In highly alkaline soil, any added Fe, Mn, Zn, Co is promptly precipitated and rendered unavailable to the plant. Deficiency of these four elements are sometimes corrected by:

Options

A. Liming
B. Adding balancing elements such a Ca, Mg, K.
C. Foliar spray
D. Adding straight fertilizers

Answer

To solve the question regarding how to correct the deficiency of Fe, Mn, Zn, and Co in highly alkaline soil, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Problem**: In highly alkaline soils, certain micronutrients like iron (Fe), manganese (Mn), zinc (Zn), and cobalt (Co) become unavailable to plants due to precipitation. This means that even if these nutrients are added to the soil, plants cannot absorb them.

2. **Evaluate the Options**:
- **Option 1: Liming**: Liming is used to correct soil acidity, not to address the deficiency of specific micronutrients. Thus, this option is incorrect.
- **Option 2: Adding Balancing Elements**: Adding elements like calcium, magnesium, and potassium does not directly correct deficiencies of Fe, Mn, Zn, and Co. Each nutrient has specific roles, and adding balancing elements won't resolve the deficiencies of these micronutrients. Therefore, this option is also incorrect.
- **Option 3: Foliar Spray**: This method involves applying a liquid fertilizer directly onto the leaves of the plants. This can provide the necessary micronutrients directly to the plant, bypassing the soil's limitations. This option is correct as it can effectively correct deficiencies.
- **Option 4: Adding Straight Fertilizers**: Straight fertilizers contain only one type of nutrient. Since we are dealing with multiple deficiencies, this option would not be effective in addressing all four micronutrient deficiencies simultaneously. Thus, this option is incorrect.

3. **Conclusion**: After evaluating all options, the most effective way to correct the deficiencies of Fe, Mn, Zn, and Co in highly alkaline soil is through **Foliar Spray** (Option 3).

### Final Answer:
The deficiency of Fe, Mn, Zn, and Co in highly alkaline soil is sometimes corrected by **Foliar Spray**.