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Farm Advisory

Do You Really Need to Apply P & K Fertilizer for Next Year?

Using Proper P & K Fertilization Can Pay Dividends for Crop Producers

The Farm Division of Attorney General Tom Miller's office encourages farmers to carefully examine their crop production systems this fall. Individual farmers should evaluate each practice within their system. At a time when Iowa farmers face low commodity prices, proper planning may pay big dividends in reducing input costs.

Miller's Farm Division recommends that farmers take several steps before making final decisions for the 2002 crop year:

1. Work closely with agronomic service providers and/or your local Extension office. Farmers should ask for the results of the most recent soil test done on each field. If the soil test is more than 3 years old, then a new analysis should be completed.

2. Review the soil test results, expressed in parts per million (ppm).

3. Determine the level of crop yield that is required to meet the financial goals for each farm. Prior crop production will be the best indicator of yield potential. Proven crop yields, county-wide average, and state yields can be used to determine acceptable goals.

4. Take into account all available forms of crop nutrients, including manure, composted crop residue and municipal waste, and commercial nitrogen, phosphorus and potassium.

5. Put together a plan for each crop. Consider the nutrients available to the plant from the soil and prior crops and the nutrients applied to the field. Also consider nutrients removed in the harvested parts of the crops to be grown.

6. Take into account the timing and placement of the recommended application of crop nutrients.

Iowa State University has noted that over the past 40 years most soil test values for phosphorus and potassium (P&K) have risen to "High" and "Very High" levels. ISU research data indicate that there is little if any economic benefit to applying P&K to soils that test "High" and "Very High." This information and the ISU recommendations can be used as benchmarks for the nutrient management decisions that need to be made by Iowa farmers. The recommendations can be found on the internet at www.extension.iastate.edu/Publications/PM1688.pdf

Proper planning for the next crop can reduce the potential for less-than-acceptable returns from each field crop. Farmers with questions concerning P&K fertilization application recommendations may contact the Farm Division at (515) 281-5351 or ISU Extension at (515) 294-1923.


Iowa Attorney General Farm Division
321 East 12th St., Room 018
Des Moines, Iowa 50319
Phone: 515/281-5351
Fax: 515/242-6072
Email: farm@ag.state.ia.us