Composting is a great way to transform household vegetable and lawn waste into fertilizer for your garden.
Even if you don’t want to go through the process of making it yourself, compost is widely sold in hardware stores and garden centers. Adding some to your garden is a great way to battle soil depletion.
Still, you might be wondering, just how much compost do my plants, flowers, and vegetables need to thrive? Is there such a thing as too much compost?
Right off the bat, adding even a small amount of compost will certainly help just about any lawn or garden. However, you’ll find that the best results come from using compost as part of an effective fertilizing strategy. This means you’ll need to take into account several factors like the size of your lawn or garden, the current state of your soil, and the type of plants you want to grow.
In this article, we’ll take a closer look at the characteristics of compost, as well as how to apply it in some of the more common lawn and garden applications.
This includes things like overseeding your lawn, preparing planting beds in spring, and a fertilizing strategy for feeding plants during the summer growing season.
What’s The Difference Between Compost And Mulch?
People sometimes mistakenly think that mulch and compost are the same thing. In certain applications compost is topped dressed like mulch. However, it serves a very different purpose.
Mulch is usually made up of slow-decomposing organic matter with little nutrient value, or inorganic artificial substances.
This includes things like bark chippings, leaves, grass cuttings, hay, pine needles, shredded rubber, and plastic shavings.
Mulch is primarily intended to block protect the upper surface of the soil from compaction and potential weed problems.
In many applications, it can also play a cosmetic role to enhance a landscaping feature or a planting bed.
Compost is made strictly from organic matter and is typically richly populated with beneficial bacteria, fungi, and other important microbes.
When it’s properly balanced, the microbial presence in healthy compost breaks down and releases nutrients from organic waste, which makes them more available for plants to use.
This makes compost a very effective fertilizer for many common plants. When top dressed it can be used as a type of mulch, but it will breakdown much faster, and may accidentally promote new weed growth.
How Do I Calculate how much compost do i need?
Calculating the amount of compost your need by volume can help you understand if your current source is enough, or if you will need to purchase some more from a hardware store or garden center.
Step One: Calculate the number of square inches by multiplying the length and width of your lawn, garden, or planting bed.
Step Two: You can then convert this into cubic inches by multiplying the result by the intended depth you need to apply.
Step Three: Calculate the cubic inches into cubic yards (Which is the unit of measure compost is sold in). For reference, there are 46,646 cubic inches in a single cubic yard.
For example, let’s say that your planting bed is 10’ by 10’ and you want to evenly apply 2” of compost.
Another example factoring in depth, let’s say you have a planting bed that is 20-feet by 20 feet and you want to apply a two inch deep layer of mature compost.
Step One: Convert feet into inches.
20ft = 240 inches. This means the planting bed is 240 inches x 240 inches = 57,600 square inches of planting bed.
Step Two: Factor in the depth
To do this you need to multiply 57,600 by 2 inches of depth= 115,200 cubic inches of compost.
Step Three: Convert the volume to cubic yards
To do this you divide 115,200 by 46,656 = 2.47 cubic yards of compost.
How Can Compost Benefit My Lawn?
The organic material, that makes up the majority of, compost is essentially humus. This provides structure for the soil and the layers of turf that support the blades of living grass.
When the turf is properly aerated, and compost is applied, the roots of the grass spread easier into the loose, airy soil, while also being able to access the nitrogen and other nutrients they need to encourage vigorous growth.
Of course, this boost of nutrients is just one of the compost’s many benefits. Compost also helps:
- Neutralize the pH of acidic and alkaline soils
- Deliver additional macro and micro-nutrients
- Prevent erosion and runoff problems by strengthening root mass
- Reduce the need for artificial or hazardous lawn chemicals
Incorporating Compost To Feed Your Lawn
If you want to use mature compost to feed your existing lawn, in the spring, you might only need to spread about one-quarter to half an inch to give the grass a boost.
This can be done through the same kind of inexpensive spreader you would use to spread commercial granulated lawn fertilizer.
Once you’ve spread the compost evenly, you can then gently rake it over the lawn to help it integrate into the turf.
This should be done after any seasonal aeration. If necessary, you can then reseed any thin or dead spots in your lawn.
If you are seeding your lawn for the first time, you should plan on working a one to two-inch layer of mature compost into the soil before seeding.
When watering the lawn, it’s best to use two to three light applications of water, rather than one heavy watering session.
Not only will this help keep the soil moist and the microbial soil culture active, but it will also keep the grass seeds from washing away.
Grass needs sunlight to germinate. When it does a small root emerges and grabs hold of the soil.
If it’s washed away by heavy watering, it can prevent the seed from making the most out of the composted nutrients. It could also potentially damage the fledgling root turning the seed inert.
Can Compost Be Used In Spot Applications On My Lawn?
Compost can be used in a variety of lawn applications. Turf fungus, weeds, lawn pests, pet damage, and inadequate seasonal aeration can cause dead spots throughout your lawn.
When this happens, simply spreading new grass seed, or trying to cover the area with sod, may not be enough to restore the dead spot.
This is often due to the changes in soil chemistry, the lingering presence of harmful microbes, or soil compaction.
When mature, balanced compost is worked into these bare patches it can help balance the pH, while replacing harmful microbes with beneficial ones, and of course providing the key nutrients new grass needs to take root.
To determine how much compost you will need for a circular area you will first need to calculate the circumference.
Step One: Measure the general diameter of the area. If it’s not a perfect circle, choose the farthest distance from the center to the edge.
In this case let’s say that the diameter is 10 feet, which is 120 inches. And you want to apply half an inch of compost to rejuvenate the dead spot in your lawn.
Step Two: Multiply the diameter by 3.14 to determine the square inches.
120 x 3.14 = 376.8 square inches
Step Three: Multiply that number by .5 for the depth. This will give you the cubic inches.
376.8 x .5 = 188.4 cubic inches.
Step Four: Convert cubic inches to cubit yards by dividing it by 46,656 to determine the cubic yards of compost you need.
188.4 / 46,656 = .004 cubic yards of compost.
How Much Compost Do I Need For Overseeding?
Overseeding your lawn can help augment your regular maintenance. The concept has been around for decades, yet many homeowners don’t use it effectively.
The process involves applying augmented grass seeds to help take root in areas where the existing grass may have become thin or died back.
It typically requires you to dethatch and aerate your turf to allow water, nutrients, and air to feed the root layers.
If you have heavy soil compost can be mixed with an equal volume of sand and top dressed with a drop spreader.
In this application, you can use around three-quarters of a cubic yard per 1000 square feet of lawn.
The general rule of thumb is that you want to apply one-quarter to one-half inch of compost to the soil before you spread the grass seed.
Using Compost To Feed Your Garden
Compost is a very common and welcome friend in the modern-day garden. It’s particularly popular with people who are looking for organic alternatives to feeding their cherished fruits and vegetables.
How Do I Use Compost In My Spring Garden?
The previous summer and fall, your plants drew up soil nutrients to grow flowers or fruit. This can significantly deplete the soil.
Fall rain, melting winter snow, and early spring rain can further wash available soil nutrients deep into the subsoil where young spring roots simply can’t access it.
Adding compost to your garden and planting beds can rejuvenate the soil nutrients as well as the beneficial microbial population that plants also need to thrive.
There are a few ways to do this. The first is to dig out the planting bed 12 to 16 inches and apply a two-inch deep layer of brown or mature compost.
You then back fill with the original soil, which will help aerate it and make it easier for young roots to spread quickly.
If your soil has been significantly depleted, you might also want to work in one to three inches of green, or mature compost into the top four to six inches of soil. This will help give young plants a boost.
Can I Use Compost To Fertilize My Garden In The Summer?
Compost can play an important role in fertilizing your garden during the summer. However, you do need to be a little bit careful.
You don’t want to apply “Hot” or “Green” compost too close to plants and their vulnerable stems. This could also potentially damage plants with a shallow root mass.
If you are willing to put in a little bit of elbow grease, you can use a small garden fork to gently work in a quarter to a half-inch of mature compost.
Just be careful not to disturb the roots of the plants. You want to be especially careful around perennial plants and bushes.
Can Compost Be Used To Feed My Trees?
Most mature landscaping trees in your yard have roots that run so deep, compost will barely affect them.
However, young landscaping trees and shallow-rooted fruit trees will certainly benefit from some compost in the spring and fall.
With many of these trees, the roots are defined by the drip edge of the branches.
You can lightly spray a small tree with a hose or watch it after a rainstorm to get a basic idea of the maximum perimeter of the drip edge.
Garden centers and hardware stores sell tree rings and flexible landscape edging that you can then lay around the drip edge.
You can then apply half an inch of compost directly to the soil. Covering it with a layer of neutral pH, organic mulch, will help prevent weeds from stealing nutrients from the tree’s roots.
To determine how much compost, you will need for this you will need to first calculate the circumference.
Let’s say you want to add 2 inches of compost.
Step One: Measure the diameter of the drip edge with the tree trunk as the center. Then convert to inches.
Let’s say you come up with a 5 foot diameter, which is 60 inches.
Step Two: Multiply the diameter by 3.14 to determine the square inches.
60 x 3.14 = 188.4 square inches
Step Three: Multiply that number by 2 for the depth of 2-inches of compost. This will give you the cubic inches.
188.4 x 2 = 376.8 cubic inches of volume
Step Four: Convert to cubic yards by dividing by 46,656.
376.8 / 46,656 = .008 cubic yards of compost.
What Is Compost Tea?
Compost tea is another effective way to apply fertilizer to your garden and flower beds in summer. Making it is a relatively straightforward process.
You can then use the compost tea in a garden sprayer or by hand watering plants. Just keep in mind that it’s not going to be as potent as solid fertilizer.
You can feed it to plants once a week to help encourage healthy growth throughout the summer growing season.
If you have a smaller lawn, or you have the proper lawn spraying equipment you can use compost tea to feed your grass.
It’s a great way to encourage vigorous growth in times when your turf has been dried out by drought or washed out by frequent summer rains.
A few things to note with this approach.
When you are “Brewing” the compost tea, there needs to be some type of breather hole. This can be little more than a nail hole.
Compost tea can sometimes produce excess gas, which can build up in warm summer conditions.
If you don’t have a breather hole to release this increase in pressure, you could be due for a serious mess when you open the lid.
When applying compost tea, to edible vegetables like lettuce, beans, and peas, you want to make sure that you aren’t getting it on the vegetables themselves.
Dangerous E. Coli bacteria can sometimes populate in compost and compost tea, to linger on the surface of the vegetables.
Even with a good wash, some of the bacteria could remain, when you eat them raw. To prevent this from happening, you should only spray the compost or compost tea on the surrounding soil.
Can You Have Too Much Compost In Your Garden?
It is indeed possible to have too much compost in your garden. This is especially true if it’s “Green” or “Hot” compost or the compost consists of manure, which has not been fully broken down by the inherent microbes.
Plants need more than just nitrogen and carbon to thrive. They also need phosphorus to develop roots and vigorous flower growth.
Potassium, which is also known as “Soluble Potash” also plays a critical role in fruit development and disease resistance.
Giving your plants too much nitrogen-rich compost can lead to problems with burn out, or plants with foliage levels that simply can’t be supported by the roots.
Plants in this condition are also increasingly vulnerable to fungal problems like early blight, as well as other plant diseases.
If you aren’t sure of your soil’s current nitrogen, phosphorus, and potassium levels, there are basic test kits sold in hardware stores and garden centers.
Some can be as cheap as $5 and the test can be performed in a matter of minutes to give you a basic idea of the state of your soil.
If you want a more accurate soil analysis that includes key minerals like calcium, and copper, most county extension offices will offer a soil testing service for a modest fee.
You can then use the result to develop an effective fertilizing strategy for your lawn, garden, or flower bed.
When in doubt, it’s better to incorporate a small amount of compost every two to three weeks, rather than one single heavy application.
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Lindsey Hyland grew up in Arizona where she attended University of Arizona’s Controlled Environment Agriculture. She has supplemented her formal education by working on various organic farms, including spending a semester abroad in India.
Growing and/or raising just about anything gets her excited. She is especially passionate about environmental justice and low-tech, sustainable ways to better run small-scale farms and homesteads. Lindsey started Urban Organic Yield to discuss gardening tips and tactics.