Ag. Order 4.0 aims to improve water quality

Ag. Order 4.0 is an essential new regulation in California that affects 540,000 acres of irrigated land in the Central Coast region. To Dr. Eric Brennan, “This is a game-changing regulation that’s important for workers and consumers to know about.”

California State University, Monterey Bay’s (CSUMB) Agribusiness Club invited Brennan, their first guest speaker of the semester, to speak on his research on Feb. 15. 

Lindsey Nichols, Agribusiness club president, Nawied Amin, vice president and Sumadhur Shakya, staff advisor, hosted the Zoom meeting and introduced Brennan to share his presentation with assembled guests. 

Brennan is a research horticulturist and lead scientist at the USDA Agricultural Research (United States Department of Agriculture) in Salinas, an organization he has been with since 2001. His area of expertise is organic production and climate-smart farming. His current research focuses on organic strawberry and vegetable production, cover crops, weeds, soil fertility management and biological control of insects and pests. 

He is passionate about long-term agricultural research and effectively communicates practical results to farmers and consumers. Before USDA, Brennan worked as a farm advisor in Thailand and researched tree propagation, plant breeding and insect interactions. His educational background includes degrees from the University of Hawaii, Cornell and UC Davis.

Coming from this background, he has recently focused on educating the public on Ag. Order 4.0. This regulation was passed in April of 2021 and affects nitrogen management. “In a nutshell,” explained Brennan, “Ag order 4.0 aims to minimize movement of nitrogen down into our drinking water, keeping farms’ aquifer clean and improving the quality of surface water, rivers and the bay while also improving the efficiency of nitrogen use in our systems.”

Cool-season crops like strawberries have enormous nitrogen demands for big yields. The aquifer we depend on for our drinking water is a shared resource with farms’ irrigation water. Ag. Order 4.0 aims to protect this resource and improve water quality by encouraging cover crops.

A cover crop is a crop that farmers don’t necessarily sell but incorporate back into the soil to improve the soil in some way. These crops include mustard, rye, oats, barley, wheat and legumes. 

Cover cropping is not inherently beneficial due to its risk. “Think of juggling,” said Brennan. “When we grow two crops in a year, we juggle two balls. Cover crops are a third ball that makes things more complicated. It increases risk, which we try to minimize, so we don’t lose profit.”

Cover crops increase risk because they impede opportunity cost. If the cover crop grows too long during the winter, farmers can’t terminate it in time, meaning the first vegetable of the season is set back. That will have some pretty expensive consequences in subsequent vegetable production. But despite making management more difficult, cover cropping is good for the environment and the soil.

“Can we grow organic vegetables sustainably without cover crops?” This question was posed by Brennan in his paper published in 2017. “It’s a complex question, but simply put, no, we can’t. Large-scale farmers cannot grow vegetables sustainably unless there are cover crops to clean up the leftover nutrients. 

“Think about the Ag. Order as a speed limit. It’s a way to slow things down, to slow down the movement of nitrogen into the aquifer,” said Brennan. “Nobody likes regulations, but we can all agree if it was a free for all out on the roads, it wouldn’t be safe.”

Discharge is the difference between the nitrogen applied to soil in fertilizer, irrigation, etc. and the nitrogen removed from the harvested product. Using the example of broccoli, if growing this crop contributes to 450 pounds of nitrogen, harvesting the broccoli takes 100 pounds of nitrogen out of the field in harvested material. The difference would be 350 pounds – 100 pounds meaning 350 pounds is considered discharge nitrogen potentially leachable down into the aquifer the public drinks from.

Because of newfound conservation efforts, the amount of allowable nitrogen discharge will decrease each year. The permissible release per acre, year and field is about 500 pounds. By 2027 it’ll be lowered to 300 pounds, which is when farmers will start finding it a complex regulation to meet without a cover crop.

Under Ag. Order 4.0, cover crops will give farmers credit toward meeting a sustainable amount of nitrogen leaching. A cover crop forgives some nitrogen discharge. “Let’s say it’s 2027; you’re 50 pounds above the limit.” Said Brennan. “If you grew a cover crop that gives you a credit of 100 pounds, you can drop under the regulatory requirement.”

To receive credit as a farmer, there are two options. A standard option gives 30 pounds of nitrogen credit to an acre of cover crop or a calculated option that includes higher standards. These higher standards include four requirements; the cover crop must be a nonlegume, grown for 90 days from October to April, have a certain amount of biomass (shoots above the ground) and have a carbon-to-nitrogen ratio of 20:1 or more. 

According to Brendan’s published research, nonlegume cover crops can stop or reduce the amount of nitrate going down into our drinking water. Ag. Order 4.0, made law, introduces incentives for farmers to start prioritizing cover crops. As a result, cover cropping will increase in Salinas Valley.

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