Clients & SureHarvest in the News
August 11, 2012

Nitrates and Water in California

Dr. Cliff Ohmart
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A report released in March about nitrate contamination of groundwater has triggered a process by California's regional water quality control boards that will potentially affect farmers across the state. Although winegrape growers apply less nitrogen than farmers of other crops, it appears they will not escape scrutiny.

In 2008 a bill was signed into law requiring the California State Water Resources Control Board to prepare a report for the state legislature assessing nitrate contamination of groundwater. The goals of the report were to better understand the sources of the contamination, to propose ways of treating the groundwater to ensure safe water for drinking, suggest ways of reducing or preventing further contamination as well as ways to recover the state's costs for cleaning up or treating groundwater designated for drinking.

The water board contracted with the University of California, Davis, to undertake the study. Many growers awaited the report's release with trepidation because of an active rumor mill connected with the report. As one of my colleagues from UC Davis said, the report was one of the university's worst-kept secrets from the past several years. Winegrape growers seemed much less worried as the report's release date neared; many felt the they would avoid the spotlight because they apply far less nitrogen per acre than growers of many other crops.

Now that the report is out, however, it seems likely that regional water quality control boards will increase the regulatory requirements for any California growers applying nutrients to their fields.

Some are in denial
The report is sobering. (Download it at to read for yourself.) The role agriculture has played in today's groundwater quality in these regions is clear. Editorials in a few agricultural trade journals have questioned the report's conclusions, casting doubt on the soundness of the science behind the report. Some have hinted that the source of the nitrates has not been proven. Those who believe this, however, are in denial.

That is not to say the situation is cut and dry. Nitrate leaching and groundwater contamination has been occurring for several decades. The time it takes for nitrates to leach from a source to wells and/or groundwater ranges from years to many decades. Therefore current nitrate levels in the groundwater of many regions are due to nitrogen applications that occurred long ago. Likewise, actions taken today to reduce nitrate leaching may not affect drinking water sources for several years or even many decades.

Another complicating factor is the local nature of groundwater quality. The permeability of soils and hydrology varies greatly from site to site, so problems are very much local in nature. Finally, there is no data to show that high nitrate levels in drinking water have a significant effect on normal, healthy adults. The deleterious effects express themselves through the blue-baby syndrome that affects newborn infants exposed to high-nitrate drinking water consumed by their mothers and themselves.

Four areas of action
Despite the fact that altering current farming practices related to nitrogen inputs will not show effects on groundwater quality for a long time, the government will take immediate action to address groundwater quality related to nitrates. The UC Davis report concludes that regulatory actions up to this point have been insufficient to control nitrate contamination of groundwater.

It suggests action in four areas: 1) Assuring safe drinking water in affected areas; 2) Reducing sources of nitrate contamination; 3) Monitoring and assessment of groundwater and drinking water; and 4) Revenues to help fund solutions. Action in any of these four areas could affect California winegrape growers in the ways outlined below.

Treatment of drinking water containing high nitrates in situations not protected by existing water treatment would be very expensive. Monitoring domestic drinking water supplies for nitrate contamination is also expensive. And finally, the cost of state or local monitoring of a grower's nitrogen-management practices would be significant. Several revenue-generating schemes to pay for these actions were suggested in the report. One is to add a mill assessment rate to nitrogen fertilizer sales, similar to the mill assessment on pesticide sales in California. Another is to add a substantial excise fee to nitrogen fertilizer sales. A third is to implement a comprehensive statewide water-use fee, part of which would fund some of t he actions mentioned above. Any of these actions would increase the cost of farming for California winegrape growers.

Farming costs for state winegrape growers also will be affected by new regulations passed by California's regional water quality control boards (RWQCB) to address groundwater quality issues. Up until now, these regulations have focused on surface water quality through the Irrigated Lands Regulatory Program, better known to growers as the Ag Waiver Program. It is clear that new regulations will be developed that also focus on groundwater quality. The requirements will most likely differ from one regional board to another, as they do now with surface water regulations.

No RWQCB has yet passed and implemented regulations pertaining to groundwater quality. However, discussions are in progress and rumors are spreading as to what they might look like. It is likely they will involve growers developing written management plans before the growing season starts for any inputs containing nitrogen. They may involve monitoring of water percolating below the plant root zone for nitrate concentrations. They may involve a post-season assessment of how actions in the field matched the preseason nutrient-management plan. And finally, they may require tracking of management practices that mitigate nitrates percolating below the plant root zone.

One of the many topics of discussion is to what degree there will be policing of these activities. For example, in the Central Valley Region there is discussion about grower nutrient management plans having to be developed with assistance from a certified crop advisor. The UC Davis report suggests nitrogen management in California might take a lesson from the model of pesticide regulation, for which data collection, analysis, education and enforcement occur under the direction of the Department of Pesticide Regulation.

Central Coast requirements
The Central Coast RWQCB has the most well developed draft requirements for growers and the most advanced in terms of timeline for implementation. In mid-March the board voted to accept the recommendations put forth by board staff members. Farms and ranches will be assigned to one of three different tiers, according to their location and certain current practices. Tier 1 farms have the fewest requirements and Tier 3 have the most.

Interestingly, if winegrape growers in this region have their vineyards certified by the Sustainability in Practices (SIP) program developed and implemented by the Central Coast Vineyard Team, they automatically qualify for Tier 1. The result is that some growers of other crops in the region are considering developing certification programs so their farms can be classified as Tier 1. However, the fact that a farm is certified according to a sustainable farming program like SIP does not guarantee regulatory recognition. SIP has gained recognition through many years of working with the Central Coast RWQCB on water-quality issues so that the board has confidence that a SIP grower is meeting their regulatory requirements. If farmers of another crop developed a sustainable certification program, the RWQCB would have to vet the standards to ensure it met their requirements before any regulatory recognition was bestowed.

Except for the Central Coast region it is not possible to determine for certain how a California winegrape grower will be affected by new regulations that follow from the UC Davis report about nitrates in the groundwater. However, because winegrapes require far less nitrogen per year (10-20+ pounds per acre, with some vineyards in some years requiring no additions) compared to that required by many other crops (e.g. almond farmers use more than 200 pounds per acre per year), vineyards are not going to be singled out as fields requiring closer scrutiny.

However, if a RWQCB requires farm fields to have written nutrient management plans and demonstration of practices that minimize leaching of nitrates, then vineyards will need to comply, too. Good viticulture involves written nutrient management plans based on the budget approach. If this approach is a part of your vineyard management program, you will have no trouble meeting any requirements the RWQCB decides to implement.

Dr. Cliff Ohmart
serves as vice president of professional services for SureHarvest. He is the author of "View from the Vineyard: A practical guide to sustainable winegrape growing,” published by the Wine Appreciation Guild. Previously he served as research/IPM director at the Lodi-Woodbridge Winegrape Commission. He has been writing about sustainable winegrowing issues for Wines & Vines since 1998.