Which essential plant nutrient is not readily available from the atmosphere or water?

Which essential plant nutrient is not readily available from the atmosphere or water?

• A. Nitrogen
• B. Phosphorus
• C. Potassium
• D. Calcium

Answer: (A)

Nitrogen is essential for plant growth, but even though the atmosphere is full of nitrogen gas (N2), plants cannot use that form directly. It has to be converted into usable forms like ammonium (NH4+) or nitrate (NO3−) by nitrogen-fixing bacteria or through industrial processes, and then made available in the soil. Because this conversion step is required, nitrogen is not readily available to plants from the atmosphere or from water in its native form; it must first be fixed into a soluble form they can uptake. In contrast, nutrients like phosphorus, potassium, and calcium generally enter the plant through soluble mineral ions that come from soil minerals and can be dissolved in water, making them readily available for uptake. That’s why nitrogen is the nutrient that isn’t readily available from the atmosphere or water.

Nitrogen is essential for plant growth, but even though the atmosphere is full of nitrogen gas (N2), plants cannot use that form directly. It has to be converted into usable forms like ammonium (NH4+) or nitrate (NO3−) by nitrogen-fixing bacteria or through industrial processes, and then made available in the soil. Because this conversion step is required, nitrogen is not readily available to plants from the atmosphere or from water in its native form; it must first be fixed into a soluble form they can uptake. In contrast, nutrients like phosphorus, potassium, and calcium generally enter the plant through soluble mineral ions that come from soil minerals and can be dissolved in water, making them readily available for uptake. That’s why nitrogen is the nutrient that isn’t readily available from the atmosphere or water.