Decayed organic matter, the transformed remnants of once-living organisms, is a key component in natural ecosystems. It plays a significant role in fostering robust plant growth and maintaining soil health. Understanding how to effectively utilize this natural resource can enhance the productivity of various growing environments.
What is Decayed Organic Matter?
Decayed organic matter is the product of decomposition, a natural process where plant and animal residues break down. Microorganisms, including bacteria and fungi, are the primary agents facilitating this transformation. As these organisms consume and process raw materials, complex organic compounds convert into simpler, more stable forms. The result is often a dark, crumbly, earthy-smelling substance known as humus.
Humus is a stable form of organic matter that resists rapid decomposition. It is a complex mixture of humic and non-humic substances, originating from sources like fallen leaves, grass clippings, food scraps, and animal manures. These diverse organic inputs undergo biochemical changes, forming this nutrient-rich soil amendment.
Why it Benefits Soil and Plants
Decayed organic matter improves soil structure, which supports healthy plant development. In clay soils, it binds fine particles, creating larger pore spaces to enhance aeration and water drainage. In sandy soils, organic matter acts like a sponge, increasing moisture and nutrient retention. This improved structure allows plant roots to penetrate deeper and access resources efficiently.
The material also serves as a slow-release reservoir for plant nutrients. As microorganisms mineralize organic compounds, they convert locked-up nutrients into forms plants can absorb. This process steadily supplies nitrogen, phosphorus, potassium, and various micronutrients, reducing the need for synthetic fertilizers. Plants receive consistent nourishment, promoting sustained growth.
Decayed organic matter helps buffer soil pH, stabilizing it within a range favorable for most plants. It contains components that neutralize changes from external factors like acid rain or certain fertilizers. This buffering capacity ensures optimal nutrient availability, as extreme pH levels can render some nutrients inaccessible. A stable pH environment supports robust root development and plant vigor.
Organic matter supports a thriving population of beneficial microorganisms. These organisms, including bacteria, fungi, and protozoa, play a direct role in nutrient cycling, disease suppression, and producing plant growth-promoting substances. By providing a consistent food source and habitat, decayed organic matter fosters a diverse and active soil food web. This biological activity links directly to healthier, more resilient plants with enhanced growth and increased yields.
How to Obtain and Prepare It
One common method for obtaining decayed organic matter is composting, a controlled decomposition process. This involves layering “greens” (nitrogen-rich materials like food scraps and fresh grass clippings) with “browns” (carbon-rich materials such as dry leaves, wood chips, and shredded paper). Maintaining a proper carbon-to-nitrogen ratio (typically 25-30:1), along with adequate moisture and aeration, encourages rapid microbial activity. Regular turning of the compost pile aerates the mixture and distributes moisture, accelerating breakdown.
Vermicomposting offers another effective way to produce high-quality organic matter using earthworms, primarily red wigglers. These worms consume organic waste like fruit and vegetable scraps, coffee grounds, and shredded paper, excreting nutrient-rich castings. Vermicompost is prized for its fine texture and concentrated nutrient content. A vermicomposting bin requires a consistent food supply, a moist environment, and protection from extreme temperatures to keep worms healthy and productive.
Aged manure from herbivores like cows, horses, or chickens also provides valuable decayed organic matter. Fresh manure contains high levels of ammonia and salts that can burn plants, so it must be aged or composted for several months to a year. This aging process allows harmful compounds to dissipate and pathogens to die off, making the manure safe and beneficial for garden use. The resulting material is a rich, dark amendment that improves soil fertility.
Leaf mold, produced by allowing leaves to decompose over time, offers a simple, passive method. Leaves are collected and piled or bagged, then left to break down slowly, typically over one to two years. This process yields a dark, crumbly material effective at improving soil structure and water retention. While lower in nutrients than compost or manure, leaf mold excels as a soil conditioner and provides a habitat for beneficial soil organisms.
Applying Organic Matter as Fertilizer
Once prepared, decayed organic matter can be applied to gardens in several ways to enhance soil fertility. For new garden beds or before planting, incorporate it directly into the soil. Spread a 1 to 3-inch layer over the surface, then mix it into the top 6 to 8 inches of soil. This provides an even distribution of nutrients, improves overall soil structure, and ensures young roots have immediate access to beneficial compounds.
For existing plants, top-dressing is an effective, non-disruptive application method. Spread a 1 to 2-inch layer of decayed organic matter around the base of plants, extending to the drip line. This layer slowly releases nutrients into the soil as water percolates. Side-dressing involves placing a band of organic matter along rows or around individual plants, allowing nutrients to leach into the root zone over time.
Using decayed organic matter as a mulch layer offers multiple benefits beyond fertilization. A 2 to 4-inch layer applied over the soil surface helps suppress weeds, conserve soil moisture by reducing evaporation, and moderate soil temperature fluctuations. As the mulch slowly breaks down, it continuously contributes organic matter and nutrients to the soil below. Consistent, rather than excessive, application is recommended, perhaps once or twice a year, to maintain soil health without overwhelming plants.