Quantifying Nitrate Leaching from Agricultural Soils

Abstract

Minimizing nitrogen (N) loss to groundwater is important for human health, the environment, and long-term farm profitability. Quantifying nitrate leaching – a primary pathway of nitrogen loss from agricultural fields – can help you understand the influence of different management practices on water quality, and identify options for reducing nitrate leaching.

Here we outline several common ways to quantify nitrate leaching (Figure 1). We focus on the nitrate form of nitrogen (and not nitrite or ammonium) because nitrate is typically present in higher concentrations. Most of the methods described can be used to measure other forms of N leaching as well. Each method has different benefits and tradeoffs in terms of data accuracy, equipment needed, and time and labor requirements, which are discussed below.

When choosing a method, start with the specific question you want to answer and work backwards to determine the most appropriate and feasible approach. Table 2 at the end of this article highlights some common research questions around nitrate leaching and agricultural practices.

No matter which method you use, it’s important to keep detailed records of the amount of N applied (e.g., in fertilizer, manure, or through irrigation) and the crop yields. These values will help put your results in context.