A couple of years ago a University of California, Davis study was released claiming that nitrates found in fertilizers were seeping into California’s groundwater and contaminating drinking water supplies.

While the agricultural community refuted many of the assertions in the 2012 report, state water regulators used much of the study’s data to justify new regulations that include requiring growers to come up with nutrient management plans.

These would entail important factors such as documenting the application of nutrient rates necessary to achieve realistic crop yields, improving the timing of nutrient applications, and using agronomic crop production technology to increase nutrient use efficiency.

Along with these suggestions, water authorities requested that growers submit on a periodic basis reports about soil testing and monitoring results associated with nitrogen inputs.

Progress report

I thought it would be interesting to follow up on the progress of the new nitrogen management standards and talk to some growers on California’s Central Coast — the Salinas Valley region being one of two areas mentioned in the UC study as having the most contaminated groundwater from agriculture (the other is in the Tulare Basin.)

What I discovered was pretty much what I expected. For more than a decade, most growers have been well aware of the problems linked to mismanagement of nutrients and have been working diligently to remove the black eye from farming.

Tim Borel is the production manager for Blanco Farms in Salinas which produces 3,000 acres of lettuce, cauliflower, broccoli, celery, green onions, and other vegetables. Over the past decade, Borel calculates that the business has seen a 38 percent savings due to effective nutrient management practices.

“We started out more than a decade ago following some agricultural guidelines laid down by the University of California,” Borel said. “We farm with a nitrogen budget for our crops. Our budgeting process includes soil, water, and input nitrogen."

He continued, "The 38 percent savings came from the input sector, because we have complete control over what we put on the crops. I don’t want you to think we were able to change how much nitrogen was in the soil or in the water. Actually, we reduced our fertilizer input by 38 percent from our grower standards of 15 years ago, and we are now lower than we’ve ever been.”

Formula for success

What is Borel's formula for this success?

“We’ve embraced a couple of new technologies in the additive market. We blend all our nitrogen with humic acid complexes, and this helps us out a lot.”

He added that Blanco Farms also utilizes drip irrigation for a delivery vehicle for the fertilizer, and that has paid a lot of dividends as well.

“It’s important to me that we farm in a way that allows us to be good stewards of the land and to properly manage the resources that we have," Borel explained. "I try to operate at the point of maximum efficiency.”

Rio Farms

For another perspective about nutrient management and farming on the Central Coast, I contacted Bob Martin and Jocelyn Gretz of Rio Farms in King City.

Martin is general manager and Gretz is the director of science and environmental resources and is also a California certified crop adviser. Rio Farms operates 17,000 crop acres in California and Arizona and grows everything from onions, lettuce and cauliflower to celery, broccoli, and baby greens.

“We started out 12 years ago or so and we started using composting. We manufacture a lot of our own compost,” Martin said.

“A lot of our ground was out of balance with magnesium and calcium. So we started using lime and compost and in a few years we raised our calcium levels and lowered magnesium so the clods weren’t so hard anymore. We basically were able to farm the ground better and more efficiently.”

In 1997, Martin began nitrate soil testing with agronomist Tim Hartz of UC Davis.

“Over the years, we’ve implemented more drip irrigation. We’ve pretty much taken fertigation (irrigation containing fertilizers) out of the picture on our ranches, so a lot of our operation is now sprinkler or a sprinkler-drip combination so we have minimized runoff," Martin said.

"On all our acres we have no irrigation tail runoff. We actually keep everything on the farm.”

One improvement in nutrient management is the use of solar-powered soil moisture sensors. Martin says most growers unfortunately cannot afford them, and a rental system is yet to be worked out, but he says he’s convinced every grower needs one.

He tested the moisture sensors on his onion crops on sandy, medium, and heavy soils. The device informs him when soil moisture from drip irrigation reaches six inches. When it reaches 12 inches, it tells him that he is over-irrigating.

“We were able to cut back our hours on each of those soil types,” Martin said. “Basically, it is a tool that we use over a lot of different fields with the same soil types. We cut back our irrigation hours so we don’t run any nutrients below the root zone.”

But what about the small-to-mid-size growers on the Central Coast who perhaps cannot afford modern devices that larger operations use to manage their crop nutrients?

Smaller farms

For a smaller-scale perspective, I contacted Richard Smith, a farm adviser at the Cooperative Extension in Monterey County. In his role as a farm adviser in vegetable crop production and weed science, Smith interacts with growers farming 1,000 acres or less.

“I think the soil quick test is still the main tool, and it’s not that expensive,” Smith said. “This simply involves testing the soil for soil nitrates prior to making a decision on how much to fertilize.”

The other tool is an effective irrigation system.

“You can’t separate nitrate nutrient management from irrigation, which involves managing the water carefully so you don’t leach nitrogen away. A good drip irrigation system allows you to do that,” Smith said.

If smaller growers need additional advice in nutrient management, he says they sometimes hire private soil consultants who can help then find the answers they need.

Weather-based irrigation

Smith said a website used by large and small growers called CropManage — created by his colleague, Michael Cahn — contains a wealth of UC research in a format that makes it easy for growers.

“It introduces growers to weather-based irrigation scheduling,” he said. Smith worked with Cahn in obtaining some of the early trial data for the website.

The website allows farmers to quickly calculate the precise fertilizer and water needs of their crops, thereby saving money while protecting drinking water sources from nitrate contamination.

The technology uses weather information gathered by the California Irrigation Management and Information System, a state program which manages a network of more than 120 automated weather stations in California.

“Water and nitrogen management decisions require specific calculations that can be automated in CropManage, which would be too difficult for a busy farm manager with many fields to track on their own,” Cahn said.

According to Jocelyn Gretz of Rio Farms, the website currently provides information on only a handful of crops, including lettuce and strawberries — the top crops in Monterey County. Other vegetables include romaine lettuce, iceberg lettuce, and broccoli. Research is underway on leafy greens, including spinach and baby leaf lettuce.

“Generally, we know how much fertilizer we need and where. We somewhat do our own version of CropManage,” Gretz said. “We take our own soil samples, and we have a private weather station in King City for our own local data.”

So, even though you may not hear a lot about what growers are doing, know this. Central Coast growers are continually working toward implementing best management measures designed to keep crop production plentiful and profitable in the region, while improving the quality of our water supplies for now and for future generations to come.