Eric Holst is Managing Director of EDF’s Center for Conservation Incentives
A guest blog post by Eric Holst, Managing Director of EDF's Center for Conservation Incentives.
Nitrate pollution in groundwater is a critical and under-reported problem associated with food production in California—an issue that journalists Julia Scott, Sasha Khokha, Christopher Beaver and Lisa Pickoff-White have reported on over the past week.
Nitrate is a reactive form of nitrogen that can leach into groundwater as a result of a number of agricultural practices including over-application of nitrogen fertilizer or manure on crops, and pastures. Additionally, discharges from wastewater treatment plants and septic tank leakage can lead to nitrate pollution in surface and groundwater supplies. Excessive levels of nitrate in groundwater threaten California’s drinking water supplies, public health and the environment.
Nitrogen, like water, is an essential input to agriculture. In fact, Nitrogen is among the most abundant elements on earth; virtually inert nitrogen gas (N2) makes up nearly 80% of the air we breathe. However, under natural conditions, reactive forms of nitrogen (nitrates) would be much less abundant. The availability of reactive nitrogen, like nitrate, is one of the key factors controlling crop and other plant growth. Fertilizers are industrially produced to overcome the limited availability of natural reactive nitrogen needed by plants to provide the extensive crop production that sustains the world’s population today. But, if not managed properly, reactive forms of nitrogen can have a variety of negative impacts by elevating risks to public health and the environment.
Nitrate in groundwater is a particularly troublesome problem because it is difficult if not impossible to clean up. The best way to ensure clean groundwater is to prevent or minimize nitrate leaching to begin with. This can be accomplished in two ways: 1) by applying fertilizer and manure more efficiently to crops and 2) by filtering the runoff of irrigation water through natural filters such as vegetative filters and wetlands.
EDF’s Center for Conservation Incentives works in partnership with farmers throughout the US to show that both approaches are feasible, economically viable, and allow farmers to maintain profitability while reducing environmental impact. Farmers in the Chesapeake Bay, in North Carolina, and Western Lake Erie Basin participate in the On-Farm Network®, a voluntary program designed originally by the Iowa Soybean Association. The On-Farm Network® provides farmers with site specific information about the nitrogen needs of crops and creates a forum for sharing this information within groups of farmers in the same area. Farmers enrolled in the On-Farm Network® have experienced an average of 20% reduction in nitrogen use with no impact on yield and in so doing have saved substantially on input costs.
A range of state and federal programs exist to help farmers install vegetative filters on and around farms. Nitrogen laden runoff effectively fertilizes plants in riparian and wetland buffers transferring the nitrogen from the water to the plants and storing it for long periods of time. More importantly, bacteria associated with plant roots remove the nitrate by converting it into N2, a benign end product, through a process known as denitrification. Many farmers in the California’s San Joaquin Valley are installing tailwater retention ponds (tailwater is the excess water that leaves the farm after irrigation) to help them comply with surface water quality rules. When surrounded by native wetland vegetation, these ponds can act as effective nitrate filters and provide wildlife habitat at the same time. Valley farmers are eligible to receive financial support from the US Department of Agriculture to install tailwater ponds.
These are just a few of the incentives for good environmental management that EDF is committed to implementing in California and beyond.