In a soil test report, what does the 'N' value represent?

• A. Nitrogen gas
• B. Available nitrogen
• C. Nitrates only
• D. None

Answer: (B)

The main thing this value measures is the nitrogen that plants can actually use in the near term. In soil, nitrogen exists as different forms, but the part that matters for growth is the plant-available nitrogen—the forms that roots can take up now or soon, mainly ammonium (NH4+) and nitrate (NO3-). Nitrogen gas in the soil isn’t usable by plants under normal conditions, and nitrogen in other organic forms will need mineralization over time before it becomes available. So the N value on a soil test report represents available nitrogen, not nitrogen gas and not nitrates alone. This is why it’s the best descriptor for guiding fertilizer decisions.