In today’s article, I want to cover in brief 3 aspects of how nutrient interactions happen within the plant.
- Antagonistic and Stimulant nutrients
- Law of minimum
- Mobility of nutrients
Antagonistic and Stimulant nutrients:
Antagonistic nutrients have a negative effect on the uptake of other nutrients. Possibly you have seen that an excess of Phosphorus (P) creates an imbalance with Iron (Fe) and Zinc (Zn)?
Some nutrients do the opposite and their presence has a positive effect on the uptake of other nutrients. These are called Stimulant Nutrients and an example of this is would be when increasing the nitrogen (N) availability to the plant, it will allow the plant to take in more magnesium (Mg) and up the demand for it. To show this we have the Mulder Chart.
(Copied from Bariya et al. 2014)
Put simply, high levels of a particular nutrient can interfere with the availability and uptake of other nutrients. The nutrients which interfere with one another are referred to as antagonistic. For example, high nitrogen levels can reduce the availability of boron, potassium, and copper; high phosphorous levels can reduce the availability of iron, calcium, potassium, copper, and zinc, and high potassium levels can reduce the availability of magnesium and calcium. For this reason, unless care is taken to ensure an adequate and balanced supply of all nutrients too much nitrogen, phosphorus, and potassium (and others) in fertilizers/nutrients can induce plant deficiencies of other essential elements.
Stimulation occurs when the high level of a particular nutrient increases the demand by the plant for another nutrient. For example, increased nitrogen levels create a demand for more magnesium. If more potassium is used then more manganese is required etc. Although the cause of stimulation is different from antagonism, the result is the same; induced deficiencies in the plant if it is not supplied with balanced nutrition.
Law of minimum:
Liebig’s Law of the Minimum is a principle developed in agriculture that states that if one of the nutritive elements is deficient or lacking, plant growth will be restricted and not in its full potential even when all the other elements are abundant. Any deficiency of a single nutrient, no matter how small the amount needed, will hold back plant development. If the deficient element is supplied, growth will increase. Excess supply however will not be helpful, due to the laws of nutrient antagonism discussed above.
For instance, excessive phosphorus will reduce the availability of iron, calcium, potassium, nitrogen, copper, and zinc. This is particularly true of the microelements iron, copper, and zinc. What this means is that the overuse of phosphorous in solution will potentially starve out other important nutrients/elements that are required for healthy growth/optimal yields.
Low nutrient levels will result in deficiencies, while high concentrated nutrient solutions lead to the potential for excessive nutrient uptake and, therefore, toxic effects may result. Many people think that more is better when supplying nutrients and additives and that it is better to have excess nutrients in the solution than levels that are only adequate. This is not necessarily true and this thinking can potentially lead to serious imbalances in nutrient uptake.
Mobility of nutrients:
All nutrients move relatively easily from the root to the growing portion of the plant through the xylem. Interestingly, some nutrients can also move from older leaves to newer leaves if there is a deficiency of that nutrient. Knowing which nutrients are ‘mobile’ (i.e., able to move) is particularly useful in diagnosing plant nutrient deficiencies because if only the lower leaves are affected, then a mobile nutrient is most likely deficient. Conversely, if only the upper leaves show the deficiency, then the plant is likely deficient in an immobile nutrient because that nutrient cannot move from older to newer leaves. The below table lists the six mobile and eight immobile mineral nutrients. Sulfur is one element that lies between mobile and immobile elements depending on the degree of deficiency.
| Mobile Nutrients | Immobile Nutrients |
| Chloride | Boron |
| Magnesium | Calcium |
| Molybdenum | Copper |
| Nitrogen | Iron |
| Phosphorus | Manganese |
| Potassium | Nickel |
| Zinc | |
| Sulfur (intermediate between mobile and immobile) | |
Finally, Please note that Proper nutrient management should include the “Four R’s” of fertilizer use: apply the right nutrient, at the right rate, at the right time, and in the right place for the selected crop (Mikkelsen 2011).
References
Bariya H, Bagtharia S, Patel A. 2014. Boron: A Promising Nutrient for Increasing Growth and Yield of Plants In: Nutrient Use Efficiency in Plants.153–170. DOI: 10.1007/978-3-319-10635-9_6