By Gabriele Ludwig, Associate Director, Environmental Affairs; and Bob Curtis, Associate Director, Agricultural Affairs

Fertilizer costs have more than doubled over the last decade, and regulations on the use of fertilizer will be on the rise soon. Because almonds are California’s third largest crop, and the nuts have a high demand for nitrogen fertilizer, the state’s almond growers are likely to be most affected by both these dynamics.

As a result, it is important that growers manage nitrogen fertilizers to minimize impacts to the environment while maximizing crop potential. This three-part series over the next several months will help almond growers better understand the regulatory issues as well as to craft an efficient, cost-effective nitrogen fertilizer management program that has minimum impact on the environment.

UC Davis Pomologist Patrick Brown, leader of a multi-year, multi-disciplinary fertilizer management research project funded by the Almond Board, USDA, and other ag groups, says there is a direct correlation between adequate nitrogen fertilizer and kernel yield in almonds. Proper management, therefore, directly links to the grower’s bottom line. At the same time, nitrogen has become a primary focus of local, state and federal agencies as they draft new water quality and air quality regulations.

Proper management means applying nitrogen fertilizer under the “Four Rs” — the right rate, right time, right place and the right source, Brown says.

Why N?

Before we discuss managing nitrogen, it is important to understand why it is so important for growers to not only ensure adequate nutrition, but also to avoid applying nitrogen in a way that it will leave the orchard and become a regulated pollutant.

Nitrogen is a complicated element. There are a number of interactions in the soil that make N subject to cycling within the soil and to loss through runoff, leaching and off-gassing into the air. That has placed N squarely in the crosshairs of regulators. The good news, according to Brown, is that regulatory goals and agronomic goals are pretty much in line — that is, to get most of what you apply into the plant where it can be converted into crop yield.

A number of new regulations are on the near horizon that will impact the way growers manage nitrogen. Among the environmental issues related to each form of nitrogen are:

  • Ammonia (NH3 and NH4) is under scrutiny as a contributor to PM2.5 (airborne particulate matter), in surface waters, and for nitrogen deposition in the soil;
  • Nitrous Oxide (N2O) is a potent greenhouse gas;
  • Nitrates (NO2 and NO3) are showing up in ground and surface water; and
  • Organic-N (i.e. the form of N in manure or plant matter) is also being looked at for its effects in surface water.

Furthermore, nitrogen oxides (various NOx) contribute to ozone (smog) formation.  In other words, virtually every form of nitrogen other than basic N2 in the air is being regulated.