How Long Does Compost Last in Soil? Compost for Soil Health

At the beginning of the vegetable growing season you may wonder, how long does compost last in soil? Should you add compost at the beginning of every growing season for a thriving garden?

How Long Does Compost Last in Soil?

Depending on the organic materials used in the composting process and how mature the compost is when added to the garden will determine how long does compost last in the soil.  Overtime 100% of the organic matter will be consumed by any worms or microbes in the soil.  The type of soil you have also determines how long does compost last in the soil. 

How Often Should I Add Compost to My Vegetable Garden?

Generally speaking, I like to add compost to my vegetable garden at the beginning of every growing season for optimal plant growth and healthy soil. I also like to side dress on the soil surface of my vegetable garden plants and flower beds with mature compost. I do this a couple times throughout the growing season to be sure they are getting the essential nutrients they need.  

Your soil type is a factor on how much compost you will need to add to your vegetable beds. I started my garden with extremely sandy soils, which tends to eat organic matter.  Overtime, adding lots of compost has helped improve the structure of my sandy soils. Heavy clay soils can also benefit from a heavy dose of mature compost on a regular basis.  Adding compost to heavy clay soils will help lighten and break up the structure of the finely packed soil particles found in clay soils.  

How Much Compost Should I Use in the Vegetable Garden?

Generally speaking, I like to add at least 1-3 inches of finished compost to my vegetable garden beds at the beginning of every growing season.  Compost is a beneficial soil amendment that will promote optimal plant growth and healthy soil. 

No-till growers add the compost to garden beds and plant directly into the compost. Traditional growers will mix the compost into the top few inches of soil.

What is Compost & How Long Does Compost Last In Soil?

Compost, also known as black gold, is the natural process of recycling organic matter, such as dry leaves and food waste, into fertilizer. Compost will also help improve the structure of your soil. Organic matter is broken down into a useable form during the composting process. 

Why Compost & How Long Does It Last In Soil?

Recycling food and other organic waste through the composting process provides a host of heavy hitting benefits.  Composting not only Improves soil health and structure, it regulates soil temperatures, helps retain soil moisture, reduces erosion, recycles nutrients, reduces greenhouse gas emissions, and benefits human health.

Benefits of Using Compost In My Vegetable Beds

Using compost has many benefits. Using it in your vegetable garden beds is the best way to improve the structure of your soil. Improving the structure of your soil will make nutrients and water readily available. Compost also increases the water-holding capacity, ensuring your soil doesn’t dry out. It’s as easy as mixing in some finished compost to the top few inches of soil.

If I Use Compost in the Vegetable Garden Do I Still Need a Fertilizer?

Compost and fertilizer are two different things. Adding compost to your vegetable garden achieves certain results that fertilizer can’t, such as improving the structure of your soil. While compost can be used to fertilize your vegetable beds, it may lack certain nutrients that some plants need to thrive, making a separate fertilizing plan necessary for your heavy feeders. 

How to Make Compost From Organic Matter

​While making compost from organic materials is relatively easy, it must be done the right way. Let’s breakdown the basics of making compost from organic matter, shall we?

Choose the Right Organic Materials

The right organic materials must be in a compost heap for the composting process to work efficiently. Generally speaking, the correct ratio of organic materials is 2-3 brown materials to 1 of your green materials. The other two key components for the composting process to work are oxygen and water. 

Nitrogen-Rich Materials (Green Materials)

• Food Scraps or Kitchen Scraps
• Grass Clippings
• Garden Waste (Plant Material) That is Still Green
• Coffee Grounds
• Animal Manures

Carbon-Rich Materials (Brown Materials)

• Wood Chips, Wood Shavings, or small twigs
• Brown Yard Waste (Small Pieces of Yard Trimmings)
• Dry Leaves
• Sawdust from Untreated Wood
• Egg Shells
• Brown Paper Bags or News Paper
• Wood Ash

Compost Materials You May Want to Avoid

While technically, these things can be composted they often come with foul odors and will attract more critters to your compost pile. It may have you wondering, do all compost bins smell?

• Dairy Products
• Raw Meat

Get an Outdoor Compost Bin or Pick a Site for Your Compost Heap

For years I tried to make a compost pile directly on the ground and couldn’t keep my chickens out of it. Finding a compost bin was a game changer for me. It was the first time I was able to build a successful compost pile.

My compost bin ended up being a large, broken chest freezer.  I’ve even seen nice compost bins built using cement blocks or wooden pallets. Whatever you decide, just be sure its close to a water source to keep the pile moist.

How Do I Build a Compost Pile Using the Correct Carbon-to-Nitrogen Ratio

Using the correct carbon-to-nitrogen ratio, 2-3 browns to 1 green, is essential for the composting process to work efficiently. I like to collect enough brown and green materials to build a compost pile that is 3 feet tall x 3 feet wide x 3 feet deep.  

This is the minimum size for a compost pile to properly heat up.  You can make a smaller, cold pile but they take forever to break down.  I need the composting process to work quickly to keep me interested in making homemade compost. 

The Best Way To Start A Compost Pile

The best way to start a compost pile is by starting with finished compost, which acts as an inoculator of beneficial microbes and bacteria to get the pile going.  In your compost bin, put a layer of mature compost a couple inches thick as your base layer.  

From here, you will layer your brown materials and green materials, watering each layer as you go.  Be mindful of how much water you are adding. You only want to add enough to moisten the organic materials, not soak them.  Continue layering 2-3 browns to 1 green, watering each layer, until you run out of materials.  

Add a layer of mature compost to the top of your pile. I like to add a thermometer to the pile so I can see that it is heating up properly to kill bad bacteria, grass, and weed seeds.  

When should I turn My Compost Pile?

As organisms decompose waste, they generate high temperatures. Decomposition is most rapid when the temperature is between 90-140*F. I prefer to get my compost pile up to 140*F and let it sit at that temperature for three days.  I then flip my pile to the other side of the compost bin, which adds oxygen to the pile. Next, I let it heat back up to 140*F for another 3 days,  flipping at back over to the empty side of my bin. Continue this process until the pile is no longer heating up. 

How Long Does the Composting Process Take?

Depending on the method you use and the organic materials used to build your pile, you can have finished compost in as little as 30 days, if building a hot pile. Whereas a cold pile can take up to a year to properly break down.  Regardless of the method you use, please know that unfinished compost can be detrimental to plant health.

How to Do I Tell if My Compost is Ready

• Texture- Finished compost should have a crumbly texture.
• Smell- When the composting process is finished, your compost heap should smell earthy with no bad odors. 
• Temperature- The compost pile should be completely cooled when finished but that doesn’t mean that a cooled pile is finished. 
• Color & Appearance- A finished pile should be dark brown with no recognizable ingredients left in the pile. 

Factors That Affect How Long It Takes for Compost to Be Ready 

It seems like every pile I build is different, as I am building my compost piles with different materials and in different seasons. No two piles are the same. There are 6 factors that effect how long it takes for the composting process to work. 

• Your Climate- In the winter months you may find that it takes longer for your compost to heat up.  Covering it will help conserve and build heat.
• The Materials You Are Using- Some green materials, like chicken manure and grass clippings, are higher nitrogen and will will lead to a pile that heats up better than other green ingredients.
• Carbon-to-Nitrogen Ratio- If you have the correct ratio, 2-3 browns to 1 green, your pile will go through the composting process relatively quick.
• The Size of the Compostable Materials You Ae Using- Shredding your organic materials will help speed up the composting process.
• The Size of Your Compost Pile- Building a pile at least 3 feet tall x 3 feet wide x 3 feet deep is the minimum size for a pile to go through the composting process. Do you have enough material?
• The Moisture Levels in Your Compost Pile- Too much water and you’ll have a cold soggy messy whereas not enough moisture will not support the biological activity.

Tips to Speed Up the Composting Process

If you find that your pile is taking forever to finish, there are some things you could consider to help the composting process along. Evaluate your compost pile and see where you could make changes. Possibly it’s too wet, too dry, or an incorrect carbon-to-nitrogen ratio.  

Turn Your Compost

Turning your compost pile helps provide necessary oxygen and is an important factor to help along the biological process of composting. While turning, you can evaluate if the pile has too much moisture, to which you could add some browns.

Or maybe its too dry and you can add some moisture while you are turning it.  Not hot?  Add some green materials, like grass clippings or kitchen scraps. This is a great way to give your compost a boost..

Add Worms to Your Compost

Adding some red wiggler worms to your compost pile will help break down the organic materials.  As an added bonus, they will also be adding valuable worm castings to your compost pile. 

Add Compost Activators

Most compost activators speed up the composting process by adding nitrogen. There are compost activators you can buy or simply add your best source of nitrogen or green materials.

Compost accelerators should increase the rate of decomposition in a cold pile by providing more nitrogen. This will increase the temperature of the pile, making it an active compost pile. My favorite activator is chicken manure.

Shred Your Organic Materials

Shredding your materials will speed up the composting process. It’s an easy way to get a head start on breaking down the organic materials.  For best results start with smaller pieces to help along the decomposition process. 

Try Different Ways of Home Composting to Find One That Works For You

Just as there are different styles of gardening, the same its true with home composting. A one-sized approach doesn’t fit all.  Some folks, like me, insist on a hot compost pile for its quick ability to go through the decomposition process. Now that I know how long does compost last in soil I need batches to finish quickly.

On the other hand, some home composters are fine with a cold pile that is built slowly and breaks down over time.  There are other methods in addition to a hot pile and cold pile. 

Compost Tumbler

A compost tumbler is an attractive solution for composting, especially in urban areas. It’s a sealed bin that with the right conditions can produce compost in 3-4 weeks. Many back yard gardeners like the tumblers because they are sealed up, containing unpleasant odors and are easy to turn every few days. 

Vermicomposting

Vermicomposting, or a worm bin,  is a process that relies on earthworms and microorganisms to help breakdown organic materials and convert them to a valuable resource for the vegetable garden. Earthworms will consume most organic materials breaking down ingredients quickly, all the while adding worm castings to your compost. You can learn more about How Earthworms Help the Soil and why they are Important.

Bokashi Bin Composting

Bokashi Bin composting is an anaerobic fermentation process relying on inoculated bran to ferment kitchen waste. It is a small indoor system in an airtight container to keep smells down. The end product is fermented organic waste that can be buried directly into the garden or added to a larger compost pile. The bonus of the bokashi bin is the compost tea that is produced during the fermentation process.

​Hot Pile Composting

Hands down, my favorite method. Hot composting can give you a bulk of finished compost in just 3-4 weeks. I recommend collecting enough materials to build your 3x3x3 foot pile all at once. Building a big pile and managing it correctly, in a compost bin with the correct carbon-to-nitrogen ratio will give you mature compost in a quick few weeks. Not only is it fast, but a pile that gets nice and hot can kill grass and weed seeds.

Cold Composting

If a hands off approach to composting is what you are after, building a cold pile that breaks down over time may be your best bet.  With this method, the size of the pile doesn’t really matter. The ratio of ingredients is also a little more flexible. Essentially, any organic materials will break down if given enough time. A compost bin may be something you still consider so its contained and covered, keeping rodents and such out. 

How Long Does Mature Compost Last?

Overtime mature compost will continue to break down and loose volume.  If it’s compost that is bagged or covered, keeping the rain from washing out the nutrients it can still be a valuable soil amendment for the vegetable garden. 

​Nutrient Value of Mature Compost

Many home gardeners are a little shocked to find out the nutrient value of mature compost. On average, most finished compost is 1.5-1-1 NPK.  Every compost pile is different though because they are often made from different materials. The nutritional value is only one of the benefits of adding compost to the vegetable garden though.  It has many other benefits, such as improving soil structure, making nutrients more available to plants, retaining soil moisture, and contributing to plant root growth.

Biological Activity in Mature Compost

According to LSU Ag Center, “Throughout the composting process different microorganisms work at degrading large materials into smaller materials. In the process depending on what type of microorganisms are present, they will increase or reduce the production of two gases: CO2 and NH3. Once microbial activity is low (compost is mature) these two gasses and heat will be reduced.”

How Should You Store Finished Compost?

Compost can be stored in a plastic bag or empty garbage can. Make sure the compost remains moist by occasionally adding a little water and turn it.

How Long Does Bagged Compost Last?

Bagged compost will last for years if kept moist, not wet.  Adding too much water can wash out the nutrients in mature compost.

Can Mature Compost Go Bad?

Mature compost will only go bad if stored improperly, such as uncovered and out in the rain. Overtime, it will continue to break down losing volume. This is the reason why we need to add compost to our vegetable garden beds at the beginning of every growing season.  As it breaks down, it is used up by the plants. 

​How Long Does Compost Last in Soil

Now that you know the nature of compost and how it breaks down, I think you’ll find that adding a top dressing layer of compost to your garden soil or raised beds at the beginning of every growing season is the best way to have a thriving, healthy vegetable garden.

Go ahead and get busy finding a compost bin and collecting ingredients for some homemade compost. In a few short weeks, you can have a valuable soil amendment and fertilizer for your vegetable garden.

Happy Homesteading & Compost Making,

Jenny @ The GrahamStead Family Farm

Jenny and her family have been homesteading for over 20 years. They are currently farming on their 10 acre Florida farm, that they built from the ground up, 8 years ago, growing 100% of their meat and a lot of their vegetables. From their small herd of Aberdeen Angus Cattle, Pastured Poultry, Sheep, and seasonal pigs, they are able to raise enough meat for the family while selling extra to the community. All the while, striving to butcher at home, as much as possible, and use the bits and pieces of their harvest by preserving food, making bone broth, and (Jenny’s favorite) tanning all kinds of hides!

Sources: https://www.lsuagcenter.com/articles/page1651504355385