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Improved understanding leads to better management of nitrogen fertilizer on the central coast

The Issue

Vegetable, strawberry, and cane berry growers in the coastal valleys of California are under regulatory pressure to limit off-site movement of nitrate into ground and surface water. Water quality regulations for irrigated lands require that growers monitor water use and nutrient discharges, and report nitrogen fertilization rates as a ratio of crop nitrogen uptake. However, growers and regulatory agencies lacked information on how much nitrogen many coastal crops require.

What Has ANR Done?

A team of 10 UC ANR researchers evaluated the nitrogen content of the most common vegetable and berry crops grown in the coastal region of California during a 3-year study. Plants in more than 150 commercial fields were sampled and analyzed for nitrogen content throughout the season from locations as far south as Ventura County and as far north as Santa Clara County. These data helped the team determine the amount of nitrogen that these crops need to achieve commercial yields. The team extended the information to clientele and stakeholders through 30 presentations. The data were also incorporated into technical guidelines and CropManage, an online tool for growers that provides crop-specific recommendations for nitrogen and water needs. https://v3.cropmanage.ucanr.edu/

The Payoff

Research is being applied to better manage fertilizer use

The information collected by the UC ANR team was used to develop guidelines that growers are now using to better manage fertilizer and potentially reduce water quality impacts of farming. One example demonstrating grower benefits of this research is that the CropManage fertilizer and irrigation recommendations during the production season increased from less than 500 to more than 1000 per month between the beginning and end of the project. The data are also helping water quality regulatory agencies to develop meaningful policy and regulations that protect the environment without unfairly harming agricultural producers. The Central Coast Regional Water Quality Control Board used the crop nitrogen uptake values to guide regulations on nutrient management. The project has also led to additional funding from other agencies that will enable UC ANR to expand CropManage to include commodities produced in the central valley such as warm season vegetables (processing tomato and pepper), trees (almond and walnut), and forage crops (alfalfa). As effort is made to increase the number of commodities in CropManage, the team of UC ANR researchers and industry involved in developing information on nitrogen management has also grown and strengthened collaboration.


Supporting Unit: Monterey County

Michael Cahn, Farm Advisor, Irrigation and Water Resources