We have so many new GardenLine listeners asking questions about compost top-dressing, I thought it was worth revisiting my 2017 write-up about using high-quality compost for the project.
Here’s a breakdown of why high-quality compost is unlike any other product when it comes to value. And, like most products, there is a huge variation in its price, quality and value. So read on if you want to learn “The Real VALUE of Compost!”
To begin, how does one determine the value of compost?
First, you should know that the following information applies only to HIGH-QUALITY compost. Sadly, there are many products available that are purported to be compost, but their quality is iffy at best. In most cases, the longer compost has aged, the better it becomes – like a fine wine. I contend that vegetative composts that have been aged at least six month will provide the benefits I’ll outline below. A compost aged three months or less will have suspect quality.
And, yes, dirt/mulch yards will lie about the age of their compost. Companies I trust for bulk compost include Nature's Way Resources and The Ground Up. As for bagged composts, there are plenty on the market, and some are good while others are questionable. You should always open a random bag and see if it looks like supremely enriched dirt. If it’s chunky or smells bad, then its aging and quality should be questioned.
For this discussion, I’m focusing on high-quality compost as a top-dressing for lawns. But I'm also a huge fan of course compost as a mulch these days, and hopefully you’ll be able to see its benefits for that as well.
There is a Nitrogen, Phosphorus and Potassium (K) (NPK for short) component of compost that equates to over $100 worth of fertilizer. Put another way, you would have to purchase over $100 in organic fertilizer to get the same amount of nutrients in one cubic yard of compost, which would cost only about $65.That cubic yard of compost would also contain scores of other minor nutrients … like iron, calcium, sulfur, magnesium, zinc, copper, boron, manganese, and molybdenum … that would cost another $7-10 if bought separately.In addition, the compost breaks down deploying over 60 trace elements that are naturally found in plants. For example, you’ll get the equivalent of over $40 worth of fish emulsion. All life forms … from beneficial bacteria, beneficial fungi and beneficial critters like earthworms … require the energy that comes from carbon. If dried molasses was used as a carbon source to provide the energy found in one cubic yard of compost, it could cost over $100. Organic matter matters: Organic matter is critical for healthy soils along the Gulf Coast. If humates are used as a source of organic matter, instead of the organic matter found in a cubic yard of compost, it could cost upwards of $100. Microbes: Compost is teeming with beneficial microbes. If you were just to buy the microbial inoculants found in a cubic yard of compost, they would cost over $100. Compost naturally contains many plant growth-promoting hormones. It would require at least $5 worth of hormones to provide a similar benefit as found in a cubic yard of compost. (You just thought I was going to say over $100.)So, even if a cubic yard of high-quality compost costs over $75, it’s still a much better deal than paying nearly $450 for all the other stuff put together, right?! Cubic yards of the highest quality composts I’ve recommended for years from Nature’s Way Resources and from The Ground Up, range in price from $60 to $80. And that’s why I and many GardenLine fans consider high-quality vegetative compost as “BLACK GOLD!”
So, maybe you are asking why I even recommend fertilizing if top-notch compost is seemingly all we need.
Well, first, it's hard work. It is not the simplest task for a do-it-yourselfer. Plus, the aesthetics are not what you'd want constantly - your lawn would always look like it's covered in dirt.
Fortunately, we don't need compost as a top dressing but maybe once a year. Maybe twice a year on a lawn that has been ignored for a while. Great companies like Green Pro and Year Round Lawn Care to do that kind of work, and eventually you will find yourself needing it done just once every few years. You may even be able to eliminate some fertilizations - organic or synthetic.
MORE ON MICROBES: In recent years, we have come to understand that all life on Earth is dependent on microbes. For plants, the microbes live in the soil and on the roots, leaves and stems. Research has shown that microbial inoculants can have a tremendous benefit on plant growth and health.
The best inoculants on the market have only 100-200 species of bacteria, 20-30 species of fungi, and very few protozoa, nematodes, arthropods or other beneficial life forms. By comparison, good compost will easily have 25,000 species of bacteria, 10,000 species of fungus, many species of protozoa and beneficial nematodes to cycle nutrients, prevent disease, and create soil structure.
The microbes found in compost provide disease suppression and improve nutrient retention in soil. They also mineralize nutrients and make them available to plants. Additionally, they improve soil structure allowing water and oxygen to move into the soil, they decompose toxic materials, they produce plant growth-promoting compounds, and they improve crop quality. All that brings additional value by making the purchase of expensive toxic fungicides and pesticides unnecessary.
MORE ON HORMONES: Research is just beginning to identify and understand the many substances in good compost that promote plant growth. They range from enzymes and hormones to vitamin-like substances. Numerous studies have shown that compost helps all plants grow faster, stronger and healthier.
Other Value-added Benefits of Compost
By John Ferguson of Nature's Way Resources
Compost holds water in the soil and helps create soil structure so that water from rainfall and irrigation soaks into the soilPlants use far less water when compost is used. And with some turfgrass, 50-70 percent less water is required.Compost stimulates disease- and insect-resistance in plants, so expensive toxic chemicals are no longer requiredCompost-enriched soil holds in nutrients from fertilizer better. This means less fertilizer runs off to pollute our waterways.Compost buffers the soil, neutralizing both acid and alkaline soils, bringing the pH levels to the optimum range for plants.Compost helps sandy soil retain water and nutrientsCompost loosens tightly bound particles in clay or silt soil so roots can spread, excess water can drain out, and air can penetrate the soilCompost alters soil structure, making it less likely to erode, and prevents soil spattering on plants, reducing the spread of disease.Compost can hold nutrients tight enough to prevent them from washing out, but loose enough that plants can easily take them up as needed.Compost makes any soil easier to workCompost enriched soils has a lot of beneficial insects, earthworms and other organisms that burrow through the soil keeping it aerated. (No need to rent expensive aerators, wasting time and money.)Compost encourages healthy root systems which decrease runoff reduces floodingOnly a 5 percent increase in organic material in the soil from compost quadruples its water-holding capacity.