Not all micronutrients are made equal - The importance of solubility
The importance of micronutrients in growing higher yielding, higher quality, and more profitable crops is well known, although the differences between the types of micronutrients is less so. Not recognizing these differences may mean you’re leaving some yield potential in the field. The key to any fertilizer is how much is available to the plant that growing year. Yield increases are a result of knowing the nutrients applied are in a plant-available form (source) and were applied at the appropriate rate, the right time, and right place.
Plants are only able to take up nutrients that have been dissolved (i.e. water-soluble sulphate forms) into the soil solution. When talking about plant-available nutrients, the solubility of the fertilizer product must be evaluated to ensure the crop is being fed the nutrients it needs. Applying a low-solubility (i.e. less than 30% water soluble) micronutrient has very little benefit to the crop in the year the product is applied. If there is a need of a certain micronutrient for the planted crop and a low-solubility product is used, that crop will show symptoms of deficiency since the nutrient is not readily available.
Forms of Granular Micronutrients
The three forms of granular micronutrients available on the market are sulphates, oxysulphates, and oxides.
- Sulphates are 100% water soluble and highly available to the crop in the year applied.
- Quickly provides nutrients to plants and soil build.
- Oxides are relatively insoluble, making them unavailable to the crop in the year of application.
- Used to build soil nutrient levels on a long-term basis but not to correct nutrient deficiencies in the year of application.
- Oxysulphates are a combination of oxides and sulphates within the same granule. The availability depends on the balance of sulphate and oxide nutrients.
- Effective when needing to correct deficiencies, and to soil build.