New fertilizer management rules begin in Central Coast
By Bob Johnson A moment of truth has arrived for Central Coast vegetable growers, who face the challenge of meeting fertilizer water quality regulations that will steadily grow stricter between now and 2051. March 1 marked the beginning of the first year that growers in impacted areas will have to record and report fertilizer applications under rules approved in 2021 by the Central Coast Regional Water Quality Control Board. The first year, the regulations will al- low 500 pounds of nitrogen per acre to be applied over and above what is removed with the crop. Under the water board’s Ag Order 4.0, the rules will grow steadi- ly stricter until 2051, when the standard tightens to a maximum of 50 pounds of nitrogen per acre after crop removal. “We have sampled 4,000 ranch wells and a third of them came back above 10 parts per million nitrate-nitrogen, which is the safe drinking water stan- dard,” said Sarah Lopez, executive di- rector of Central Coast Water Quality Preservation Inc. The group is an inter- mediary between area growers and the water board. Lopez joined researchers, growers and regulators in discussing the new
rules—and how to meet them—during a meeting in Salinas last month on irri- gation and nutrient management. The event was sponsored by the University of California Cooperative Extension. Regulations are particularly strict on the Central Coast, where regional water officials set discharge requirements for irrigated lands to protect water quality in underground aquifers that people rely on for drinking water. “Our region is unique in that we get about 90% of our drinking water from groundwater,” said Jillian Flavin, envi- ronmental scientist at the regional board. Many regional vegetable growers al- ready meet the standard allowing appli- cation of 500 more pounds of nitrogen than is removed at harvest. But the in- creasing standards over the next three decades could be challenging. When Central Coast water officials ap- proved the rules for reporting fertilizer applications, they noted that the region produces multiple crops per acre per year, with high-value commodities such as lettuce, spinach, broccoli and straw- berries requiring significant nitrogen. “If you apply 2 inches of well water that is 30 parts per million nitrate-nitrogen, that is almost 14 pounds of nitrogen per
A lettuce field is irrigated in the Salinas Valley. Farmers in the region now have to report their fertil- izer applications under new mandates of the Central Coast Regional Water Quality Control Board.
acre,” said Michael Cahn, UCCE irrigation farm advisor. The nitrogen in the irrigation water can climb to 100 pounds an acre or more— and growers will have to include that information in their fertilizer budgets to meet the regulations. Fertilizer budgets will also have to account for nitrogen al- ready in the root zone and available to the crop. Cahn advised growers to “estimate the crop uptake over the next 10 days, sub- tract what will be in the water and what is already in the root zone” to get their fertilizer need.
Nitrogen in the water and topsoil can be calculated using test strips. But effi- cient irrigation management is needed to keep these nutrients in the root zone and available to the crop, while keeping them from leaching deeper. More precise fertilizer and water appli- cations will be enough to meet the regu- lations in the early years, but additional steps will be needed as the rules grow more strict, some regional producers say. “Cole crops in your rotation are a big resource because they have the ability
See FERTILIZER, Page 15
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March 8, 2023 Ag Alert 5
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