Biotrash Pit, aka : Hugelpit

"What is a biotrash pit?", I've been asked. I have used the term often enough on the blog, so perhaps I need to explain. It's a hole in the ground.....in Hawaiian, a puka.....into which I throw my coarse organic debris. Some of the dips on my farm are big enough to hide a truck or car in, for real! Over the years I've filled a few in then planted bananas. No need to water or fertilize the bananas, ever. Even during drought, the bananas seem to do fine. And since I add a generous layer of coarse mulch seeded with a bit of manure each year, no need to use commercial fertilizer. 

My pits are a good place to throw twigs, branches, tree limbs, chunks of tree trunk, dirty cardboard boxes, banana trunks, discarded coconuts, palm fronds and any other large organic matter that will take time to degrade. Plus I throw in lots stuff to fill in the gaps.....just about anything. Weeds, sawdust, dirt, excess manure, old kitty litter, dog poo, paper trash, macnut shells, rotten fruits, pulled out ferns from the pastures, garbage that's too rotted for even the chickens to eat, and just about any and all biodegradable waste. 

Above -- It's really difficult to make sense out of this photo, but believe me, this was once a giant hole that easily could have swallowed my truck. I've spent the past several months filling it in with the debris generated by our last wind storm. Lots of leaves, twigs, and tree branches. But also some knarly tree trunk chunks.  I would throw in about a two foot thick layer of stuff then squash it down by either tramping all over it or running the ATV over it. Then I add a light covering of soil Inorder to add soil microbes, and add some water to wet it down a tad. If I have them handy, I'll also throw in rocks as I fill the hole,mabout 3 per cubic foot, to add a tad of stability. The reason for the rocks is that I plan to plant banana trees. If the ground is too soft, the trees will simply fall over from the weight of the bananas. 

I've thrown pickup truckloads of green waste into this hole. As I said, months worth of clean up. Many layers upon layers. It amazes me just how much green waste it takes to fill up a hole. 

As the pit is being filled, I'll add water if needed to keep things lightly moist. This year has seen a lot of rain, so I've been spared the chore of hauling water to the pit.  Once the pit is filled, I'll top it off with a light layer of dirt/compost, then apply a couple inches of coarse mulch. Whatever I happen to have handy.....ti leaves, banana leaves, sugar cane waste, bamboo leaves, coarse weeds, guinea grass. It all works as a coarse mulch. I'll now add water to these layers so that everything is moist. 

Ah-ha, time to plant bananas! I'll make a hole for each young tree, a hole large enough to hold about a 5 gallon bucket of soil.

Above -- Hole made in the debris. I set the bucket into the hole so you could see it.

Above -- Fill the hole with dirt.

The tree gets planted and watered in. Then I'll mulch around it with a 6 inch layer of mulch, such as bamboo leaves or grass clippings. Ta-da. Done! I can now walk away, only to add mulch from time to time to keep the soil covered. Of course, this is a good spot to dispose of my coarse, large leaves. Leaves and stalks from bananas, ti, sugar cane, guinea grass, etc all make good mulching material around the bananas. 

The homestead farm is 20 acres. There are lots of good sized pukas on it, so I don't think I'll run out of biotrash pits in my lifetime. I never need to haul any of my green waste to the dump. 

One thing I've learned is that all that green waste decomposes over time. Thus the hole sinks. So I initially grossly overfill the hole knowing that it will sink at least 50%. Once I plant the bananas, I continuely add mulch. This helps keep the hole filled in, but not completely. The more tree trunks and limbs used to fill the pit, to slower the sinking process proves to be. 

Putting Unwanted Logs and Branches to Good Use

First of all, most wood round here gets used for firewood or building material. But I have plenty that I don't want to use for those purposes, for one reason or another. Many a time hubby wanted to load this stuff into the truck and cart it to the dump. But I balked. It just didn't seem right. It had to be useful for something on a farm. I just hadn't discovered its use yet.

First thing I did with this debris was use it to fill in a truck sized hole we had in the pasture. This is the hole I almost drove my truck into one day while clearing the land. So I was bent on filling it in. It took a lot of material and time to fill that giant hole, but eventually it was done. I topped it off with a thin layer of soil, then I started looking round for more holes. I found them alright, but after a year or so I noticed that something unusual was going on at the first hole I had filled in. It had sunk down a bit but that wasn't unusual. The weeds and grass grew very nicely there, staying lush even during drought months. I never watered the area, but things stayed green and perky while the grass around it had stopped growing. Checking it out with a shovel, I unearthed some of the branches and logs. It was quite apparent that they had absorbed and retained scads of water. Plus the smaller pieces were already decomposing. Hummmm. It got me thinking.

I finally found a beneficial use for woody debris, other than just as fill for holes. It could be used as the foundation for growing beds. We get plenty enough rain here in normal times for the decomposing wood to become very water ladened. It would retain this water, making it available for growing plants. And if I supplied nitrogen to the pile, it could serve as a nutrient source too. So I went off to experiment.

The driveway slopes off. I've rolled big rocks to form a back
wall. It's 2 1/2 feet deep in the back. Next step is to fill in the
hole with trunks, branches, etc. This will become a flower bed.

I had planned to create flower beds along the driveway, so I opted to make these my experimental areas. There were spots where the ground dropped away from the driveway sides. By building a rock retaining wall a few feet back from the driveway, I now had a hole that I could fill in. Into the hole  went all sorts and sizes of woody material: logs, branches, twigs. As it went in, I attempted to eliminate all air spaces using smaller pieces, plus some dirt, plenty of weeds, and horse manure. I packed it down as the hole filled. If it didn't rain as I filled, I added water to start the wetting process. When the hole was full, I topped it off with a couple of inches of soil just so that there was soil to plant into.

The first flower bed I made I planted sweet potatoes into because I hadn't yet grown any flowers to transplant into the bed. The sweets did great! I never had to add fertilizer or water. After the sweets I planted a banana tree and flowers. They too did fine and were lush and beautiful. The banana tree clump is still there and doing good, but I have since replanted sweet potatoes. This is the third year. I've never irrigated the bed, but I have used compost for mulching it.

I'm working on the fourth bed now. The only problem I am seeing so far is that the neighboring trees are aggressively growing roots into the beds. This is a boon for the trees, but means that the beds become less useable as flower beds as time goes by. Ohia trees can form a very dense root mat.

I plan to use this idea on my arid south farm, which by the way has no ohia trees on it. So the beds should work better since they won't be getting root-choked.

Recently I discovered that using woody material for making beds is nothing new. There is a system called "hugelkultur" for making growing beds as ditches, swales, and mounds. Wow, looks like I inadvertently reinvented the wheel!