PO 19. Recognize how the following affect soil test interpretation.
- Probability of crop response to added nutrients
- Estimate of nutrient sufficiency level
- Results reported as ppm or lbs/acre
- Within-field variability
- Laboratory choice
- Environmental risk
- Extraction method
As a first requirement, a good soil testing laboratory needs to have a good quality control system in place. However, even high-quality laboratories can give different results if you were to split samples and send subsamples to different laboratories. This is because soil testing laboratories can differ in:
The table below shows the soil test P results made by different laboratories on identical soil samples, and compares the different soil test methods. Again, be sure to always use the same laboratory to avoid improperly fertilizing your soil! |