Soil could be deficient in any of the following nutrients. If you had to supply one of them, which would be needed in the smallest amount?

Options

A. S
B. P
C. K
D. Fe

Answer

To determine which nutrient would be needed in the smallest amount if soil is deficient, we need to categorize the nutrients provided in the options. Here’s a step-by-step solution:

### Step 1: Identify the Nutrients
The question provides four nutrients:
1. Sulfur
2. Phosphorus
3. Potassium
4. Iron

### Step 2: Classify the Nutrients
Next, we classify these nutrients into macro and micro nutrients:
- **Macro Nutrients**: These are required by plants in larger quantities. The nutrients listed in the options that fall under this category are:
- Sulfur
- Phosphorus
- Potassium
- **Micro Nutrients**: These are required in smaller quantities. The nutrient from the options that falls under this category is:
- Iron

### Step 3: Determine the Requirement Amount
Since macro nutrients are required in larger amounts, they would not be the answer to the question. Micro nutrients, on the other hand, are required in smaller amounts.

### Step 4: Conclusion
Among the options provided, iron is the only micro nutrient and is required in the smallest amount compared to the macro nutrients. Therefore, if soil is deficient in any of the nutrients listed, iron would be the one needed in the smallest amount.

### Final Answer:
**Iron (Option 4)** is needed in the smallest amount.

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