It’s important to understand nutrient mobility and relationships, to be able to apply supplements in the correct way and the proper quantities for maximum benefit.
While all nutrients can translocate through the xylem – the channel from the root to the plant — the phloem is another matter. The phloem is the channel for moving food produced by photosynthesis from leaves to other parts of the plant such as roots and stems. We need to look at what minerals don’t move fluidly through the phloem so we can be smart about how to make sure they’re applied in the right manner for maximum impact.
In addition, all nutrients have antagonistic or synergistic relationships that influence their efficiency. Interactions among nutrients affect uptake, accumulation and crop yield. These relationships can be zero-interaction, synergism, or antagonism, and we need to understand them to balance the composition, amount, timing, and mode of delivery of fertilizers to plants and soil. If we can get a better understanding of these relationships, we can be more adept at diagnosing nutrient deficiencies and the corresponding actions to resolve these deficiencies.
For example, potassium is very mobile in both xylem and phloem, so it can be applied as a foliar spray or through the soil and root system. We need to be mindful, however that high levels of potassium can reduce the uptake of magnesium and to a lesser extent calcium, iron, copper, manganese and zinc, and we should pay particular attention to the potassium-calcium relationship.
Low levels of manganese and magnesium impact photosynthesis. Manganese, which is not phloem-mobile, needs to be applied through the soil, while magnesium, which is very phloem-mobile, can be applied by foliar spray. Meanwhile, calcium and copper are antagonistic to manganese, and calcium and potassium are antagonistic to magnesium. Interestingly, when potassium is abundant, the application of magnesium fertilizer shows a positive effect. But when both potassium and magnesium in the soil can’t meet the reproductive needs of the crop, the application of potassium fertilizer will lead to further magnesium deficiency. For example, a study of magnesium deficiency chlorosis in tomatoes showed that it was induced by heavy dressings of potassium, causing a depression in magnesium uptake and thus a reduction of photosynthesis.
These relationships among nutrients are important to understand, and I’ve only exposed the tip of iceberg. Grasping these relationships is very important, to be able to deliver counterpunches to mineral excesses and deficiencies. In addition, recent technological advances in measurement and analysis have revealed the importance of many of the minerals on the periodic table. Silicon, nickel, selenium and cobalt come to mind as now being thought of as important to agriculture. We sell a product called Sea-Crop that contains all the minerals in the ocean, literally, providing a good portion of the periodic table, the minerals that all plants had access to from the beginning of plant life.