| Crop | Critical Soil Test Levels | ||||
|---|---|---|---|---|---|
| P | K at CEC1 | ||||
| 5 | 10 | 20 | 30 | ||
| ppm (lb/acre) | ppm (lb/acre) | ||||
| Corn | 15 (30)2 | 88 (175) | 100 (200) | 125 (250) | 150 (300) |
| Soybean | 15 (30) | 88 (175) | 100 (200) | 125 (250) | 150 (300) |
| Wheat | 25 (50) | 88 (175) | 100 (200) | 125 (250) | 150 (300) |
| Alfalfa | 25 (50) | 88 (175) | 100 (200) | 125 (250) | 150 (300) |
1 Critical level for ppm K = 75 + (2.5 x CEC) for all crops
2 Values in parenthesis are lb/acre.
Note: A CEC of 15 is used to calculate the K2O recommendation for calcareous soils (soils with pH equal to or greater than 7.5 and a calcium saturation of 80% or greater) and organic soils (soils with an organic matter content of 20% or greater or having a scooped density of less than 0.8 grams per cubic centimeter).