A recently released UC Davis report on nitrates in drinking water in the Tulare Lake Basin and Salinas Valley has elevated discussion about the impact of agricultural activity and nitrogen fertilizers on the quality of drinking water.

The State Water Resources Control Board commissioned the UC Davis Center for Watershed Sciences to conduct a study on nitrate contamination and issue the resulting report, “Addressing Nitrate in California’s Drinking Water,” as required by state legislation. The report states that 10 percent of the people living in agricultural areas in the Tulare Lake Basin and Salinas Valley are at risk for harmful levels of nitrate contamination in their drinking water.

The study implicates agricultural activity — specifically nitrogen fertilizers and dairies — as the source of 90 percent of the human-generated nitrate contamination in groundwater in those regions. While much of the nitrates present in groundwater have accumulated over the course of decades, it is a problem that will be addressed by, and likely assessed on, growers today.

The report not only lays out the problem based on a collection of existing data, but also offers a number of solutions that may have direct consequences on users of nitrogen fertilizers. It is further mandated that agriculture must do all it can to improve the efficient use of nitrogen fertilizers and minimize off-site movement where fertilizers are applied.

Nitrogen use efficiency

University of California research has demonstrated nitrogen use efficiency, or the percentage of applied nitrogen that is harvested by the crop, in almonds averaging 75 percent to 85 percent under current growing practices. This is among the most efficient measure of any crop in California, and in all agriculture, for that matter.

California almond growers, most of whom are multi-generational family farmers who live and raise their families in rural areas where almonds are grown, share concerns with all Central Valley residents about protecting groundwater quality. These growers, through the Almond Board of California, have invested more than $1.5 million in scientific research focused on improving nitrogen management.

With guidelines generated by this research, almond growers have adopted environmentally responsible farming practices and technologies that have led to significant strides in nitrogen use efficiency in almonds, particularly over the last 20 years.

Twenty years ago almond growers applied nitrogen through broadcast or banded nitrogen materials in large doses, once or twice a season, followed by flood or sprinkler irrigation. Today nitrogen is managed much more efficiently. Thanks in large part to industry-funded research, advances in irrigation and fertilization practices allow for multiple spoon-fed rates of nitrogen that are suited and timed to tree growth and crop demand during the growing season and applied through micro-irrigation systems.