Posts Tagged: aquifer recharge

Evaluation of sudangrass and sorghum-sudangrass hybrid cover crops for control of winter storm water runoff and erosion in vegetable systems.

Introduction

Traditional winter cereal cover crops planted in the Salinas valley have many potential benefits including, scavenging nitrate in the soil profile, increasing organic matter in the soil, and protecting the soil from erosion during storm events.   However, when grown for 3 to 4 months during the late fall and winter, cereal rye, triticale, or barley can accumulate 5 to 6 tons of dry matter biomass that must be incorporated into the soil before planting a spring vegetable crop.   Tilling in a high amount of cover crop biomass can be disruptive to spring planting schedules.  Consequently, only a small fraction of the vegetable ground in the Salinas valley is cover cropped each year.  

Previous studies demonstrated alternative strategies can limit the biomass growth of these cereal cover crop species so that they can more easily be tilled into the soil, and therefore less disruptive to spring planting schedules.  After fall land preparation, the cereal cover crops are seeded into listed beds and/or in the furrow bottoms.   After they become established they can reduce runoff and protect the soil from erosion during early winter storm events.  Before the cover crops grow too big, they are terminated with an herbicide to limit the amount of above ground biomass that needs to be incorporated in the spring.  For organic systems, planting a mustard cover crop on listed beds or furrows which can be terminated mechanically by mowing is another strategy to limit biomass.   A good target for these low biomass cover crops is between 0.5 to 1 ton of dry matter per acre by the date of termination.  Once terminated, the biomass begins to decompose.  However, the residue on the surface continues to protect the soil from erosion and can significantly increase infiltration from rain events.   This helps to leach accumulated salts in the soil as well as recharge groundwater aquifers.   The remaining decomposed residue can easily be incorporated into the soil during bed preparation in the spring. 

One risk of this low biomass approach is accessing fields during the winter to terminate the cover crop.  If soil conditions are too wet or if there is not enough available labor, it may be difficult to fit in a spray application or to run a flail mower.    This termination step also increases the cost of managing the cover crop.   A possible solution is to use species that grow slowly during the winter when temperatures are cold.   Sudangrass and sorghum-sudangrass hybrid are warm season adapted species that could be used in this low biomass approach to managing winter cover crops.

Field trial with warm season adapted cover crop species

A field trial was conducted with sudangrass and sorghum-sudangrass in the 2023-2024 winter to evaluate biomass growth, and the effect on storm water runoff and soil erosion compared to bare-fallow plots.   The site was located on an Arroyo Seco gravelly loam soil with a slope of more than 5%.   Plots measuring 1050 ft in length by four 40-inch wide peaked beds were planted with either sudangrass, sorghum sudangrass hybrid, or left bare fallow.  Treatments were replicated 4 times.   The cover crops were seeded at 60 to 80 lbs/acre on October 4^th and were subsequently sprinkle-irrigated several times.  Total water applied for establishment was 2.6 inches.  One application of the herbicide Bromoxnil (Maestro) was applied about 45 days after planting to kill emerged broadleaf weeds.  

Air temperature and rainfall were monitored at the field site and flumes were installed in late November at the end of each plot for measuring runoff during winter storm events (Fig. 1).   The flumes were equipment with automated sampling pumps that could collect runoff during storm events.   Runoff samples were evaluated for sediment and nutrient concentration at the UC Davis Analytical Laboratory.

Results

 Above ground biomass, N uptake, and carbon accumulation

Both cover crops had limited biomass growth, accumulating only 0.35 to 0.5 tons/acre of dry matter by early January and less than 1 ton/acre by mid March (Table 1).  Growth was set back by cold conditions that occurred from mid November through early January, occasionally reaching freezing temperatures which caused damage to leaves (Fig. 2).   However, the freezing temperatures lasted only a few hours and were not severe enough to kill the cover crops (Fig. 3).  By March 13^th the cover crops had taken up 45 to 55 lbs N/acre and had a carbon to nitrogen ratio of 15.   The C:N ratio of 15 would suggest that after soil incorporation the residue would decompose rather quickly and release N for the following vegetable crop. 

Runoff, rainfall infiltration, and control of soil erosion

Total rainfall measured at the trial site was 10.2 inches for the winter season.   The most intense period of rainfall occurred in late January and early February which resulted in several runoff events (Fig. 4). During this period about 50% of the rainfall in the bare fallow plots was lost as runoff compared to 15% lost as runoff in the cover crop plots (Fig.5).  Over the entire winter season, runoff was reduced by an average of 70% under the cover cropped plots compared to the bare fallow plots, and significantly more rainfall was infiltrated into the ground in the cover cropped plots.  In addition, suspended sediment concentration was 90% and 77% less in thesudangrass and sorghum-sudangrass cover crop plots, respectively, compared to the bare plots.  Turbidity, total P, and total N concentration in the runoff were also reduced under the cover crop plots compared to the bare fallow plots (Table 2).

Seasonal soil erosion losses could be calculated based on the volume of the runoff and sediment concentration in the runoff.  The total loss of sediment averaged more than 3500 lbs per acre in the bare fallow plots during the winter, while erosion losses were reduced by 96% to 98% in the sorghum-sudangrass and sudangrass plots (Fig. 6).   Total N losses were reduced by 83% to 86% in the cover crop plots compared to the fallow plots, and total P losses were reduce by 81% to 85% in the cover cropped plots compared to the bare fallow plots.   

 

Conclusions

The use of warm season species such as sudangrass and sorghum-sudangrass hybrids as winter cover crops provides several advantages compared to planting cereal cover crops.   Biomass growth through the winter is self-limiting due to cold conditions that typically occur in the Salinas Valley.  Because the final biomass would likely be less than 1 ton per acre, these species can be planted on listed beds in the fall rather than on flat ground.  In the spring, the remaining cover crop can be lillistoned into the peaked beds a few weeks before final bedshaping and planting.  Cover crops planted on flat ground that accumulate high amounts of biomass over the winter usually require many tillage passes to prepare ground for planting in the spring.   Despite, having less biomass than traditional winter cereal species, sudangrass and sorghum-sudangrass hybrid cover crops provided excellent erosion control compared to leaving the ground bare, and increased infiltration of rainfall during storm events. Also these species may be able to scavenge significant amounts of nitrogen from the soil which can limit nitrate leaching during the winter months. 

On the east-side of the Salinas Valley groundwater levels have been in the decline for several decades.  Infiltrating as much rainfall as possible during the winter using strategies such as low biomass cover crops could potentially help recharge the aquifer in this region.  We plan to continue field trials with these warm season cover crop species in vegetable systems during the upcoming winter.

Acknowledgments

This project was funded by the California Leafy Greens Research Board.

Lawn-pocalypse! Surviving Drought

Ah, summer! The season of sunburns, pool parties, and… lawn droughts. If your once lush, green carpet now looks like a crunchy brown doormat, you're not alone. Let's dive into why your yard is staging a dramatic death scene and what you can do to...

Bermuda grass and weeds overtaking drought stressed turf grass.

A patch of former lawn, mostly dead, with a few green weeds and Bermudagrass

Climate-Change Resources

University of California UC ANR Green Blog (Climate Change and Other Topics) https://ucanr.edu/blogs/Green/index.cfm?tagname=climate%20change (full index)

Examples:

     -  Save Trees First: Tips to Keep Them Alive Under Drought https://ucanr.edu/b/~CdD 

     - Landscaping with Fire Exposure in Mind: https://ucanr.edu/b/~G4D

     - Cities in California Inland Areas Must Make Street Tree Changes to adapt to Future Climate  https://ucanr.edu/b/~oF7

Drought, Climate Change and California Water Management Ted Grantham, UC Cooperative Extension specialist (23 minutes) https://youtu.be/dlimj75Wn9Q

Climate Variability and Change: Trends and Impacts on CA Agriculture Tapan Pathak, UC Cooperative Extension specialist (24 minutes) https://youtu.be/bIHI0yqqQJc

California Institute for Water Resources (links to blogs, talks, podcasts, water experts, etc.) https://ciwr.ucanr.edu/California_Drought_Expertise/

UC ANR Wildfire Resources (publications, videos, etc.) https://ucanr.edu/News/For_the_media/Press_kits/Wildfire/ (main website)

      -UC ANR Fire Resources and Information https://ucanr.edu/sites/fire/ (main website)

            -Preparing Home Landscaping https://ucanr.edu/sites/fire/Prepare/Landscaping/

UC ANR Free Publications https://anrcatalog.ucanr.edu/ (main website)

- Benefits of Plants to Humans and Urban Ecosystems: https://anrcatalog.ucanr.edu/pdf/8726.pdf

 -Keeping Plants Alive Under Drought and Water Restrictions (English version) https://anrcatalog.ucanr.edu/pdf/8553.pdf

  (Spanish version) https://anrcatalog.ucanr.edu/pdf/8628.pdf

-  Use of Graywater in Urban Landscapes https://anrcatalog.ucanr.edu/pdf/8536.pdf

-  Sustainable Landscaping in California https://anrcatalog.ucanr.edu/pdf/8504.pdf

 

Other (Non-UC) Climate Change Resources

Urban Forests and Climate Change. Urban forests play an important role in climate change mitigation and adaptation. Active stewardship of a community's forestry assets can strengthen local resilience to climate change while creating more sustainable and desirable places to live. https://www.fs.usda.gov/ccrc/topics/urban-forests

Examining the Viability of Planting Trees to Mitigate Climate Change (plausible at the forest level) https://climate.nasa.gov/news/2927/examining-the-viability-of-planting-trees-to-help-mitigate-climate-change/

Reports and other information resources coordinated under the auspices of the United Nations and produced through the collaboration of thousands of international scientists to provide a clear and up to date view of the current state of scientific knowledge relevant to climate change. United Nations Climate Action

Scientific reports, programs, action movements and events related to climate change. National Center for Atmospheric Research (National Science Foundation)

Find useful reports, program information and other documents resulting from federally funded research and development into the behavior of the atmosphere and related physical, biological and social systems. Search and find climate data from prehistory through to an hour ago in the world's largest climate data archive. (Formerly the "Climatic Data Center") National Centers for Environmental Information (NOAA)

Think tank providing information, analysis, policy and solution development for addressing climate change and energy issues (formerly known as the: "Pew Center on Global Climate Change"). Center for Climate & Energy Solutions (C2ES)

Mapping Resilience: A Blueprint for Thriving in the Face of Climate Disaster. The Climate Adaptation Knowledge Exchange (CAKE) was launched in July 2010 and is managed by EcoAdapt, a non-profit with a singular mission: to create a robust future in the face of climate change by bringing together diverse players to reshape planning and management in response to rapid climate change. https://www.cakex.org/documents/mapping-resilience-blueprint-thriving-face-climate-disaster

Cal-Adapt provides a way to explore peer-reviewed data that portrays how climate change might affect California at the state and local level. We make this data available through downloads, visualizations, and the Cal-Adapt API for your research, outreach, and adaptation planning needs. Cal-Adapt is a collaboration between state agency funding programs, university and private sector researchers https://cal-adapt.org/

Find reports, maps, data and other resources produced through a confederation of the research arms of 13 Federal departments and agencies that carry out research and develop and maintain capabilities that support the Nation's response to global change. Global Change (U.S. Global Change Research Program)

The Pacific Institute is a global water think tank that combines science-based thought leadership with active outreach to influence local, national, and international efforts to develop sustainable water policies. https://pacinst.org/our-approach/

Making equity real in climate adaptation and community resilience policies and programs: a guidebook. https://greenlining.org/publications/2019/making-equity-real-in-climate-adaption-and-community-resilience-policies-and-programs-a-guidebook/ 

Quarterly CA Climate Updates and CA Drought Monitor Maps (updated each Thursday) https://www.drought.gov/documents/quarterly-climate-impacts-and-outlook-western-region-june-2022

 

 

 

 

Drought focus of Water Resources IMPACT magazine special issue

UC ANR experts address emotional toll of drought

Preparing the American West for prolonged drought is the focus of a double issue of Water Resources IMPACT magazine. The California Water Commission staff are guest editors for this special open-access edition of the magazine, which is published by the American Water Resources Association.   

Faith Kearns, academic coordinator of University of California Agriculture and Natural Resources' California Institute for Water Resources, is among the authors delving into how drought impacts people and the environment and how we can better prepare for the inevitable. 

The first issue, published on Feb. 14, focuses on water scarcity issues confronting California and the ways these issues affect different sectors. 

In “Trauma, Care, and Solidarity: Addressing the Emotional Toll of Chronic Drought,” Kearns highlights the effects of drought on mental health. She points to the spike in suicide hotline calls when wells ran dry in Southeast Asian communities in California's Central Valley.

By listening to Southeast Asian farmers, Ruth Dahlquist-Willard and Michael Yang of UC Cooperative Extension were able to “lighten the load” for them by providing pragmatic support, Kearns writes.

“The scale of some of these highly emotional issues – drought, wildfires, climate change – can make them seem incredibly difficult, if not impossible, to deal with,” Kearns said. “At the same time, they are affecting everyone living in the western U.S. on a daily basis. I wanted to highlight and provide models based on work that people – whether they are researchers, clinical psychologists, or Cooperative Extension advisors – are doing right now to ease the way.”

The authors who contributed to the double issue are a diverse array of Tribal experts, academics, nongovernmental organization thought-leaders, water managers and water policy influencers, each of whom brings their own perspective on the topic of drought. Their expertise and perspectives in climate science, water policy and water management will help inform drought-related decision-making and support policies that better prepare the state to thrive during periods of prolonged water scarcity.

In addition to Kearns, the first issue includes articles contributed by:

• Samantha Stevenson, University of California, Santa Barbara
• Jay Lund, University of California, Davis
• Ron Goode, North Fork Mono Tribe
• Andy Fecko, Placer County Water Agency
• Jeff Mount, Public Policy Institute of California, and Ted Grantham, University of California, Berkeley/UC Cooperative Extension
• Nat Seavy and Karyn Stockdale, National Audubon Society
• Kjia Rivers, Community Water Center
• Cannon Michael, Bowles Farming
• Michelle Reimers, Turlock Irrigation District

The January/February edition of Water Resources IMPACT magazine can be accessed, free of charge, on the American Water Resources Association website at https://www.awra.org under “Publications.”

The second issue, to be published in March, will focus on drought response, considering the options for adaptation. This two-part series complements the Commission's work on strategies to protect communities and fish and wildlife in the event of a long-term drought.

 

 

Your water-efficient landscape doesn’t have to be barren

UC climate-ready landscape trials identify low-water yet attractive plants

Good news: roses can be a part of your water-efficient landscape. Lorence Oki, UC Cooperative Extension environmental horticulture specialist in the UC Davis Department of Plant Sciences, identified rose cultivars that remain aesthetically pleasing with little water.  

Oki is the principal investigator of the Climate-Ready Landscape Plants project, which may be the largest irrigation trial in the western U.S., and the UC Plant Landscape Irrigation Trials (UCLPIT), the California component of that project. These projects evaluate landscape plants under varying irrigation levels to determine their optimal performance in regions requiring supplemental summer water.

“There are some assumptions that pretty plants use a lot of water, like roses,” Oki said. “Everyone thinks they need a lot of water, but we've found some that don't, and they still look great. A water-efficient landscape doesn't need to look like a Central Valley oak-grassland in the summer. It can look really attractive.”

In 2021, Oki's team at UC Davis identified Lomandra confertifolia ssp. pallida "Pom Pom" Shorty and Rosa "Sprogreatpink" Brick House® Pink as two of the best low-water plants in the trial. 

“The useful tip or information that is shared at the end of each trial is the selection and designation of plants as Blue Ribbon winners. These are the plants that looked good with an overall rating of 4 or higher throughout and were on the low (20%) water treatment,” said Natalie Levy, associate specialist for water resources, who manages the project at the UC ANR South Coast Research and Extension Center.

How plants earn a blue ribbon

Each trial year, the selection of new plants is based on research recommendations and donated submissions from the nursery industry. The landscape plants are trialed in full sun or 50% shade cover.

Irrigation treatments are based on the rate of evaporation and plant transpiration (evapotranspiration) measured through a local California Irrigation Management Information System (CIMIS) weather station that provides a reference evapotranspiration (ETo) rate.

Three levels of irrigation are provided to the plants equal to 20%, 50%, and 80% of ETo. The volume of water applied is the same at each irrigation based on soil characteristics, but the interval between applications varies with weather and the treatment. Using this method, irrigations for the 20% treatment are less frequent than the 80% treatment.

“The 20% treatment during the 2022 trial was irrigated an average of once per month while the 80% treatment was irrigated weekly,” explained Levy.

During the deficit irrigation trial, monthly height and width measurements are taken to determine the plant growth index. Monthly qualitative aesthetic ratings on a scale of 1 to 5 are determined for foliage appearance, flowering abundance, pest tolerance, disease resistance, vigor and overall appearance.

A second round of flowering abundance and overall appearance measurements are also taken to capture more of the blooming period. For example, UCLPIT identified in the 2020 trial at South Coast REC that the "Apricot Drift" rose had a mean overall appearance score of 3.5 out of 5, deeming it “acceptable to very nice” and a low water use plant within the Water Use Classification of Landscape Species or WUCOLS guide.

Project expands options for landscape planting

While attending UC Davis as a master's student, Karrie Reid, retired UCCE environmental horticulture advisor for San Joaquin County, assisted Oki with landscape water conservation research. The landscape plant irrigation assessments were initiated at UC Davis in 2004 and the UCLPIT project, now in its 20^th year, originated from her master's thesis project from 2005 to 2007. A CDFA grant supported duplicating these fields at the South Coast REC in 2017.

“(WUCOLS) only has 3,500 plants in it. There are guesses that there are close to 10,000 cultivars in urban landscapes in California, if not more,” said Oki. “WUCOLS also didn't have numerical ratings. Instead, you'll see verbal ratings like ‘low water use' or ‘high water use.'”

The UCLPIT project has not only developed numerical recommendations for irrigation, but it has also added new landscape plants that are compliant with California's Model Water Efficient Landscape Ordinance. In fact, UCLPIT's data is one of the few sources that can be used to supplement WUCOLS.

Geographic diversity of trial sites adds to knowledge base

In addition to UC Davis and South Coast REC in Irvine, the trials have expanded beyond California as the Climate-Ready Landscape Plants project and is in progress at Oregon State University, University of Washington, University of Arizona and Utah State University thanks to a USDA/CDFA grant awarded in 2020.

Lloyd Nackley, associate professor of nursery production and greenhouse management at Oregon State University, is the principal investigator of the trial in the Portland metro area, which is entering its third year.

“People know that there are drought tolerant plants, but there are many. We're trying to highlight lesser known or newer varieties. And even though the trial is three years, most gardeners would hope that their garden lasts longer than that,” said Nackley.

One of the observations that Nackley recalls is of the Hibiscus Purple Pillar plant. Unlike the trial at South Coast, the Purple Pillar did not perform well in Oregon in the spring.

“It wasn't until August that we saw the plant bloom and begin to look like what we saw from South Coast in April,” Nackley said.

Ursula Schuch, horticulture professor and principal investigator of the trial taking place at the University of Arizona, was also surprised at the range of performance among different plant types and the effects of irrigation, heat and temperature.

“This research will reassure green industry professionals that they can stretch their water budget to successfully cultivate more plants, watering them according to their needs instead of irrigating every plant according to the highest water-using plants,” said Schuch.

Although research is only conducted in the West, the hope is that there will be trials in other regions of U.S.

Doing so would yield comprehensive information about the plants and their performance in different climates. As extreme weather events persist in the U.S., disease pressure and risks do too. Trials throughout the country would provide location-specific data regarding disease susceptibility. 

To learn more about the UCLPIT research project, visit https://ucanr.edu/sites/UCLPIT/

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