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Fall Crop Residue Removal

Oct 14, 2020

By Jeff Blauwet, CFE Technical Agronomist

An early harvest will lead to a sizable number of round bales of corn stalks and bean stubble made this fall. After the last couple of years in which the weather made this quite difficult, those in need welcome the sizeable number.

This does come with some consequences that we will need to consider relating to fertility management. Removing the stalks/stubble also removes a lot of nutrients from the field, especially potassium. The old rule of thumb on corn is the weight of grain an acre produces is close to the weight of stover produced. For example, a 200 bu corn would be about 5.5 tons of stover produced.  You would then estimate the percentage of what you are removing to calculate an estimated nutrient removal.  If you remove 70% it would be estimated to be 3.85 tons of residue. Estimates vary but ISU Extension publication PM1688 states that stover at 15% moisture has about 5 units P and 18 units K/ton of stover in it.  This would calculate the removal being 20 units P & 70 units K (this is in addition to the grain removal).

The 2020 weather is another component of this. It is important because the potassium in the residue is in a soluble (leachable) form in the stalks. This means it can leach out of the stalks back into the soil if we have adequate rainfall after the corn is mature but before baling.  Since we have not had much rain, likely the potassium has not leached into the soil and thus removals will be higher than a normal estimate. Keep this in mind in your fertility planning.

If you are removing stover, you are also removing organic matter, smaller amounts of other nutrients, as well as increasing wind & water erosion potential.  Manure applications on those acres help a lot, especially cattle manure which brings amounts of potassium back to the acre.  Liquid hog manure has much less potassium so it would not replace all the potassium removal. 

Understanding what is happening out on the fields and managing accordingly will help keep the acres productive for the next crop rotation.

 


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