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Corn stalks - fertilizer bill?

Fri, Nov 4th, 2011
Posted in Agriculture

Jerrold Tesmer, Extension Educator for Fillmore/Houston Counties

This past week, I have had considerable conversations about how much fertilizer is going off the field when corn stalk bales are removed. The farms I'm talking about are those without livestock. If you have livestock and large amounts of manure are hauled back on the field, you have created a value added product and are in a totally different ballgame.

After checking fertilizer prices from a couple of sources, I arrived at a price of $.62 /lb. of actual P (phosphorus) and $.58 /lb. of K (potash). From the chart "Nutrient Removal by Major Minnesota Crops" for each bushel of corn raised, the stover (corn stalks) .25 lbs. P and 1.05 lbs. K are contained in the stover.

For easy math, I'm going to estimate 200 bushels per acre corn with 50 percent of the stalks removed in big round bales. First the P: 200 bushels X 50 percent X .25 lbs P X $.62 per lb. = $15.50 of P. Next the K: 200 bushels X 50% X 1.05 lbs K X $.58 per lb. = $60.90 of K. This totals $76.40 per acre fertilizer being removed.

A few years ago, Jeff Coulter, Extension Corn Agronomist, estimated 200 bushel per acre corn crop produces 4.22 tons of dry matter per acre as corn residue. Once again, assuming 50 percent is harvested, we would have just a little over 2 ton of stalks removed or about four bales per acre. If your cornstalk bale weighs 1,000 lbs, each bale would then contain $19.10 in fertilizer plus baling costs.

A couple of recommendations from Jeff Coulter:

Residue harvest is best suited to continuous corn systems that consistently have high yields and utilize little or no tillage. If corn residue is harvested, do not remove more than 45 percent of the residue. Harvesting only 45 percent of the corn residue is tricky, but it can be done if stalks are cut high during grain harvest and if stalks are not chopped prior to baling. If a rake is used prior to baling, make sure that the rake is set as high as possible to avoid collecting too much residue.

Another useful idea when harvesting residue is to rotate residue harvest among fields. This ensures that residue is not harvested from the same field every year. In addition, think seriously about reducing tillage following residue harvest. Also target manure applications rather than fertilizer for these fields if soil test levels indicate that phosphorus is needed.

Winter cover crops should also be considered for fields where residue is removed.

While it is critical to maximize profitability from the land, we need to balance short-term economics with long-term sustainability. When removing residue this fall, be aware of the affect on fertility, soil organic matter, and increased erosion potential.

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