GYO #6: COMPOSTING

We hoted a workshop with composting cooperative Compost Mentis in July as part of our Grow Your Own 2024 series.

Compost Mentis have been helping us look under the microscope at our compost and soil for the last three years now. It has been fascinating to track the changes in our compost.

We are passionate about composting at Global Gardens since it really is the heart of the garden - and with a better heart, you have better health! A healthy compost system can build soil fertility significantly and support crop health and quality.

The Compost Mentis team suggest what we are aiming for with compost is something that is not too wet, has a good smell and is chocolatey brown., When you squeeze it you want it to feel like a damp towel - with not much moisture being released but signs of moistness. The composting team encouraged us to add more woodchip to our compost pie to increase the fungal populations.

Looking at the ecology of soil and compost under the microscope can help us understand better the health of the soil, with the diversity of species of microbes and mycorrhiza giving indications of potential remediations, additions or changes that may be needed.

Windrow Compost

Currently, we have a windrow system at Global Gardens for our compost. We stack compost about chest height, layered with a mix of green (grass clippings, fleshy stems, veg waste, coffee and tea grinds) and brown (twiggy material, cardboard).

Observations of our compost seemed to show positive signs:

Not too wet- damp sponge
Smelt good
Brown (carbon) material
Heat (warm, not hot)
Currently in windrows and shaded

pH analysis of our compost heap indicated that it is a slightly higher pH (increasing from 5 in 2023 to 6.5 this year).

Our compost heaps are packed full of worms and investigation under the microscope indicated a lot more invisible life present. We saw nematodes, amoebas, bacteria and protozoa - many of which are feeding our worms! We also found a number of beneficial fungi but not as much as last year so the Compost Mentis team encouraged us to add more woodchip to try to nurture higher levels of beneficial fungi.

Compost Mentis team reflections from Compost Heap 2023:

"Noticing quite a lots of fast moving ciliates, paramecium and others who are most likely feasting on anaerobic bacteria – possibly due to compost not having enough carbon material, being a bit wet. Also a high density and diversity of bacteria (protozoa can live symbiotically with bacteria, increasing the populations as they graze). There may be some examples of protozoa in cyst forms, though much less as this is wet compost (good conditions for protozoa) contrasting with the humanure, which is maybe on the dry side. There were a couple of nematodes too, high numbers of protozoa can outcompete nematodes because they rely on the same food source (bacteria and fungi). There weren’t as many examples of beneficial fungi compared with last year when we looked at the compost."

You can watch the video too to see some of the life in our compost heap under the microscope:

Compost Mentis team reflections from Compost Heap 2024:

"Bacterially rich, with lots of smaller strands of beneficial hyphae, probably feeding off the slightly higher carbon content introduced through adding cardboard. We saw 1 nematode, and some testate amoeba, suggesting that nutrients are being cycled as larger organisms graze on bacteria and fungi. The organisms we saw suggest the pile is fairly well aerated with a good supply of oxygen. If you want to increase the fungal population, considering adding more carbon materials like woodchip or wood shavings."

Ciliate: protozoa with hairs on them, they use their hairs to move around!

Humanure

Our humanure has also increased in pH (increasing from 4.5 to 5) - following investigation last year, we were encouraged to add more woodchip and sawdust to counter balance the human poop! To feed bacteria, you can add more nitrogen rich foods including human poo, garden waste, food waste and green leafy materials.

Compost Mentis team reflections from Humanure 2023:

"We saw 1 nematode, and a generally quite bacterially rich sample, with lots of different species of bacteria and protozoa around feeding on them. Protozoans were mostly testate amoeba and flagellates, with the occasional ciliate – suggesting bacterial species are mostly aerobic, with maybe some anaerobic types."

Compost Mentis team reflections from Humanure 2024:

"We saw a very different picture to last year, with a high number of protozoan organisms (ciliates, amoebae and flagellates), and very sparse population of bacteria. The presence of ciliates suggests slightly anaerobic conditions, and low bacteria count could mean not enough nitrogen foods are being added. You could consider adding some green garden waste every now and then to add more diversity. It’s possible that the willow woodchip is also decreasing the pH, though humanure is generally slightly acidic."

Suggestions from Compost mentis to improve our composting:

~ consider adding a variety of composting systems, e.g. a wormery, leafmould and thermal system for pervasive weeds and weed seeds. (see this video for a cool DIY method for thermal composting)

~ a batch system may also help to keep track of your composting process and be more inviting / accessible for garden members to get involved with

~ you could consider more of a shelter for your windrows, to protect compost from the elements

Tools and equipment that can be helpful for getting to know a compost heap:

~ pH meter can be useful indicator of nutrient availability, contaminant risk, and biology

~ a compost thermometer is essential for monitoring the changing temperatures of your piles

~ nutrient tests are also helpful to do every season to understand a) any deficiencies in your soil and b) the nutrient content of the compost you are making and adding.

~ a petrol hedge trimmer could be useful for chopping up twiggy material into smaller, more compostable chunks

Summary of learnings & what’s next for Global Gardens compost piles! (from 2023)

Using the humanure soon, possibly to boost phosphorus in orchard soils, or to experiment with using it for food growing. This would mean switching the chambers over in 2025, and leaving the existing pile to rest for 2 years.
Interest in creating a leafmould pile, and mixing leafmould with woodshavings and compost to inoculate the humanure soak with more diversity of organisms, and moisture.
Adding more fungal foods to your compost, chopping up brown materials. Woodchip deliveries can be organised for free via chipdrop
Capturing and using urine to address low phosphorus levels in orchard (diluted with rain water 1:10). Humanure could also be a good source of phosphorous, and nitrogen in ammonium form (good for trees)
Planting around the soakaway to create a wildlife area, nettles, comfrey, willow / other nutrient hungry plants
Doing more contaminant tests with Safe soils / local university labs
Carry on composting, as this seems to be having a good effect on the veg beds, and can help to immobilise possible lead contamination in soil.
Developing a more formal soil, compost and humanue monitoring programme to check how soils may be responding to management and to help inform decisions eg when to move humanure.