- (Focus Area) Yard & Garden
- Author: Ryan Daugherty
I recently helped one of our local student gardens install a drip irrigation system in some raised beds. During the installation, I had to explain why we were using ½” tubing for most of our system instead of ¼”. Some believed that using the smaller tubing would give us better pressure, like putting your thumb over the mouth of a garden hose. I explained why this would actually result in less pressure and worse water distribution throughout our system. This misconception is common, so I thought I'd discuss it here.
If you think there's no way I'm about to talk physics in a garden blog, prepare to be amazed!
First, a review. Friction is the force that opposes the sliding or rolling of one solid object over another. There are a few different types of friction, but the one most relevant to our irrigation lines is kinetic friction.
Kinetic friction is the force that opposes the movement of two objects in contact while in motion. Think of it like using the brakes on a bicycle: when you pull on the brake lever, the brake pads contact the wheel, and the kinetic friction between the pads and the wheel opposes the wheel's forward motion, eventually stopping the bike. As water moves through our irrigation lines, it is in contact with the inside of the tubing. The kinetic friction between the water and the tubing surface opposes the water's forward motion, resulting in a loss of pressure. In irrigation lingo, we call this "pressure loss from friction" or just "friction loss."
If you could see a cross-section of your tubing while water was running through it, you wouldn't see a solid cylinder of water. Instead, it's more turbulent, with empty space, bubbles, and vortices. If the amount of water moving through the line remains constant and we decrease our tubing diameter, that empty space shrinks, and more water comes into contact with the sides of the tubing. More surface area of the water in contact with more surface area of the tubing generates more friction, resulting in more pressure loss.
Like tapping the brakes on a bicycle, there isn't much friction generated when it's just your thumb at the end of a garden hose. The real pressure loss comes from consistent friction over distance, like holding the brakes down until the bike stops. Multiply even a small amount of friction over any real distance, and you're looking at significant pressure loss.
In response to this, drip irrigation experts developed “rules” or guidelines for drip irrigation. For ¼” tubing, we call it the 30/30 rule: no more than 30 feet in any given run of ¼” line, drawing no more than 30 gallons per hour (GPH). More than 30 feet generates too much friction loss, and hydraulically only so much water can move through any given volume of tubing, hence 30 GPH. For ½” tubing, it's the 200/200 rule, for ¾” it's 480/480, and so on. As our system grows in length and demand, our tubing diameter has to increase accordingly.
If we don't match our system to the length and demand, we risk poor distribution uniformity. We might have to overwater or underwater one part of our garden to properly water another, leading to water waste and poor plant health. For most home landscapes, 1/2" tubing works well since we seldom run more than 200 feet on a single line.
These principles are simple but powerful, and by understanding them, you can make more thoughtful decisions in the design of your drip systems to get the most out of them.
- Author: Belinda Messenger-Sikes
The emerald ash borer (EAB) may be beautiful, but it is the most destructive forest pest ever seen in North America. Hundreds of millions of ash trees across 36 states and 5 Canadian provinces have been killed by this invasive insect. Fortunately, EAB has not been found in California, but it was discovered in Oregon in 2022, the first time this insect has been detected on the West Coast.
Emerald Ash Borer Awareness Week is May 20-26th of 2024. During this week, the Don't Move Firewood campaign is offering SIX webinars over the first three days (May 20, 21, 22). Webinar topics include exciting new developments in ash tree breeding and resistance, research findings on best management strategies, and important updates on management responses to EAB. Register for any or all of these free webinars at https://www.dontmovefirewood.org/eabweek2024/.
If you think you've seen the pest or ash tree damage caused by an EAB infestation, report it to your local County Agricultural Commissioner's Office or the California Department of Food and Agriculture at https://www.cdfa.ca.gov/plant/reportapest/.
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- Author: Ryan Daugherty
It's a common frustration that anyone with a garden or landscape can relate to. I think that the temptation to apply undiluted herbicide stems from a widely held belief that the language on the label about human safety, environmental hazards, and the mixing instructions are just veiled regulatory activism designed to water down an effective product, sacrificing potency in service of some ulterior green agenda.
If you're like my friend and the conventional concerns aren't persuasive in the face of your weed woes, you may find it more persuasive (like he did) to know how declining to mix herbicides can actually make them a less effective tool in your quest for weed vengeance.
Misapplication Can Be a Waste of Your Time and Money
Herbicides can be broken up into several different categories, but two big ones are contact vs. systemic. A contact herbicide damages only the parts of the plant that it touches. Systemic herbicides translocate, meaning they move throughout the plant and poison the entire plant regardless of the point of contact.
Many well-known, home-use, brand-name weed killers sold at your garden center are systemic herbicides. When you use an excessive dose of systemic herbicide, it can damage the conductive tissue at the point of contact. This means that the material doesn't get translocated effectively and ends up working more like a contact herbicide, burning the parts of the plant it came into contact with and leaving others healthy and able to regrow. Systemics typically cost more than contact herbicides, making your cost per application higher.
Using systemics undiluted (and thus using more product) means that your cost per application is even higher than that. If you didn't mix your herbicide, you may not get the control that you need, and perhaps worse, you will have paid a premium to do it! This wastes your time and money. Don't do it to yourself. (And it's not legal and could be unsafe to you or animals.)
Microbial Breakdown
Some herbicides boast longer control for weeks or months. In the pesticide industry, this is called “residual action” or “pre-emergent action” in the weed control game: an herbicide that continues to work for a period of time after the application to ward off future weed incursions. Several things affect an herbicide's residual action, but one of the big ones is microbial breakdown.
Soil microbes are microscopic life forms like bacteria, fungi, protozoa, etc., that live in the soil. They break down all kinds of materials in the soil into their basic parts for use in their own growth and development, with different microbes being better adapted to breaking down one kind of material or another. Those materials include herbicides, which is great news because it means that herbicides don't hang around in our soils forever. However, it can be bad news when we abuse herbicides.
When we over-apply our herbicide either through dosage or application frequency, we could create a microbial imbalance in the soil. We kill some species of microbes vulnerable to the material while encouraging the population of others that are adapted to thrive on breaking down that specific material. In addition to the implications for the health of your soils, this imbalance also means that our residual herbicides are actually shorter-lived as they come into contact with a super population of soil microbes that break it down more rapidly. This is called “enhanced microbial degradation,” where pesticides are broken down more rapidly than they would be under normal conditions, even within a few hours. Like systemics, residual/pre-emergent herbicides typically come at a premium price, and your money can be wasted if your applications start becoming dinner time for a booming population of hungry microbes.
It will also mean that you won't get the longer-lasting control that you wanted and paid for, making breakout weeds and headaches more likely.
Spray Adjuvants
When you buy an herbicide, you aren't just paying for the active ingredient(s); you're also getting what they call the adjuvant package. Adjuvants are materials added to the herbicide formulation not necessarily to make the poison more poisonous, but to enhance the act of applying the herbicide itself.
If you were an herbicide manufacturer and you had a product that would work great if it didn't just bead up on the plant's surface, you would add an adjuvant to reduce the surface tension of the product. If it is too thin and runs off the plant before it can deliver the material, then there's an adjuvant for that too. Does it break down and become inert at certain soil or water pH levels? Does it gum up sprayers? Does it foam? Are the droplets too fine and prone to drift? Adjuvants have you covered. There's an adjuvant for nearly any application.
When manufacturers formulate their adjuvant packages, they do so with the assumption that you will follow the mixing instructions on the label. The adjuvants are designed to work best at the concentrations listed. Some of them are even activated by mixing them with a solvent like water or oil. If you apply the herbicide without mixing, then the active ingredient may not be delivered, or its mode of action hindered, all because you thought you knew how to use the product better than the people who designed and tested it.
Manufacturers want their products to work and to make you a satisfied customer willing to repeat your business. The label is how manufacturers communicate to their customers how to use their product for best results. When herbicides are used judiciously and responsibly, they can be powerful tools, especially when integrated with other weed management practices such as mulching, hoeing, and sensible irrigation practices. But don't skip the label!
Failure to follow label guidelines can lead to unintended consequences not just for the environment but for your busy schedule and your wallet as well.
/h3>/h3>/h3>- Author: Dustin W Blakey
Vegetable gardening is both an art and a science, and an important technique for success is crop rotation.
By rotating crops, you can improve soil health, reduce pests, and increase yields. Continuous planting of the same kind of plant in the same place every year is a recipe for creating problems.
Here are 8 rules to follow for effective vegetable garden rotations.
Rule 1: Have Light Feeders Follow Heavy Feeders
Heavy feeders, such as tomatoes and corn, consume large amounts of nutrients from the soil. Following them with light feeders, like carrots or lettuce takes advatage of this difference.
Rule 2: Include Some Soil Improvement Crops
Soil improvement crops, such as legumes, enrich the soil by fixing nitrogen. Planting crops like peas and beans can naturally enhance soil fertility, reducing the need for chemical fertilizers.
Rule 3: Rotate Plants with the Change of Seasons
Different plants thrive in different seasons. Rotating crops with the seasons ensures that your garden is always productive and that soil nutrients are used efficiently throughout the year.
Rule 4: Rotate by Plant Families
Plants within the same family often share pests and diseases. Rotating by plant families (e.g., moving from nightshades to brassicas) can break pest and disease cycles, promoting healthier plants.
Rule 5: Use Rotation to Reduce Pest Populations
Pests can quickly become a problem if the same crop is grown in the same spot year after year. Rotating crops disrupts pest life cycles, reducing their populations and minimizing damage to your garden.
Rule 6: Rotate to Deprive Weeds of Light and Space
Different crops have varying growth habits and can outcompete weeds differently. By rotating crops, you can deprive weeds of the consistent conditions they need to thrive, thereby reducing weed pressure.
Rule 7: Winter is a Good Time to Use Cover Crops
Cover crops planted in the winter protect soil from erosion and add organic matter when they are turned into the soil. They also help to suppress winter weeds and can fix nitrogen, preparing your garden for spring planting.
Rule 8: Don't Be Afraid to Change Your Rotation Plan
Flexibility is crucial in gardening. If something isn't working, don't hesitate to adjust your rotation plan. Pay attention to your garden's needs and be willing to experiment to find the best solutions for your specific conditions.
For more information
There are many resources online that cover garden rotations. There aren't too many bad ones, in fact. Perhaps my favorite is a book called Crop Rotation on Organic Farms: A Planning Manual by Mohler & Johnson. You can buy the print version, but it's also available as a free PDF file. It's nerdy and information dense. Probably overkill for the casual gardener, but if you get serious about gardening or Organic production, it's excellent.
For a simpler introduction, see this article from the Royal Horticultural Society.
/h3>/h3>/h3>/h3>/h3>/h3>/h3>/h3>/h3>- Author: Kathy Keatley Garvey
Those are some of the activities planned when the Bohart Museum of Entomology hosts an open house on managed bees and wild bees on Sunday, May 19.
The open house, free and family friendly, takes place from 1 to 4 p.m. in Room 1124 of the Academic Surge Building, 455 Crocker Lane, UC Davis campus.
It's perfect timing for "World Bee Day," observed annually on May 20.
At the Sunday open house, UC Davis graduate student Richard Martinez of the lab of apiculturist Elina Lastro Niño, associate professor of Cooperative Extension, UC Davis Department of Entomology and Nematology, will staff the honey bee booth.
Martinez, enrolled in the master's graduate studies entomology program, says that the E.L, Niño Lab booth will display an observation hive and offer honey tasting from a variety of floral sources. He will be sharing recent projects aimed at improving honey bee health via dietary supplements. He also plans to showcase beekeeping suits and hive tools.
Among others scheduled to participate (as of 4 p.m. today) are:
- the laboratory of community ecologist Rachel Vannette, associate professor and chair of the UC Davis Department of Entomology. She will participate with lab members doctoral candidate Lexie Martin, doctoral student Dino Sbardellati, and junior specialist Leta Landucci. "At the Vannette Lab booth, you will be able to look into the life of a bee--both in terms of where they live and how they develop!" said Martin. "A live bumble bee nest and solitary bee nests will be available, so you can peer inside a bee's house! Additionally, there will be live bee larvae to observe under a microscope and interactive displays on the bee life cycle."
- Bohart Museum bee scientists Thomas Zavortink and Sandy Shanks
- Doctoral student Sofía Meléndez Cartagena of the Stacey Combes lab, Department of Neurobiology, Physiology and Behavior. She will focus on local bee diversity.
- Chancellor's Fellow Santiago Ramirez, associate professor, Department of Evolution and Ecology, who studies orchid bees
- Doctoral student Peter Coggan of the Ramirez lab. He studies the neurological and genetic basis of orchid bee courtship behavior and evolution.
- UC Davis distinguished professor emerita Lynn Kimsey, who retired as director of the Bohart Museum on Feb. 1, after 34 years as director. Kimsey, known as "the wasp woman," is a past president of the International Society of Hymenopterists. She studied orchid bees in Panama for her dissertation.
The Bohart Museum houses a global collection of eight million insects, plus a live petting zoo, and a gift shop. Professor Jason Bond directs the museum as of Feb. 1, succeeding Kimsey, who served 34 years. Bond is the Evert and Marion Schlinger Endowed Chair of the Department of Entomology and Nematology, and the associate dean, UC Davis College of Agricultural and Environmental Sciences. He also serves as president-elect of the American Arachnological Society.
For more information, access the website at https://bohart.ucdavis.edu or contact bmuseum@ucdavis.edu.
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