Smart Irrigation for Agriculture Leads to More Efficient Carbon Capture

Farmers are key to carbon capture, though many plans to reverse greenhouse gas emissions—such as the one described in Lawrence Livermore National Laboratory's 2020 report on California's efforts, Getting to Neutral—largely ignore them.

Let's take California as an example. Nearly 70,000 farmers across the state steward more than 24 million acres of land—37,500 square miles of cropland, pasture and range that can be a prime carbon sequestration medium.

As I wrote recently in the Bakersfield Californian, farmers can capture a vast amount of atmospheric carbon in their crops and soils...if they have the water to do it. In fact, according to the scientists at Lawrence Livermore National Laboratory, improvements in land management can capture carbon in plants and soils at a cost of $11 per ton—about one-sixth the cost of engineered solutions.

Farmers sequester atmospheric carbon by two primary methods: by producing plant biomass and by managing soil where microbial communities capture carbon from plants and the atmosphere and turn it into soil organic matter. They can also reduce the emissions of greenhouse gases—including nitrous oxides—by managing their microbial communities and tillage.

Best of all, the byproducts of sequestering carbon on farm and ranch land are food, feed, fiber, and fuel. And California is the envy of the world in the productivity and quality of its agriculture.

There are two keys to unlocking California's massive carbon-capturing resource: agricultural technology and connecting with farmers. Ag tech represents a broad range of approaches, from buried sensors in the soil to satellite monitoring technology and a wide array of tools in between. However, smart irrigation is where the rubber meets the road.

A fundamental ingredient in helping farmers sequester carbon in plants and soils is water. Plants require water to grow, and most soil microbes need water for their life cycles and biogeochemical reactions, too. As a result, carbon capture and greenhouse gas mitigation plans must consider water as integral to their success.

Of course, a major focus of smart irrigation is water efficiency, which is highlighted in many outstanding research projects throughout academia, industry, and government. Monitoring water stress, zeroing in on actual crop needs, precision placement—it all improves with precision agriculture and improves the yield of crop per drop.

When we look at the massive corporate interest in reducing the carbon footprint of their operations, we see an added importance of helping farmers sequester carbon. In the consumer space, particularly in the food and beverage sector, agriculture's carbon footprint is a major contributor to the carbon footprint of the products we consume. For instance, beer is comprised of barley, rice or corn, and hops...and, of course, mostly water. Soda is water plus sweeteners. Milk, beef, pork, breakfast cereal—the trails all lead back to water and agricultural land.

In July, the U.S. will celebrate Smart Irrigation Month, and technology is what makes it smart. We, as a society, will be smart to put that technology—and some of our water—to work for the dual benefit of producing food and sequestering carbon.

Another of the most environmentally sustainable elements in smart irrigation is precision fertilizer application, which is facilitated by an array of technologies from remote sensing of crop health to carefully metering nutrient doses to meet plant needs.

Precision nutrient management optimizes crop growth, which obviously contributes to capturing carbon from soil and the atmosphere in plant tissues both above and below the ground. But it also has other environmental benefits. For instance, spoon-feeding nutrients to crops minimizes overapplication of fertilizer and reduces the chances that excess nutrients will be available to leach into groundwater or run off into surface water.

Minimizing leaching can reduce nitrate contamination of groundwater, which causes blue baby syndrome. On the surface, reducing runoff can cut down on nutrient enrichment that contributes to algal blooms, like the cyanobacteria proliferation that cut off water supplies from Lake Erie to the city of Toledo in 2014.

Less nutrients in water supplies also reduces the need to treat drinking water, reducing the carbon and chemical footprints of water treatment plants. It also reduces overall waste of nutrients, which is especially critical in times like these, when fertilizer supplies are tight globally.

Even where supplies of fertilizer are available and affordable, they represent a large carbon footprint. Urea and ammonia, the most common forms of nitrogen fertilizer in many developed economies, are created from natural gas. Phosphate and potash, the sources of the two other major crop nutrients, are heavy and bulky and require a tremendous amount of energy to source, process, transport and apply. Reducing wasted application can significantly drive down demand and all the associated emissions that go along with it.

One of the most exciting frontiers in smart irrigation is our growing understanding of oxygenation—delivering a slurry of water and air to the crop root zone. Scientists have long understood that healthy soils require a balance of oxygen and moisture.

In short, air in the root zone is a biostimulant. It's a necessary ingredient in the molecules that operate inside roots and plant cells. It's fuel for the trillions of microbes that play vital roles in nutrient transfer, organic matter formation, and soil health. And today, we have a greater appreciation than ever for the role that those microbes play in plant health and growth.

There are several ways to aerate irrigation water, from using a compressor to push air into the water to costly nanobubble systems, incorporating oxygenating chemicals like hydrogen peroxide, or using venturi injectors to create a vacuum in the drip system that draws in air or oxygen and mixes it thoroughly with the irrigation water stream just by using the energy of the water's flow. Because venturis aerate the soil much as previous generations used to do by tilling the land, we refer to the venturi-driven approach to oxygenation as "plowing without a plow." This process opens the door to root zone aeration so farmers can practice no-till and other regenerative farming practices.

Since the mid-'90s, agronomists and agricultural engineers around the world have documented significant improvements in the yield and quality of a wide range of crops when subsurface drip irrigation water has been augmented with oxygen. Studies in Fresno, California also documented thicker roots where oxygenation took place. Thicker roots, more biomass—it equals more carbon beneath the ground.

Scientists at California State University, Fresno; Memorial University in Newfoundland and Labrador, Canada; and University of the West Indies in Trinidad and Tobago working with Mazzei's AirJection system also discovered that the process resulted in a shift of soil microbial populations towards bacteria known to fix nitrogen in the soil. That can make more nitrogen immediately available to plants and reduce the production of nitrous oxide and NOx compounds.

Oxygenation and precision nutrient management are key technologies in controlled environment agriculture, agriculture's new frontier. Where economics and the environment support it, indoor agriculture is poised to grow exponentially. Controlled environment agriculture is resource intensive, so efficiency is paramount, whether we're talking about energy, water, nutrients, or crop protection. All those inputs are closely managed in modern indoor agriculture, tapping into ag tech via sensors, SCADA systems, and finely tuned injection systems. Once again, oxygenation and automated fertigation dominate the conversation and can tip the balance of productivity and profitability into the black.

American agriculture, led by California, is uniquely positioned to contribute dramatically to sequestering carbon and reducing the emissions of greenhouse gas. California's farmers can tap into outstanding universities, professional advisors from the California Agricultural Irrigation Association and The Irrigation Association, and some of the best farmers on the planet.

Along with fostering smart irrigation and engaging farmers in the effort, there's one key step: just add water.