Compost Tea & Extracts

WHAT IS COMPOST?

Compost is organic matter that is being transformed back to soil. The workforce doing this are billions of micro-organisms that breakdown carbon materials, produce exudates that feed and bind the particles together, and stabilize the nutrients found in the parent material. As composting is a process the compost you buy can be anywhere along that process. If you get compost that still has a lot of parent material visible it is far from finished. A finished compost should be dark in colour (but not black as this indicates it has become too hot in the process and has lost some of its benefits), have an earthy soil smell or very neutral, but should not smell bad. The end result of a good composting process results in humus which can remain stable in the soil for many years, full of microbes and nutrients like humic and fulvic acid that benefit plants. Compost has many benefits for your farm and garden, but we will save that for another article.

COMPOST TEA

Compost tea is a method of extracting and multiplying micro-organisms in water. This process was popularized by Elaine Ingham of Soil Food Web fame, truly the mother of soil biology. Elaine has helped thousands of farmers restore and improve their soils through the work she has done and guides people through the process of making compost teas.

The compost tea process involves several components:

• compost

• water

• agitation

• air

• food

The most common way this is done is in a vessel with some type of aeration system that creates enough agitation to extract the micro-organisms from the parent material and put them in a liquid suspension (like our Dynamic Mixers), then you feed them with things like fish, seaweed, humates and a wide variety of other concoctions. The process can take between a few hours to days depending on the practitioners’ beliefs and experiences. The most common cycle is 24 hours. Some people also use the process with minerals added, this is supposed to make the minerals more available to plants. 

Cyclone Dynamic Mixer

This process gets the micro-organisms to reproduce rapidly. This is very evident if you follow the process with a microscope, you can watch the population of organisms increase over time. The idea is that you can get the benefit of a large amount of compost by using just a small amount and increasing the organism population through the brewing. Figures vary but some say you can get the effect of a ton of compost by only using 10 kilos.

The advantages here seem obvious, if I only have to use 10 kilos instead of a ton there is a huge cost savings, and there are a great many success stories of using this method. 

But what are the down sides?

Around 2005 Elaine Ingham conducted a series of speaking engagements around New Zealand on soil biology, compost and compost teas. This fuelled a lot of excitement around the country along with many experimenters and compost tea operations. Today those compost tea operations are mostly gone and I only know of a few farmers and growers that still use the process, so what happened?

Compost tea has several challenges…

First you need a high-quality compost to have success, for the most part the compost in New Zealand did not meet this standard, but things are improving.

Second to get a good result you need to monitor the process with a microscope. This takes specialized training and time.

Next it takes 24 hours (more or less) to make a brew.  A lot can happen on a farm in 24 hours so getting the process finished and applying it is another challenge.

Once brewed now you must apply it. For most agriculture sprayers this requires straining the liquid so it will go through the spray pumps and nozzles. When straining out the liquid you are often straining out what you actually want to be putting on the land. (See Cyclone Multi-Task Sprayers to solve this problem).

While you are brewing you are creating very specific environmental conditions. One big question is, have you then created conditions for only a select group of organisms? As diversity is the key to soil biology is this process limiting the end result?

As you can see the process can be complicated. Time shows us that most people did not get it right as very few compost tea companies still exist (at least in New Zealand). Now we know that compost has great benefits to soil so what is the answer?

Cyclone Multi-task Sprayer in action

Compost Extracts

A much simpler method is compost extracts. This process requires some of the same things as compost tea. However, the extraction process is much shorter, say 30 minutes and we don’t add any foods until we apply the extract to the field. Air is probably not needed, but vigorous agitation is generally used.

Another method is to simply put the compost in a container with water and drain out the water after a period of time, this can be as short as an hour or up to several days. The liquid should be dark in colour and not have any bad odours, if it smells bad it has gone anaerobic.

So, which do you use? If you think about the compost tea process it is designed to create an aerobic environment rich in foods for microbes to flourish. But if you have an aerobic environment on your farm or in your garden then why not just but the microbes and food out in that environment let them do there flourishing out there? Much simpler and we believe it works just as well, at least for soil applications. If you are trying to use microbes in a foliar application to help the arboreal food web on the leaf surfaces, then probably brewing compost tea should be your choice.

But there is one more thing… One experience that led us to using extracts was a large pile of debris that we had strained out of our compost tea brewer before putting it in the sprayer. It was full of beautiful long white strands of fungi and worms.  We realized then that we were leaving out a big part of the equation. So, while the extraction process was easier we still had to strain the liquid before putting it out. This is what led to us developing the Cyclone Multi-task Sprayers. Although we still have to screen the compost before we put it in the sprayer, we are getting a lot more of the parent material out on our farm. This parent material is really like the home for all those microbes which in theory should make their survival rate into the soil much higher.

Our farm is testimony to this process. We have been making compost and applying compost teas and extracts for over 20 years now with no commercial fertilizers and only small amounts of lime. You can come and see the results for yourself.