
Do you have heavy clay soil that water can’t penetrate? Composting can help your soil absorb water better. Loose sandy soil that simply will not hold water? Composting will help your soil to hold water for your thirsty plants. How about weak looking or anemic plants and plant growth? Composting helps here too by providing much needed vitamins, minerals and micro-organisms to your soil.
It is important though, as we talk about compost, to remember that compost is not fertilizer. In the simplest terms, fertilizers feed plants. Compost feeds the soil. While this may not sound like it makes a very big difference, it really can make a big impact on the future of your garden and the garden soil, and there is actually a difference.

Compost, unlike fertilizers, actually promotes healthy microbe growth within the soil. It feeds the soil food web and increases the health of the natural soil. Over time, this creates a more nutrient rich soil that is beneficial for the plants and vegetables that you place in it. This is because compost is actually made up of microscopic fungi and bacteria. Other organisms like crickets and earthworms are also present in compost, which further benefits the soil. The end result is soil that allows the plants and vegetables to feed themselves over a long term.
Composting also helps the soil retain much needed moisture, and research has also shown that composting can also assist in enhancing the disease resistance of some plants, like tomatoes and vegetables. This can reduce the amount of crops you lose to disease, which often leads to wasted expenses.
Fertilizer and compost can be used together. However, it is important that you remember how fertilizer can affect the future composition of your soil. If you do choose to use fertilizer, I recommended that you stick to organic fertilizer or only use chemical fertilizers it for the short term.
The first question most people ask me about compost/composting is “How can you tell when your compost is finished and ready to use?” The good news here is that the answer is pretty simple.
Compost is ready to use when it is dark, brown, and crumbly with an earthy odor. It would not be moldy and rotten. Crumbly compost will be sort of fluffy; it does not need to be decomposed to a point of being powdery. The original materials that went into the compost pile should no longer be recognizable in finished compost, except for some woody pieces. The temperature of the finished compost should be the same as the outside air temperature, and the material should not reheat. You will see earthworms and other insects now that the temperature is lower. If your compost is still hot, smells like ammonia, or you can still recognize much of the original material which went into the pile, then it is not ready to use yet. Once the compost appears finished, let it sit for at least 3 weeks to make sure the decomposition process has stabilized.
You may be tempted to use compost before it is ready. However, if incompletely decomposed material is added to the garden compost, bacteria may compete with plants for nitrogen in the soil. Plants will look stunted and yellow. Unfinished compost has been found to also retard germination and growth of seedlings.
Whether a compost pile is quick and hot or slow and cool, when the ‘decomposers’ have completed their work the contents of the pile will have been transformed to an entirely new material. The volume of the finished compost will have been reduced because of biochemical breakdown and water respiration to about 40% of what went into the pile. This finished product offers numerous benefits to our garden soil.
Compost will improve the quality of almost any soil, and for this reason it is most often considered a soil conditioner. Compost improves the structure and texture of the soil enabling it to better retain nutrients, moisture, and air for the betterment of plants.
Incorporating compost into soil dramatically improves soil structure. Soil structure refers to how inorganic particles (sand, silt, clay) combine with decayed organic particles (compost, humus). Soil with good structure has a crumbly texture, drains well, retains some moisture, and is easy to turn over. “Crumbly” is a rather vague descriptor referring to how it is held together. A soil amended with compost shows that it is made up of many round, irregular aggregates. Aggregates are groups of particles loosely bound together by secretions of worms and compost bacteria giving it this crumbly appearance. If you lightly crush one of these aggregates, it breaks down into smaller aggregates. Crumbly soil allows air to penetrate and holds moisture well but allows excess water to drain away. Tender young roots also have an easier time penetrating into this material.

A garden with sandy soil has very little water and nutrient retention. Sandy soil feels loose and has coarse particles that won’t hold their shape when squeezed in your hand. Water and nutrients pass through quickly since there is nothing to hold them there. In loose, sandy soil compost helps to bind these particles together and increase the soil’s ability to retain moisture and nutrients. In other words, there is now something to hold onto. Plant roots penetrate easily, finding moisture where there was none before.
Clay soils appear heavy and dense. The soil particles are small and tightly bound together. When wet, clay is sticky and easily holds together when squeezed in your hand. When compost is mixed with clay soils, it binds to the clay particles forming larger particles that now have larger air spaces between them. These spaces allow better surface water drainage and air penetration.
Compost also adds nutrients to your soil. Compost contains a variety of the basic nutrients that plants require for healthy growth. In addition to the main three; nitrogen, phosphorous, and potassium, of special importance are the micronutrients found in compost such as manganese, copper, iron, and zinc. Micronutrients are only needed in small doses, like vitamins in our diet, but they play an important role in the plant's ability to extract nutrients from other foods. In a commercial fertilizer micronutrients are often missing. Compost is basically a free nutrient boost for your plants!
Compost is made up of different ingredients, some of which rot more rapidly than others. As a result, nutrients are released over a long period of time. Making compost kind of like a slow-release fertilizer. Actually, if everything decomposed at the same rate, compost would not be so valuable. The nutrient content of each batch of compost is impossible to predict because it depends on so many variables. What was the carbon to nitrogen ratio of the pile? Were any amendments added in the way of activators? We do know that the greater the variety of materials used in making compost, the greater the variety of nutrients in the finished product.
Adding compost to your soil creates an ideal situation where it breaks down over time and provides Nitrogen to your garden and landscape plants. Sufficiently aged compost releases organic nitrogen after soils warm in the spring. It has been show that the breakdown of this organic material provides 25% of its Nitrogen the first year, 10% the second and third year, and declines to 5% the fourth and fifth year.
Compost attracts earthworms and provides them with a healthy diet. The presence of earthworms, red-worms, red wigglers, centipedes, sow bugs, and other soil critters shows that compost is a healthy living material. The presence of these ‘decomposers’ means that there is still some organic material being slowly broken down releasing nutrients as foods pass through their digestive tracts. They also represent a balanced soil ecology.
Research is showing us that soil treated with compost tends to produce plants with fewer pest problems. Compost helps to control diseases and insects that might otherwise overrun a more sterile soil lacking natural checks against their spread. Leaf based compost is showing promise suppressing nematodes. Compost application to turf has suppressed many fungal diseases.
Here are a few more reasons why:
- Compost conserves resources!
- Water - Compost helps soak up water, slowly releasing it to plants. With enough compost in your soil, you won't have to water as much. Also, compost applied thickly as a top dressing has some of the benefits of mulching. It will keep water from evaporating from deeper levels
- Energy and Fuel - Composting at home not only keeps the material out of the landfill; it keeps the material from being transported too! Because many organic wastes contain a lot of water, they are some of the heaviest wastes to transport. Not transporting these heavy wastes saves fuel and energy.
- Water - Compost helps soak up water, slowly releasing it to plants. With enough compost in your soil, you won't have to water as much. Also, compost applied thickly as a top dressing has some of the benefits of mulching. It will keep water from evaporating from deeper levels
- Composting can save you money!
- Trash Service - If you're able to reduce the amount of trash you throw away; you could reduce your trash bill.
- Buy Less at the Garden Store - When you produce compost at home, you don't need to spend your hard earned dollars buying it from the gardening store. Not too shabby!
- Composting is Fun!
- Okay, maybe "satisfying" is a better term. When you compost, you're much more aware of trash in general, and you're truly completing the recycling loop.
- Using your own compost helps your yard and gardens become the envy of the neighborhood – now honestly, who wouldn’t like that!?!