One of the key things we are trying to achieve by adding additional materials to our compost is microbial diversity. Many microbes produce natural antibiotics that help plants resist disease. Every microbe will have foods they prefer over others. Therefore, keeping your compost pile as diverse as possible helps support the diverse microbial life you would want to end up in your soil. In this article I go through some ingredients you can add to boost the quality of your compost at home.
Table of Contents
1. Stinging Nettel
Stinging Nettle has amazing benefits to your garden. While it makes an amazing natural liquid fertilizer. It is beneficial to add to your compost as well. Stinging nettle sends roots down into the soil and pulls these nutrients up into their leaves. Stinging nettle is arguably one of the most nutritious plants on earth. Stinging Nettle is full of vitamins A and C and the minerals iron, potassium, manganese and calcium.
To add stinging nettle to your compost you can cut them ( if you have them growing in your garden) and add them to your compost pile. This gives nutritious green manure to your compost.


2. Seaweed
There are many types of seaweed all over the world. As a nutrient, most seaweed varieties have low levels of potassium and phosphorus. However, they contain over 60 trace elements essential for plant growth (including iodine and calcium). Many seaweed varieties have been shown to prevent fungus and disease in plants.
If you’re in the Caribbean you’ve probably heard about sargassum seaweed washing up on our shores. This seaweed in particular is especially good at promoting root development in plants. A stronger root system will allow plants to absorb more nutrients. This leads to earlier flowering and fruiting in vegetables and larger tubers in root crops.
High levels of sodium can damage your soil. Before adding seaweed to your compost washed it thoroughly to remove as much salt and any pollutants from the ocean as possible.
3. Blackstrap Molasses
Molasses is a by-product of the sugar industry. It contains sugars that make a good source of carbon for the microbes in your compost pile. Blackstrap molasses contains the micronutrients plants need for healthy growth. These nutrients include calcium, potassium, manganese and iron.
Most sugars in your food waste go through several stages as it brakes down. The sugars available in molasses are readily available for the microbes to consume. Adding molasses to your compost causes an explosive growth of the microbial population in the pile. After adding molasses you will notice, the temperature in your pile heating up quickly. The increase in microbial activity will lead the material in your pile to break down to useable finished compost faster as well.
To add molasses to your compost pile dilute a cup of molasses to a gallon of water and either spray it onto the pile or water it in using a watering can.
4. Manure
Manures are high in nitrogen and full of microbes. I would recommend using animal manure from a herbivore ( goats, cows etc) when adding it to your home compost pile. Animal manures from carnivores or omnivores generally take longer to break down. The bacteria found in the gut of animals that consume meat often contain pathogens. Getting the temperature of the pile high enough to kill off pathogens isn’t always possible in a home system.
All manures are nitrogen and microbe-rich. They can quickly heat up your compost pile and speed up the decomposition process. And, since the microbes in your food waste are different from those in animal waste you end up with a rich, diverse microbial population that will support a healthy soil food web in your garden.
5. Your Best Garden Soil
If you already have healthy soil in your garden adding a shovel of your best soil can also boost your new compost pile. When you are just starting your pile, the microbes are slowly reproducing. By adding some of your blessed soil you’re also adding trillions of microbes into your compost pile as well. These microbes will multiply quickly and populate your compost pile.
“There are more microbes in a handful of healthy soil than there are stars in the sky”
From the book “Kiss The Ground”
Adding soil to your compost pile is also good because it absorbs nitrogen and reduces the amount of nutrients leached from your pile.
If you ever have an issue with your compost giving a foul smell adding some garden soil (especially one that contains heavy clay) to your compost pile will quickly absorb the smell.
6. Compost Teas
Compost teas are great because they can contain a wide range of microbes from many sources. When starting your pile the only the microbes that are already present can multiply. By utilizing a compost tea you can not only spread up the composting process but add to the diversity of microbes present. The greater the diversity of beneficial aerobic microbes in your compost pile, the better it will be for your soil as well.
7. Eggshell powder
Eggshells are another good addition to your compost pile. Eggshells are almost 100% calcium. Calcium is important for building the cell structure of plants. It is also a natural buffer in soil and helps regulate soil pH.
Calcium is particularly important for plants like tomatoes and eggplants. Without enough available calcium, these plants are susceptible to blossom end rot. When making calcium powder from eggshells you want it to be as fine as possible. This allows a greater surface area for the microbes to work. Breaking down that calcium powder into a form that is available for your plants.


8. Bokashi Bran
Adding bokashi bran to your compost bin may seem a bit counterproductive. After all, bokashi is used for fermenting food waste in the absence of oxygen. While this logic is sound, It is also oversimplified. Bokashi composting doesn’t work simply because of one type of bacteria. It actually works because of a group of bacteria living in symbiosis.
The lactobacillus bacteria found in bokashi can quickly break down organic matter and convert it into a plant-available form. LAB is also particularly good at suppressing plant pathogens and diseases.
While managing your compost pile some small areas of the pile can easily go anaerobic; especially if the pile isn’t being turned regularly. Adding a handful of bokashi bran can speed up the composting process while ensuring plant beneficial microbes will be present. Even if parts of your compost pile become anaerobic.
9. Alfalfa Meal
Alfalfa meal adds nitrogen and protein to help speed up the composting process. Adding alfalfa meal will heat up the pile within a few days. If your compost pile has stalled, alfalfa meal is a great way to get it going again.
10. Biochar
Biochar is a solid material obtained from the thermochemical conversion of biomass in an oxygen‐limited environment. Biochar is a useful amendment to soils. It sequesters carbon and improves the soil properties.
However, new studies suggest that the addition of biochar to our compost also has benefits. The addition of biochar can lead to significant reductions in volatile organic compounds (VOCs). VOCs hinder plant growth and are usually responsible for making compost smell bad. The result suggests that something occurred during the co-composting process that affected the co-compost’s ability to promote plant growth. The mechanism by which co-composted biochar increased plant growth has yet to be fully understood, but the study authors suggest that these effects may be due to positive impacts on soil health, particularly the composition and activity levels of the microbial community.
While biochar can be a bit on the expensive side you should be able to see a significant difference with it making up 2.5% to 5% of your compost pile.
Final thoughts
Compost produced from a wide range of organic materials is a huge benefit to the garden. Ensuring we encourage the growth of beneficial microbes in our compost products will pay off in the running of our garden. Having healthy, microbial diverse soil helps reduce disease and increases nutrient availability.
Chemical fertilizers will only benefit your plants for as long as they are present in the soil. If you are using chemical fertilizers and seeing “increased benefit” this is a sure sign that the nutrients either weren’t present in the first place or the right mix of microbes weren’t available to make the nutrients present in the soil available to the plants.
By ensuring you have healthy soil you are always adding and strengthening the soil food web which will have long term benefits on your plants and ultimately your health.
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