No-till & Woodchips Gardening

Asanga Jayasinghe, a journalist from Sri Lanka who reports on agriculture posted a question on the Regrarians Facebook page:

I have read that Zero tillage is a good practice, so how do I cultivate annual crops without tillage? How do I make growing beds, how do I mix organic matter without tillage? Please help me to understand the Zero tillage concept.

On a grey and snowy morning in the woods, I had a little time to respond.

IMG_7233You are correct, Asanga, zero tillage is a good practice. How you actually go about it depends on your scale. It depends on what machinery you have available or how much you are dependent on hand labor. It also depends on what kinds of organic matter mulches you can grow or are available in your area. The terms “zero-till” or “no-till” can be somewhat misleading. What we are really trying to achieve is “reduced tillage” agriculture– greatly reduced tillage. When I garden no-till-style, I consider any soil disturbance deeper than 4″ to be tilling, but that does allow me to practice hoeing or surface cultivation when appropriate, like when you are preparing a fine seed bed, without going against the principal of reduced tillage. In nature, soil is most often built by adding nutrients to the surface. There is no need to “till in” composts and manures. Often you can distribute these on the surface and leave them there. Mulching afterwards is always best when feeding in this way, or using a shallow cultivation, no deeper than 4″, to mix the amendment in, putting the amendment in greater contact with the soil. My aim is to allow the majority of the topsoil layer and upper subsoil to remain undisturbed for as many seasons as possible. A major key to all this is to eliminate all sources of compaction whether it comes in the form of foot traffic or machinery. A soil left to its own devices will develop a texture like a loaf of bread. This arises in multiple ways: In reduced-till growing, often spent plants are cut off at ground level and their roots are left in place in the soil to decompose. As the roots decompose, the channels they have formed remain to facilitate air and moisture movement and provide pathways for soil flora and fauna to use when traveling. The channels left by worms and the like will also serve these functions if they are not destroyed by tillage.

Sometimes tillage occurs anyway like when you dig potatoes or other root crops that might require it. You can plan your crop rotations to include one time in several seasons when the soil in any given location is more deeply disturbed, but the elimination of tillage is always the goal. Carrots and the like that are often dug out with much soil disturbance, I don’t dig out. I use a garden fork to loosen the soil only and pull them out vertically leaving the soil in place as much as possible. Whenever possible, I use mulch. It is said that nature abhors bare soil and uses many different methods to make sure there’s always something on top, protecting the soil. For instance, I will prepare a fine seed bed for carrots which might lie bare for several weeks, but once the carrots are tall enough, I will place mulch between the rows. The carrots can be harvested without removing the mulch (in fact you will discover carrots to be so much easier to harvest in the pliable, loose soil that’s always found under a good layer of mulch).

Transplants can be planted into the mulch for a follow-on crop. Just make a well in the mulch and plant your starts right in. You can try this: Do an ample feeding and a shallow cultivation on a bed where you will grow potatoes. Take your seed potatoes and place them on top of the soil where you want the plants to grow, possibly pressing them in so they’re half exposed. Now cover the entire bed with a think mulch. A minimum of 8″ of wood chips (any kind, it doesn’t matter). You can put on 12″ to 16″ of wood chips if you have enough. I would use a minimum of 18″ of mulch if straw or a similar, looser material is used, 2 feet thick or more if available. It will settle some. The potatoes will grow under the mulch. No light should reach them if mulched well. You won’t need to hill the potatoes. Just make sure when you harvest them that you pull off all the mulch first. A layer of course organic material on top of your soil protects and builds your soil without any binding up of nutrients. Soil fauna rise to feed on the mulch where it touches the soil and they carry the nutrients obtained deeper into the soil. It’s when you mix your mulch into your soil that your nutrients get bound up. Remember, even if this does occur, the binding up lasts only as long as it takes for the organic matter to fully decompose. Then your soil will be richer than when you started. Weeds that make it through mulch are always easy to pull out because the soil under the mulch will be loose. They can be pulled without disturbing the mulch.

If you are transitioning from a tillage system to a no-till system, often there is much soil compaction to overcome. Again, depending on your scale, there are different ways to mitigate this. On a broad scale, using a deep shank subsoil ripper is often used. Some people utilize the “Keyline” system when doing such subsoiling using a “Keyline Plow.” The Keyline system is a way to increase the utilization of water within a system and also as a way to restore tilth to abused soils. I’ve never really liked the use of the word “plow” when talking about Keyline. To me, to plow implies something gets turned, or rolled over. A Keyline plow is really a proprietary version of a “deep shank,” “ripper” or “subsoiler.” The idea being to fracture the soil without turning it in order to aerate it, break up hard pan (also known as plow pan) and compaction and facilitate deep water absorption. Chisel plows utilize shanks, but they are often arranged in relatively close-spaced gangs. They are usually spaced so close that there really is a huge amount of soil disturbance even if the soil isn’t being turned over excessively. This amount of disturbance results in much death and destruction of the soil biome which, like all tillage, results in a flush of available nutrients in the short-term, but robs the soil of its long-term fertility and structure (also known as “tilth”). In Keyline plowing the rips are often made by pulling a single shank with passes many feet apart, leaving large volumes of undisturbed soil between them. So it’s useful to run a deep shank through soil that has been badly managed as a one-time mitigation measure to start one on the road to no-till. From then on, you eliminate sources of compaction. This often involves laying out permanent pathways between permanent beds. In my gardens, my permanent beds are four feet wide and my permanent paths are two feet wide. No feet (or knees) on the beds is a strictly enforced rule. Often much plant wastes end up in the paths (although you should get into the habit of leaving weeds that have been pulled on the surface of the bed as mulch). Your pathways become nutrient reservoirs and will become a source of nutrients to your beds by virtue of the nutrient mobilization that is occurring under our feet every day. Deep rooted cover crops also assist in mitigating compaction and maintaining low compaction. A good example are fodder radishes. These can be grown in combination with other cover crops and green manures. The difference in no till situations is you will not be tilling your cover crops in. You will be cutting them off at soil level, leaving their roots in place and carrying the top growth to the compost pile or using it as mulch. The deep taproots of the radishes poke holes right through soil compaction and their decomposition adds to the bread-loaf texture that you are trying to encourage in your topsoil and upper subsoil.

IMG_6832On a smaller scale, soils transitioning to no-till can be prepared for a future of no-till with the use of deep broadforks. I use a long-tined (16″ to 21″) broad fork (U-bar) on soils where I sense there is more compaction than I like (these are the best ones I know of: ). I ride the broadfork into the ground with both feet on the crossbar, rocking back and forth as my weight lowers the tines all the way into the ground. I needn’t exert any more force than my weight affords. U-barring is enough work just moving the tool from one spot to the next and pulling back on the handles to add extra exertion by jumping up and down and forcing the tines in. They are just as happy to slide in on their own with the assistance of gravity. Then I only pull the handle back to about a 45 degree angle. I don’t lift the soil up and shake it through the tines. I’m just cracking the soil open but leaving large chunks intact. A well-managed no-till soil might never need to see a broad fork.

After a couple of years of not tilling, you will see positive results.

For larger scale no-till information, you might find this website of interest:

One of the other comments someone left pointed me to a pretty good article on wood chip gardening.

The suggestion to till chips mixed with a high nitrogen source into the topsoil is intriguing. Certainly this would give a boost to very poor soils. If you already have good fertility from composting and you want to try wood chip mulching, you’re good to go without that. Go ahead and spread them. Thick is good. Just try to keep the mixing of topsoil and chips to a minimum so you have distinct layers– soil and chips. The critters in your composted soil know what to do with the wood chips. There should be a lot of wood chips available considering the recent wind storm.

So, that is that. Next time, maybe sheet mulching.