underground huglelkultur

Hello - I have a small garden in UK with heavy red clay that had been compacted by machinery before I moved in (what a nightmare).

I'd like to dig a composting pit perhaps 3 feet deep to fill with vegetation. I won't want to access this later - the idea is just to slowly work my way around the garden making these pits to get some much needed life in the soil.

I am stuck on the science bit. Should I get fungal life going first with underground hugelkultur type composting (tree branches/composted bark)? And would fungal growth happen down at the bottom of a cold clay pit?

I thought of putting the branches/woody stuff on the bottom half of the pit and then filling the rest with used organic straw/manure. However, would the heat from the decomposing straw/manure kill off the fungal growth developing (hopefully) on the woody stuff underneath?

I thought that once my pit gets activated and sinking into the ground, I'd top it up with kitchen waste type composting.

It seems that composting wood to get fugal growth is very different to traditional type composting of kitchen waste. In the woods with the deep spongy leafmould ground, there doesn't seem to be any worms amongst the years of falling leaves. However, when I've composted my kitchen waste there are worms and obvious insect life aplenty.

I'd really appreciate your opinions!

We started doing this two years ago and the results are excellent this year.

Our situation was that, we terraced a hill with 3foot x 10foot rows. We only had around 6 inches of soil on top and then it was all pure sand and granite as a base, anywhere from 3feet to 10feet down. It was very hard to grow in, and required constant fertilizing and watering.

I've dug out a couple of these terraces, one at a time, 3feet deep. The first foot or so was filled with logs and sticks placed in tight, and then I covered it all with composting material. The top couple inches were then covered with soil and finished compost. I made sure to have at least 16inches of space from surface to log; I didn't want any issues with a pitchfork when aerating.

The ones that were made at least a year ago, were planted in this year. Everything is growing twice as large on those terraces, as opposed to our bad ones.

I know you see most people making hugelkultur mounds to take advantage of the north/south effect, but it definitely works to just dig a hole in the ground and fill it up. Composting and being patient for a year, meant we started out with fresh soil and there was a year for everything to balance.

Also, I've no idea about how the biodynamics would work out, or if this is pro/con growth for fungi or bacteria. We've just had good results with this.

Your idea sounded fine. You want the top to compost into soil over the year. But, the fungal growth and decomposition of the logs should hopefully take 10 years or more. The log sits there holding nutrients and moisture for what's above during dry spells, while it decays. I'd say the fungus gets there sooner or later.

I know exactly what you mean, Georgia is famous for its heavy red clay. On my particular plot, it can be found 6" to 12" below the surface, and as soon as I hit it I stop digging. I leave that to the worms and radishes. They have more energy to bore holes into the clay than I will ever have. I build my hugelkultur from the clay bed up, with well rotted wood, brush chippings, grass clippings, and leaf mulch, layered with whatever topsoil I was able to set aside while digging down to the clay.

Yes, heat can kill off fungal growth. You don't want to be burying a compost pile, as the heat-loving composting bacteria are going to outcompete the fungi. You can accomplish this by making sure the pile is low in nitrogen (greens). If you keep the amount of manure low, and the pile is mostly straw, then you can achieve a fungal dominated pile. The other thing that kills off fungi is lack of oxygen. If your pile of straw gets so wet that it begins to clump together and smell bad, then you have anaerobic conditions and the fungi are dying off. If you have chipped wood and lots of little twigs and branches in your pile, they will usually have enough surface irregularities so that the whole mass won't be sticking together and excluding oxygen.

Another way to keep up the fungal diversity is to collect mushroom that you come across and toss them onto your pile. There are many species of fungi and they each find their niche in the decomposition process. By adding lots of different kinds, you can be sure that all the niches are working to break down the organic matter in your pile and are making the nutrients available to the plants you want to grow.