Paul continues answering permies' members questions about hugelkultur with Cassie.
If you live in an area where there is 100% sand should you import topsoil? When you have pure sand, Paul says to never buy topsoil, however he will see a spot in a field with good soil and they are about to develop it he might take some of that soil. Most commercial topsoils are laced with persistent herbicides. Paul's says do not buy it. If you can not find topsoil from a natural area, then you should try to convert you sand into topsoil. Plant legumes and nitrogen fixers. Consider planting grasses too. Where Paul is, millet grows well and builds topsoil. You need to try different mixes and figure out what works the best in your area. This question was directed with respect to a hugel mound. If you just covered the wood with sand, then all that happens is a petrification of the wood. The soil needs organisms to help break the wood down. Try criss crossing the wood. Load up the mound with legumes. We want them to set root in the wood. Don't be surprised if some wood at the top of the mound becomes exposed. Paul says it again: do not bring in topsoil because of the persistent herbicides.
Next question is the Hugel-Swale? Mythical creature?.
Paul says these are best used in tropical and sub tropical areas. These are not so good in colder climates. Much like bio-char which does not work well in cold climates as well. Paul refers to a conversation with Geoff Lawton where they debate swale versus terrace. Paul called the swale a frost pocket. A year after the first debate Geoff conceded to Paul's description. Paul feels that you want to keep cold air OUT of your system with a few odd exceptions. Hugle-mounds should be run perpendicular to the contours where swales typically run parallel to contour. When using a swale, water seeps into the ground and saturates the down stream area but when it is cold it creates a frost pocket. Paul refers to an article in Permaculture News where the hugel-swale debate was continued. Paul says that mixing lasagna gardening and hugel mounds is a big mistake. Do not mix the two techniques.
Next question deals with pests Paul talks about his infestation of chipmunks in his hugelbed. There was an explosion of life with the chipmunks. After doing nothing for a year, a predator seemed to help clean up this problem. The moral of the story is, if you have two many pests, the predators will find your problem. Pill bugs work the same way. Critters that like to eat pill bugs will be coming along soon. Pill bugs are helpful making compost but sometimes they stray into your garden. Paul feels that if a plant is doing very well, it will be ignored by the pill bug. If the plant is stressed or not doing well, the pill bugs will find it and devour it. Slugs are another common garden pest. Part of what you are trying to do is build and ecosystem and that takes time, sometimes years. When you are building these beds you will build them over the course of several years. The beds built first will me more mature than the ones most recently built. If you have mice and pill bugs, you could always run chickens or pigs over the mound. You could incorporate these into your design.
Next question deals with beds that are more than ten years old.
What are some of the maintenance issues with older beds. Paul built some beds 11 and 10 years ago on a farm he use to work on. He has not been back to that bed in a long time so he can not say how the bed is doing. Paul has not been to Sepp's beds in Austria. Sepp does talk about rebuilding his beds every 30 years. Paul may make a trip to Seattle to see the beds he built ten years ago. He visited the beds four years after they were built they looked beautiful and were full of life but the next owner was ripping out Paul's plants and putting in ornamental flowers. Paul went back two years later and saw magnificent sunchokes and rhubarb and lots of volunteertomato plants growing. Paul feels a trip to Seattle may be in order and it would be interesting to see how the mounds are doing. These mounds were built between the sidewalk and the road so it is easy public access. Paul does not have a good answer to this question at this time.
Next question is about when should hugle-mounds not be used? When no wood is available? or when there is very wet weather? In a tropical climate, it is difficult to have mulch so when you mix wood and soil it breaks down very very fast so that you would not get much benefit. This is a guess on Paul's part because he has not worked in that climate. Biochar might be a better solution in this climate. By Sepp's rule the hugelmound would be replaced in about thirty years. You want to make sure you are giving the wood something to build the soil with. It is possible to build a mound without wood. It might not be called hugel, but you are adding lots of organic matter to a raised bed. You can build a raised bed garden and some people think of that as a 3" raised bed but a hugel bed might be 6 or 7 feet tall. There are mounds of varying height all over. Someone might build a hugel mound that is only 2 feet tall.
What is the best form and way to hold the soil in place over the mound? Wood that composts quickly will cause a great deal of shrinkage. Paul says that the best form is steep sides. If the bed deflates a lot, several feet, then you should add to the top of the pile where you have things growing that you do not care about killing off.
What is the one thing you should never do with hugel-mounds?
Placement, squiggly lines perpendicular to contour is good. Diversity on the inside and outside of the bed is good. If plants are not going well, cut it out sooner rather than later. Stay away from the hugel-swale. The rules with sand are similar to using clay. You need to plant things that will grow thru the sand or clay. Do not put cedar or honeylocust in the mound. Woods that are slow to decompose are bad. Do not chip the wood. Do not ever use a wood chipper EVER. Big chunks of wood are better to use then small chips. They decompose quickly and immobilize the nitrogen causing the bed to not work for growing things. In the early stages Paul put big sticks in his early mounds but when the stick is embedded it wicks water out of the bed. Do not use commercial topsoil or compost because they contain chemicals that have a half life of ten years. Do not introduce persistent herbicides into your soil.
Age of wood? Does the age of the wood matter?
When wood is green there will be very little fungus in it. After about four days the fungus can start to move in. Paul would say that wood that has brown cubicle rot, it looks like the log is made of cubes. This fungus will last as long as biochar. This wood is so rotten that if you try to move it it falls apart but it will last for a very long time.
When to hugel and when to swale?
Paul pretty much already covered this.
Is it possible to place to much wood in a bed?
Paul says yes, the proper way is a layer of wood, then apply a layer of soil, then add more wood and another layer of soil. You do not want to add to much wood. Lots of wood with a small amount of soil will not grow anything well. You want to try and boost the nitrogen as quickly as possible to get the bed going.