Posts Tagged: soil
Grubs in your garden?
While preparing your garden for planting this spring, you may have found white grubs in the soil....
CASI hosts the Soil Health Institute's US Regenerative Ag Cotton Program leaders - April 11 and 12, 2024
April 12, 2024
The UC ANR CASI Center hosted five members of the Soil Health Institute's US Regenerative Ag Cotton Program in the San Joaquin Valley on April 11th and 12th, 2024. The Soil Health Institute (SHI) is a non-profit organization based in Morrisville, NC that conducts research and extension education related to soil health management. Five SHI members, Diana Bagnall, David Lamm, Jessica Kelton, Emily Ball, and Nate Looker, took part in the two-day tour of six San Joaquin Valley farms and the California Cotton Ginners and Growers Associations. San Joaquin Valley farmers who hosted the SHI members included Mark Borba of Borba Farms in Riverdale, CA, Mark McKean of McKean Farms also in Riverdale, Tony Azevedo of Stone Land Company in Stratford, CA, Cannon Michael and Derek Azevedo of Bowles Farming in Los Banos, Gary and Mari Martin of Pikalok Farms in Mendota, and Gary Smith of Ingleby Farms in Burrel. Roger Isom, President of the CCGGA in Fresno, also hosted the SHI guests.
SHI requested help from CASI with the cotton tour and discussions that took place as an effort to expand their national Regenerative Ag Cotton Program to California in 2024. The tour provided excellent opportunities for SHI to learn about California cotton and to make connections with leading cotton farmers in the San Joaquin Valley who may become part of the baseline soil sampling project that SHI is looking to conduct with cotton producers this year.
In addition to the farmers who generously hosted the SHI guests, several other local California folks including Cary Crum, Kimber Moreland, Rob Roy, Jacob Wright, and Olivia Peters helped CASI's Jeff Mitchell in sharing information about California cotton systems.
DSC0148-1 FINAL
DSC0172-1 FINAL
Soil Health Assessment Report
Soil Biodiversity in California Agriculture: Framework
and Indicators for Soil Health Assessment
Prepared by: California Department of Food and Agriculture Below Ground Biodiversity Advisory Committee
Soil health depends on soil biodiversity.
However, external pressures from land-use change, climate change and certain agricultural practices threaten the biotic networks that underpin the delivery of soil's many ecosystem services. Yet measuring soil biodiversity is a complex task, with a wide variety of possible indicators, and methodologies that are evolving with recent technological advances. This report, prepared by the Belowground Biodiversity Advisory Committee (BBAC) convened by the California Department of Food and Agriculture (CDFA), focuses on how best to assess soil biodiversity in the context of working lands and considers current and future challenges faced by California agricultural producers, policy makers, governing agencies, and related stakeholders. The report presents information on the taxonomic and functional diversity of soil organisms, ecosystem services they provide, threats to soil biodiversity, assessment frameworks, and biodiversity indicators. Examples of how biodiversity indicators can be applied to specific use cases provide insights for soil health, sustainable and climate-smart agriculture, and biodiversity conservation in California.
Soil biodiversity is the interconnected ‘social' network of numerous species of living organisms that contribute to soil functioning. As these organisms grow, die, and interact with soil's abiotic components, they perform essential functions in carbon, water and nutrient cycling and plant growth, collectively described as multifunctionality, benefiting ecosystems and humans alike. Comprehensive assessment of soil biodiversity involves measurements of organism abundance, identity, and functional diversity or traits, ideally in tandem with measurements of soil processes, as well as interactions among organisms. Soil biodiversity and soil processes vary in space and time due to factors like location, climate, vegetation, and land management practices across California's diverse landscapes.
Soils are incredibly biodiverse habitats, containing a vast array of organisms ranging from macroscopic organisms like gophers to microscopic worms, fungi, and billions of bacterial cells. The physical and chemical properties of soils – soil texture, pH, water and oxygen content, salinity, organic matter inputs, and nutrients – determine the types of organisms found in a particular habitat. The array of organisms inhabiting soil spans over six orders of magnitude in size, and includes microorganisms (viruses, bacteria, archaea, and fungi); microfauna (protists, nematodes, and tardigrades); mesofauna (mites and springtails); and macrofauna (earthworms). Life in soil exists in ecological communities that are complex and interconnected. These interconnections provide stability to soil functions. Soil organisms are critical to regulation of greenhouse gases, both by consuming and producing gases such as nitrous oxide, carbon dioxide, and methane. Mycorrhizal fungi in symbiosis with most plant species promotes root growth and availability of water and nutrients. A broad range of soil organisms mediate the decomposition of organic inputs and enhance nutrient cycling. Other functions of biodiverse soils include soil structure formation, organic matter formation, carbon storage, water regulation, and pathogen suppression. But despite these critically important functions, the diversity and complexity of soil biodiversity makes it challenging to decipher these intricate relationships and understand the impact of human activities.
Soil biodiversity faces many of the major threats from human activities and global change that also impact soil health and sustainability of California's agroecosystems. Land use changes, intensive agriculture, climate change, pollution, invasive species, overexploitation, and loss of habitat connectivity all pose risks. These threats disrupt soil biological networks, reduce biodiversity, impair ecosystem functions, and degrade soil structure and fertility. Soil biodiversity loss reduces multifunctionality and the provision of ecosystem services, highlighting the need to recognize the value of belowground communities to overcome challenges such as climate change, land degradation, and overall biodiversity loss. Addressing these challenges through sustainable land management, agroecological approaches, and awareness campaigns is crucial for preserving belowground biodiversity to maintain provision of essential ecosystem services.
READ ALL ABOUT SOIL DIVERSITY in the Report:
https://www.cdfa.ca.gov/oefi/biodiversity/docs/Soil_Biodiversity_California_Ag_July_2023.pdf
soil food web image
How Many Earthworms are Enough?
Perhaps you've seen them. You're digging into the soil to plant something and as you dig you run across a few earthworms. Most of us have heard from childhood that worms are good for the soil. You may also be aware of vermiculture, or worm composting, using worms to help turn organic waste into nutrient rich compost for the soil. When you see earthworms in your garden, what does their presence suggest about the soil health? Should you add more?
Earthworms and Wigglers
The earthworms you typically see in your garden are considered "migratory" which means they will travel to find the habitat best suited to their success. They tend to cluster in the top 6 to 8 inches of soil around the roots of plants where they feed on decaying material and the fungi and other organisms that live there. As they travel through the soil, they drag leaves and other litter down into their burrows where soil microorganisms also begin digesting the material. These worms can tolerate colder temperatures through the winter months when they burrow deeper into the soil.
Earthworms need a light airy soil and rely on decaying organic material for nourishment. Introducing these earthworms to an inhospitable environment such as heavy clay, or compacted and/or dry soil, will result in them either leaving or dying. Where they flourish, however, they are important in mixing the dead surface litter with the main body of the soil. If you regularly add compost and a layer of mulch to your garden to improve the soil you may find the worms 'magically' appear, attracted to the habitat you are creating. In turn their constant burrowing and feeding activities help mix and distribute organic matter throughout the soil, improve soil aeration and water penetration, promoting a healthier root environment for your plants. Their excrement, known as castings, is richer in nitrogen, potassium carbon, sulfur, and other minerals than the rest of the soil, and acts as a natural fertilizer.
There is a second type of worm which lives close to the soil surface in areas of abundant organic material. These worms, including the popular species red wigglers, reproduce rapidly and thrive in warm, crowded conditions. They are less likely to survive in your garden environment, particularly during cold weather. Instead, these worms are ideally suited to worm bins, and you will usually find them for sale for use in vermiculture. In a bin they can rapidly break down food scraps and other organic waste materials, and their castings also act as a natural fertilizer when collected and added to garden soils. Think of these worms as composting specialists.
A Note of Caution
There is a type of worm known as a jumping worm, an invasive species capable of harming native forests which has been seen in California and many other states. It is recognizable by a milky-white band wrapping all around its body near the head. When disturbed, jumping worms have been known to throw themselves into the air and thrash around. It is very difficult to eliminate these worms once established, so make sure to check new mulch, compost, and potting soil for the worms, as well as soil in nursery pots. Because they live close to the surface their castings are often visible as a coffee-ground-like substance on the soil. Don't use these worms for fishing, vermiculture, or gardening. You can learn more about jumping worms at https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=56929.
The Bottom Line
Should you add worms to your garden soil? Ultimately, it's a chicken and egg situation. Do earthworms create healthy soil or are they attracted to healthy soil? Few valid studies have been done to link the presence of earthworms with improved plant growth. However, both plants and earthworms need temperatures between 60°F and 100°F, water (but not too much or too little), oxygen, and a soil that isn't too acidic, basic, or salty. It's clear the conditions that are good for plants are also good for earthworms, and improving your soil by regularly adding compost and mulch ends up supporting a thriving community of both healthy plants and earthworms.
Help Desk of the UC Master Gardeners of Contra Costa County (RDH)
Organic strawberry yields boosted by technique refined through UCCE research
Anaerobic soil disinfestation helps suppress weeds, disease without fumigants
Troubled by puny plants, low yields and persistent mite problems, third-generation Southern California strawberry grower Glen Hasegawa was ready to give up on his transition from conventional to organic 12 years ago.
“I've always liked a challenge – but it turned out to be more of a challenge than I thought it would be!” he said.
But then, with the help of scientists including Oleg Daugovish, UC Cooperative Extension strawberry and vegetable crop advisor in Ventura County, Hasegawa tried a technique called anaerobic soil disinfestation (ASD). When applied correctly, the multi-step ASD process creates a soil environment that suppresses pathogens and weeds and makes for healthier, more robust crop growth.
“Back in the day, it was really hard to get the plant growing vigorously in organic,” said Hasegawa, owner of Faria Farms in Oxnard. “So we started using the ASD and then you could definitely see that the plant had more vigor and you could grow a bigger, better plant using it.”
Seeing that he could produce yields “in the neighborhood” of those grown in conventional strawberry fields fumigated with synthetic fumigants, Hasegawa was able to expand his original 10 acres of organic strawberries to 50 acres.
“I guess you could say I'm kind of a convert,” he said, noting that he now applies ASD to all his acreage each year in late spring.
Joji Muramoto, UC Cooperative Extension specialist in organic production based at UC Santa Cruz, has been experimenting with ASD since it was first brought to the U.S. from the Netherlands and Japan in the early 2000s. Carol Shennan, a professor in the Department of Environmental Studies at UCSC, and Muramoto were among the first to try the technique in California. They found that ASD successfully controlled an outbreak of Verticillium wilt – caused by the pathogen Verticillium dahliae – at UCSC's small organic farm in 2002.
Since then, Shennan, Muramoto, Daugovish and their colleagues have seen encouraging results at 10 trial sites across the state.
“We demonstrated that ASD can provide comparable yields with fumigants, in side-by-side replicated trials,” Muramoto said.
ASD promotes host of beneficial changes to soil ecosystem
ASD comprises three basic steps: incorporating a carbon source that is easily digestible by microbes in the soil (traditionally, rice bran has been used), further encouraging fermentation by covering the soil with plastic to limit oxygen supply, and finally adding water through drip irrigation to initiate the “anaerobic” decomposition of the carbon source and maintain the three-week “cooking” process.
The resulting cascade of chemical, microbiological and physical changes to the soil creates an ecosystem that is both conducive to strawberry growth – and inhospitable to pathogens and weeds.
“It's not like a pesticide where you have a mode of action, and thus resulting in ‘A' and ‘B' for you,” Daugovish explained. “There's a sort of cocktail of events that happens in the soil; they all happen interconnectedly.”
Compared to similar fields that did not undergo the process, ASD-applied organic strawberry fields across California have seen yields increase by 60% to 70% – and even doubling in some cases, according to Daugovish.
The UCCE advisor also shared the story of a longtime grower in Ventura County, who came to him with fields in “miserable” condition; they were plagued by one of the world's worst weeds, yellow nutsedge, and infected with charcoal rot, a disease caused by the fungus Macrophomina phaseolina. But after applying rice bran and following the ASD recipe, the grower saw phenomenal results.
“The only complaint he said to me was, ‘Now I have too many berries – we have to have more pickers to pick the berries!'” Daugovish recalled.
Via researchers' meetings, online resources, on-farm demonstration trials and word of mouth from peers, use of ASD by California strawberry growers has grown significantly during the past two decades. Tracking the purchase of rice bran, Muramoto estimated that about 2,500 acres were treated by the ASD-related practices in 2023 – covering roughly half of the 5,200 total acres of organic strawberries in California.
Muramoto directly links the growth of California organic strawberry production – which now comprises about 13% of total strawberry acreage in the state – with the increasing adoption of ASD.
“If you remove the acreage with the applied rice bran over the last 10 years or so, organic strawberry acreage is just flat,” he said.
Within the last decade, acreage of organic strawberries with ASD-related practices increased by 1,640 acres, which is a boon for air quality, human health and long-term soil vitality. According to Muramoto's calculations, that increase in organic acreage translates to a reduction of about 465,000 pounds of fumigant active ingredients that would have been used in growing conventional strawberries.
“There are hundreds of reports of acute illnesses related to fumigation in the record, so it's very important to find alternatives to fumigants,” said Muramoto, citing California Department of Pesticide Regulation documents.
Research continues to make ASD more economical, effective
The popularity of ASD has come at a price, however, for organic strawberry growers.
“There's more organic out there, and I think most of the organic guys are using it, so there's more demand on the rice bran; the price has been steadily going up every year, like everything else,” said Hasegawa, adding that he has been trying to decrease the amount of carbon while maintaining ASD's efficacy.
On top of greater demand from other growers and from beef cattle and dairy producers (who use rice bran as feed), the price also has increased due to higher costs in transporting the material across the state from the Sacramento Valley. So Daugovish and his colleagues – including Peter Henry, a U.S. Department of Agriculture plant pathologist – have been searching for a cheaper alternative.
“We all want an inexpensive, locally available, reliable, easy to use and functional carbon source, which sounds like a big wish list,” Daugovish said.
Carbon sources such as bark, wood chips, or compost are ineffective, as the crucial ASD microorganisms are choosy about their food.
“Microbes are just like cows; you can't feed them straight wood; they get pretty angry,” Daugovish explained. “And if you feed them something with too much nitrogen, they can't digest it – they get the runs. Microbes are the same way – you have to have the right proportion of stuff so they feel comfortable doing what they're doing.”
In search of an ideal replacement, researchers tried and ruled out grass clippings, onion waste, glycerin and coffee grounds. Finally, they pivoted to a material with properties very similar to rice bran: wheat bran, in the form of wheat middlings (also called midds, a byproduct of flour milling) and dried distillers' grain (DDG, a byproduct of ethanol extraction).
After field experiments in Santa Paula, the UC and USDA researchers found that midds and DDG were just as effective at controlling soilborne pathogens and weeds as rice brain – but at 25% to 30% less cost. Their results were published last year in the journal Agronomy.
“Not surprisingly, the wheat bran has worked almost exactly the same as rice bran,” Daugovish said.
He and Muramoto are now conducting trials with wheat bran at commercial fields, and the initial results are promising. Daugovish said the grower at one site in Ventura County has seen a 90% reduction in Macrophomina phaseolina, the causal pathogen of charcoal rot, in the soil – and an 80% to 90% drop in yellow nutsedge germination. They are waiting for final yield numbers after the coming summer.
While ASD has been beneficial to organic productivity and soil health, both Daugovish and Muramoto acknowledged specific limitations in suppressing the “big three” strawberry diseases: Verticillium wilt, Fusarium wilt and charcoal rot. In coastal areas with cooler soil temperatures, for example, ASD can actually exacerbate the latter two diseases, as the fungal pathogens feed on the rice bran.
“We know it works at warmer temperatures, but, practically, it's hard to do in coastal California,” Muramoto said. “It would be nice if we can find a way to suppress Fusarium wilt at a lower temperature, but we don't have it right now.”
That's why researchers emphasize that ASD is not a “silver bullet.” It's just one tool in the organic toolbox, which includes careful crop rotation, disease-resistant strawberry varieties and better diagnostic tests that help growers pinpoint outbreaks and make the application of various methods more targeted and more efficient.
And scientists will continue to optimize ASD to make it more effective and economical for growers in the different strawberry regions of California – from the Central Coast to the Oxnard Plain.
“We know it can work really well; it's just finding the most sustainable way to do this in our region,” Daugovish said. “We've got to just have an open mind and keep trying.”
/h3>/h3>/h3>