Every drop of rain that falls on your landscape ends up somewhere. Where that water falls and where it ends up is called a watershed. Rainwater may be absorbed by plants, sipped by local wildlife, or it may evaporate back into the atmosphere. Rainwater can also wash away valuable topsoil, carrying fertilizers and pollutants into our groundwater supplies, rivers, lakes, and oceans. In fact, the California Native Plant Society tells us that urban drool is the #1 source of ocean pollution. To prevent water waste, pollution, and runoff, a new approach to landscape design was created to protect our precious watersheds. Watershed approach to landscape design The watershed approach to landscaping uses garden design, installation, and maintenance methods that take advantage of natural processes to create spaces that are water efficient, while providing abundant plant growth, good habitat, and an enjoyable place to be. The watershed approach captures, cleans, and collects rainwater to slow, spread, and redirect its flow in ways that reduce the need for other irrigation. The benefits of using a watershed approach include:
How much rainfall do you get? Every yard is different, but your average 2700 sq. ft. roof in the Bay Area can collect more than 25,000 gallons of water each year! You can use the USGS rainfall calculator to determine how much rain water falls on your roof in any given storm, simply by entering your home’s footprint dimensions (length x width) and the amount of rainfall measured by you* or reported by your local news station. During a storm that drops one inch of rain onto a half-acre lot turns out to be nearly 14,000 gallons of water! Rain barrels, ponds, swales, and filtration tanks are all different ways you can collect rainwater.
Where does that water go?
All too often, rain water falls on buildings, roads, and concrete, where it collects pollutants and debris, and carries them to our groundwater. Our garden plants never have the opportunity to soak it up. On the other end of the spectrum, rain water either floods an area, carrying away valuable topsoil, or it gets stuck in one place, where soil, plants, and organisms begin to rot. Using the watershed approach removes those problems by studying where water comes from, where it goes, and taking actions that redirect water flow to be more efficient and environmentally sound. First flush and absorption areas First flush refers to the first 3/4 to 1 inch of rain that falls after a dry period. This rain water contains higher levels of pollutants and debris than the rain that follows. Can you filter those pollutants out or redirect this water to less vulnerable areas? After that water is dealt with, how much permeable soil is needed to absorb your expected rainfall? First, you will need to know how deeply your soil absorbs water. You can determine this by going outside after a few days of rain and digging in with your shovel. How far down did the rain actually go? This number can help you determine how big of an absorption area you will need for the expected rain. Example: You live in a 1,000 square foot house in San Jose, CA, where you receive an average of 15 inches of rain each year. Using the USGS rainfall calculator, you would discover that your house can collect 9,351 gallons of water in a year. To absorb all that water, you would need to divide the volume of water by 7.48 for a per foot absorption area. (There are 7.48 gallons of water in a one cubic foot of space.) This gives you 1250 square feet needed to absorb all that water, assuming that your soil absorbed water down to a depth of one foot. If it only went down 6 inches, the 1250 sq. ft. figure would have to be doubled. If you don’t have that much space, how can you prevent runoff? What if that’s not enough water? What are other sources of irrigation water? Be sure to check with your local municipality for laws regarding water collection (there have been countless wars started over water rights). You can collect water from your bath or shower, as it heats up, in a bucket. You may be able to redirect the outflow from your washing machine to irrigate ornamentals. Even the water left over from cooking pasta and vegetables makes useful water for the garden. How much water do you really need? There is no excuse for wastefulness when it comes to water. You might be surprised at how little water you and your garden actually need. Our household has reduced water consumption to only one-fourth of what it was three years ago and we get more production from the garden! This is possible by:
Other factors to consider when using the watershed approach:
Start using the watershed approach in your yard by asking yourself these questions:
What’s really nice about the watershed approach is that it takes advantage of natural processes that have evolved over thousands of years to work without any help on our part. Native plants and those suited to your microclimate require less care, which translates into less work, less expense, and a healthier environment. Activity: Inventory your landscape’s water needs
Every drop of water that you are able to use more efficiently protects the environment and your bank account.
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Perlite has a distinctive feel, lightweight and crispy, but what is it and how do we use it in the garden? (This one's for you, Jim!) What is perlite?
Perlite is actually a form of obsidian. Obsidian is a dark volcanic glass that forms when lava cools quickly. Obsidian is very brittle and extremely sharp. It was commonly used to make cutting and hunting tools by primitive peoples. [Back in the early 80’s, I had an archeology professor at Seattle Central Community College. He loved to tell us how, when he needed chest surgery, he found a surgeon who was willing to use obsidian tools. Being sharper than surgical scalpels, the obsidian left a scar that was practically invisible!] How perlite is made Coming out of a volcano, obsidian is less than 1% water. As it comes into contact with rain and groundwater, it starts to absorb moisture. This hydrated obsidian is mined and then baked in a 3,000°F oven where it pops like kernels of popcorn, growing to twenty times its original size! These glassy kernels look more like a froth of bubbles, but the outer bubbles are broken, leaving jagged edges. How perlite is used Perlite has many industrial uses, including insulation, mortar, plaster, and ceiling tiles. The broken glass bubbles of horticultural perlite are used to aerate soil, increasing porosity. Perlite does this by increasing the number of macropores and micropores that carry and hold air and water for plant roots. Perlite can hold 3 to 4 times its weight in water. Perlite is also used in hydroponic garden systems as a filtration medium. (Did you know that perlite is used to filter beer?) Perlite is also found in many planting mixes. You will see them as small white chunks. Sometimes these white particles are pumice, like the volcanic foot scrubbing stone you buy at the drugstore. Sometimes those white bits are styrofoam. Both perlite and pumice improve soil structure, but styrofoam does not. If you are going to use perlite to improve heavy clay soil, don’t just pour it on top. You will need to dig it in a bit, otherwise you will simply end up with a layer of perlite on top of your clay. Perlite is an excellent soil additive for roof gardens, balcony plants, and extra large planting containers, because it is so lightweight. Perlite is sterile, inert, and incombustible. Mold and mildew won’t grow on it and pests won’t eat it. Adding perlite to your soil can lighten heavy clay and it can help sandy soils retain more water and nutrients. Mulch can be anything placed on top of soil to cover and protect it. Naked soil is vulnerable to erosion, weed seeds, compaction, and water waste. Mulching provides many benefits:
So, what makes a good mulch?
A good mulch allows air and water to pass through easily, while blocking the sunlight needed by weed seeds for germination. Obviously, gravel fits that description, but do you really want to pick out all those rocks at planting time? Or, what about black plastic landscape cloth - doesn’t that do the same thing, without all the work? No, it doesn’t. Ultimately, the plastic will break down, allowing weeds easy access and adding chemicals to the soil. Instead, take advantage of natural processes and use plant-based mulches. They add nutrients and improve soil structure as they break down and they can often be found for free!
How to apply mulch Mulch should be applied 2"–6” thick, depending on particle size. Smaller pieces fit together more closely, so you don’t need as much as for larger bits. If weeds are a serious problem, or you are eliminating a lawn, it is a good idea to use a really thick layer of wood chips. Be sure to keep mulch several inches away from trunks and stems. If mulch is in constant contact, problems such as crown rot can occur. As worms, beetles, weather and microorganisms breakdown the mulch, you will need to add more mulch, usually every 3–5 years. Creating and applying compost is one of the very best things a gardener can do for their soil. Composting is the natural process by which organic materials are broken down, making them available to plants and microorganisms. It is a major component of pedogenesis, or soil creation. Without healthy soil, we begin to lose our food, water and air. Yeah, it’s kind of important. More benefits of composting include:
One of the nicest things about composting is that bacteria and fungi do most of the work for you! Other organisms, such as worms and insects, also pitch in to help. Now, it is possible to simply dump everything in a pile and wait for nature to takes its course. Eventually, there would probably be a nutrient rich soil amendment, but it might take years. Or it can turn into a stinky, rotten mess. Follow these tips for successful composting in a reasonable amount of time. Selecting a site for composting
Wire bins work well and are highly mobile. You simply move the wire away to flip the pile and pitch the material back in, watering as you go. If you look online or in your local library, there are many DIY compost bin instructions available for free and these simple structures do not require a contractor's license or skill set to build. For me, I find that simple piles work the best. I keep my regular compost pile near my chicken coop, for convenience. Occasionally, I move it to an exhausted bed for a season to supercharge it with nutrients and organic material. Understand the process: Organic matter + air + water = compost Organic matter consists of yard and kitchen waste that has been cut into 2” or smaller sized pieces. Smaller pieces compost faster because there is more surface area for decomposers to reach. Organic matter is considered either “green” or “brown”. Green matter includes cut grass, pulled weeds, kitchen scraps and manure, and it is rich in nitrogen. Brown matter is rich in carbon and includes dried leaves, straw, and shredded newspaper. The ratio of green to brown is a major factor in how long it takes a compost pile to breakdown. “Hot” piles work fastest and use a 30:1 carbon-to-nitrogen ratio, while slower piles can have a 2:1 carbon-to-nitrogen ratio. If material is continually added to a single pile, it will slow the process. A better choice is to have 2 or 3 piles, at various stages of decomposition. Meat and dairy in the compost pile? Most recommendations warn against using meat, dairy, and grease in compost piles. Other people have no problems with it. Personally, I use the majority of my kitchen “waste” to make soup stock. The solids are then fed to my chickens. Whatever they don’t eat (along with what they did eat) ends up in the compost pile, bones and all. I have had no problems and my plants seem to appreciate the calcium. Of course, my dogs do a very good job of keeping opossums, rats, and raccoons out of my yard. It's your call. One other method of decomposition that uses fermentation, rather than decomposition does allow you to add meat and bones without difficulty. This method is called bokashi. Decomposition Decomposition is an aerobic process, which means it needs air. Air helps breakdown organic matter and those tiny workers need it, too! Air enters a compost pile by turning it every few days. [Read: good exercise.] Water is needed for the same reasons as air: it aids in decomposition and it keeps microorganisms and other decomposers alive. Keep the compost as damp as a wrung out sponge and avoid simply watering the top, as this tends to cause runoff. Watering as the piles are turned works the best. If the pile gets too wet, spread it out and let it dry, or it will rot. Temperature is another composting factor. As materials break down, especially the green ones, energy is released in the form of heat. If you’ve ever watched a big pile of freshly cut grass, you know exactly what I mean. Under the right conditions, a pile of grass clippings can burst into flames! (And it stinks to high heaven). Ideally, the right conditions will generate temperatures between 122 - 131 degrees Fahrenheit. If temperatures remain above 140 for at least 10 days, weed seeds and pathogens will be killed. If temperatures stay above 160, however, decomposers will die and the process will stop. Because temperature is a factor, do not expect much out of a compost pile in winter. Material can still be added, or another pile started. In spring, the whole process will begin again. Also, if an area is especially hot or wet, cover the compost pile to maintain desirable moisture levels. Some people take composting very seriously and monitor temperature. I didn’t until I started composting the bedding from my chicken coop. Composting manure Animal bedding and manure are reasonably good sources of nitrogen and organic material, but they can make you sick. To be safe, manure must be composted for at least 45 days, 15 of which must be at temperatures between 131°F and 170°F, and turned at least 5 times. Assuming it hasn’t been recontaminated by air-dropped bird poop or other pathogens. Raw manure should never be applied to the soil while plants are growing. If it is, be sure that the manure does not touch the plants. Composted manure and bedding have significantly improved my soil health and helped to reduce compaction. Apparently, all those earthworms and burrowing beetles love the stuff! When is compost ready?
Compost is called “finished” when it is ready to use. There is simply no way to say how long finishing will take because of the factors already mentioned. Generally, speaking, under reasonably good conditions, a compost pile is ready for use within 45 to 60 days. Finished compost takes up 25-40% of the original occupied space, depending on its ingredients. Compost can be dug into beds before planting, a 2” layer can be applied over lawns as an amendment, or it can be used as mulch or top dressing. I like to add just a little compost to the bottom of potted plants before adding high quality potting soil and my plants seem to like it a lot. Composting with worms For those who do not have space for a compost pile, bin, or drum, try composting with worms! This is called vermiculture. Worm bins can compost an amazing amount of yard and kitchen scraps pretty quickly. Did you know that worms can eat their body weight in scraps every single day? Learn how to build worm bins and compost with worms at the UC Agriculture and Natural Resources page about worms. Remember, composting is easy and it provides a powerful boost to the garden. Start composting today! Recent heavy rains have brought much needed water to the drought stricken San Jose, California, but one of my fruit trees was not happy about it. Take a look at the photo below to see how water pooled around the tree. The drainage around trees with irrigation rings was fine. I can only assume that it was the cement curb around the tree that was at least partially to blame for flooding my poor little nectarine tree. At the same time, the drainage pattern was so significantly different, that I will have to explore other possible causes and remedy them. Rainwater generally moves down, due to gravity, and sideways, toward drier areas. The curb prevents that sideways movement. All that standing water can lead to crown rot, root rot, and many other fungal diseases.
What is porosity? Porosity, or permeability, in the garden refers to the ability of air and water to move through tiny pockets in the soil. These tiny spaces are called macropores and micropores, depending on their size. Soil that is rich in organic material tends to have a variety of macropores and micropores that improve its porosity. Porous soil allows roots to reach out freely to find water and nutrients. In my yard, we tend to have heavy clay soil that is made up of very tiny particles that leave few spaces in between. Porosity is measured as a percentage of spaces compared to the soil around them. What happens when it rains? When rain starts to fall, or the sprinklers kick in, the soil is initially hydrophobic, causing runoff and urban drool. This is because the water is repelled, the same way a dry sponge allows water to run off the top, rather than being absorbed. Now, we all know that sponges are very porous. They have lots of holes that can hold water. That’s why we use them! Once the soil becomes damp, like a sponge, it can then hold a surprising amount of water. When all the pores are full, gravity then pulls the water downward into groundwater, where it is taken to creeks, lakes and oceans. That’s why it is so important to not overuse fertilizers, pesticides, fungicides or herbicides. All those chemicals leach into our water supply! Porosity and plant health As plants become saturated with water, tiny pores, called stoma, open wide and the plant starts panting in a process called evapotranspiration. Just as we can see steam when we breathe on chilly days, plants exhale moisture along with other gases. When there is no water to be found, and the plant risks the other side of water stress, the stoma close, to hang on to every bit of moisture possible. When the ground gets muddy, whether from too much rain or over-watering, roots cannot breathe and the plant can drown. In the case of my nectarine, I used plastic tubing to redirect the standing water away from the tree. That’s not something I want to do every time it rains, so I will use these methods to improve the porosity around the nectarine tree:
If you see standing water after a heavy rain, these tips can help you improve the porosity of your soil and the health of your plants. UPDATE (1/10/2017) After heavy rains, I was very happy to see that the soil around my nectarine tree is draining very nicely. It really is amazing how effective just a little mulch, compost, and cover crop treatment can change an area for the better! We may not need Noah just yet, but many areas are prone to winter and spring flooding. Years with El Nino events can bring severe rain and flash floods, wreaking havoc with homes, drainage, and the garden. After making sure that your family and home are safe, it is important to protect your landscape and garden from the negative effects of flooding. Rain and soil Too much rain at one time can cause mountain creeks and streams to overrun their boundaries, carrying debris, mud, and even more water crashing down into already soggy bottom lands. Soil is an amazing structure, but the bedrock that holds it in place also creates a water barrier that can lead to pooling, flooding and more mud than your landscape can handle. As we have discussed earlier, permeability refers to the ability of water to drain. Our heavy clay soil does not drain well, which makes it great at holding on to water during the dry months, but creates significant problems when rainfall rates overrun carrying capacity. Flooding and standing water can drown your plants. Roots need air space to breath and to conduct photosynthesis. Standing water and poor drainage also encourages the development of fungal infestations, mosquito breeding grounds, and disease-carrying pests such as fungus gnats. Just as over-watering causes leaching of nutrients, salts, and chemicals, flooding can wash away valuable topsoil and pollute local groundwater. When you notice standing water in your garden, it is time to take action.
Floods can be devastating, but you can reduce the negative impact with these simple steps. Keep yourself and your garden healthy and safe!
No, I’m not talking about Medieval medical practices!
Clay soil holds far more water than sandy soils, but every soil has a holding capacity. Once that limit is reached, gravity will pull the water downward into underground waterways where it will ultimately flow to lakes and oceans. As it flows away, the water carries nitrogen, salts, fertilizer, pesticides, fungicides and whatever else was in your soil with it - leading to a potentially dangerous chemical soup that can wreak environmental havoc. Leaching also moves valuable nutrients out of reach from your plants roots.
To avoid leaching, it is always a good idea to water only as much as is needed. You can see for yourself where your irrigation water is going simply by inserting a moisture meter next to the plants you intended to water (but not too close). Many people are surprised to discover that the water intended for their tomato plants actually went in another direction due to hardpan, sandy pockets, or poor soil structure. Improving soil structure with compost can improve drainage and help prevent leaching. If it has holes in it, water will find a way through it. This is true for your tent, your roof, and your garden. In fact, permeability is pretty much the name of the game when it comes to plants and soil.
The rate at which water flows through something else is called permeability. If you’ve ever tried buying a home, you were probably required to pay someone to conduct a perc test. Real estate percolation tests are done to make sure that your house won’t wash away when it rains and that your septic system won’t back up into the living room. A percolation test In the garden can help plants get the water and nutrients they need without drowning. Before we learn how to conduct a perf test, let’s find out why it’s important. Water in the soil In the garden, water and air flow in and out of soil, leaves, and even individual plant cells. For a plant, this is the Stuff of Life. The water and air that flow in and out of a plant’s cell walls carry sugars, minerals, oxygen, carbon dioxide, hormones, waste products, and chemicals that allow your plants to thrive or die. [If you’ve ever battled poison ivy or poison oak on your property, you can use a leaf spray that gets absorbed through the stoma (sort of like pores) and carried down to the roots through the phloem. The chemical kills the plant at the roots. This only happens because of the permeability of the leaves.] Now, too much of a good thing is a bad thing. Without adequate permeability, your plants will drown, suffocate, dehydrate, or starve. Not good. Healthy soil is made up of different size bits of sand, loam and clay. The spaces between these bits are called macropores and micropores, depending on their size. Air and nutrient-rich water pass through these spaces, feeding and nurturing your plants. If the spaces are too small (or absent), plant roots cannot get to the food and air they need to live. So, how can you, as a gardener, improve the permeability of your soil? • avoid overwatering • aerate compacted soil • apply mulch and compost • avoid walking on wet soil Signs of permeability problems: • mud • standing water • hydrophobic soil • chlorosis (loss of green color) How to conduct a percolation test for soil permeability:
Ideally, you will want the water to drain at a rate of one or two inches per hour. Of course, sandy soil will drain much faster, taking valuable nutrients with it. You can improve the holding capacity of sandy soils by adding aged manure or compost. If your soil contains more clay, like mine does, you can improve permeability by adding… you guessed it - aged manure or compost! Compost and aged manure add organic material to the soil, creating a wider variety of sizes of both soil and spaces. This variety allows for healthier growth and drainage. Paved areas can lead to drainage and permeability problems. Permeable paving materials solve this problem by creating a firm surface for walking and parking while still allowing water to seep through. Permeable paving materials are affordable and attractive. They can also eliminate weeds growing up between paving stones! Do your garden a favor by learning about permeability and composting! Mud pies may have been a blast in childhood, but your garden will appreciate it if you play elsewhere when the soil is wet. Soil, silt and clay, mixed with water, creates a slick, slimy ooze that has been used to make adobe bricks, functional pottery, facial masks and exterior stucco. Mud also provides a nutrient-rich habitat to snails, clams and frogs. When your garden soil is muddy, however, it is time for patience. Muddy soil is easily compacted, making life difficult for young (and not so young) plant roots. Too much of a good thing All plants need water, but heavy rains and flooding are another story. As soil becomes saturated with water, oxygen is forced out of the ground. Plants need oxygen to survive. Even after the soil dries out, some plants may be stunted and production may be lower. If the soil stays too wet for too long, plants can die. Extended periods of wetness can actually drown the soil, creating a black, stinky mess.
Unless you live in Florida, where sand is predominant, walking on muddy soil can crush those pockets, reducing drainage. Walking on muddy ground can also damage delicate plant roots. Compacted soil requires aeration. Once compaction occurs, you must wait until the soil dries out before repairing that damage.
Mud over time If there are places in your yard or garden that do not drain well, you can dig a shallow trench or install a rain garden nearby. In both cases, water is redirected away from plants. Then, try to determine the cause of your drainage problem. Is a slope causing water to converge on an area? Is more organic material needed? Is there a leaky pipe or sprinkler nearby? It may even be an overflowing septic system. In that case, your family's health could be at risk. Reduce potential mud problems In addition to creating a rain garden or swale, and eliminating water leaks, there are several other ways that gardeners can reduce the potential for problems caused by mud and poor drainage. Continue incorporating aged compost and other organic matter, once the soil is dry. Install moisture-loving trees, shrubs, and other plants in low areas. With all that moisture, slugs and snails will be out in force, carrying diseases and feeding, so putting in some extra time hand-picking these pests can keep plants healthier. Rather than damaging your soil and your plants' roots, take advantage of muddy days and do something else: sharpen your tools, clean planter pots, or, my favorite, peruse seed catalogs! Late autumn and early winter often leave gardens looking bare and unsightly. One way to improve both the appearance and the health of your garden is to use winter cover crops. Cover crops can provide a living barrier against the elements, or they can be grown as a green manure, to be cut back before they flower. Cover crops reduce erosion, suppress weeds, and improve soil health. Even before summer crops are harvested and the last, struggling tomato plant has succumbed to frost, you can plant your cover crops. Any rains that come will help speed their growth.
Grass family cover crops Cereal grains, such as rye, wheat, and barley, can also be grown as cover crops. As an added bonus, they help break up compacted soil as their roots grow deeper than your shovel or rototiller will ever go. Then, before they go to seed, these plants are cut off and left to lay where they fall, or where they are needed. Inexpensive and easy to grow, cover crops are a simple investment in your garden’s long term health. They look nice, too! If you want something that's even easier, simply cover your soil with a mulch of wood chips.
Good drainage is crucial to plants, both containerized or in the ground, to avoid things like root rot, fungus gnats and, well, drowning. So, how do you know if you have a drainage problem?
If you see pooling, puddling, or muddy spots, you may have a drainage problem. Water will either be held in the soil or it will go someplace else. Now, soil is pretty amazing. Picture the spaces between grains of sand. Water passes through those spaces easily. Loamy soil has medium-sized spaces that slow water movement a bit. Clay soil is made of really tiny bits that create lots and lots of tiny pockets for water to hang out in. If you have mostly clay soil, poor drainage can be a real threat to plant health. How can you correct a drainage problem? Adding organic material to your soil is the best way to improve drainage. Period. It doesn’t matter what type of soil you have. Adding compost improves soil structure, increases the level and variety of nutrients available to plant roots and, hey, it reduces the amount of stuff in landfills! As long as it isn’t diseased, you can compost just about any plant material and use it to improve your soil’s health and drainage. By adding compost to sandy soil, you provide smaller bits of stuff that help hold water and nutrients in place. Loamy soil is already rock star material, but adding compost just makes it even better. When you add compost to clay soil, you create bigger pockets that allow air and water to move more freely, keeping the soil and your plants healthier. Really big drainage problems can be resolved with swales, ditches, or French drains. Quite simply, you dig a trench that gets progressively deeper as you move away from the problem area. Gravity and surface tension pull the water away and deposit it in areas better able to handle that much water. Rain gardens are another option. One thing to keep in mind when considering drainage is what is in the water that is draining away. When water drains out of or away from your yard or garden, it’s not going out alone. Every drop of that water contains precious nutrients and microbes. When people use fertilizers, pesticides, herbicides or fungicides, those chemicals are also leached away. This nutrient soup is usually dumped into nearby creeks, rivers, lakes or oceans, disrupting the natural cycles of growth that take eons to evolve (and repair). Just sayin’… The first time I saw a lawn that had been aerated, I couldn’t help wondering how or why so many dogs had pooped on that particular yard. Of course, what I had seen was the hundreds of plugs of soil that had been pulled from the ground. So why is aeration a good thing? Aeration is a good way to reduce soil compaction. In compacted soil, the particles are too close together to allow water, air, nutrients, or roots to move through the soil. Here in San Jose, California, we have a lot of clay, which is prone to compaction.
Professional aeration removes hundreds of small plugs of soil and deposits them on the lawn surface. The plugs are generally 1/4-1/2” in diameter and 3-4” long. Ideally, a plug is taken every 6”, but this can be a bit much when doing the job by hand. Aeration machines are heavy, so the benefit is a mixed bag. Personally, I use my soil sampling tube, but that’s a very slow process. You should not use a screwdriver or aeration shoes as these simply poke a hole by compacting the surrounding soil even more. There are hand aerifiers that will make the job go much faster than my soil sampler but without the compaction of heavy machinery. Over time, these plugs break down into healthier soil. The holes also provide access for water and air to nearby roots. When you aerate your soil, it is best done a few days after watering, so that the soil is easier to work. Spring is the best time to aerate your soil. Summer is not a good time to aerate because the soil can dry out too much and damage root systems. Soil pH can make or break your plants' ability to absorb nutrients and thrive. What is pH? Everything is existence is either acidic, alkaline, or somewhere in the middle. The pH scale is a simplified version of an algorithmic equation that measures the number of hydrogen ions in a specific quantity of a material in solution. The scale ranges from 0 to 14, with lower numbers indicating acidity and higher numbers indicating alkalinity. In the middle; 7.0 indicates neutral. Testing soil pH Soil pH can be tested with an over-the-counter product found at all garden supply stores. Testing the soil will tell you if your soil is neutral (7.0), alkaline (greater than 7.0) or acidic (less than 7.0). While over-the-counter pH tests are accurate enough, other soil tests available from retail outlets are not. To get your soil tested, and I urge you to do so, use a local, reputable soil test lab. Nutrient availability and soil pH Plants grow best when they have access to all of the nutrients they use to grow and reproduce. At certain pH levels, some nutrients become unavailable. At the same time, soil microbes, which help plants absorb nutrients, are also restricted by certain pH extremes. Also, some plants, such as blueberries, prefer more acidic soil. Using the chart below, you can see that more nutrients are available, and there is greater microbe activity, when soil pH is between 6.0 and 6.5. Most plants can survive in soil pH from 5.2 to 7.8, but the narrower range allows plants to thrive. Altering soil pH
Soil pH is, for the most part, a function of your local bedrock material. This isn’t going to change any time soon. What you can do is integrate certain practices in to your normal gardening routine that will temporarily alter soil pH. East of the Rocky Mountains, soil tends to be more acidic; west of the Rockies, soil is more alkaline. Traditionally, acidic soil is treated with lime, to bring is closer to a neutral pH. If your soil pH is too high, you can acidify your soil with sulfur. Some people claim that adding peat moss or pine needles to the soil can increase its acidity, but research has not shown this to be true. Unfortunately, altering pH takes time and repetition to see any results. Also, it is more difficult to alter the pH of clay soils. Once you begin treating your soil, it is important to continue monitoring pH levels. In the long run, a soil pH of 6.0 to 7.0 will help your plants become healthier and more productive. No, hydrophobic does not refer to an unreasonable fear of water. Instead, hydrophobic describes the point where soil becomes so dry that it actually repels water (read: bad for your plants). Much like a dried out sponge, when water is applied to overly dry soil, it simply rolls off and is lost. If your potted plants become hydrophobic, simply pouring water on them is not enough. Instead, you can revive your plants and thoroughly hydrate the soil by forcibly submerging the pot in a bucket of water until the pot no longer floats. Until the soil is saturated with water, the air pockets in the soil will make the pot float. It's pretty cool, watching all the air bubbles percolate up from your submerged pot!
Another method of rehydrating hydrophobic soil is to place the pot in a large container and pour water over the top. The water will run out of the soil but, over time, the water will eventually be absorbed. Larger planting areas can be relieved of their hydrophobic tendency with light sprinklings of water, followed by moderate watering. Just as a slightly damp sponge will hold on to the water it touches, so will your garden soil. (This one's for you, Sabrina!)
Sheet mulching is touted as one of the easiest ways to reduce weeds in your yard or to get rid of a water-hungry lawn and replace it with something more drought-tolerant. (Solarization is a more extreme method that can rid an area of many fungal diseases, as well as weeds.) To sheet mulch an area, trim any current plant growth to the lowest possible height, water the area (to provide for soil microbes) and then cover the area completely with a 4" layer of wood chips. We used to urge people to cover the area with layers of newspaper or cardboard, but then we learned that those materials attract voles and termites. Those layers also interfere with evaporation, percolation, and gas exchanges. Your local tree trimmer will be happy top give you a truckload of fresh wood chips, perfect for blocking weeds and protecting your soil. For free. Vermiculite is a brownish silicate mineral commonly used to help create air spaces in soil, which improves drainage and nutrient movement. Seed starting
A layer of vermiculite is often placed over newly planted seeds, in pots. This helps retain moisture, which improves germination without encouraging fungal diseases, such as damping off disease. Soilless growing medium Vermiculite is also a component of soilless growing medium. Combined with materials such as peat or composted bark, this mixture provides a very light medium, filled with water, air, and nutrients, making it easy for new roots to become established. Root and bulb storage If you store root crops or bulbs over the winter, keeping them in a bed of vermiculite can stabilize moisture levels, preventing rot. Soil conditioner Because it is so light, vermiculite can be mixed with heavy clay to create more macropores and micropores. This improves soil structure, making it easier for roots to move through the soil. With all of those good characteristics, you would expect more people to use vermiculite, right? Unfortunately, until 1990, many sources of vermiculite contained asbestos. Pure vermiculite does not contain asbestos, but there is no way to be 100% sure that the vermiculite in the bag at the garden center hasn’t absorbed asbestos or some other harmful chemical. Using it in small doses is probably fine. I prefer renewable resources, such as aged compost, which I know is healthy for everyone involved. Pedogenesis is the process of soil creation. People used to think that dirt was just made up of rocks. Now we know that soil is far more than that. Healthy soil is 25% water, 25% air, 45% minerals and 5% organic matter. Of the organic matter, 10% is plant roots, 10% is microorganisms that make nutrients available to the roots, and 80% is decomposing plant and animal material.
Twenty years ago, there were over 20,000 different types of soil arrangements (called "soil series"), with specific characteristics and symbiotic relationships that evolved over thousands of years. These soil series can be destroyed in a matter of seconds with a bulldozer. There are currently over 3,000 extinct soil series in the USA alone. Pedogenesis creates healthy soil that provides us with clean air, water, food and more, so start composting and mulching! Macropores and micropores are the spaces found between particles of soil, much like the holes seen in a sponge. Like a sponge, those holes can hang onto water, or they can be filled with air. They also provide habitat for important soil microorganisms.
Moving through space
Macropores and micropores are critical to the movement of air, water, and roots through the soil. While both micropores and macropores can hold air and water, their sizes play different roles in plant and soil health. Being larger, and normally found between soil aggregates, macropores allow water to drain away through gravity and are often filled with air and soil microorganisms. Because of this, macropores determine a soil’s aeration and porosity. Insufficient macropores can mean compacted soil and drainage problems. Micropores, often found between and within soil aggregates, are so small that surface tension holds water in place. Instead of draining away, water moves through micropores only when suction is created by thirsty roots. This determines a soil’s water holding capacity. If you want to get really picky, there are also mesopores, ultramicropores, and cryptopores. Cryptopores are so small (<0.1 μm), most organisms cannot enter, preventing decomposition, and water is held too tightly for plants to use. Ultramicropores are 0.1-30 μm and tend to be populated by microorganisms. And mesospores are larger than macropores at 30 μm–75 μm. Mesospores are filled with easily accessible water at field capacity, providing plants with plenty of water. [Field capacity is the amount of water found in soil after the excess has drained away.] Most of us, however, don’t need to go into that much detail, so we will stick with macropores and micropores. Too many, or not enough? Sandy soil can have so many macropores and micropores that water and nutrients simply leach away. Heavy clay soil, at the opposite end of the spectrum, has more micropores, so water and nutrients are held tightly. Loamy soil, in the middle, provides a healthy balance of micropores and macropores within the soil structure. One common mistake people make, when trying to improve the structure of clay soil is to incorporate sand. It sounds right, but it’s not. The tiny clay particles fill the spaces between sand particles, creating an even denser soil, frequently referred to as concrete. To improve soil structure, the best methods are to regularly incorporate organic matter and to apply 3 to 4 inches of coarse wood chips as mulch to unplanted areas. The wood chips will, over 2 or 3 years, break down, adding organic material that helps create a range of aggregate sizes, with plenty of macropores and micropores. Thank you, Moshe and Robyn! I owe you both a pack of seeds! Alluvial soil is a deposit of clay, silt, sand, and gravel left by flowing streams in a river valley or delta, typically producing fertile soil. This is some of the most fertile soil on earth. In fact, over 12,000 years ago, our agricultural beginnings nearly all started around creeks and rivers. (Carrying water is hard work).
Rain, snow, and flowing water erode rocks, carrying minerals downhill, where they collect in lowlands with regular supplies of water. Nutrient rich alluvial soil plus readily available water and you have it - a garden! Vermiculture refers to the care and feeding of worms. Vermicomposting refers to raising worms to generate valuable worm castings by feeding them compostable materials. Worms are amazing at breaking plant and animal materials into the best compost available while improving soil structure. While worms prefer temperatures between 60 and 80°F, they can tolerate 40 to 90°F. Anything hotter or colder than that and the worms may be harmed and feeding is slowed. Raised in artificial beds, worms provide high quality fertilizer by eating the equivalent of their bodyweight in yard and kitchen waste each day. Properly maintained worm beds do not have a smell. According to the EPA, 20-30% of the material currently found in landfills could be used more productively as compost and worm food. You can put worms to work for you, even in an apartment, using these simple steps:
You can raise worms under your kitchen sink, in the garage, outside, or pretty much any place you want, as long as the temperatures are reasonable. The nice thing about raising worms is, even if you totally fail the first time around, you still have valuable compost for your plants! |
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