Nutrient Replacement with Corn and Soybean Stover Removal

By Aaron Saeugling

This article is Part 4 in a series of 5 ICM blogs on how to best allocate fertilizer dollars with tight margins.

With harvest in full swing and some farmers considering baling crop residue for forage and bedding, it’s important to consider the amount of nutrients being removed from the field not just from the grain harvested but also with the residue. It’s important to account for and replace these nutrients to maintain soil fertility levels. While the most effective tool to assess soil nutrient supply is to take soil samples of the field, sometimes this may not be practical or timely enough to adjust fertility applications. An alternative method is to look at the nutrient removal based on Table 2 from PM1688, A General Guide for Crop Nutrient and Limestone Recommendations In Iowa (https://store.extension.iastate.edu/product/5232).

When looking at this table to estimate nutrient removal, the first question we need to answer is how many tons of crop material have been removed per acre. For example, 3 corn stalk bales removed per acre weighing 1,200 pounds each removes 1.8 tons of corn residue. Once we know how much is being removed per acre, we can use the numbers from Table 2 to estimate how many pounds of P and K are being removed.

Phosphorus:  1.8 tons of corn stalks x 4.8 pounds of P₂O₅/ ton corn stover = equals 8.6 pounds of P₂O₅removed per acre.

Potassium: 1.8 tons x 18 pounds of K₂O/ton corn stover = 32.4 pounds K₂O removed per acre. 

These removal rates are in addition to the P₂O₅ and K₂O removed in the grain.

A similar calculation can be made for soybean residue removal. Soybean residue contains 4.7 pounds of P₂O₅ per ton removed and 23 pounds of K₂O per ton removed.

Nitrogen considerations should also be factored into corn stover removal. The economic optimum N rate is often less with partial stover removal (20 lb. N/acre less). And while this seems counterintuitive, with stover removal, less carbon is added to the soil requiring less N.  See discussion in PM 3052C Nutrient Considerations with Corn Stover Harvest (https://store.extension.iastate.edu/product/14052).

In summary, stover removal for use in bedding, forage, and potentially cellulosic ethanol must account for nutrient removal to maintain adequate soil test levels for crop production.  Continue to monitor soil tests levels and fertilize accordingly.