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Because the effect of residue removal is not apparent in the short-term, multiple variables can impact results. Tillage, crop rotation and yield level are factors that will dictate how much crop residue can be harvested and still ensure sustainability of the system.
Phosphorus and potassium
“Ultimately, the amount of phosphorus and potassium present in corn cobs is far less than that in stalks and leaves, so removal of corn cobs represents less removal of nutrients from the field,” Fernández said.
However, removal of corn cobs alone is not practical for all farmers and many are interested in removing as much residue as is sustainably possible, Fernández said.
While there are many factors that can influence the amount of nutrient removal when crop residue is baled, the way to calculate actual removal is straightforward. Following are a few simple steps that can be used to calculate nutrient removal and value when stover is taken out of the field.
Calculate the amount of stover produced
The first step in determining total nutrient removal in stover is to calculate how much stover is produced. This is typically estimated from a harvest index (also known as residue-to-corn grain ratio). The most widely used dry weight ratio is 1:1 residue:grain. Using this 1:1 ratio to calculate the pounds of dry residue produced, the grain yield (in bushels per acre) is multiplied by 47.3. The value can then be divided by 2,000 to obtain the number of dry tons produced.