The “19-19-19” Upper Peninsula fertilizer program

Can you really afford to continue with a habit-based fertilizer program?

Your crops are all in now and the planting rush is over. Let’s reflect for a minute on how we make some of our annual fertilizer decisions.

I hear it from farmers over and over, “I usually put on 250 pounds of fertilizer per acre.” Maybe they say 200 or 300 pounds per acre. At the risk of being offensive, I may ask, “What kind of fertilizer?” The answer is frequently 19-19-19, maybe 8-32-16 in the eastern Upper Peninsula.

This leads me to believe that there are producers out there following the path of tradition, or habit, and not carefully considering the cost and benefit relationship between various crops and fertilizers.

Using estimated Michigan retail fertilizer prices from late winter, 2011:

  • An MSU soil test costs $15 and should represent 20 acres.
  • Possible fertilizer costs:
    46-0-0 -- $494/ton = $0.53/lb N
    0-0-60 -- $569/ton = $0.47/lb K2O
    18-46-0 (DAP) -- $678/ton = $0.53/lb P2O5 (N value subtracted)
    19-19-19 -- $675/ton
    20-10-20 -- $506/ton

It is easy to see that the $15 cost of soil testing 20 acres, not including labor, is a potential bargain; 1.6 lbs of 0-0-60 fertilizer times 20 acres = the price of a soil test.

Many soils in the central Upper Peninsula already contain significant levels of phosphorus and require little, if any, phosphorus fertilizer. Soils in the eastern and western ends of the peninsula are very different, often requiring large phosphorus applications.

For example, if you are applying 250 lbs 19-19-19 per acre to fertilize a crop requiring 45 lbs N, 20 lbs P2O5 and 30 lbs K2O per acre (as determined by soil test), then you are over-applying 27.5 lbs P2O5 and 17.5 lbs K2O per acre, for a total cost of excess fertilizer equaling $22.81 per acre. Choosing a lower P fertilizer or having your fertilizer custom-blended will be a cost saving to you.

If you choose to concentrate your fertilizer budget on the nutrients that will provide the best “bang for the buck,” there are long-term consequences. Grass hay will give the biggest response to nitrogen fertilizer, but this should be considered a short-term strategy. Removing phosphorus and potassium in crops year after year will result in “worn out” fields requiring a lot of expense and attention to bring back into a productive condition. There are fields like this scattered all over the Upper Peninsula.

You can contact your local MSU Extension office or your fertilizer dealer for information on soil testing and crop fertilization.

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