Awhile back I attended a workshop at Moss Landing Marine Labs concerning water quality issues in Elkhorn Slough. Elkhorn Slough is a large brackish wetland whose main channel starts at Moss Landing Harbor (about 10 minutes south of us on Highway 1) and winds its way inland and to the North over six miles. Many of the issues facing Elkhorn Slough are similar to those affecting Harkins Slough, which borders our farm here in Watsonville.
As someone who farms within the watershed, I have a keen interest in how the farms on the hillsides surrounding the slough are affecting the water quality. What was shocking to me in the information presented at the workshop is the fact that the Nitrate levels washing directly into the slough from farms pales in comparison to those coming in from the Old Salinas River.
Those of you who have been to the famous Phil’s Fish Market have driven over the Old Salinas River to get there. Before the creation of a man-made river mouth some four miles to the South, the Salinas River used to meander northward behind the sand dunes all the way to its original mouth North of Moss Landing Harbor. During the summer, or in drought years, when the flow isn’t strong enough to break through the sand barrier, the river reverts to its original channel and all of its contents are dumped into the Harbor—nitrates and all. From the harbor, the Old Salinas River flow is entrained on the flood tide into the main channel of Elkhorn Slough.
The problems associated with excess nutrients, like nitrogen, are numerous. Chief among them are algal “blooms”—the vast mats of brilliant green algae that are a common sight around the slough. These blooms can result in the depletion of oxygen available to aquatic animals and the mats themselves can smother vegetation on the banks of the wetlands.
The source of these nitrates in the Old Salinas River is almost exclusively agricultural run-off. Most of the farms in the lower Salinas Valley area are conventional vegetable and strawberry operations which use highly soluble, high analysis fertilizers. It is common practice to leave fields bare–listed up into beds ready to plant into in late winter/early spring. With no cover crops in place to tie up the high levels of nutrients left over after harvest, they freely wash into open waterways when the winter rains come and end up in the Salinas River.
There are practices that farmers can take to prevent the run-off of nutrients into the waterways. Organic farming reduces potential run off problems simply because organic farmers do not use those super high nitrogen synthetic fertilizers. But planting cover crops is one of the best practices that can be implemented for farms during the rainy season. The plants absorb the nutrients and store them to be reincorporated into the soil when the cover crop is disced in and the field is replanted. The roots hold onto the soil so that it is not washed down hills or into drainage channels during rain events.
Organic agriculture is about much more than simply not using pesticides that might be dangerous for people to consume as residue on the crop. It is a whole different approach to farming that addresses the many and serious issues that are caused by large scale conventional farming techniques. For many of these issues, we need more than just consumer pressure for organic food. We need to recognize and talk about the huge impacts that are caused by the practices being used and, as environmentalists have always pleaded, to find ways to “internalize the externalities.”
(A version of this article was originally published in 2015)
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