UCCE Ventura County- Blogs

Hans Jenny and the Art of Soil or Soil in Art

Hans Jenny (1899-1992) was a soils teacher at UC Berkeley, a pedologist. He distilled the factors that drive soil formation into an equation signified as CLORPT. The CLimate, Organisms, Relief, Parent material and Time that create soil. This might all sound academic, but this approach has helped us better understand how soils form from rock or a base material (Parent Material) to become what we see as soil today. And what we will see as soil tomorrow. He was a firm advocate for soil organic matter (SOM) and spent much of his energy showing the value of protecting SOM and how to show its value to not just agriculture, but the landscape and its health. In a 1980 Science magazine letter he said, “The humus capital, which is substantial, deserves being maintained because good soils are a national asset.” It fits right in with our ideas of carbon sequestration today.

He had a real love for soil and an eye for its beauty. He was interviewed back in 1984 for the Journal of Soil and Water Conservation where he shared some of his views.

http://nesoil.com/upload/Hans_Jenny_Interview.pdf

“Over the years I have acquired a kind of reverence for the soil, for the creature-world inside it, and for its character expressed in the profile features.”

“Soil speaks to us through the colors and sculptures of its profile, thereby revealing its personality: we acknowledge it by giving soil a name, albeit in a foreign tongue, but we don't mention our emotional involvements…”

Hans Jenny went “Hollywood” in 1983 by collaborating with David Bellamy of the BBC.  The documentary covers the concept of CLORPT referred to in the interview. It's spoken in a pretty thick English accent, so you might want to read up about the Ecological Staircase that exemplifies soil formation. The transect of soils and plants that are discussed are at Jughandle State Park in Mendocino.

David Bellamy's New World explaining Hans Jenny's CLOPRT, Part 1 y

CLORPT, Part 2

“Soil contains over a thousand different species of lower animals, the earthworms, pill bugs, nematodes, millipedes, termites, ants, springtails, and amoebas, not to mention the millions of molds and bacteria…If all the elephants in Africa were shot, we would barely notice it, but if the nitrogen-fixing bacteria in the soil, or the nitrifiers, were eliminated, most of us would not survive for long because the soil could no longer support us. I can't help thinking of the claim that healthy soils make healthy people, and as an extension, I am intrigued by the thought that good soils make good people, but that notion seems untenable. Well, not wholly so. Working in the garden with spade and hoe soothes the minds of many people….”

“Soil speaks to us through the colors and sculptures of its profile, thereby revealing its personality: we acknowledge it by giving soil a name, albeit in a foreign tongue, but we don't mention our emotional involvements…”

Jenny also studied how we have viewed soil in art over the ages.  He gave presentations on the progression over time of how our views have changed from broad nondescript representations to elaborate characterizations and on to more idealized shapes.  Check out this essay he did for the Pontifical Academy of Sciences in 1968 after years of roaming art museums - The Image of Soil in Landscape Art.

And more on the art of soil through the ages from a different author

https://www.sciencedirect.com/science/article/abs/pii/S034181620900112X

 

Arbor Day - Grant Wood

arbor day grant wood

UC Riverside Happenings

UC Riverside awarded $1.5 million for sustainable agriculture initiatives

RIVERSIDE, Calif. -- The University of California, Riverside, has been awarded $1.5 million in grants from the California Department of Food and Agriculture to lead three interconnected projects aimed at transforming California's specialty crop farming. The initiatives focus on youth engagement, sustainable waste management, and advanced agricultural technologies.

“These multidisciplinary projects are designed to address complex food system challenges by integrating diverse perspectives,” said Deborah Pagliaccia, a professional researcher in the UCR Department of Microbiology and Plant Pathology and co-principal investigator of the grants. “They aim to foster a learning environment where students and stakeholders contribute to a cohesive curriculum that bridges the gap between theoretical knowledge and practical application.”

Each of the three projects has received about $498,000 in funding and will integrate education, research, and practical application to help shape a sustainable future for global food systems.

“We are also committed to equipping and informing students with the knowledge and skills necessary for careers in agriculture,” said Georgios Vidalakis, a professor of plant pathology and director of the UCR Citrus Cloning Protection Program, who is the grants' principal investigator. “We will use a holistic teaching approach to enhance academic and professional development and prepare students to continue their education or enter the job market as effective change agents.”

The first project is titled “Seeding Success: Youth Engagement and Skill Development for Sustainable and Resilient Specialty Crop Farming in California.” Led by UCR in collaboration with UC Agriculture and Natural Resources, the Growing Hope Project, John W. North High School, and San Andreas High School, the project aims to cultivate a skilled, diverse, and adaptive workforce prepared to meet emerging climate and socio-economic challenges in California's specialty crop sector. 

A key component is the development of a new course, “Sustainable Agri-Food Systems and Circular Economy,” which is designed to educate, engage, and empower high school and UCR undergraduate students to address global food security and environmental sustainability challenges. Students will participate in workshops, labs, field visits, and internships that offer them practical experience in sustainable farming technologies such as controlled environments, insect-based farming, climate-smart agriculture, and nature-based farming.

The second project is titled “Closing the Loop: Transforming Agri-Food Waste into Sustainable Carbon-Based Soil Amendments and Fertilizers.” Researchers will address climate change, improve soil health, promote sustainability, and enhance carbon sequestration practices. Specifically, they will divert waste from landfills, reduce greenhouse gas emissions, and lower reliance on synthetic fertilizers. They will also transform agri-food waste into valuable soil amendments, research the impacts of organic waste-based soil amendments on field-grown trees and greenhouse-grown vegetables, engage underserved farmers, and create internships for UCR students.

The third project is titled “Sustainable Citrus: Unlocking the Potential of Controlled Environment Agriculture for Commercial Nursery Growers.” With the goal of translating scientific discoveries into practical solutions for commercial growers, the project will enhance controlled environment agriculture technologies for citrus nursery growers. Researchers will focus on optimizing light conditions to improve plant growth and stress resilience while also enhancing the quality of disease-free plants and improving energy and cost efficiencies. Researchers will train underserved farmers and offer internships to UCR students to give them hands-on experience in advanced agri-food systems technologies.

All three projects, which begin November 1, 2024, and end June 30, 2027, will be interconnected through their use of labtofarm.org, a platform dedicated to bridging the gap between laboratory research and practical farming applications. The platform will allow researchers to disseminate their findings, engage with a broader community, and develop sustainable methodologies that are economically viable and environmentally friendly.

“LabtoFarm.org will allow us to engage undergraduate students, underserved farmers, and various stakeholders in a meaningful exchange of knowledge and innovation,” Pagliaccia said. "The platform also serves as a hub for student internships and collaborative projects, offering valuable opportunities for professional growth, hands-on experience, and direct involvement in sustainable agri-food systems practices."

According to Vidalakis, UCR is well positioned to conduct the three projects because of its location.

“We are one of very few universities conducting agricultural research that are located in urban environments,” he said. “Ours gives us access to more young minds that we can train to become business owners, entrepreneurs, and government officials. Traditionally, large urban centers have been generators of research, development, and new technologies and ideas.”

Pagliaccia, who has extensive expertise in sustainable agri-food systems, said the idea for the three projects was conceived during her service as managing director of UCR's California Agriculture and Food Enterprise, or CAFÉ.

“In CAFÉ, we worked to empower the community to make well-considered decisions toward a sustainable and economically successful future for global agri-food systems, which is also the overall goal of our three projects,” she said.     

Pagliaccia and Vidalakis will be joined in the projects by co-principal investigators Samantha Ying, Robert Jinkerson, Sohrab Bodaghi, and Arunabha Mitra at UCR; and Jonathan Kaplan at Sacramento State University.

Iqbal Pittalwala
University of California - Riverside
iqbal@ucr.edu
Office: 951-827-6050

 

 

citrus and mountains

My Frost Protection Spray Trials

The use of foliar nutrients as frost protectants has been promoted for years. Research published by Steve Lindow at UC Berkeley explained that certain naturally occurring bacteria ,such as Pseudomonas syringae and Erwinia herbicola act as nucleating agents for ice formation. The presence of these ice-nucleation-active bacteria results in the formation of ice crystals in plant tissue at temperatures several degrees higher than in their absence. When water in plant cells freezes, it expands and ruptures the cell walls, leading to cell necrosis. The bacteria can be killed or prevented from acting as nucleating agents, thus providing several degrees of frost protection.

This discovery provided a plausible explanation for the previously observed positive effects of foliar sprays on freeze tolerance. While the mechanism can be explained, there is no general agreement on which chemicals are most effective in controlling the ice-nucleating bacteria. These products need to be applied early enough to remove the ice-nucleating bacteria, but not so early that they have a chance to return.

Several specially formulated products are commercially available, but in controlled tests these have generally not given better results than copper-based fungicides or micronutrient mixtures. Certain urea-based products, antibiotics, anti-transpirants, and surfactants have also claimed to be effective.

At issue is not only these surface-dwelling bacteria, but also the age of the tree, development of the canopy, the length degree of the freeze event, the health of the tree, nutritional and irrigation status and when the event occurs. Trees that gradually go into a quiescent stage of winter, are better able to sustain cold stress than those that are hit early on before they start shutting down for winter. Trees develop a cold-hardiness. And plant growth regulators, those both internal and external, play a roll.

I have run trials where I have seen incredible effects after using a certain type of kelp. Kelp has all kinds of ingredients, and they vary depending on what part of the ocean, what species, when it is harvested and how it is processed. When trying to reproduce the effect I had initially seen with the same kelp or other sources, I was not able to get the same effect. This was in three separate trials. It's hard to reproduce the same conditions or the right time of application. The river never runs the same.

Foliar sprays are capable of influencing frost tolerance. Copper and zinc have most consistently shown a positive effect. And the most vulnerable would be small trees that are the easiest to spray. It's a relatively inexpensive treatment and depending on the mate4rial, can be used in both conventional and organic orchards.

You can read about our four-year evaluation of materials for reducing frost damage. There were some positive results, but they are also equivocal - https://ceventura.ucanr.edu/Com_Ag/Subtropical/Publications/Frost/Foliar_Sprays_for_Frost_Protection_of_Young_Citrus_and_Avocado_-_1995_/

frost damage

Frost Terminology

A Frost Primer

Definitions:

Dry-bulb temperature:  the temperature of the air as measured with a thermometer.

Wet-bulb temperature:  the temperature that the tree will likely sense due to evaporative cooling of the leaves.

Dew point temperature:  the air temperature required for condensation (dew or frost) to occur.  This is an indication of the amount of humidity in the air.  The higher the dew point, the lower the rate of cooling.  As dew forms, the water releases heat (heat of condensation), and the temperature levels out.

A high dew point -- above 40 degrees

A moderate dew point -- between 25 - 40 degrees

A low dew point -- between 10 - 25 degrees

"Cold night":  any night at or below 32 degrees F.

"Key stations":  in the days of a weather stations with at least a max/min thermometer and a thermograph in a white box facing north.  Now with digital stations.

Temperature inversion:  an atmospheric layer in which temperature increases with altitude.  High temperatures during the day promote the formation of the inversion.

"Temperature ceiling":  height to which heated air rises during orchard heating.  The lower the ceiling, the stronger the inversion and a greater amount of heat can be obtained from wind machines and orchard heating.

Radiation freeze (frost):  local cooling due to rapid heat loss from plant and soil surfaces under clear skies and light or no wind conditions.  Daytime temperatures are usually in the 45-55 degree range which causes the formation of a nighttime inversion.  Any significant breeze will cause temperatures to rise due to mixing of the inversion.

Advective freeze:  cooling of a wide area by dry polar air.  Typically, the temperature is at or below 32 degrees for 2 or more days.  The temperature ceiling is high or non-existent.  This was what we got in the devastating freeze of December 1990.

1 gram of water = 1 calorie/degree of temperature change (¡C)
1 gram of water = 79 calories released on freezing
1 gram of water = 607 calories consumed when evaporated

Gauging Wind Speed 

Effect of air movement	Wind force (mph)	Terms used in      forecasts
Calm; smoke rises vertically	less than 1
Wind direction shown by smoke drift	1 - 3	light
Wind felt on face, leaves rustle	4 - 7
Leaves and small twigs in constant motion	8 - 12	gentle
Raises dust and loose paper; small branches move	13 - 18	moderate
Small trees in leaf begin to sway	19 - 24	fresh
Large branches in motion	25 - 31
Whole trees in motion	32 - 38	strong
Breaks twigs and weak branches	39 - 54	gale

The last major freezes in southern California were in 2007 and 2013.  The last really big one was December 1990.  Here's a fascinating history of major weather events in S. CA focusing on the San Diego area from NOAA

https://www.weather.gov/media/sgx/documents/weatherhistory.pdf

 

 Temperature Inversion Above a Fire, Smoke Flattens Out

images: Out with the Olde, in with the Knew

thermometer

inversion

Now is NOT the Time to Prune Avocados

When to Prune Avocados and Suggestions of How to Prune

In the past avocados were rarely pruned. In fact, if the trees got very big, growers would stump them down to 3-4 feet and then let them regrow. This would often be a disaster, since the trees rapidly grew to stupendous sizes again. They also might regrow then suddenly collapse, because all that regrowth was coming at the expense of energy being sent to the roots. If the roots were compromised by root rot, they would then not have the energy to fend off the disease. So, by bringing the canopy into balance with a sick root system that was continuing to die and was not being fed by a big canopy, the root death would accelerate and when the canopy and root system became imbalanced again, the whole canopy would collapse, and the tree would die.

Also, this wild regrowth was wild and hard to manage. The adage of “prune avocado trees cautiously” was heard round the avocado community and as a result many growers would not do anything. The trees growing larger and larger and larger with the fruiting canopy going higher and higher and higher and picking costs and liability going up. Tree thinning was practiced, where every other tree would be removed so that light could penetrate into the orchard, encouraging more fruit production and slowing tree growth. But they would still grow, and another thinning would be needed. The original commercial ‘Hass' orchard in Carpinteria started out in 1954 with 140 trees and 40 years later was down to 17 trees and was still productive, but they were monsters that were finally felled by root rot.

Many commercial avocados are now routinely pruned to keep the trees short, so that harvesting costs and other tree maintenance expenses are reduced. Also, more light shines into the trees, so that more fruit is borne on the lower branches. Light or minor pruning can be done any time of year to correct imbalances or limb breakages. However, major or heavy pruning should only be done in the early part of the year from January through April.  Fall or early winter pruning can open up the canopy so that it is more prone to frost damage. The closed canopy holds in the heat better.

The major reason not to prune in fall and early winter is that a perennial, evergreen subtropical like avocado goes into a quiescent stage during the fall in preparation for winter cold. The tree does not go dormant like an apple or peach but goes into a metabolic state that can better handle cold. By pruning in the fall, the tree becomes actively metabolic and more prone to frost damage. The tree needs to slow down to better handle the cold.

Avocados flower and bear fruit at stem terminals, so if you give the tree and buzz cut (heading cuts), all the flower terminals will be cut off and there will be no flowering the following year. It also leads to an explosion of water sprouts that result from bud break up and down the branch because the terminal bud which controls the buds lower down have been removed. Naphthalene acetic acid (Tre-Hold) painted on the cut end can be used to restrict some of this wild bud break.

Whenever possible, thinning cuts should be made, where the branch is removed back to a subtending branch. This results in much less wild growth. Also, when there are buds that start growing into water sprouts, they can be nipped back to force lateral growth. These laterals will then slow down the growth of the sprout and the side terminal buds will also be able to grow and transition of flower buds later.

Work in Carol Lovatt's lab at UCR has shown that terminal buds need a certain maturity to flower and the transition from a vegetative bud to a flowering bud occurs sometime in late summer/early fall. If pruning is done in July, there is not enough time for the new buds to mature by August and there will be no flowers from that branch the following spring. New vegetative buds formed on growth from spring will often have enough maturation time to make the transition to flower buds, resulting in flowering the next spring.

Any major pruning done in later spring and summer is also going to require some protection for the remaining scaffolds from sunburn. Get ready to paint the scaffold with dilute latex paint to protect the once protected bark from sunburn damage. This can pretty rapidly kill the underlying cambium within days if it heats up newly exposed wood.

Again, light pruning can be done at any time of the year, but removing terminals is removing potential fruiting wood. Therefore, if heavy pruning is needed, it is best to remove one branch at a time. To reduce the height of a tree, cut out the tallest branch one year, the next tallest branch the following year, and so on until the tree is down to the height required. The process may take three to four years. By reducing the height over several years, the tree is put under less stress, less disease is likely to occur and fruit production is not drastically reduced. Pruning the sides of the tree should be done in the same way. Prune off a side branch that most impinges on a neighboring tree one year, then the next worst offender in the second year, and over the years continue this process until there is light all around the tree.

If pruning creates major open areas in the tree to sunlight where there once was shade, the exposed branches should be painted with white latex paint diluted with water so that it can be sprayed on. It needs to be white enough that it can reflect sunlight and avoid heat damage that can cause sunburn. Sunburn can utterly destroy all the work that has been done.

If the trees are really monsters, the only real alternative is to bring the whole tree down. But not stumping, rather scaffolding where much of the structure is maintained. This is where the tree is brought down to as high a height as is convenient and safe. By cutting the tree to a height of 8 feet or so, there is not so much rank regrowth because a greater portion of the tree is retained. Also, many times there are leafy branches that remain that will flower and fruit and slow the wild regrowth. Water sprouts that form should be headed back to force lateral growth that encourages stems that will flower, which will also slow the wild regrowth.

And one last warning. Do not. Do not. Do not. Got it? Prune sick trees. If the roots are compromised, the regrowth is going to be hard on the roots. Get the trees perked up with one of the phosphite products so that they are ready to go through this process. You may have to wait a couple years to start the pruning process until the trees are in shape for the rigors.

In summary: Late winter to early spring is the sweet spot for pruning your avocado trees. This timing is key because it sidesteps the risk of cold damage and aligns with the tree's natural flowering cycle. Pruning too late can lead to sunburned branches and a reduced fruit set the following year.

 

Image:  Don't make cuts like this. Those stubs or going to create a royal mess of new, wild growth.

avocado pruning stub 1

Read more