SOIL AMENDMENTS
Compost, Manure, Mycorrhizae, Rock Dust
For Healthy Vegetable + Plant Growth
Article by The Urban Farm Colorado
Keeping your soil healthy and fertile is the most important thing for the success of your garden.
Healthy soil means better yields, lower pests and diseases, and more nutrient-dense vegetables (The Point of Having a Garden!)
While amending soil is a complicated, misunderstood, and often controversial topic among gardeners, there are three simple things to know:
The best time to amend your soil is in the fall. The winter gives time for soil microbial life to break down organic matter and digest other minerals, making them available to the plants. If you didn’t amend in the fall, still do it in the spring.
Get a soil test. A professional soil test will cost about $30, and can save you hundreds of dollars in the long run. It’s always useful—and interesting—to know what exactly is in your soil.
Adding compost or manure is a healthy amendment, but be aware it isn’t always the best amendment option for organic raised bed gardens. Compost beautifully represents how a closed-loop system can work – with dead organic matter decomposing and turning into loose rich fertility for plants. However, large amounts of compost can increase salinity (specifically sodium) and potassium to unhealthy levels. If you’re going to use compost, consider making it in your backyard or do your research to find a high quality compost to purchase that is low in sodium. We recommend only adding about 1-2″ of compost to your garden each year, not more. If you are using manure in your garden, make sure it is well aged, or till a light amount into your garden in the fall to allow it all winter to age and break down.
A good across-the-board amendment, if you haven’t gotten a soil test, is:
Mineral rock dust (Contains many of the 60 minerals necessary for healthy plants)
A Slow-Release High-Nitrogen (NPK) Organic Fertilizer (Nitrogen is the fastest nutrient to leach out of raised beds, add in the spring before planting)
Humate fertilizer (Acts as an organic binding agent and microbial stimulator)
Mycorrhizae and other bacteria inoculants (Fungi and bacteria drive the entire soil-plant system. These should be added in the spring before planting.)
If you are using existing topsoil that hasn’t been amended with compost in the past, then you can probably go a little heavier than the 1-2″ recommendation that we have for raised bed gardens.
Amending Clayey Soils
If you have very clayey soil, the best option is to plant a cover crop in the fall, and till it into your soil in the spring. Or, mix a large quantity of leaves into your garden in the fall. Finally, adding peat or coco coir is a good way to break up the clay.
Creating Your Own Compost
Article by Denver Botanical Gardens
As most Colorado gardeners know, the first step to growing strong and healthy vegetables is to have good soil; and the first step to having healthy soil is to add organic matter by way of compost. While there are many sources for purchasing finished compost, creating your own compost is often a more rewarding alternative that will allow you to divert plant material from the waste stream (compostable materials comprise a staggering one-fifth of all waste in landfills in the United States) and will improve your overall soil quality.
An active compost pile is a 2:3 mixture of inputs high in nitrogen to inputs high in carbon. The nitrogen inputs, or “greens”, are things like non-dairy/meat food scraps, coffee grounds, weeds and trimmings from your vegetable or perennial plants, and pet/human hair. The carbon inputs, or “browns,” are things like newspapers, straw, dried leaves, branches, and egg cartons. By maintaining the 2:3 ratio, chopping items into small pieces when adding to the pile, monitoring your pile for appropriate size and moisture content, and occasionally turning the pile, your scraps will be transformed into finished compost in as little as six weeks.
When the compost is finished, the pile will be about half the original size. Finished compost can be tilled directly into new garden beds or it can be used as a top dressing throughout the season. In addition to improving soil tilth (the ability to promote plant growth), compost also serves as a fertilizer and can provide nutrients to outdoor gardens and indoor potted plants alike.
Fertilizing With Alpaca Manure
Alpaca farms have become big business in the U.S., which means an abundance of alpaca manure. Alpaca manure has some definite advantages in the garden over cow or horse manure, but you should still follow general safety guidelines for fertilizing with it. When used carefully, it can improve soil fertility and drainage.
Benefits
Alpacas are ruminant animals with three stomachs for efficient digestion. Because of this, alpaca manure is lower in organic matter than manure from cows or horses, so it's less likely to burn plants. Aged alpaca manure is light, dry and odor-free. The small pellets are easy to spread. If you've got a neighbor with alpacas, you can probably get manure for free or at little cost. You'll also have the satisfaction of knowing you're using a natural, renewable resource while maintaining organic gardening practices.
Drawbacks
The main drawback to using alpaca manure -- or any manure, for that matter -- is its low nutrient profile. Alpaca manure has a nutrient profile of 1.5-0.2-1.1, which is considerably lower than the nutrient profile of synthetic fertilizers. You'll need at least 10 times the amount of manure as you would synthetic fertilizers to provide the same nutritional benefits. Although alpaca manure is occasionally available at garden centers, in most cases, you'll need to dig and haul it yourself from an alpaca farm.
Safety
In theory, raw alpaca manure is safe to place on the soil because it contains little decomposing organic matter that can potentially burn plants. However, raw alpaca manure, like any other manure, may contain pathogens such as listeria or salmonella that can cause foodborne illness when you apply the manure to food crops. Use alpaca manure that's been properly composted at a temperature of 140 degrees Fahrenheit for several weeks. If you use fresh or aged alpaca manure, apply it to leafy crops and root crops at least 120 days before harvest. Apply it at least 90 days in advance of harvesting crops that don't make soil contact, such as staked or caged tomatoes (Lycopersicon esculentum).
The Dirt On Mycorrhizae
Myco-what? Pronounced my-coh-RYE-zay, scientists and gardeners both have been learning more in recent years about this fungus and how it benefits the garden and ecosystem. But just what is it, and why do your plants need it?
Tiny plant helpers
Mycorrhizae, meaning “fungus-root,” are a kind of fungus that live symbiotically with plant roots. Approximately 95% of the world’s plant species are able to form symbiotic relationships with mycorrhizae. A notable exception is vegetables in the Brassica family, such as cabbage, broccoli and radish, which do not form any mycorrhizal relationships. While few plants require mycorrhizae to survive, those that can grow with the help of this fungus are bigger, stronger and healthier than they would be without mycorrhizae. Mycorrhizae help plants in many different ways. Their primary benefit is in plant nutrition. Mycorrhizae help both by increasing nutrient availability in the soil and by directly depositing nutrients in or near plant root cells. In legumes, nitrogen-fixing bacteria work in concert with mycorrhizae to function at peak efficiency. Mycorrhizae also improve soil structure, locate good soil for the roots to spread, take up nutrients from the soil and carry them to the roots, and inhibit other soil microbes.
Endo or Ecto?
There are two kinds of mycorrhizae: endomycorrhizae and ectomycorrhizae. Both live partially within the roots of their host plants, and also spread away from the plant roots into the soil. Endo (meaning “in”) mycorrhizae penetrate into the cells of the roots of plants with which it forms relationships. These mycorrhizae deliver nutrients directly into the plant cells. A wide range of plants can live symbiotically with endomycorrhizae including most vegetables, grasses, flowers, shrubs and fruit trees. Ecto (“out”) mycorrhizae live in between the cells of roots forming a “net” through the root, and also coat the outside of the root. These mycorrhizae deliver nutrients to the outside of plant cells with which they are in direct contact, but the plant must absorb the nutrients into the cells itself. Ectomycorrhizae form relationships with only a few kinds of trees including oaks and conifers.
Improving your soil with fungi!
There are many species of mycorrhizae, which typically can form relationships with multiple species of trees, flowers and garden veggies. Scientists have even discovered that one mycorrhizal fungus can simultaneously inhabit the roots of two or more different species of plants, and this connection is so strong that the health of one plant directly affects the other. Mycorrhizae is present in most soils, and it can be encouraged to grow and flourish by caring for your soil with mulching, cover cropping, adding organic matter, and by not making rapid changes to the soil nutrient levels or pH. Low or no-till farming and gardening is better for mycorrhizae than conventional tillage. To add more mycorrhizae to your soil, you can inoculate your garden with Chappy’s Root Booster or Granular Root Growth Enhancer, or select potting soils or fertilizers with this ingredient. Some mycorrhizae also produce edible “fruiting bodies”: growing your own morel mushrooms is a delicious way to help your garden at the same time! Check out the book Mycelium Running by Paul Stamets for in depth and practical information on these and other fungi.
Rock Dust Adds Essential Trace Minerals
As your garden grows year after year, the minerals that are native to your soil are used up and need to be replenished. Rock dusts are a natural, easy to use soil amendment for this! Using rock dust in your garden is a great way to add trace minerals and micronutrients to your soil. Rock dust is also sometimes called rock flour, rock minerals, rock powder, stone dust, soil remineralizer, and mineral fines. It can be made of any kind of mined rock that is ground to a powder.
What Does Rock Dust Add to My Soil
Adds trace minerals and micronutrients
Increases the Cation Exchange Capacity, or CEC, of your soil.
Feeds the beneficial microbes that live in your soil.
Not All Rock Dusts Are Alike–How to Choose Which One to Use
All rock dusts provide minerals for your soil, but different rocks are made up of different minerals. Getting a complete soil analysis done on your soil can help you determine which type of rock dust is best for your needs. Rock dusts cannot burn your plants’ roots, so there is no risk of over application. However, applying more than the label’s directions indicate will not provide any additional benefit to your soil or plants. The minerals it provides are only needed in small amounts, and there is a natural limit on how much can be utilized at once and how fast it can be used up.
There are three primary sources for rock dust: Glacial Rock Dust, Basalt Rock Dust, and Azomite. Let’s take a closer look at what their differences are.
Glacial Rock Dust
Glacial Rock Dust as the name says, is made from rocks deposited by glacial action. When glaciers move across the landscape, they pick up rocks and carry them for tens or even hundreds of miles. Glaciers that spill out from a mountain range onto a large flat area are called piedmont glaciers; when they melt they leave behind a moraine, which is basically a field of rocks that the glacier had carried along. This mixed pile of rocks is where glacial rock dust comes from.
Made of a wide variety of rocks, it contains a complex blend of minerals.
It is particularly good for adding calcium, iron, magnesium, and potassium.
It also contains some manganese, cobalt, silicon, and small amounts of other minerals as well.
Top dress it in your garden, potted plants, or raised beds.
Use 2 1/2 lbs per 100 square feet of garden, or 1 Tbsp per gallon of soil or potting mix.
Sprinkle around the plants and gently rake it into the surface. Reapply as needed, or up to once a month.
Basalt Rock Dust
Basalt Rock Dust is made of the volcanic rock called basalt. It is actually a byproduct of mining basalt for other purposes, such as landscaping decorative rocks, construction, and industrial uses. When the rocks are crushed to the size needed for those purposes, some of it is rendered into powder in the process. This is collected and sold as rock dust for gardening. Because of this, of the three main types rock dusts, basalt can be considered the most environmentally friendly. Some gardeners prefer basalt over glacial rock or azomite because of the risk of heavy metal contamination in those other products. Although our Azomite and Glacial Rock Dust have been tested and are safe to use, this may be a factor in your decision of which rock dust to choose.
Basalt rock dust contains a more limited variety of minerals than the others.
Excellent source for calcium, magnesium, iron, manganese, silicon, cobalt, zinc, boron, and aluminum.
Top dress 10 lbs per 100 square feet of garden before planting, and another 5 lbs mid-season.
For potted plants, mix in 1 cup per cubic foot of potting soil before planting, or top dress with 1 tsp per inch of pot diameter.
For trees or shrubs, use 1 cup per 1 inch of trunk diameter, spread over the root zone. Rake in and water thoroughly.
For lawns, use 50 lbs per 1000 square feet, or if you’ve aerated your lawn first use half as much.
Azomite
Azomite is a unique type of rock that comes from only one mine in central Utah. Azomite is an acronym of the phrase “A to Z Of Minerals” followed by –ite: the common ending for a rock name. Azomite was formed when a volcano spewed tons of ash into a nearby seabed millions of years ago. The water dried up and the resulting ash-and-marine muck turned into rock. In geology terms, Azomite is called “hydrated sodium calcium aluminosilicate.”
Contains the widest range of minerals of all the rock dusts.
Good for magnesium, calcium, potassium and silicon, and also provides about 70 additional trace minerals.
Apply 10 lbs per 100 square feet of garden, or 1 lb per 25 root feet by top dressing or watering it in.
For potted plants, use 1/2 teaspoon per inch of pot diameter mixed into the soil before planting, and 1 tsp every 3 months while the plant is growing.
For trees, use 1 to 5 lbs each, depending on the tree size. For shrubs, grapes, and roses, use 1/2 to 1 lb per plant. Spread it around the root zone and rake it in.
For new lawns, use 5 lb per 1000 square feet, and for established lawns use 3 lb. Apply once per year in spring or fall, broadcast evenly and water it in.
When you’re planning what to feed your garden this year, don’t forget about adding trace minerals. Choose a rock dust and grow organic for life!
How To Use Humates, Humic Acids, and Humus
Humates, humic acids, humus… these soil amendments sound so similar! They are all good for the garden even though they are not really a fertilizer (since they do not add any nutrients to the plants), and they are not all the same. Let’s look at what they are, and how to choose the best one for your needs.
The 411 on Humus
All fertile soil contains several components: decomposing organic matter, living organisms including plant roots, microbes, worms, insects, and small animals; and humus – the carbon-rich matrix made of fully decomposed organic matter.
Found in any soil containing decomposed organic matter, as well as in compost, worm castings, sphagnum peat moss, and other aged organic matter.
The older and darker in color that it is, the more humus it contains.
Made up of lignins, fats, and sugars, as well as three types of chemical compounds called “humic substances”: humin, humic acids, and fulvic acids. These are each a class of chemicals comprised of many different biologically active compounds.
Humin is very stable, improving soil structure but not easily used by plant roots.
Fulvic acids, on the other hand, are the most bio-available of these chemicals but have little effect on improving the soil.
Humic acids can be applied to your soil to provide the most benefits over time, improving both the soil and the plants growing in it. Humic acids work to raise the Cation Exchange Capacity, or CEC, of your soil, which is important for increasing nutrient and water retention and uptake, as well as improving the soil structure. In field studies, plants grown with humic acids are bigger and have stronger roots. Even though they are called acids, they will not make your soil acidic and can be used in any type of soil, and for all your veggies, flowers, trees, and lawn.
So Where do Humates Come into This Equation?
Humic acids are naturally a liquid. Humates, also called granular humic acids (Activate 80), are what you get when humic acids are rendered into a solid, through what is essentially a dehydration process. Humates contain the same compounds and thus have the same benefits as applying liquid humic acids such as Humax. Once applied to the soil and watered in, they will dissolve into their active liquid form again. The best way to add humic acids to your soil is with humates derived from leonardite shale. Leonardite is a rock formed from pressurized peat, which has a very high humic acid content–45 to 50%! Humax, which is also derived from leonardite, is a faster acting humic acid source, but has been diluted to 12% humic acids. It is best for foliar and fertigation applications.
Adding Humic Acid to the Garden-Forms
Granular Humic Acids–Derived from Leonardite shale, contains 50% humic acids. Similar to Activate 80-Course, but in a smaller size.
Acivate 80-Course Grade Humate–Derived from Leonardite shale, contains 45% humic acids.
Activate 80 Micronized Humate–Derived from Leonardite shale, contains 55% humic acids. Can be delivered through irrigation lines. Does not fully go into solution, must keep agitated.
Humax–Derived from Leonardite shale, contains 12% humic acids. Liquid humic acid, fully water soluble.
Application of Humate
To get the benefits of humic acids in your garden, only a little humate is required.
Use 1 to 2 pounds per 100 square feet of garden, or 3 to 10 pounds per 1000 square feet of lawn. Top dress or mix into the root zone, and water well.
For potted plants, use 2 Tablespoons per cubic foot of potting mix, or water in by mixing 2 teaspoons per gallon every six to eight weeks.
If you’re using liquid humic acids, apply 1 to 2 quarts of Humax per acre, diluted with at least 30 gallons of water for soil application or 6 gallons of water for foliar application. For the home gardener, 1 Tablespoon per gallon of water.
Adding "Whole" Humus to the Garden
Humic acids can also be applied to your garden by adding “whole” humus. Although earthworm castings, compost, and sphagnum moss all contain some humus, an ideal source for this is from Arctic Humus. Although applying humus provides a much lower percentage of humic acids than using leonardite-derived humates, humus does have additional advantages such as providing organic matter, beneficial microbes, and even better water retention than humates. Humates, humic acids, and humus are all great choices at planting time. Just don’t get them mixed up with hummus, which your veggies are dipped in after harvest! Help your garden with humic acids, and grow organic for life!
