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

FertilizerYara Tampa Ammonia Terminal Garners ResponsibleAg Honors
November 25, 2015
Yara has received its first ResponsibleAg Certification for its Tampa, FL, Ammonia terminal location. This achievement demonstrates Yara’s commitment to Read More
Tiger Sul Crop Nutrient Calculator
FertilizerH.J. Baker Launches New Nutrient Calculator App
November 12, 2015
H.J. Baker, a global agriculture firm, has launched a new agronomic nutrient calculator app. This innovative and powerful tool will Read More
FertilizerH.J. Baker Hosting Chinese Delegation
November 12, 2015
International Agricultural firm, H.J. Baker, is hosting a delegation from Beijing Xinhefeng Agrochemicals Co., Ltd. (XHF), a leading distributor of Read More
corn field
FertilizerWest Central Distribution Launches Levesol DFC
November 5, 2015
Levesol DFC, a dry fertilizer compatible version, joins the original Levesol as another option for growers to maximize the potential Read More
Top 100 Articles
CropLife 100United Cooperative Acquires Four ADM Wisconsin Facilities
November 12, 2015
United Cooperative, based out of Beaver Dam, WI, recently acquired four grain and agronomy locations from Archer Daniels Midland (ADM) Read More
CropLife 100BRANDT Car Makes NASCAR Xfinity Series
October 29, 2015
BRANDT will join JR Motorsports with driver, Justin Allgaier, for the 2016 NASCAR Xfinity (NXS) Series season. Allgaier will pilot Read More
CHS Building exterior
CropLife 100CHS Leaders Help Shape Succession Report
October 22, 2015
Succession planning was listed as a main concern of cooperative leaders at this summer’s 15 regional CHS owner town hall Read More
Fall Harvest
CropLife 100Pinnacle Purchases Eight Regional Seed Companies
October 12, 2015
Pinnacle Agriculture Holdings has announced the purchase of eight regional seed companies to advance its seed business. Pinnacle has acquired: Read More
MRM Agricultural Service
CropLife 100Pinnacle Acquires CropLife 100 Ag Retailer
October 8, 2015
Pinnacle Agriculture Holdings, LLC has successfully acquired the Missouri-based agronomy business of MRM Agricultural Service, LLC and its affiliates (MRM). Operating Read More
Eric Jenks, Wilbur-Ellis
CropLife 100Wilbur-Ellis Opens Dry Fertilizer Storage And Blending Facility In Washington
October 8, 2015
Wilbur-Ellis Co., ranked No. 4 on the CropLife 100, has constructed and opened a 22,000-ton dry fertilizer storage and blending Read More
Latest News
HerbicidesBREAKING: EPA Pulls Registration On Dow’s Enlist …
November 25, 2015
EPA on Wednesday withdrew approval of a controversial new weed killer to be used on genetically modified corn and soybeans, Read More
FertilizerYara Tampa Ammonia Terminal Garners ResponsibleAg Honor…
November 25, 2015
Yara has received its first ResponsibleAg Certification for its Tampa, FL, Ammonia terminal location. This achievement demonstrates Yara’s commitment to Read More
ManagementReviewing The Top Ag Stories For 2015
November 24, 2015
Editors Eric Sfiligoj and Paul Schrimpf discuss the most noteworthy events from this past year in agriculture. Read More
EmployeesAgriculture Jobs May Be Plentiful, But New Grads Are Sc…
November 24, 2015
Close to 60,000 jobs are set to open up in agriculture each year for the next five years, but there's not enough grads to fill them. Read More
Radish cover crop
StewardshipCover Crops Guide Helps Growers Improve Water Quality
November 23, 2015
A publication that teaches growers the advantages of using cover crops to improve soil health and crop yields has won Read More
Crop InputsThe Andersons’ Products Receive California Organi…
November 23, 2015
The Plant Nutrient Group of The Andersons, Inc. announced today that its Humic DG and Black Gypsum DG products are Read More
Eric SfiligojNew European Study Seems To Support Glyphosate Safety
November 23, 2015
Looking at any international news over the past few years, it might seem as if the European Union (EU) is Read More
Toggle Biostimulant corn roots
Crop InputsTwo New Biostimulants Added To United Suppliers’ …
November 20, 2015
Winfield US announces the launch of two new products in the United Suppliers portfolio for the 2016 crop season, Optify Read More
StewardshipNRDC Report: Cover Crops Contain Vast Benefits
November 19, 2015
As harvest season ends and farmers in the United States ready themselves for winter, one small change could make a Read More
Fall Harvest
Seed/BiotechArysta Launches New Seed Protectant
November 19, 2015
As spring wheat growers begin planning for a strong start to their season, Arysta LifeScience North America announces RANCONA V Read More
Crop InputsInocucor Receives U.S. Patent For Microbials
November 19, 2015
Inocucor Technologies Inc., the Montreal-based agriculture biotech company, was issued patent No. 9,175,258 by the U.S. Patent and Trademark Office to protect Read More
ManagementSyngenta Rumors and ARA 2015 Preview
November 19, 2015
CropLife Editor Eric Sfiligoj looks at the latest rumors involving Syngenta selling its crop protection business and talks about events Read More
EquipmentAGCO Announces Finalists For Operator Of The Year Honor
November 19, 2015
AGCO Corp. has announced the four top operators chosen as finalists for AGCO’s 10th Annual Operator of the Year program, Read More
High Plains Aquifer
StewardshipStudy: High Plains Aquifer Overall Usage In Decline
November 18, 2015
A new Kansas State University study finds that the over-tapping of the High Plains Aquifer’s groundwater beyond the aquifer’s recharge Read More
Golden Harvest Corn healthy leaves
FungicidesArysta Launches New Corn And Soybean Fungicide
November 17, 2015
Arysta LifeScience North America has recently launched ZOLERA FX Fungicide. The highly systemic, powerful fungicide delivers broad-spectrum disease control with Read More
Young corn plants in soil
Crop InputsBioAg Alliance: Microbials Targeted For 250-500 million…
November 17, 2015
Monsanto and Novozymes have announced a new 2025 acreage target that will guide the companies’ microbials business for the next Read More
Syngenta Sign
Crop InputsSyngenta Still Being Eyed For China Takeover
November 16, 2015
China National Chemical Corp. approached sovereign wealth funds including China Investment Corp. to help pay for a potential acquisition of Read More
Cedar Country Cooperative
Eric SfiligojCooperative Consolidation Continues
November 16, 2015
As I put this enewsletter column together, we’ve just put the finishing touches on our magazine’s annual CropLife 100 report. Read More