Plants need nitrogen to grow, but excess nitrogen – from livestock facilities, septic systems, car exhaust and other sources – that escapes into groundwater and the air can impact the environment, human health and the climate.
A new report from the Agricultural Sustainability Institute at UC Davis offers a big picture look at the scale and impacts of nitrogen in California. According to the California Nitrogen Assessment, excess nitrogen in the state comes primarily from agriculture and fossil fuel combustion.
The report, published by UC Press, offers a scientific foundation to develop practices and policies that allow nitrogen's benefits while reducing the risk.
For years, UC Agriculture and Natural Resources scientists have been working with farmers throughout the state to refine fertilizer management, irrigation efficiency and other farming practices to manage nitrogen, and the work continues.
The following are some examples of UC ANR research and extension projects underway.
App helps farmers better manage nitrogen fertilizer and water
Growers can use CropManage, developed by Michael Cahn, UC Cooperative Extension advisor in Monterey County, and UC ANR Communication Services and IT staff, to track and manage water and nitrogen fertilizer applications for their crop fields. The online application can be used on mobile devices or computers to help farmers use two tools to conserve water and make better use of nitrogen fertilizer while maintaining crop productivity and quality. Growers use the soil nitrate quick test in the field to measure the nitrogen level of their soil and the app to determine the optimal level of nitrogen fertilizer to apply based on UC ANR research on crop nitrogen use. CropManage also recommends water needs of a crop from weather station data and crop development models.
Matching nitrogen applied to crop need improves efficiency
Richard Smith, UC Cooperative Extension advisor in Monterey County, is leading several research projects evaluating the nitrogen requirements of vegetables including including cole crops, spinach, baby lettuce, a salad mix and cilantro. Smith is evaluating crop rotations with broccoli to scavenge nitrogen from the soil profile. He is also evaluating slow-release fertilizers to minimize nitrate leaching losses in shallow-rooted crops such as baby lettuce and spinach in the Salinas Valley.
Wood chips remove nitrogen in tile drain water
Using wood chips and supplemental carbon sources, Tim Hartz, UC Cooperative Extension specialist in the UC Davis Department of Plant Sciences, worked with Cahn and Smith to refine a process to remove nitrate from tile drain water, which typically is very high in nitrate. The carbon in the wood chips supports the activity of anaerobic bacteria that chemically reduce the nitrate to N2, a benign gas.
Irrigation water fertilizes vegetables
Water quality regulations in many regions of California now require farmers to report the amount of nitrogen fertilizer that they apply to their fields and the nitrate concentration of their irrigation water. Smith, Hartz and Cahn have just finished three seasons of field trials that demonstrated that the nitrate in groundwater supplied a substantial portion of the fertilizer requirements for lettuce and broccoli. By accounting for the nitrate in irrigation water and using the soil nitrate quick test to monitor soil nitrogen levels, growers may be able to significantly reduce the amount of fertilizer nitrogen they apply to vegetable crops.
Micro-irrigation offers almond growers a tool to control leaching
The majority of almond growers apply fertilizer through micro-irrigation systems and an increasing number of growers are irrigating with water that is saline. Patrick Brown, professor in the UC Davis Department of Plant Sciences, is studying how to use micro-irrigation to reduce nitrate leaching and manage soil salinity by varying the frequency of irrigation and the length of time water is applied during irrigation.
Managing irrigation to reduce nitrate leaching
To identify the best irrigation management practices to control soil salinity and to minimize nitrate leaching to groundwater, Laosheng Wu, professor and UC Cooperative Extension specialist in the UC Riverside Department of Environmental Sciences, is using computer simulation to consider soil, water, crop nitrogen demand and fertilization with irrigation methods. In collaboration with UC Cooperative Extension advisors, Wu is conducting field experiments on alfalfa in Imperial County, almonds in the Central Valley and avocados at South Coast Research & Extension Center in Orange County to validate the simulations.
Online tool being developed to estimate soil nitrogen mineralization rates
To develop a tool for growers and crop advisers to estimate soil nitrogen, Daniel Geisseler, UC Cooperative Extension specialist in the Department of Land, Air, and Water Resources at UC Davis, is gathering data throughout California to estimate field-specific nitrogen mineralization rates. This project, funded by UC ANR's California Institute for Water Resources, will use nitrogen mineralization data to develop an online tool to help growers adjust their applications of fertilizer. The tool has the potential to increase nitrogen use efficiency in crop production, resulting in lower risks of nitrate leaching to groundwater.
Nitrogen management training for Certified Crop Advisers
Between 2014 and 2016, approximately 900 Certified Crop Advisers participated in a nitrogen management training program coordinated by UC ANR's California Institute for Water Resources with support from CDFA's Fertilizer Research and Education Program. The technical and applied training improves CCAs' understanding of sound nitrogen management practices to make informed recommendations to growers.
The California Nitrogen Assessment book
The book, “The California Nitrogen Assessment: Challenges and Solutions for People, Agriculture, and the Environment,” is available for purchase at ucpress.edu. The 20-page executive summary can be downloaded for free at asi.ucdavis.edu.
This story is also available in Spanish: "La evaluación del nitrógeno en California ofrece oportunidades para mejorar http://ucanr.edu/sites/Spanish/Noticias/boletines/?uid=6884&ds=199
“Given California's drought and the need to use all available water supplies, even those of marginal quality, there will be great interest in Ken Schmidt's and UC Cooperative Extension advisor Blake Sanden's talks about Valley water supplies and quality,” said Louise Ferguson, a UCCE specialist in the Department of Plant Sciences at UC Davis and organizer of the event.
Sanden, who is based in Kern County, will give a presentation on his research on the effects of using saline water for pistachio irrigation on crop yield and soil quality.
“In 2014, there were problems of fruit set and pollination,” Ferguson said. She expects there will be strong interest in the talk about the effects of climate and other factors on pollination requirements and fruit set by Gurreet Brar, UCCE advisor in Fresno County.
An emerging problem that growers have been seeing in California and Arizona in the past three years is what scientists are calling Pistachio Bushy Top Syndrome in clonal UCB1 rootstocks. Affected trees are short and stunted, have closely spaced internodes, exhibit bushy growth and twisted roots. The cause is unknown, but scientists have found it to be associated with the bacterium Rhodococcus.
Jennifer Randall, a professor in the Department of Entomology, Plant Pathology and Weed Science at New Mexico State University, will deliver the first public presentation of research results on the "bushy top" syndrome.
A full day of research presentations are scheduled.
Themis Michailides, a researcher in the Department of Plant Pathology at UC Davis, will give an update on pistachio diseases.
David Haviland, UCCE advisor in Kern County, Kris Tollerup, UC IPM advisor, and Bob Beede, emeritus UC Cooperative Extension advisor will discuss management of navel orangeworm, Phytocoris, leaf-footed bug and stink bugs.
Brad Higbee, director of entomology research for Paramount Farming Company, will discuss how winter sanitation of orchards can decrease pest pressure and, in turn, reduce the need for pesticides.
Joel Siegel, USDA-ARS research entomologist, will explain how to how to anticipate pest pressure based on past infestation levels.
Patrick Brown, professor in the Department of Plant Sciences at UC Davis, will discuss nutrient management in pistachios.
The 2015 Statewide Pistachio Day will be held from 8 a.m. to 4:30 p.m. at the
Visalia Convention Center. For more information, visit http://ucanr.edu/sites/pistachioday.
For more than 100 years, the University of California Cooperative Extension researchers and educators have been drawing on local expertise to conduct agricultural, environmental, economic, youth development and nutrition research that helps California thrive. UC Cooperative Extension is part of the University of California's systemwide Division of Agriculture and Natural Resources. Learn more at ucanr.edu.
The 2014 Experiment Station Section Excellence in Multistate Research Award presented by the Experiment Station Committee on Organization and Policy on Nov. 2 recognizes the universities' exceptional collaboration on a multistate research project.
Patrick Brown, professor in the Department of Plant Sciences at UC Davis, Jan Hopmans, professor in the Department of Land, Air and Water Resources at UC Davis, Larry Schwankl, UC Cooperative Extension specialist emeritus, and Ken Shackel, professor in the Department of Plant Sciences at UC Davis, are the UC researchers participating in the project “Microirrigation for Sustainable Water Use.”
"The Multistate Research Program is one of the best kept secrets of the land-grant university system, and this award recognizes outstanding interdependent efforts of researchers and extension specialists that have come together to tackle a priority issue that no one institution can address on their own,” said H. Michael Harrington, executive director of the Western Association of Agricultural Experiment Station Directors. “This microirrigation project was selected out of more than 300 multistate projects because, since 1972, the group has made major advances in sustainable agriculture and water conservation.”
Using more precise irrigation management, California growers have increased water use efficiency on processing tomatoes by 54 percent and on almonds by 33 percent since 1990.
Conventional irrigation systems that apply high volumes of water over wide areas can lose a lot of water through runoff, wind, or evaporation. As a result, conventional irrigation systems often over water or under water plants. Instead, microirrigation, or drip, systems use special timers, sensors, and a network of narrow tubes to deliver the right amount of water at the right time.
In the last five years, the group's research has led to new microirrigation equipment and tools that are easier to install, more durable, and more precise. These advances, along with engagement with farmers, have encouraged adoption of microirrigation systems, which has led to significant economic and environmental impacts.
“As director of USDA-NIFA, my goal is to ensure the science we invest in leads to solutions to today's most pressing challenges,” said Sonny Ramaswamy. “One of those challenges is finding ways to feed the growing population while minimally impacting the environment. A safe, reliable supply of water is inextricably linked to food security. The five-fold increase in irrigated acres that took place during the 20th century cannot be repeated in the 21st century — there isn't the space. Instead, we must increase efficiency of the irrigated farmland we have, and that is what this project is doing.”
In addition to UC, other participating land-grant institutions include Auburn University, University of Arizona, Colorado State University, University of Florida, University of Hawaii, University of Idaho, Iowa State University, Kansas State University, Mississippi State University, University of Nebraska, New Mexico State University, Cornell University, Oregon State University, University of Puerto Rico, Texas A&M AgriLife Research, University of the Virgin Islands, Washington State University, and University of Wyoming. The universities collaborated with the USDA's Natural Resources Conservation Service and Agricultural Research Service.
The award was presented by ESCOP chair Bob Shulstad and Ramaswamy at the Association of Public and Land-Grant Universities annual meeting in Orlando, Fla.
The project's name will be added to a plaque at the USDA Waterfront Centre in Washington, D.C., and the group will receive $15,000 to support their ongoing work. The group's continued efforts are more critical than ever as the U.S. continues to experience extreme droughts that threaten water supplies and crops that depend on irrigation.
These efforts are supported, in part, through USDA-NIFA by the Multistate Research Fund, established in 1998 by the Agricultural Research, Extension, and Education Reform Act (an amendment to the Hatch Act of 1888) to encourage and enhance multistate, multidisciplinary agricultural research on critical issues. Additional funds were provided by contracts and grants to participating scientists. For more information about the microirrigation project, visit http://www.cropinfo.net/MI.
- Author: Jeannette E. Warnert
California almonds are on a roll. In the last 20 years, scientific discovery and grower ingenuity have nearly doubled almond per-acre productivity. A good yield in the 1980s was 1,400 pounds per acre. The average yield for 2011 was 2,670 pounds of shelled almonds per acre.
Forty years ago, California farmers produced less than 100 million pounds of almonds on about 200,000 acres of almond orchards. Mechanization, improved irrigation efficiency, advances in insect and disease management, pruning research and fertilization studies have fueled explosive growth in the industry. Farmers in California’s Central Valley now tend 760,000 acres of almond trees, producing about 2 billion pounds of shelled nuts a year. The crop, which represents 100 percent of U.S. almond production and 75 to 80 percent of world production, was valued in 2011 at $3.87 billion, surpassing table, wine and raisin grapes, which were valued at $3.86 billion.
“Even with this record production, we have more demand than we have supply,” said Bob Curtis of the Almond Board. “The driver behind that is nutrition studies that show almonds are a healthy food and snack.”
A tremendous amount of UC research is behind the California almond success story, said Bruce Lampinen, UC Cooperative Extension specialist in the Department of Plant Sciences at UC Davis, an expert in almond canopy management.
“Higher density plantings of almonds and a trend towards less pruning, and improved water management have led to much higher yields,” Lampinen said.
Many almond growers have replaced flood irrigation with micro-sprinkler or drip irrigation, said Larry Schwankl, UC Cooperative Extension specialist in the Department of Land, Air and Water Resources at UC Davis. These irrigation systems increase the precision of water and fertilizer application. Over the years, UC Cooperative Extension advisors and specialists established demonstrations of micro-sprinkler and drip systems in many parts of the Central Valley and reached out to farmers to show how they could be managed to optimize production.
“Twenty years ago, we simply guessed at the amount of water that the trees needed and we applied it on a calendar basis,” said Joe MacIlvaine, president of Paramount Farming Company in Kern County, one of the state’s largest growers of almonds, pistachios and pomegranates. “Today, we are delivering water and nutrients directly to the root zones when they are needed.”
Two decades ago, a granular form of nitrogen fertilizer was generally applied to almond orchards in the fall to allow winter rain and irrigation to move it into the soil for use by the trees in spring and early summer. Nitrogen use efficiency was believed to be about 40 percent. Now, nitrogen fertilizer is applied through the irrigation system during the growing season, when the tree needs it.
“Today, our nitrogen use efficiency can be as high as 85 percent,” said Blake Sanden, UCCE advisor in Kern County, an irrigation expert. He and Patrick Brown, professor in the Department of Plant Sciences at UC Davis, have conducted nitrogen trials in almonds with Paramount Farming.
“When you increase the conversion of applied nitrogen fertilizer to higher crop yield, there is significantly less potential for nitrogen to leach below the rootzone and contaminate groundwater,” Sanden said. “But each field is unique and requires site-specific management to achieve these high levels of efficiency.”
Another area where UC research has led to significant crop yield growth is in canopy management and tree spacing. Research by Mario Viveros, UCCE advisor emeritus in Kern County, and other scientists showed that a tendency among growers to over prune was taking a toll at harvest time.
“A lot of farmers who are now growing almonds had experience with fresh fruits, where you do need to prune to get light on the fruit for good color. In almonds more canopy generally means more yield,” Lampinen said. “Today, most almond growers only prune when branches are growing in the way of tractors or other equipment.”
UC research also found that orchards planted with traditional wide spacing between the trees weren’t making the most efficient use of sunlight on the farms. Older orchards had 60 to 70 trees per acre. Today, almond orchards are planted at an average density of about 110 trees per acre based on results of UC research.
However, studies have also shown that crowding still more trees into orchards triggers diminishing returns. In almond production, the nuts are shaken from the trees to dry on the ground before they are harvested.
“If the orchard floor becomes too shaded by trees planted too densely, the orchard floor temperature and humidity become optimal for growth of pathogens that could become a food safety problem,” Lampinen said. “You want enough sunlight to hit the orchard floor to reduce potential pathogens, like salmonella.”
MacIlvaine acknowledged the role of UC Cooperative Extension in helping the almond industry achieve the production milestone in 2011.
“The University of California has been a wonderful partner in improving our farming practices,” he said. “The whole system is not only more efficient, but more sustainable at the same time.”
Hear more of MacIlvaine's comments in the video posted below: