Nutrient removal rates in harvested grain: corn, soybeans, wheat, oats, dry beans and canola
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EmailNutrient removal by harvested portions of grain crops is an important consideration in deciding fertilizer rates.
Harvesting crops removes valuable nutrients from the soil. Nutrients removed must be accounted for when planning fertilizer rates for the next several crop rotations. When making nutrient management plans, soil test nutrient concentrations must be considered and factored into future nutrient applications and removals.
This article will focus on phosphorus (P) and potassium (K). Both P and K can be stored in the soil year to year and can take years to build up once soil test concentrations diminish.
Nutrient removal rates vary across cropping systems and have been modified through the years as grain nutrient concentrations diminish due to greater grain yield, greater quantities of biomass production, and reductions in root mass and density. According to the Tri-State Fertilizer Recommendations, crops are removing less P and K per bushel of yield.
The removal amounts can be calculated easily by multiplying the removal rate per bushel by the actual yield achieved. For example, a 150-bushel-per-acre corn will remove 52 pounds per acre P2O5 and 30 pounds per acre K2O. Likewise, a 49-bushel-per-acre soybean crop will remove on average 39 pounds per acre P2O5 and 56 pounds per acre K2O. Since total removal is dependent on bushel harvested, greater yield means more total nutrients are removed from the soil. As a result of this removal, the soil test P and K levels will gradually decrease over time if no fertilizer is added.
It is important to note, however, that nutrient grain removal and soil nutrient depletion are not necessarily one and the same and are not related in a linear fashion. Soil texture, physical properties, and soil mineralogy will all influence how quickly nutrients are removed or in some cases replenished from the soil.
|
Crop |
P2O5 removal pounds per bushel |
K2O removal pounds per bushel |
|
Corn1 |
0.35 |
0.20 |
|
Soybean1 |
0.80 |
1.15 |
|
Wheat1 |
0.50 |
0.25 |
|
Canola2 |
0.80 |
0.40 |
|
Oat2 |
0.28 |
0.19 |
|
Dry Bean2 |
0.79 |
0.92 |
1Data from Tri-State Fertilizer Recommendations 2020
2Data from International Plant Nutrition Institute 2016
Michigan State University Extension moved away from the build-up, maintenance and draw down framework in 2020. The current, simplified framework contains build and maintain to allow for greater flexibility depending on external considerations including rented versus owned acres and fertilizer prices. Figures 1 and 2 from the Tri-State Fertilizer Recommendations offer a visual representation of this framework.
If you want even more detail about these changes, the Tri-State Fertilizer Recommendations bulletin goes into this in greater depth. If soil tests are below a critical level, you need to apply crop removal plus “build-up” rates to increase the soil test P or K levels. Soil tests below critical level are considered deficient, and there is a greater probability that a crop yield response to applied fertilizer may occur. When soil tests are above the critical level but below the maintenance limit, crop removal rates are suggested because a yield response to applied fertilizer is less likely, but maintaining soil test concentrations within the maintenance range is still important.
If a field is above the maintenance limit, there is no agronomic reason to apply fertilizer (this is the section that used to be called drawdown).
It is important to note that building up both P and K soil concentrations can take multiple years. In addition to crop removal, build-up rates often must be applied each year over a three-to-four-year period to see soil test values increase.
Soil testing every three to four years would enable farmers to monitor the changes in the P and K levels. Please refer to the Tri-State Fertilizer Recommendations for fertilizer recommendations and nutrient removal rates of Michigan field crops.
Nutrient removal rates are an important consideration in fertilizer rate decisions for sustainable crop production. As the nutrient removal rate amount is a function of yield, an over-estimated yield goal will always lead to excessive fertilizer application and greater production costs.
