More
Crop InputsWilbur-Ellis Receives ResponsibleAg Certification At Mo…
December 5, 2016
Wilbur-Ellis Co., a recognized leader in precision agriculture technology and the distribution of crop protection products, announces the ResponsibleAg certification Read More
Young Corn Closeup
Eric SfiligojThe Read On 2017 For Agricultural Fortunes Is Anybody’s…
December 5, 2016
As I (and others) have written in recent months, the nation has just experienced one of the most offbeat election Read More
Acceleron B-300 seed coating
Crop InputsThe BioAg Alliance Launches New Yield-Boosting Microbia…
December 5, 2016
As part of their commitment to develop and commercialize innovative microbial solutions for farmers through The BioAg Alliance, Monsanto Co. Read More
ManagementCorn and soy planting update; Takeaways from Climate Co…
December 2, 2016
AgriBusiness Global Editor Dave Frabotta Joins Paul Schrimpf for a discussion of global corn and soybean planting trends, and a Read More
Radish cover crop taproot
Crop InputsSoil Health Institute, Datu Research Receive Grant To E…
December 1, 2016
The Soil Health Institute (SHI) and Datu Research have announced a $626,000 grant from the Walton Family Foundation to quantify the Read More
Mike Stern
Precision AgClimate Corp. CEO Talks Retailer Support For Digital Ag
December 1, 2016
CropLife Magazine’s sister publication, AgriBusiness Global, recently sat down with Mike Stern, CEO of The Climate Corp., following the Monsanto subsidiary’s Read More
ManagementAg Industry Comes Together To Address Climate Change
December 1, 2016
Addressing climate change — and more specifically, decreasing greenhouse gas emissions from agriculture — can only be achieved through collective Read More