As more and more compost is produced and utilized and as the body of end-use related research grows, the benefits of using compost have become more evident and measurable. Because of its many attributes, compost is extremely versatile and beneficial in virtually all soil enrichment applications. Compost has the unique ability to improve the properties of soils and growing media physically (structurally), chemically (nutritionally), and biologically. Although many equate the benefit of compost use to lush green growth, caused by the plant-available nitrogen, the real benefits of using compost are long-term and related to its content of living-organic matter. This has been observed and known for thousands of years.
Physical Benefits
Improved Soil Structure
Compost can greatly enhance the physical structure of soil. In fine-textured (clay, clay loam) soils, the addition of compost will reduce bulk density, improve friability (workability) and porosity, and increase its gas and water permeability, while reducing erosion.
When used in sufficient quantities, the addition of compost has both an immediate and long-term positive impact on soil structure. It resists compaction in fine-textured (clay) soils and increases water-holding capacity and improves soil aggregation in coarse-textured (sandy) soils. The soil-binding properties of compost are due to its humus content. Humus is a stable residue resulting from a high degree of organic matter decomposition. The constituents of the humus act as soil ‘glue,’ holding soil particles together, making them more resistant to erosion and improving the soil’s ability to hold moisture.
Moisture Management
Adding compost to your soil provides greater drought resistance and more efficient water utilization; therefore, the frequency and intensity of irrigation can be reduced. Recent research also suggests that the addition of compost in sandy soils can facilitate moisture dispersion by allowing water to more readily move laterally from its point of application.
Chemical Benefits
Modifies and Stabilizes pH
Adding compost to soil may modify the pH of the final mix. Depending on the pH of the compost and of the native soil, adding compost may raise or lower the pH of the soil/compost blend. T
- The Soil Food Web
he addition of a neutral to slightly alkaline compost to an acidic soil will increase soil pH if added in appropriate quantities. In specific conditions, compost has been found to affect soil pH even when applied at quantities as low as 10-20 tons per acre, (about a pound per square foot). The incorporation of compost also has the ability to buffer or stabilize soil pH, making it more resistant to pH change.
Increases Cation Exchange Capacity
Compost will also improve the cation exchange capacity of soils, enabling them to retain nutrients longer. It will also allow crops to more effectively utilize nutrients, while reducing nutrient loss by leaching. For this reason, the fertility of soils is often tied to their organic matter content. Improving the cation exchange capacity of sandy soils by adding compost can greatly improve the retention of plant nutrients in the root zone.
Provides Nutrients
Compost products contain a considerable variety of macro and micronutrients. Although often seen as a good source of nitrogen, phosphorous, and potassium, compost also contains micro-nutrients essential for plant growth. Since compost contains relatively stable sources of organic matter, these nutrients are supplied in a slow-release form. On a pound-by-pound basis, large quantities of nutrients are not typically found in compost in comparison to most commercial fertilizers. However, compost is usually applied at much greater rates; therefore, it can have a significant cumulative effect on nutrient availability. The addition of compost can affect both fertilizer and pH adjustment (lime/sulfur addition). Compost not only provides some nutrition, but often makes fertilizer programs more effective.
Biological Benefits
Compost provides Soil Life beneficial to plants. The activity of this Soil Life is supported by the presence of organic matter. Soil microorganisms include bacteria, protozoa, actinomycetes, and fungi. They are not only found within compost, but proliferate within soil media. Microorganisms play an important role in organic matter decomposition which, in turn, leads to humus formation and nutrient availability to plant life. Microorganisms can also promote root activity as specific fungi work symbiotically with plant roots, assisting them in the extraction of nutrients from soils. Sufficient levels of organic matter also encourage the growth of earthworms, which through tunneling, increase water infiltration and aeration.
Suppresses Plant Diseases
Plant disease may be influenced by the level and type of organic matter and microorganisms present in soils. Research shows that increased population of certain microorganisms may suppress specific plant diseases such as pythium and fusarium as well as nematodes. Efforts are being made to optimize the composting process in order to increase the population of these beneficial microbes.
Additional Benefits of Compost
Some additional benefits of compost have been identified, and have led to new uses for it. These benefits and uses are described below.
Binds Contaminants
Compost has the ability to bind heavy metals and other contaminants, reducing both their leach-ability and absorption by plants. Therefore, sites contaminated with various pollutants may often be improved by amending the native soil with compost. The same binding affect allows compost to be used as a filter media for storm water treatment and has been shown to minimize leaching of pesticides in soil systems.
Degrades Compounds
The microbes found in compost are also able to degrade some toxic organic compounds, including petroleum (hydrocarbons). This is one of the reasons why compost is being used in bioremediation of petroleum contaminated soils.
Wetland Restoration
Compost has also been used for the restoration of wetlands. Rich in organic matter and microbial population, compost and soil/compost blends can closely simulate the characteristics of wetland soils, thereby encouraging the re-establishment of native plant species.
Erosion Control
Coarser composts have been used with great success as mulch for erosion control and have been used successfully on sites where conventional erosion control methods have not performed well. In Europe, fine compost has been mixed with water and sprayed onto slopes to control erosion.
Weed Control
Immature composts or ones which possess substances detrimental to plant growth (phytotoxins) are also known to be an effective weed deterrent for vegetable and fruit production. While aiding in moisture conservation and moderating soil temperatures, immature composts also act as mild and natural herbicides.
Benefits of Using Compost
• Improves the soil structure, porosity, and density, thus creating a better plant root environment,
• Increases moisture infiltration and permeability of heavy soils, thus reducing erosion and runoff,
• Improves water-holding capacity, thus reducing water loss and leaching in sandy soils,
• Supplies a variety of macro and micronutrients,
• May control or suppress certain soil-borne plant pathogens,
• Supplies significant quantities of organic matter,
• Improves cation exchange capacity (CEC) of soils and growing media, thus improving their ability to hold nutrients for plant use.
• Supplies beneficial micro-organisms to soils and growing media,
• Improves and stabilizes soil pH and
• Can bind and degrade specific pollutants.
Gardening with compost is just one of many ways you can improve the nutritional value of the food you grow while at the same time improving the health and appearance of the environment.
It’s just a good thing to do for yourself, your community and your planet.
