Vegetable gardens are a wonderful way to organically enhance one’s diet without worrying about harmful pesticides and chemicals compromising the vegetables. When it comes to fertilizing the garden, multiple options exist – the best of them all being compost and manure.
However, out of compost and manure, which is the better fertilizer for vegetable gardens? We find advantages and disadvantages of both fertilizer methods, but the general consensus is that compost is the best way to fertilize a vegetable garden.
Understanding the pros and cons of both compost and manure as they are used for fertilizer is the key to learning which is better for a vegetable garden.
What is Compost?
Compost is “partially decomposed organic matter.” It can be purchased or made, and most people prefer using compost simply because it smells better and is cleaner. It is the “black gold” of gardening – able to work with different soils and make them suitable for creating bountiful gardens.
While compost seems simple, the process to make it is based on science. A technique is involved in making proper compost that includes four main ingredients: organic matter, moisture, oxygen, and bacteria. One of the most specific measurements of compost is the carbon to nitrogen ratio.
Some of the benefits of compost include:
- It improves the structure of the soil to which it is added. For example, in sandy soil, the compost helps to hold the soil together by holding moisture.
- It attracts earthworms. Earthworms help to make soil structure better because their movements aerate the soil, allow for more water drainage, and transfer minerals.
- It conditions the soil. Instead of releasing all its nutrients at once, compost slowly releases its nutrients, allowing for its benefits to last for the entire growing season.
- It improves the health of the soil. Some research shows that compost helps to control soil pathogens and prevent plant diseases.
What is Manure?
Manure, which is defined as “animal dung used for fertilizing land,” is the first choice of fertilizer for many large-scale farmers. Like compost, it helps to improve the soil’s water capacity and supplies many nutrients for healthy plants to grow.
However, manure is not supposed to be used for food crops, especially for root crops like carrots. It can transfer disease to humans, like E. coli. If it absolutely has to be used, it should be applied to the soil at least four months before planting edible crops.
There are many reasons to make compost. It is a great way to recycle organic waste and to save money. Additionally, it is much easier to use for a small-scale vegetable garden than manure.
Materials that can be composted include:
- Grass clippings and hedge clippings
- Hay, straw, and weeds
- Chopped corncobs and cornstalks
- Shredded newspaper
- Wood ashes
- Kitchen scraps (make sure to leave out grease, fat, meat scraps and bones)
Yes, manure can be added to compost; it is an excellent source of nitrogen. Nonetheless, it must be handled with extreme caution because of the risk of illness.
Compost should feature a carbon to nitrogen (C:N) ratio of 30:1. Any other ratio causes an imbalance resulting in too little nitrogen to decompose the organic materials, and the decomposition will take much longer. Another way to express this ratio is the rule to follow of two-thirds carbon material (browns) and one-third nitrogen material (greens).
It is important to know what each part of the compost is contributing – carbon or nitrogen. Separate compost materials by greens and browns. Greens are high in nitrogen and can include grass clippings and vegetable scraps. Browns are high in carbon and include things like leaves and sawdust.
Knowing what each part of the compost contributes will help control the carbon to nitrogen ration and ensure that the compost decomposes at a suitable rate. Some other factors are important, too, when making compost, but the most critical factor is the carbon to nitrogen ratio.
Other factors needed to make good compost are:
- Proper acidity (pH 5.8 to 7)
- Proper temperature (above 50 degrees Fahrenheit)
- Good aeration
- Adequate soil moisture
Making a manure-based compost is a very specific process because of the need to kill any pathogens that may be in the manure. Even though manure is a great soil conditioner and fertilizer, it is very risky to use – especially for home gardeners.
The process for making a manure-based compost includes the following steps:
- Carefully manage the adequate mixing of materials
- Monitor temperature with a long-stemmed compost thermometer
- Make sure the temperature reaches 130 to 140 degrees Fahrenheit for at least 2 five-day heating cycles
- Cure the compost for 2 to 4 months before putting it in any soil
These steps must be followed in order to kill any bacteria in the manure that is harmful to humans. The temperature monitoring is especially important because the extremely high temperatures are what kills the pathogens in the manure.
Because of the tedious process of making manure-based composts and the risk that still remains if it isn’t done properly, most home gardeners stick to organic compost that does not include manure.
The Risks of Manure in Vegetable Gardens
While manure is definitely a suitable fertilizer, the pathogens that can be present in the manure make it incredibly risky to use with food unless it is properly composted.
Some pathogens that are found in manure include:
- E. Coli
- Campylobacter bacteria
- Giardia protozoa
- Cryptosporidium protozoa
Not only can these pathogens cause sickness in people who consume the plants that come from contaminated soil, but the pathogens can also find their way into the plant tissue.
The extremely high temperatures that are needed to kill these pathogens are rarely reached in home compost piles, so unless the manure fertilizer is acquired from a place that has the means to make it completely safe, home vegetable gardens are better off with organic compost that does not include manure.
Constructing a Compost Pile
When putting together a compost pile, one must not only consider the chemical makeup of the compost, but he or she must also consider the location and the containment of the compost.
Compost is known for a strong, earthy smell that borders on musky and unpleasant at times because of the decomposition that is going on within the compost. This is one of the most important factors to consider when choosing the location for a compost pile.
Since the compost will not be able to be moved, there should be a water source nearby that is convenient enough to be able to reach the compost during dry weather to keep it moist. However, the compost should never be kept on or near standing water. This can lead to major odor issues.
If the compost is being used for a home garden, it is best to keep the pile near the garden for easy access. It is recommended to keep it in a shaded area that has no trees because tree roots are attracted to the organic material and may grow into it, causing problems with digging and using the compost.
Containment of the Compost
Once the location of the compost pile is selected, a decision must be made on how to contain the compost. The two most common containment methods are heaps and layers. No matter which way the compost is contained, it is best to have some kind of easy opening to reach the compost to dig it out and use it.
Heaps are the simplest kind of compost containment. They are open and require more space than enclosed and layered compost piles. Minimum heap size should be 5 feet by 5 feet and at least 3 feet high. Subsequent heap piles should not be made until the first heap is decomposed enough to use.
While compost heaps are much simpler to create and maintain, enclosed layering results in the best and most proportioned compost.
Containing Compost as Enclosed Layers
There are two very important processes involved in making proper compost layers. The first is to make each layer out of the proper materials. The second is to make sure to treat each layer with proper moisture, spreading, etc.
Compost layers should follow this formula:
- First Layer – Organic Material. Shred or chop enough organic materials to create a 6 to 8-inch thick layer at the bottom of the compost enclosure. Make sure to moisten the layer but do not completely soak it with water.
- Second Layer – Fertilizer. This layer needs to be high in nitrogen. If nitrogen-rich organic materials, like grass-clippings, are used, they should be placed in a layer that is 4 inches thick. Make sure they are not treated with herbicides. If a garden fertilizer is used, place 1 cup per 25 square feet on the top of each organic layer to provide the nitrogen source.
- Third Layer – Soil. Microorganisms live inside of soil and help move the decomposition of the compost along properly. If there is no soil available, the finished compost can be used for this later. Additionally, compost activators can be used in this layer as well.
The layers in the compost should follow this pattern and alternate throughout the entire enclosure to make sure that the compost decomposes and processes as it should.
The treatment steps for layering compost include:
- Dig out a trench and place hardware cloth over it to begin placing the compost layers.
- Place branches at the bottom of the trench to help with the aeration of the lower layers.
- Firm each layer once it is placed, but do not pack the layers completely.
- Water each layer, but do not soak the layers. The pile should resemble a “well-wrung sponge.”
- Use a tool to mix the layers every two to three layers to help speed up decomposition.
- Remember: 1 pound of nitrogen for every 30 pounds of carbon makes for the best decomposition.
Check out a related article we have written on containing compost – Should a Compost Bin Be Covered? Tips for Containing Compost.
Different Composting Methods – Fast and Slow
Traditionally, slow composting methods are best. With slow composting, there is no need for turning units, and organic material can be added at any time. Many people who use slow composting methods will develop two compost piles at a time.
Fast compost methods can create compost in just six weeks but depend on turning units. Large amounts of organic materials are placed in a series of composting bins (usually three) or a large rotating compost barrel.
For more information on turning compost, check out our article When Should I Turn My Compost Pile?
Knowing When to Use Compost
Compost should never be used before it is fully decomposed and ready. When compost is ready to be used, it will not be recognizable as its original form, and it should be dark and crumbly.
Note: There is no problem with using unfinished compost in your garden as long as you are not planting in the compost. Roots of plants should be in soil and finished compost, but it is perfectly fine (and recommended!) to have uncomposted material on top of your soil as a mulch.
Because decomposition does not follow a definite timeline, we can only use estimations of time for when the compost is ready. For instance, with slow composting methods, compost is normally ready anytime within 3 to 9 months. With fast composting methods, it can be ready in 3 to 8 weeks.
Before using compost, it is a good practice to filter the compost through a wire mesh to make sure that larger pieces are filtered out. Things like twigs that are commonly used for aeration decompose much more slowly than smaller organic materials and need to be removed and returned to the compost pile.
Compost in the Home Garden
The University of California’s Agriculture and Natural Resources program gives many tips for using compost in various plants and gardens, such as vegetable gardens, flower gardens, lawns, trees, and house plants. It also details the many benefits of compost in a way that is easy to understand.
Seasonal Needs for Compost in the Vegetable Garden
In spring, it is suggested to place a half-inch to 3 inches of compost on top of the plant bed and mix it into the top 4 inches of soil. In fall, it is suggested to apply compost in the same way if the winter climate allows for gardens.
Additionally, in the growing season, compost can be used as mulch by being placed around the plants in a light layer.
Here at Do Not Disturb Gardening, we always try to disturb the soil life as little as possible, so just applying compost to the top of the soil as a mulch and never mixing or tilling it in is what we recommend.
Three things need to be considered that affect the rate of compost application in a vegetable garden, and they are:
- The fertility of the soil
- The depletion of the soil because of previous crops
- The nutritional need of the plant being planted
The Goal of Compost in Soil Structure
All directions for adding compost to the soil will instruct the planter to be gentle. The main purpose of adding fertilizer and compost to soil is to help encourage microbial activity. Microbial activity promotes a truly aerated soil that allows plenty of space for water.
The goal for a flourishing vegetable garden is to develop a healthy, living, fertile soil. A special application of compost in the fall can promote amazing soil structure. For those gardens not being planted for the winter, place a few inches of compost on top of the soil and let nature’s design do the rest of the work of sifting and “tilling” it through the soil.
Using compost correctly in a home garden promotes soil structure, supplies a steady dose of nutrients, improves moisture capacity, promotes microbial activity, and aids in creating strong plants that are resistant to disease and insects.
Another way to use compost as fertilizer is in a liquid feed form, which is more commonly known as compost tea. Compost tea is a great choice of fertilizer when planting new plants.
First, the tea must be made.
- Get a bucket. Fill it up to ¼ of the way full with compost.
- Fill the rest of the bucket with water.
- Stir the mixture often for 24 to 48 hours – the more stirring, the better.
The best compost teas have air incorporated into the “stirring” process in order to keep the tea moving and mixing. Some people will mix their teas with small aquarium pumps to achieve this effect.
Once the compost tea is finished, it can be used.
- Dilute the tea mixture with more water until it is the color of light tea.
- Pour 2 cups of compost tea at the base of each new plant once it is planted.
It is best to use the entire compost tea when it is made because it does not keep its nutritional value for very long. Larger plants can receive more than 2 cups, but careful consideration must be taken to make sure that there is not too much tea poured onto the plants.
The Verdict: Compost vs Manure for a Vegetable Garden
Both manure and compost are suitable fertilizers; however, they tend to be advantageous for different kinds of farming and crops.
Advantages of using manure include:
- Mostly free – if not free, it is cheap
- Adds organic matter to the soil
- Improves soil structure
- Increases water holding capacity
- Reduces erosion
- Provides nitrogen, phosphorus, potassium and other nutrients to plants
Disadvantages of using manure include:
- Nutrients are easily leached by the soil
- The nutrient content is incredibly variable
- Can introduce dangerous pathogens like E. Coli
- Can introduce weed seeds
Advantages of using compost include:
- It has a lower water content than manure, so there is a greater concentration of fertilizer
- Releases nutrients slowly and steadily
- Adds organic matter to the soil
- Improves soil structure
- Increases water holding capacity
- Decreases irrigation needs, which can reduce pumping costs
- Beneficial microbes increase nutrient cycling
- Few to no pathogens and weed seeds
Disadvantages of using compost include:
- Can be costly (time and money) to make
- Ground water and runoff contamination must be controlled
- May require permits to make or sell
Clearly, compost is the safest and most beneficial fertilizer for vegetable gardens. While it can be costly, it has too many advantages than that of manure to ignore – especially the possibility of introducing illness to those that consume the vegetables.
Through him all things were made; without him nothing was made that has been made.John 1:3
You can check out our Best Compost Products page to help you get started with composting!