Update from the Field: Factors for Fall Fertilizer
Posted on October 28, 2021
Proper crop fertility management is important for healthy soils and increasing profitability. Growers remove significant yields, but sometimes put few nutrients back. This negative balance of nutrient replacement versus crop removal could lead to lower yields in the future.
A bushel of corn removes about 0.75lb N, 0.37lb P2O5, 0.27lb K2O from the soil. A bushel of soybeans will remove 4lb N, 0.8lb P2O5, 1.4lb K2O, Figure 1. In a corn-soybean rotation, based on yield predictions of 200 bushel per acre for corn and 70 bushel per acre for soybeans, it would require 249lbs of MAP and 253lbs of potash per acre to replace the phosphorus and potassium removed in the harvested grain. As yields approach 250 bushels and 90 bushels per acre for corn and soybeans, respectively, it will require nearly 315lbs of MAP and 322lbs of potash per acre to replace the nutrients removed. Applying fewer nutrients than are removed in the grain will cause soil test levels to decline over time. In many cases, fields with declining soil test levels may no longer be able to sustain the most profitable yield levels, especially whenconditions are right for above average trend line yields.
Figure 1: Chart from Purdue University showing the Tri-State crop nutrient removal rate table.
It is important to keep in mind that crops require higher amounts of nutrients than just those removed by the grain at harvest. Around 80 percent of phosphorus and 40 percent of potassium taken up by corn and soybeans are removed in the grain. The remaining nutrients are retained in the stover and are recycled for future crops. This stover may take up to 3 years to release all the stored nutrients. The application of Bio Reverse® to crop residue in the fall will accelerate the release of nutrients, making them available to next year's crop, Figure 2.
Figure 2: Bio Reverse breaks down crop residues post-harvest, making nutrients more available the following season to meet crop needs.
In conclusion, cutting back on fall fertilizer programs is only a short-term cost savings. When pulling big yields off the soil, we have to refill the nutrient tank of the soil. If we just keep with the standard rates and not adjust for increased yields, we run the risk of deficiency symptoms showing up in next year's crop. Applying Bio Reverse this fall will help break down the massive amount of residue left by a colossal crop and releasing stored nutrients quickly back to the soil. If you have questions about fertility rates this fall, contact your trusted Ag Advisor from The Andersons.
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