Didn't you know that it is highly beneficial to sit in your garden and eat pitas slathered in hummus? No, no, no, just kidding. I am talking about the kind of humus that is found in the soil. Humus that is formed by the breaking down of organic matter.
There are many ways in which humus is beneficial to your garden. There are many aspects to this. We, however, are going to focus on 6 ways that humus benefits your garden. But first, what exactly is humus? It can be hard to define because there is such a thin line between organic matter and humus. Also there is variances, different qualities, and types of humus.
Here is what Wikipedia has to say:
Humus is the dark organic matter that forms in soil when dead plant and animal matter decays. Humus has many nutrients that improve the health of soil, nitrogen being the most important. The ratio of carbon to nitrogen(C:N) of humus is 10:1.
It is difficult to define humus precisely because it is a very complex substance which is not fully understood. Humus is different from decomposing soil organic matter. The latter looks rough and has visible remains of the original plant or animal matter. Fully humified humus, on the contrary, has a uniformly dark, spongy, and jelly-like appearance, and is amorphous; it may gradually decompose over several years or persist for millennia. It has no determinate shape, structure, or quality. However, when examined under a microscope, humus may reveal tiny plant, animal, or microbial remains that have been mechanically, but not chemically, degraded. This suggests an ambiguous boundary between humus and soil organic matter. While distinct, humus is an integral part of soil organic matter.
Active humus is humus that is still breaking down. This is the kind of humus that feeds our garden plants. At the other end there is stable humus that is fully humified. Stable humus benefits soil structure. We will look at these closer as we continue.
6 Ways Humus Benefits Your Garden
Helps Hold Water
How much further would the rainfall you receive go if your soil could hold more water reserving it for dryer days? Humus can hold 80-90% of its weight in water. It does this without becoming waterlogged and soggy. It is like a sponge, full but not dripping and messy. This is a great buffer against drought.
Keeps Nutrients in the Soil From Washing Away
As organic matter is broken down by the numerous micro and macro organisms that live in the soil, nutrients in the matter are changed and broken down into forms that plants can utilize. Excess nutrients are held on to by active humus (humus that is till being broken down).
Humus acts as a colloid. Colloids are substances that are made of many particles suspended in a medium. In the case of humus, it is a gel like medium. It is a unique characteristic that creates a large surface area compared to their weight. Emulsions like mayonnaise, and lotions are colloids. They are in-between a solution (the particles in solutions are molecules and smaller than colloids) and suspensions (the particles in suspension are larger than colloid particles).
This may seem complicated but hang with me, we're getting to the important part.
The unique thing with colloids is that they are covered with negatively charged particles and this my friends is what enables them to hold on to many important nutrients in the soil. These nutrients are are positively charged chemicals such as calcium, potassium, and magnesium. The negative and positive particles attract, holding them together. As plants draw up the nutrients in the soil the nutrients being held by the colloids are released like a natural, slow feed fertilizer. Isn't that awesome! So instead of the extra nutrients being washed away with the rain or some over zealous watering, humus holds the reserves in place until they are needed.
Minimizes Changes in Soil PH
Major changes in the ph of soil can greatly affect our plants and all the organisms in the soil, completely devastating the soil ecosystem and our plants. The unique characteristics of colloids I described above also work as a buffer to changes in the soil ph.
Traps Toxins and Heavy Metals in the Soil
Humus binds up heavy metals and other toxins so they are not available for plants to take up. Keeping them out of our bellies.
Improves Soil Structure
Active humus is the slow release fertilizer feeding the plants, stable humus (which takes hundreds of years to break down) is what improves soil structure. Humus is spongy yet light and fluffy. This kind of make up allows air to circulate through the soil. With out air space plant roots would be smothered and have limited ability to take up the nutrients in the soil. Furthermore, as microbes break down organic matter forming humus, they secrete gums that hold soil particles together in the favored crumb like structure.
A light, fluffy, crumb like structure also allows roots to reach down into the soil more easily. Think of the carrots you could grow when your soil has adequate amounts of humus! Long, beautiful, straight carrots!
The dark, rich, almost black, color of humus, absorbs the sun's heat more than lighter colored soils heating up the soil earlier in the season. You know we want to get out there just as soon as we can. Although this may be a minor difference it still helps by golly! That means we can get out there earlier in the spring and get our hands in the dirt.
Increasing Humus in Your Soil
Increasing the humus in your soil is pretty easy - increase the organic mater. Humus is formed when plant and animal matter decay. Animal matter includes bug and micro organisms. We don't have to worry about the animals part. Let's focus on the plant portion.
You probably have multiple sources of organic matter right at your house, including:
So many options! Use as many as you have available. The simplest way to to do things would to spread the chosen source of organic matter like mulch. This requires the least amount of work.
Compost takes a little more effort but gives great results. I have a free printable composting guide that you can find on the Guides and Printables page. This guide will lead you through every step of the process.
You can find more information on using green manure and other cover crops in this post.
After reading about the many benefits of humus you may be thinking about how you are going to load your garden with organic matter. Please take a moment to picture what nearly 100% humus looks like - a bog. We don't want our gardens to become a bog. It's not likely that any of us will get there but I wanted to point out what that much humus looks like.
How Much to Add?
Compost is a favorite for increasing humus in the garden. It is generally recommended that you add 1-2" of finished compost a year to established garden beds. For new gardens 3-4" are suggested. We have heavy clay soil so I go a little heavier than these statements. New beds usually receive around 6-8" of compost. Yearly we add 2-3" to established gardens. Every year our soil gets better. As time goes on we will not need to add so much.
It is safe to add compost any time however it is better to add compost that isn't fully composted, still has some identifiable matter, in the fall. Unfinished compost is known to inhibit seed germination. Applying in the fall allows it to break down further before seeding.
When applying compost leave space around existing plants to protect the plant stems from active microorganisms. If you don't have enough compost to make a 1-2" layer then side dress individual plants. Even a small amount of compost is beneficial to the soil and your plants.
It is important that animal manure has been aged before adding it to your garden. 6 months is the general recommendation. Some manure, such as that from chickens, is hotter (higher in nitrogen) than other manure. Placed directly on the garden without aging can burn you plants. This is not a concern with commercially produced store bought animal manure.
Cleaning out livestock pens and piling the bedding and manure into a compost pile in late summer or fall gives the pile enough time to build heat and age before planting time in spring. This kills weed seeds and unwanted pathogens. Animal manure that is mixed with bedding is best used in the same fashion as compost, apply 1-2" of aged/ composted animal manure a year.
Never use cat or dog manure.
Leaves can become matted increasing the possibility of growing mold. To avoid this shred leaves before applying them as a mulch to your garden. Shredded leaves can be added 2-3" deep. Once again, be sure to keep the mulch away from plant stems.
Wood chips make a great mulch however they are very high in carbon. The ratio of carbon to nitrogen is 400:1. The microorganisms that break down the organic matter need a ratio of 20-30 part carbon to 1 part nitrogen to keep a well balanced diet. Wood chips are a long long way from that. The microorganisms breaking down the wood chips will pull nitrogen out of the soil to help reach that right carbon to nitrogen balance. This will decrease the available nitrogen in the soil for your plants. Depending on the levels of nitrogen in your soil, it may be necessary to add nitrogen. Layer the wood chip 4-6" deep.
When using green manure you need to decide what your main purpose for it is. Young plants will decompose more quickly releasing a high volume of nutrients. Middle aged plants will take longer to decompose delaying the availability of nutrients but will add more organic matter. Both add organic matter which helps to build humus. You need to make the decision whether it is more important in your circumstance to add more organic matter or more nutrients. It is not recommended to wait until plants have reached the stage of setting seeds in order to avoid self seeding.
Which ever stage you choose to incorporate the organic matter, mow over the crop with a mulching mower and incorporate the mulch into the soil.
You can also choose to allow the crop to stay on top of the soil as a mulch, slowly breaking down. The manure will loose much of its nutrients through leaching but will still add organic matter and benefit heavy soils.
Staw and Hay:
Straw and grass hay have similar carbon to nitrogen ratios of about 80:1. Use both as you would wood chips.
Alfalfa hay has a ratio of 13:1. Any material with a ratio or carbon to nitrogen 30:1 or lower is considered high in nitrogen. Alfalfa hay should not require added nitrogen.
Grass clipping, like leaves, can form into a matted layer at risk for mold growth. Spread dry (not dried out and brown but not wet with dew or water) grass clippings in a thin layer (barely covering the soil). Repeat the process through out the season allowing several weeks between applications giving clippings time to dry.
I often leave weeds lay where they are picked. The same with healthy plant clippings. Just like grass and leave clippings, because they are green and fresh, there is the potential they can form a mat. keep any mulching loose and don't go too heavy.
Do you routinely add organic matter to your garden? What about a favorite source or way of adding organic matter? I'd love to hear about your experiences!
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Hello, I'm Jaci. I look forward to sharing my gardening and homestead adventures to help you reach your gardening goals! If you have any questions then don't be shy, I'd love to hear from you. Send me a message and I will be glad to help!