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Could a soil test show a nutrient such as Phosphorus or Potassium in sufficient amounts in the soil, yet when a plant analysis is taken, there is a deficiency of this same nutrient in the plant? Yes, this situation can and does happen. For example, when a drought occurs, the plant is not able to take up sufficient soil nutrients, yet a soil test shows that the nutrient in in a sufficient level in the soil. This is the reason we need to consider "water management" as part of a successful soil fertility program.
However, there are other factors which we have control over that can cause this same problem. For example, not maintaining q proper pH can stop or reduce uptake of nutrients. In most cases, high pH (7.0 or higher), reduces plant uptake of many nutrients, and a low pH (5.0 or lower) can do likewise. The exception would be specific crops favoring either a high pH or a low pH environment. It is important to understand that limestone (Calcium (Ca) and Magnesium (Mg)) play a "major" role in the availability of nutrients.
Nutrients do not act alone. All nutrients interact with at least one other nutrient, yet all nutrients are tested as if they stand alone.
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The example of Phosphorus (P): Zinc (Zn) relationship is explained. In order for the plant to be able to take up sufficient Phosphorus (P), ther must be available a sufficient amount of Zinc (ZN) in the soil. When the plant is unable to find sufficient Zinc (ZN), it will stop taking up Phosphorus (P). Over 60 nutrient relationships are duscussed in agronomy literature.
Finally, we know that the soil particles are negatively charged colloids, while nutrients including Calcium (Ca), Magnesium (Mg), Sodium (Na), Potassium (K), and Hydrogen (H) are all catons, or positively charged elements. Of these cations, we know that Calcium (Ca) is the strongest held cation. Magnesium (Mg) is a close second, Sodium (Na) and Potassium (K) are basically equal as the third strongest and Hydrogen (H) is the weakest or most loosely held cation. pH is a measurement of the amount of Hydrogen (H) ions in the soil.
When limestone is added (Calcium (Ca) and Magnesium (Mg) the two strongest held cations), it has a great effect on the avalability of Potassium (K), a much weaker nutrient. This relationship of nutrients is very important in the TSM® (Total Soil Management®) analysis of soil tests and making recommendations.