Pedogenesis is the process of soil creation.
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!
Soil has holes it.
Sandy soil can have so many macropores and micropores that water and nutrients leach away. Heavy clay soil, at the opposite end of the spectrum, has more micropores, so water is held tightly. Loamy soil, in the middle, provides both micropores and macropores for the healthiest soil.
Evapotranspiration describes the way water moves from land up into the atmosphere through soil evaporation and transpiration by plants.
As the sun heats the Earth’s surface, the water stored in soil evaporates, rising up into the atmosphere. Sunlight also increases the surface temperatures of lakes and oceans, causing some of that water to evaporate.
Transpiration refers to the way water is lost as plants open pores, called stomata, found on the underside of leaves, and on stems and flowers. These cells open to allow for the gas exchange necessary for photosynthesis. A large, well-watered tree can lose 100 gallons of water each day in hot weather through evapotranspiration!
Hot weather increases a plant’s need for water. At the same time, higher temperatures increase evaporation of the water found in soil. The combined affect is the reason why you need to water your plants more often and more deeply in summer.
Now you know.
Alluvium 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!
Microorganisms are tiny life forms.
Bacteria, fungi, algae, protozoa, and other microscopic critters (microbes) are all microorganisms found in soil. [The jury is still out on whether viruses are alive or not - but they are considered microbes.] According to Principles and Applications of Soil Microbiology (1998), you will find this many microorganisms in one gram of soil [one-fifth the weight of an American nickel]:
• 100,000,000 - 1,000,000,000 bacteria
• 100,000 - 1,000,000 fungi
• 1,000 - 1,000,000 algae
• 1,000 - 100,000 protozoa
With those numbers, each handful of soil can contain more microorganisms than there are human beings on Earth. Try wrapping your brain around that, the next time you’re outside pulling weeds!
Most of these microorganisms have not yet been identified, or even named, but scientists at the Earth Microbiome Project, and elsewhere, are working on that. What we do know, in the world of soil microorganisms, is that there are beneficial microbes, and there are microbes that cause us grief.
The Bad Guys
Some microorganisms are disease pathogens that can damage or kill plants. There are bacteria in the soil that can cause fireblight, cankers, and soft rot. Fungi may bring powdery mildew, eutypa dieback or rust to your garden. Viruses can cause spotted tomato wilt, cucumber mosaic, and many other diseases.
The Good Guys
Other microorganisms are critical to soil health because they make nutrients available to plants through the Nitrogen Cycle. Other microbes stimulate plant defenses and reduce stress to plants. Plants also trade the carbon they create through photosynthesis for mineral nutrients mined from the soil by microbes. These networks of beneficial microorganisms can extend a surprising distance from the plant. In the case of giant redwoods, the network of microorganisms that feed the tree can be over seven miles long, in all directions!
One soil microorganism in particular, Mycobacterium vaccae, has recently been found capable of uplifting your mood! This particular microorganism is absorbed through tiny cuts and is inhaled on dust particles, as we garden. Once inside, these microorganisms cause a chemical reaction similar to the effects of prozac. Most gardeners claim that gardening is their therapy. Ends up, they were right!
Microorganisms, like other living things, can be poisoned with herbicides, pesticides, and fungicides. The truth is, we don't really understand all of the interactions between these tiny life forms. Throwing a chemical monkey wrench into what looks like a delicate balance is probably not in our best interest.
The best way to keep a healthy balance of microorganisms in your soil is to keep the soil healthy. Very often, chemicals cause too much change too quickly. Regularly adding aged compost to your soil is the best way to keep your soil healthy.
Gardens may look peaceful and calm, but there’s really a lot going on, especially at the level of atoms and molecules. Don’t let this freak you out or chase you away. It’s actually pretty amazing.
If you’ve ever taken a chemistry class, you know that atoms and molecules can be stable or unstable. Unstable atoms and molecules have the wrong number of electrons spinning around. When an atom or molecule is unstable, it is called an ion.
So what in the world does this have to do with gardening?
Simple. Soil, minerals, and plants are all made up of atoms and molecules, just like us humans. Nutrients in solution, such as liquid fertilizer, or rain or irrigation water passing through compost, have a tendency to stick to the surrounding solids. This is called adsorption.
Don’t let the word confuse you. While adsorption looks a lot like absorption, they behave very differently. Imagine yourself at a party. As you enjoy a sip of your drink (absorption), you spill some on your shoe (adsorption).
Generally speaking, soil is negatively charged. This means soil is using adsorption to grab electrons from nearby atoms and molecules of minerals. Adsorption is a good thing because it gets the nutrients closer to where the plants need them. This is especially relevant when adding amendments or fertilizer to poor soil.
(In English: it doesn't help to add it if your plants can't get to it!)
Unless you are using hydroponics, all of your plants will grow in some sort of soil. The better we understand our soil, the easier it will be for us to take good care of it (and easier is good).
Soil tends to form layers on top of bedrock. These layers of soil are called horizons. Just above the bedrock is a layer of unbroken rock. There are generally no plant roots here. This is called the regolith.
The infographic below shows the basic soil horizons:
The U.S. Department of Agriculture has an amazing interactive map that can help you learn more about your local soil.
You can grow a surprising amount of food in your own yard. Ask me how!