Question

For applying 100 kg N/ha, how much urea would be required

• A. 46 kg
• B. 117 kg
• C. 217 kg
• D. 317 kg

Hint:

To quickly find the amount of urea needed, multiply the desired nitrogen rate by 2.17.
For example: \( 100 \times 2.17 = 217\text{ kg} \).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Commercial fertilizers contain a specific percentage of active plant nutrients, which is printed on the fertilizer bag as the nutrient grade.
Because fertilizers are not 100% pure nutrients, you must calculate the total bulk fertilizer weight needed to supply the recommended rate of active nutrient per hectare.
Key Formula or Approach:
The weight of fertilizer required is:
\[ \text{Fertilizer required (kg/ha)} = \frac{\text{Recommended Nutrient Rate (kg/ha)}}{\text{Percent Nutrient in Fertilizer}} \times 100 \]

Step 2: Detailed Explanation:
Let us apply the values to our formula:
The recommended nitrogen rate is \( 100\text{ kg N/ha} \).
Commercial urea contains \( 46\% \) nitrogen by weight.
Substituting these values into our equation:
\[ \text{Urea required} = \frac{100 \text{ kg}}{46} \times 100 \] \[ \text{Urea required} = 2.1739 \times 100 \approx 217.39 \text{ kg/ha} \] Rounding to the nearest whole number gives \( 217\text{ kg} \).
Therefore, a farmer must apply 217 kg of bulk urea per hectare to supply 100 kg of actual nitrogen.

Step 2: Final Answer:
The amount of urea required to apply 100 kg N/ha is 217 kg.