What Is Nitrate?

What is nitrate and how does it end up in our water?

Nitrogen is necessary for plant growth and is present in native ecosystems and farming ecosystems.  Animal manure, human wastes, compost, sewage sludge, legume crops, and green manure crops are organic sources of nitrogen. Some nitrogen fertilizer contains nitrogen already in nitrate form. In other fertilizer, nitrogen is in the ammonium form, which is rapidly converted to nitrate by soil bacteria at soil temperatures above 50°F.

Nitrate commonly enters groundwater when nitrogen fertilizer, manure, or some other nitrogen source is added to the soil and is leached through the root zone of the soil.  The leaching potential and the length of time required for nitrate to leach to the groundwater can drastically vary depending on land use, soil type and the amount of received precipitation.  Coarse textured and low organic matter soils under high rainfall or irrigation have the highest leaching potential.

  • Nitrate pollution can occur in numerous forms including from wastewater treatment plants and septic systems (point-source), but losses from fertilizer and manure are the main culprits in agriculture-heavy regions (non-point source).

  • Since nitrate is a primary component of fertilizer and manure, losses can occur in the form of field run-off and leaching into groundwater aquifers.

  • Nitrate dissolves readily in water and when carried through the soil below plant roots it can easily contaminate groundwater.

  • Once in the soil, nitrogen will travel to groundwater as nitrate unless it is used by plants, released into the atmosphere, or washed out in overland runoff. It may also be stored temporarily in the soil root zone or in growing plants.

  • Nitrogen is a leaky element, the most leachable nutrient applied in the farming industry.