I have been mulling over this idea for awhile. A few years back I was able to grow watermelons that produced seed without watering them but once or twice in Mediterranean Sacramento California by digging a mulch pit and planting seeds around the edge of the hole. The hole was a foot and a half deep and about as wide filled with grass leaves and any other organic matter I could find. This planting was in a relatively open field with no real protection from the wind or sun. The watermelons were small but they did produce seeds. My goal was to produce "Rambo" resilient seed stock. The success of this method got me thinking about dry farming using a similar method on a larger scale. Instead of singular holes I invision long trenches filled with wood chips alternating with beds for growing fruittrees, shrubs, other edible plants and support species. The wood chips would act as a below grade reservoir of moisture for the plants growing in the adjacent beds as well as act as pathways. The whole deal would be covered with a deep mulch of wood chips a foot deep or more. Below is a simple drawing of the whole system. My hope is that this would allow for a healthy dry farmed crop in drought stricken Sacramento and our extended 9 month dry season. The ditches would of course be deeper than the original mulch pit I described. There is a rough picture below of the idea. Tell me how I'm crazy lol...
I've used a similar method for my garden, but I've used buried wood in 4' deep, 85' trenches - mixed with old wood chips and grass clippings, and sand - for the beds, and wood chips on the paths. I think that using buried wood works well because it lasts much longer than the wood chips. I suspect that trenches filled with wood chips used as paths would have to be topped up quite often as the material breaks down and compacts. Also, if I were planting things like trees - or even shrubs, or any tall plants - I would make sure that the space between the trenches was enough to support them. Using wood chips and other bits of organic matter doesn't produce a very strong growing medium - my broccoli and kale plants even fell over - so shrubs and trees would need good solid soil in order to be strongly rooted.
But the idea of putting organic materials of some sort in trenches or pits is a great idea, and I think it is one of the best ideas for growing without irrigation. Banana circles are a great example. I'm going to do something similar for growing squash; but I'll have to rethink the process for growing taller plants such as corn and quinoa. The growing medium is just not strong enough to hold the plants up. Something like you're planning - with the trenches used as paths, and the plants growing between the trenches - might be in order. But because we have sand and very little top soil, I'll be doing a LOT of soil building to get anything to grow there.
So, yes, I can see merit in your plan (and I love your Happy Farmer), but there are a few things to consider, depending on what you plan on growing, and what your soil is like.
Do you live near or in any urban city? There are always landscaping companies that cut down trees and scrubs that might be able to dump their load on your land instead of the dump. Mix logs, leaves, branches and wood chips that you can get. Then you have a hugel culture filled pit.
One thing to think about is the size of the tree you are planting next to the wood chip pits. If they will become very small trees there is less of an issue, but if they become tall then the roots have to grow into some solid ground as well. You do not want a wind storm to knock over your trees because their roots does not have enough solid ground.
I would plant drought tolerant plants and trees that are used to living on very limited rainfall. Those that can survive in your climate.
Permaculture is all about using the resources that you have access to. If you do not have access to certain resources then you find other creative ways to trap and sink the available water, there are many....
It there is no way to get the wood chips you desire in large quantities to fill the pits, then I would simply dig the pits and refill it with the loose dirt that came from it. This alone will do wonders for soaking in any available moisture. Then with the limited woodchips and leaves you can find you can mulch the top.
Looks good to me! I'm trying a similar idea with using buried wood pits next to my tree plantings. And my entire kitchen garden except where some apple trees are planted is buried wood. Trees probably shouldn't be planted on top of buried wood because of uneven settling.
Thanks for all the replies guys. I should have made a note that I live in Sacramento which is known as the city of trees. Even though we live ina dry climate we have a lot of trees and I can get as many wood chips as I want. I figured that I would have to top off the wood chips regularly maybe twice a year but since I have a near unlimited supply and once established that would be almost all of the regular maintenance required of the system it didn't seem like that much of a chore. I could get logs as well but wood chips are more available and they will drop them off at your farm/garden for free. I was planning to have the beds be about 4 feet wide and the pits up to 3 feet deep and wide. That should be enough for fruit trees and nitrogen fixers that are chopped and dropped. I figure by the time the trees are very large the wood chips will be converted to soil. I could even add some coffee grounds or brewers grains to help them compost faster as I can get those for free in large quantities as well. My goal is a garden that can take care of itself beyond a little maintenance here and there.
Great idea, and it is a climate appropriate analogue to what I am doing in NW CA near the coast where I have wetter winters requiring elevation of root systems at times of flooding.
I would recommend two adaptations to your plan based on experience with straight wood chips and hugel beds. Hugel beds/trenches, with larger pieces of wood that may be surrounded with woodchips, are better because how the central mass of the branch/log better moderates the extremes of your climate in terms of heat and moisture. Less surface area to mass means longer moisture retention. You can take a log that will only dry out after 1000 dry hours in the sun and make it into woodchips that will dry out in one hot day.
The other advantage of larger pieces of wood is the vasculature of the tree already being there. For plants, fungus and all the nutrients and water they need to transport around to live, its like moving into an area with a trail/road system already built for you. Trees are the worlds most amazing pumps of not just water but nutrients and are incredible energy and nutrient sinks. Chipping them up loses a lot of this structural and longterm value. If you only have woodchips, use them (I'd recommend as deep mulch on top of root systems), but if you have access to in tact wood it would be very helpful for water retention, wicking and nutrient transport. Chipping up wood is a bit like tilling the soil, it seems like a good idea because its what everyone seems to do, but its wasted energy for short term gain at best.
Oh, and finally, I'd build at least one protective berm if you have the materials, it will greatly reduce your evaporation and effectively makes everything behind if a trench (cooler, moister etc).
This is all just my opinion based on a flawed memory
Building on the idea of soil building and possible dry farming... what if I used an auger to bore holes through the hardpan replicating soil ripping like key line plowing. This would allow for deeper water and root infiltration. It also opens the possibility of injecting beneficial micro organisms (compost tea) directly into and under the hard pan increasing microbial soil building and clay/ mineral fluctuation as discussed by elaine inghamhttps://www.youtube.com/watch?v=x2H60ritjag. This would also be a great breeding ground for Alabama jumpers which would feed on the wood chips and create burrows up to 12 feet deep http://alabamajumpers.com/alabama-jumpers-yard-and-garden-compost-worms/. These should be kept out of established natural areas but should be safe and very helpful in garden beds. They also make really good fish bait as they are true to their name and love to "jump."
I'm doing something like this. I've just made one bed this winter, so I can't talk about results, but some guy from Turkey adviced me to make an improved version of this, which I am now in process of building. Will talk about it once I have some nice pictures.