Corn is most often grown in rotation with soybeans in the Midsouth region; especially in Missouri and Kentucky. To raise the most profitable yields, it is important to understand the nutrient uptake demand, the nutrient removal in the harvested crop, and the soil test phosphorus (P) and potassium (K) requirements of both crops.
Nutrient uptake is shown below for corn and soybeans at different yield levels.
 | | Nutrient Uptake, lb/A |
| Crop | Yield/Acre | N | P2O5 | K2O | Mg | S |
| Corn | 120 bu | 160 | 68 | 160 | 39 | 20 |
| 180 bu | 240 | 102 | 240 | 58 | 30 |
| 220 bu | 290 | 125 | 290 | 72 | 36 |
| Soybean* | 25 bu | 148 | 23 | 87 | 10 | 8 |
| 40 bu | 224 | 38 | 144 | 16 | 14 |
| 55 bu | 288 | 53 | 188 | 22 | 18 |
| 70 bu | 364 | 67 | 220 | 28 | 22 |
The nutrient removal by the harvested crop is shown below.
Nutrient Removal, lb/A
| Crop | Unit | N | P2O5 | K2O |
| Corn | lb/bu | .75 | .44 | .29 |
| Soybean | lb/bu | 4.00 | .80 | 1.40 |
Maintaining high soil test P and K levels for both corn and soybeans:
- helps lower the per unit cost of production
- maximizes corn nitrogen uptake and utilization efficiency
- ensures that other crop inputs result in the greatest return on investment
- limits the damage from environmental extremes (cold & wet, or hot & dry conditions) better
- provides for a timely harvest
- increases nitrogen fixation by soybeans
- improves water use efficiency
- and reduces the potential for loss of soil and fertilizer nitrogen to ground and surface waters.
To learn more about optimal P and K fertility management in the cornbelt states, refer to the News and Views article entitled Maintaining High Soil Tests.
For more information on optimum P and K management for soybeans in the Midsouth region (Arkansas, Kentucky, Louisiana, Mississippi, Missouri and Tennessee) and adjacent states, refer to the News and Views article entitled Raise Soybean Yields and Profit Potential with Phosphorus and Potassium Fertilization.
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