One way to do this is to prevent nitrate leaching from chemical fertilizers by using a set of practices that ensures the soil amendments are fully taken up by the crop.

Clain Jones, soil fertility Extension specialist at Montana State University (MSU), has presented some ways farmers can maximize their bottom lines by optimizing inputs that also help reduce the chance of nitrogen being leached into water supplies:

• Soil test: If farmers know how much available nutrients are present, they can apply the right rate. Knowing more about the soil in the area where chemical fertilizers are being applied is important. Sandy and shallow soils have a low water holding capacity. Precipitation contributes to nitrate leaching, even in drier parts of Montana, according to MSU. Irrigated fields have the highest potential for leaching, especially on coarse soil.

• Right placement and timing: This can reduce nitrogen losses to the air and get more nutrients in the crop. For example, putting urea below the surface of soil decreases losses to the atmosphere. Applying nutrients during the growing season rather than the fall before, decreases leaching. Applying a conservative amount in the spring and only applying more mid-season if there’s adequate precipitation can reduce losses and increase profit. Putting phosphorus in seed rows increase its use efficiency compared to spreading on surface.

• Right source: Some fertilizers are used more efficiently by plants, including ones with coatings or “inhibitors,” which slow certain processes making them more susceptible to loss.

• Right rotation: Planting legumes can decrease nitrogen fertilizer needs. Annual legumes, such as field pea, can substantially reduce nitrate leaching compared to fallow. In addition to using soil water, they are good scavengers of available nitrogen in the upper 2-3 feet of soil and do not need nitrogen fertilizer as long as sufficient phosphorus, potassium, sulfur and the correct inoculants are available for nitrogen fixation.

Farmers can also use an online economic calculator to determine how much nitrogen is needed for the next crop cycle. The calculator is available at: https://www.montana.edu/extension/econtools/nitrogen/index.html.

Effects of leaching

Along with making sure that crop inputs are not wasted, preventing nitrogen leaching ensures that water sources are not being unintentionally contaminated. Water contaminated with nitrates can cause harmful effects in infants and pregnant women. In infants, it can manifest in a condition known as “blue baby syndrome,” where the nitrogen prevents the blood from absorbing enough oxygen.

It is estimated Montana groundwaters contain over one billion dollars’ worth of leached nitrogen, creating ground water issues and also contributing to soil acidification.

“Producers and their advisors cannot easily control some factors that affect soil nitrate leaching, such as soil properties and climate,” said Adam Sigler, MSU water quality Extension associate. “However, farmers can control other factors such as crop rotations, fertilization amount, timing and irrigation. Minimizing nitrate losses help ensure fertilizer dollars are optimally spent on growing the crops while keeping our groundwater safe.”