Applying micronutrients for plants is typically done through soil application, which is the most common method.
Providing plants with the essential micronutrients they need for healthy growth is crucial. While required in much smaller quantities than macronutrients, their absence can severely impact plant development.
Most Common Method: Soil Application
Soil application is the most common method of micronutrient application for crops. This involves adding the micronutrient source directly to the soil where plants can access them through their roots.
Methods of soil application include:
- Broadcasting: Spreading the micronutrient source evenly over the entire soil surface before planting or emergence.
- Banding: Placing the micronutrient source in a concentrated band near the seed or seedling. This method can be particularly effective as it ensures the developing roots have immediate access.
- Mixing with Bulk Fertilizers: This is a popular strategy to overcome challenges with low application rates.
Challenges with Soil Application Rates
Micronutrients are needed in very small amounts. As noted, recommended application rates usually are less than 10 lb/acre (on an elemental basis). Applying such small quantities uniformly across a large field using conventional spreading equipment is difficult. Uniform application of micronutrient sources separately in the field is difficult because of these low rates.
Overcoming Uniformity Challenges
To ensure even distribution despite the low rates:
- Mixing with Dry Fertilizers: Micronutrient sources are often blended with bulk dry fertilizers (like NPK fertilizers). This increases the total volume of material being spread, making uniform application much easier.
- Coating Dry Fertilizers: Micronutrient sources can be coated onto the surface of bulk fertilizer granules.
- Mixing with Liquid Fertilizers: Micronutrients can be dissolved or suspended in liquid fertilizers applied to the soil.
Alternative Application Methods
While soil application is most common, other methods are used, especially when rapid correction of a deficiency is needed or soil conditions limit root uptake:
- Foliar Application: Spraying micronutrient solutions directly onto plant leaves. Nutrients are absorbed through the leaf surface. This method provides a quick response but typically doesn't supply the total micronutrient needs for the entire season.
- Fertigation: Applying micronutrients dissolved in irrigation water, allowing for distribution directly to the root zone.
Choosing the best method depends on the specific micronutrient, the crop, the soil type, the severity of the deficiency, and available equipment. However, soil application, often facilitated by mixing with bulk fertilizers, remains the foundational approach for supplying micronutrients due to its ability to provide a season-long supply.
