Ground water challenges for almonds

Ground water is destined to be the subject of increased regulation in coming years as agencies in California look to address the quality of water in underground aquifers. A number of contaminants from agricultural sources, including salts, herbicides and nitrates, are showing up with significant frequency in some Central Valley aquifers. Thus, regulatory agencies are turning their attention to addressing ground water quality issues.

The Department of Pesticide Regulation has had a ground water protection program in place since 1986 in which seven pesticides that had been detected in ground water were banned from use in “pesticide management zones.” In 2004, DPR revamped the program, expanding the acreage included in ground water protection areas (GWPAs) based on geological characteristics. In those areas the seven pesticides could now be used with a permit if mitigation measures were feasible.

• Potential contaminants identified

DPR earlier this year added 40 new entrants to its list of compounds that may have the potential to contaminate ground water based on their physical-chemical properties. The additions include a number of herbicides and fungicides used in almonds: azoxystrobin (Abound); 2,4-D; halosulfuron-methyl (Sempra); mefenoxam (Ridomil); thiazopyr (Visor); and thiophanate-methyl (Topsin). Compounds that land on this list are included in ground water monitoring and additional data may be required from the registrants to determine if their use needs to be regulated in GWPAs.

More immediately, the Central Valley Regional Water Quality Control Board is developing a ground water program as part of a long-term water quality regulatory program for Irrigated Lands. The long-term program replaces the interim Irrigated Lands Program for monitoring and regulating surface water quality from agricultural runoff, which is set to expire in 2011.

In addition, the Board is developing a comprehensive strategy to protect the quality of ground water from all sources of potential contamination in the Central Valley, including industrial, agricultural and septic waste sources.

• Difficult to regulate

Regulating ground water is fraught with difficulty. Unlike surface water, in which specific watersheds drain directly into canals, rivers and reservoirs, there are still significant questions about the fate of ground water, how it moves and how underground geographical structures connect. In addition, soil structure, the depth of the water table and a number of other factors influence to what degree potential contaminants might reach ground water tables. Without an obvious geographical chain to follow, it is difficult to predict how a regulatory structure can track and follow the source(s) of ground water contamination.

The Regional Board has not yet determined how it will regulate ground water and is still collecting input on how a regulatory program should be structured for ground water for irrigated agriculture. Proposals have included emulating DPR’s pesticide ground water protection program, requiring permits for any fertilizer application, to requiring growers to monitor ground water, etc. The program developed for dairies is extremely costly to the farmers.

Despite these challenges, there is no doubt that ground water quality is something which must be addressed. Societies have risen and fallen on the quality of their ground water supply. Growers are increasingly relying on ground water to irrigate their crops amid severe cutbacks in surface water delivery. Increased pumping threatens to aggravate salinity problems in Central Valley ground water at the same time the quality of the aquifer grows increasingly important to sustainable farming in California.

• Mitigation practices

The Almond Board of California is working through partnerships such as the Coalition for Urban and Rural Environmental Stewardship (CURES) to communicate practices that can reduce the potential of nitrates, salts, and other contaminants reaching ground water.

ABC also continues to fund research to give growers crop production strategies that can help them to apply fertilizer more efficiently and thus reduce the chances for movement into below-ground aquifers.

Current studies seek to help the industry better understand how nitrogen moves in the trees, air and soil.

UC Davis pomologist Patrick Brown is leading a team of researchers in conducting a multiple-year, industry-, CDFA- and USDA-funded research project examining fertility in almonds to help growers fine-tune their fertility practices.

Applying nitrogen and other fertilizers at appropriate rates and timing will not only optimize uptake and production, but will prevent the application of excess nitrogen that might find its way into the water table.

The team is driving the industry toward a more site-specific fertilization strategy based on monitoring yields and tree nitrogen status, in conjunction with soil types and irrigations systems.

Brown encourages growers to break down orchards into smaller blocks and fertilize or fertigate specifically to the needs of that sub-block.

Annual nitrogen (N) demand in trees is driven in large part by yield. However, the uptake of N by trees varies throughout the growing season. Thus, the team is also seeking better ways to monitor tree and soil nitrogen status to allow better timing of applications with the demand for nitrogen or other nutrients by the tree.

Almond growers have been shifting to multiple smaller applications of fertilizer during the spring and early summer with the increased use of fertigation.

Growers should also test their irrigation water source for N status so they can account for existing nitrogen in the water supply before crafting a fertility budget.

It is hoped that this complex research project will provide practical approaches for growers to better manage their inputs that will both decrease input costs and reduce the chances of inputs ultimately finding their way into the ground water.

At the same time, almond growers need to be proactively involved as regulators craft ground water quality regulations that may significantly impact their farming operations.

For example the Central Valley Water Board will be holding public meetings around the Valley in October on their proposed ground water protection strategy.

While the strategy is not a regulation, it is likely to be the roadmap for additional regulations.

Watch for public meetings at the Central Valley Regional Board’s Web site ( as well as the Almond Board’s Web site ( for more information about how to be involved.

TAGS: Tree Nuts
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