- Author: Dustin W Blakey
I know you've seen them. Little caps on the end of vertical irrigation pipe that can be adjusted to control flow with a twist (or screwdriver). They are called flood bubblers and are used widely in the Eastern Sierra to deliver water to woody plants outside of a lawn sprinkler system.
Unfortunately, I see more tree problems caused by this type of irrigation than any other single cause of tree death in our area. Many dead or sick trees in our area have been irrigated (insufficiently) by flood bubblers.
What are bubblers for?
Bubblers have a few important uses and benefits. They are good at watering young trees during establishment since the water is concentrated near the root ball. In the right types of soil, they can also be good at watering shrub beds or large tree wells if the output can exceed the soil's infiltration rate. They flood the soil with water. When there is a berm or wall around the bed, and if you can fill it, bubblers are a fine choice.
In general, as a source of water there really is no problem with their use. They are cheap and low maintenance. The lack of spray helps to prevent water lost to evaporation while they are running.
The issue is how we use them locally over the long haul.
Bubblers are not drip systems
The purpose of a bubbler-type emitter is to deliver a high output rate of water to a concentrated area, like a single, young tree. I often see one bubbler per tree. The shape of the bubbler takes away some of the kinetic energy of the flow and allows a gentle flood that hopefully will not disturb or erode the soil.
Many bubblers here are used as a substitute for a drip emitter. This is the beginning of the problem. Bubblers are designed to deliver about 2 gallons per minute, whereas a single drip emitter is usually closer to ½ gallon per hour.
Instead of filling the root zone with water, only a small amount is delivered frequently, often several times a week in that same small spot. In practice I mostly see bubblers used to irrigate trees and shrubs outside of a lawn.
There are two issues that arise with this practice:
- Trees grow! And as they grow their water requirements and root area increase. You should be aiming to water the whole area under a tree, not just at the base. While it's possible to crank up the flow to deliver more water, this doesn't solve the problem of having an insufficient area irrigated under the tree.
- Most of the Eastern Sierra has coarse, well-drained soils. In our soils, the frequent, low-volume application of water only saturates a very small area much smaller than is needed. This constrains a tree's root system and eventually leads to chronic stress.
Drip systems are designed to deliver a predictable, slow rate amount of water from each emitter on the line. The key word is each. Drip lines usually incorporate many emitters to deliver water slowly to the root zone. A properly designed drip or microsprinkler system can irrigate the entire region that needs water.
Perhaps if additional bubblers are added to a row of trees along with more output from each bubbler, things wouldn't be too bad. This, however, is not how they are used.
What to do if you already have bubblers
It's not the end of the world if you have bubblers in your landscape, as long as you don't wait until your trees or shrubs begin to die to address the situation. The first step is to recognize that flood bubblers are not drip emitters.
The simplest solutions involve swapping the bubbler head with something different.
An easy, but perhaps less water-efficient, change you could make to your system would be to replace the bubblers with spray heads after the trees are established. Spray heads come in a variety of patterns, and some can be adjusted. These are an easy way to increase the coverage area. The will heads have the same threading as your bubblers. As long as you can deliver enough flow and pressure, this conversion works well. Of course, you'll need to alter your irrigation schedule.
Because you will now be hitting the trunks with water, which is less than ideal, adjust your system to deliver more water each irrigation, but less frequently. This will allow bark to dry.
If the line of plants is long or irregular, another approach could be to replace the bubblers with drip conversion heads. These will supply several connection points for ¼” drip line. At the ends of each you can either have drip emitters or microsprinklers. If you only have a few trees consider installing a clever set up called a T.R.I.C. (Tree ring irrigation contraption).
Either way, the idea is that you switch to covering a larger area with more water but less frequently.
Alternatively, you could open up the bubblers' nozzles to allow more output, assuming you can deliver enough flow to overcome the rapid water drainage of our soils and cover the root area. That may require installing some sort of containment. In most situations, I'm skeptical this can work.
In landscape beds and containers, especially in commercial situations, bubblers make some sense. The area to irrigate is usually small, and there is almost always some sort of impermeable “wall” around the bed that confines growth. This is likely their best use case. When there is pavement covering a substantial part of a tree's root system, such as a parking lot, this may be your only means of providing enough water.
Final thoughts
In theory, there is nothing wrong with flood bubblers when they are used as designed. Our local issues arise when we try to use them as an alternative to a real drip system in coarse, desert soils on mature trees...forever.
To determine how much water to provide trees and shrubs in the Owens Valley, there is a handy fact sheet available at this link. Your goal with tree and shrub irrigation should be to fill the root zone with water, but no more than, and replenish it when about half that water is used by the plants.
Don't assume that because of the prevalence of flood bubblers in our area that this is the best way to irrigate landscape trees. It's a useful tool for young trees and containers, but not usually enough for larger, established trees.
If you have questions about replacing your bubblers, contact the Inyo-Mono Master Gardeners at immg@ucanr.edu.
/h2>/h2>/h2>/h2>- Author: Ryan Daugherty
I was dealing with a gopher problem in a lawn awhile back and I came across another turfgrass pest that you may or may not be familiar with; a chafer beetle.
These white grubs are the immature larval form of a chafer beetle.
Here in California we deal mainly with the masked chafer (Cyclocephala spp.). Mature grubs have white or cream colored, C-shaped bodies, six legs on their upper half, and a chestnut brown head. They can be confused with the somewhat smaller black turfgrass ataenius larvae (Ataenius spretulus). To identify the difference between the two, look at the tip of the abdomen (the opposite end from the head) for the arrangement of bristles and overall anatomy, we call this the raster pattern. A chafer's raster will have a transverse anal slit with an indistinct pattern of bristles all over. An ataenius will have two distinct pad-like structures on the tip of the anal slit.
The chafer grubs feed on turf roots in early spring then stop around May to pupate with adults emerging around June to mate. Adults actually have non-functional mouthparts and so do not cause feeding damage, in fact they die of starvation shortly after laying eggs. Adults are about 3/4 inches long with golden brown bodies and they emerge during the night with a strong attraction to light. If you see adults during the summer, eggs are likely being laid in your grass. Eggs hatch around August and the grubs do most of their damage in September and October before moving deeper into the soil to overwinter until the spring.
Damage looks like drought symptoms in turf: brown, blueish, or gray spots, brittle straw colored grass, thinning stands, and footprinting. These symptoms are from the extensive root feeding of the grubs as the grass loses much of its ability to take up water. You may also see vertebrate feeding from birds or skunks that can cause further damage digging for the grubs. Spots of affected turf may be small, only being a foot or two across but may combine with other spots to form large sections of damaged turf. A hallmark of grub damage is that damaged turf can be peeled back from the soil like a carpet, due to the turf having no roots.
Insect damage in home lawns is rarer than you might think, with abiotic problems like poor irrigation, mowing, or fertility practices being a more likely culprit for a struggling lawn. If there is an insect pest make sure you correctly identify the insect before intervening with any control measures. Also remember that the presence of a pest doesn't always necessitate control. A healthy lawn can withstand damage from a few grubs and a robust lawn is always the best defense against pest damage.
Damaged turf can be helped by irrigating more frequently to keep soil moist around the lawns now shallow roots. Lawn aeration can also kill segments of grub populations. Reserve any kind of chemical intervention until you see 6 or more grubs per square foot. Several insecticides are available on the market for chafers or white grub control just look at the label. UC IPM has a page dedicated to masked chafers, but keep in mind the pesticides recommended there are for professionals.
Always read and understand the label of any pesticide you intend to use. Be careful to refrain from applying insecticides (especially broad spectrum) if there are flowering plants in and around the lawn; this includes weeds like clover or dandelions as it can harm beneficial insects like pollinators that may come into contact with them.
- 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: 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.
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