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Drip irrigation in arid regions can cut greenhouse gas emissions, improve air quality
Study at Desert Research and Extension Center highlights agriculture's sustainability role
Under the blistering sun of Southern California's Imperial Valley, it's not surprising that subsurface drip irrigation is more effective and efficient than furrow (or flood) irrigation, a practice in which up to 50% of water is lost to evaporation.
But a recent study also concludes that drip irrigation can dramatically reduce greenhouse gas emissions from soil – which contribute to climate change and unhealthy air quality in the region – without sacrificing yields of forage crops alfalfa and sudangrass.
“It was really exciting to see,” said lead author Holly Andrews, a National Science Foundation postdoctoral fellow at the University of Arizona. “The crop yield was at least maintained and in some cases increased, but the water use and gaseous emissions were especially decreased under drip irrigation.”
Desert REC crucial to collecting data
Andrews and her colleagues gathered data from field studies at University of California Agriculture and Natural Resources' Desert Research and Extension Center, a crucial hub of desert agriculture research for more than 100 years. Studies in that context are increasingly important, as much of California and the Southwest becomes hotter and drier.
“We already have this history of looking at drip irrigation at this site, so our study was trying to build on that,” said Andrews, who lauded Desert REC's facilities and staff.
In their study published in Agriculture, Ecosystems & Environment, researchers found that – in comparison to furrow irrigation – drip irrigation in alfalfa slashed per-yield soil carbon dioxide emissions by 59%, nitrous oxide by 38% and nitric oxide by 20%.
Nitrous oxide is a greenhouse gas with nearly 300 times more warming potential as carbon dioxide, and nitric oxide is a precursor to ozone and major contributor to air pollution.
While drip irrigation only decreased water demand 1% in alfalfa, the practice led to a substantial 49% decrease in irrigation for sudangrass. For more fertilizer-intensive sudangrass, drip irrigation also reduced soil emissions of nitrous oxide by 59% and nitric oxide by 49% – the result of drip irrigation making those fertilizers more efficient.
Water management can help mitigate climate change
Studying alfalfa and sudangrass – forage crops with very different fertilizer requirements – was a strategic choice by the researchers. They are number one and number three on the list of most widely grown crops by acreage in the Imperial Valley (Bermudagrass, another forage crop, is number two).
With so much land dedicated to producing these crops, the adoption of drip irrigation at scale could deliver significant benefits to residents' health and quality of life.
“The thought that saving water can increase yields while lowering the emission of trace gases that affect regional air quality and Earth's climate is quite encouraging,” said Pete Homyak, an assistant professor of environmental sciences at UC Riverside who contributed to the study. “This is especially true for the Imperial Valley, an arid region where water is a limited resource and where residents are exposed to bad air quality.”
Homyak, who is affiliated with UC ANR through UC Riverside's Agricultural Experiment Station, said that this study illustrates how changes in water management can substantially mitigate agricultural impacts on the environment.
The study findings should encourage growers to replace furrow irrigation systems with drip irrigation infrastructure – especially in combination with financial incentives from the state, such as cap-and-trade and carbon credit programs, that can help defray high installation costs.
“It really is worthwhile if you're thinking sustainability and environmental activism in how agriculture can actually support climate change mitigation,” Andrews explained. “These practices might be a way that we can start to change that picture a little bit – and make agriculture more sustainable by tailoring irrigation management to local climate conditions.”
In addition to Andrews and Homyak, the other study authors are Patty Oikawa, California State University, East Bay; Jun Wang, University of Iowa; and Darrel Jenerette, UC Riverside.
New research fills gap on best practices for California carrot production
One doesn't need to be a seasoned farmer to know that growing conditions in Canada are completely different than those found in the low desert of California.
And yet, for many years, studies conducted in Canada were used to generate nitrogen uptake data for the California carrot production system, so growers managed their fields based on their own experiences – and that research conducted thousands of miles to the north.
Carrots had been among the crops grown in California that did not have site-specific data to suggest the best source, rate, timing and placement of nitrogen, in the highly variable cropping seasons and locations throughout the state. That's why new information – based on local research and published in August – is invaluable to farmers in Imperial and Kern counties, where the majority of the carrots in California are grown.
Two years of data from two experimental trials at UC Agriculture and Natural Resource's Desert Research and Extension Center – as well as from 10 commercial fields – produced key recommendations for farmers to make the most of their irrigation and nitrogen applications.
“The point is we developed information in your field, based on your practices, your climate, your production system – and this is what is really happening,” said Ali Montazar, UC Cooperative Extension irrigation and water management advisor for Imperial County. Montazar conducted the study alongside Daniel Geisseler, UCCE nutrient management specialist at UC Davis, and Michael Cahn, UCCE irrigation and water resources advisor for Monterey County.
With reliable data gathered under real-world conditions, Montazar said growers now have solid reference points for when – and at what rate – to irrigate and apply fertilizers in the low desert environment. One of the key findings, for example, was that the carrots' nitrogen uptake is generally low in the first 40 to 50 days, so growers are advised to limit their fertilizer application during that period.
Then, by tailoring those basic guidelines to their own site-specific situation and optimizing their practices, growers can maximize the amount of nitrogen taken up by the carrots – and minimize the amount that is leached out.
“Improving irrigation and nutrient management in the desert production system is what local growers are themselves trying to achieve. With improving efficiency and reducing nutrient leaching, we can improve the quality of water in the Salton Sea,” said Montazar, noting the longstanding challenges of reducing contaminants from irrigated lands to protect its unique ecosystem and wildlife.
While contamination of groundwater is not a critical issue in the desert, the best practices in this study can also help carrot growers in parts of California where nitrogen leaching into groundwater and drinking water supplies is a greater concern.
Montazar is currently leading a team in studying carrot-growing management practices under slightly different conditions in Kern County, with the hopes of publishing findings in late summer 2022.
The Imperial County study, “Spatial Variability of Nitrogen Uptake and Net Removal and Actual Evapotranspiration in the California Desert Carrot Production System,” is published in the journal Agriculture, and can be found at https://doi.org/10.3390/agriculture11080752. Findings and recommendations also appear in Progressive Crop Consultant: https://progressivecrop.com/2021/09/new-knowledge-based-information-developed-to-enhance-water-and-nitrogen-use-efficiency-in-desert-fresh-market-carrots/.
Funding for this study was provided by the California Department of Food and Agriculture's Fertilizer Research and Education Program, as well as the California Fresh Carrots Advisory Board.
Drone technology on display at UC research center
“The intent of this workshop is to start bringing the knowledge about unmanned aerial systems to the University of California Agricultural and Natural Resources division and the public at large,” said Sean Hogan, coordinator of Informatics Geographic Information Systems for UC ANR. “There is so much curiosity about it right now, it's a growing industry and there is a lot of concern and controversy about the misuses on it.”
The article said the UC system now has the green light to begin using drones. Hogan is holding workshops throughout the state to share his expertise with UC ANR employees and members of the community.
Desert Research and Extension Center director Jairo Diaz said the workshop was important because participants were able to see a demonstration of how the technology works and how it can be applied to the projects and research they are currently working on.
“These workshops that give growers and stakeholders can use in the area are very important because tech like this can help in the near future help find out different types of issues on the field like management of nutrients, water and find out to improve management of field,” Diaz said.
At the UC Kearney Agricultural Research and Extension Center last week, technicians tested a drone that will be used throughout the summer to collect growth data on 600 varieties of sorghum begin produced under different irrigation regimens. With imaging and lidar, the drone collects information on leaf area and biomass in half an hour that would take a full day for a person in the field.
Read more about the sorghum research at Kearney here.
Southern Californians get another reason to love pizza
“Pizza can be a healthy meal, if you build it right,” said Stephanie Collins, outreach assistant at the Desert REC. “We can teach kids to add vegetables and educate them about whole grains and non-fat cheese.”
Collins initially envisioned the pizza garden teaching tool when she joined UC Cooperative Extension four years ago as a nutrition educator. The recent removal of a large tree stump made the location available.
The pizza garden will be part of the center's UC FARM SMART program, in which about 5,000 school children and “snowbird” winter residents annually visit the station to learn about UC's ongoing agricultural research in the desert area, tour the 255-acre facility on a hay wagon and taste products that are grown in the vicinity.
“Alfalfa is cheese in the making,” Collins said.
Tomatoes, onions and arugula are planted in the next wedge. The tomatoes are used for traditional sauce and onions are a healthy and flavorful topping, but arugula?
“Arugula is great on pizza,” Collins said. “It has a strong, peppery flavor.”
In another section, visitors can smell, feel and taste the herbs that season pizza sauce. Oregano, basil, sage, thyme, chives, parsley and rosemary fill the third wedge.
The fourth section holds bell peppers and rhubarb.
The garden is encircled with marigolds for the appearance of crust, and the wedges are dotted with a variety of non-pizza plants, like ornamental kale, vinca and lavender. These plants also serve an educational purpose, said Sam Urie, the UC FARM SMART manager at the Desert REC.
“A diversity of plants attracts beneficial insects, so they help the garden out,” Urie said.
The mostly senior citizen visitors pay $20 per person for the station tour, which includes a homemade lunch featuring locally produced foods. This year, the centerpiece of the meal will be carrot-ginger soup.
The visitors' fees help offset the cost of the tours for local children, who pay just $3 each.
For more information or to schedule a tour, contact Urie at (760) 791-0261, surie@ucanr.edu.
An initiative to enhance competitive and sustainable food systems is part of the UC Division of Agriculture and Natural Resources Strategic Vision 2025.
UC's winter FARM SMART program kicks off at Desert facility
FARM SMART is offered in January and February each year. Attendees learn about irrigation and soils, pick vegetables to take home and enjoy a lunch of local produce.
"We want to pass on the message that agriculture is important," said Sam Urie, FARM SMART manager at the UC Desert Research and Extension Center in Holtville.
The tour was eye-opening for visitors Joe and Nadyne Greschner, farmers from Goodsoil, Saskatchewan.
"What surprised me is that there is no rain here," Joe said.
The 2015 FARM SMART program continues through Feb. 26.
