Let's start off by saying that no-till gardening is much different than no-till farming. No-till farming often includes the use of herbicides to control weeds before planting, rather than discing them under. Then herbicides are used again post-harvest to lay-down one crop in the field before another is planted. No-till gardening for homeowners and market gardeners utilizes natural
methods to build and maintain healthy soils.
There is debate on the subject. Some gardeners contend that tilling improves the soil through breaking up large soil particles and working organic matter into the soil. They also think that tilling is an effective way to manage weeds that grow between their crops.
There are valid points on both sides of the subject. I tossed the subject around for many years. I used to own a large rear-tine tiller, and I used it with delight. I tended a large garden, mostly by myself, and a tiller made short work of a big job. It was satisfying to look back and see the freshly tilled soil at the end of the day.
But the more I learned about how soil works, the more I questioned the practice of tilling. My own personal gardening journey led me away from the practice of tilling. I want to discuss it here in sufficient depth for you to make your own decision. You may decide that tilling is right for you, and you may decide it is not, and you may also decide on a "hybrid" method which we will discuss below.
Why do we deeply cultivate the soil?
Traditional agriculture tells us to deeply cultivate the land to remove existing vegetation and aerate the soil. Plowing, followed by discing, is usually used on a commercial or market scale, and tilling is used on a home garden or truck garden scale.
The manufacturers of tiller-cultivators will tell you that they can also be used to deal with weeds between the rows during the growing season, and to turn under the end-of-season plant residue. Tilling equipment is also used to create the hills and furrows common to row cropping. It's become an iconic image in rural America - the cleanly plowed field and its meticulously spaced furrows. We do love our machines.
Doesn't plowing improve the soil?
There is no doubt that the plow enabled agricultural pioneering in 18th - 20th centuries. Heavy plows drawn by draft animals loosened and aerated the soil in a way not previously possible and freed the nutrients that had been stored there for centuries . The plow was a large part of western expansion and the success of colonial and post-colonial America.
But if you have ever had a chance to observe a plow as compared to modern tilling machines, you will begin to see why they cannot be compared. A plow uses angled blades that dig deeply into the soil and turn it over. The soil is inverted and broken up in the process, similar to the action of a spade. Plows are used for the initial turning of the soil. Plowing is followed by discing, which further breaks up the already plowed soil and prepares it for planting.
A tiller, on the other hand, has L-shaped tines that rotate quickly, pulverizing and mixing the soil. It is akin to a food processor or blender.
People who begin a garden by tilling the soil often see a dramatic surge in growth in the following season. This abundant production is the result of improved aeration and the immediate availability of nutrients due to the rapid decomposition of the existing vegetation, which is accelerated by tilling it under.
This short term positive result convinces them that tilling was the magic ingredient to their success and they want to hang on to the practice. However, as the seasons pass, repeated tilling generally begins to start showing its weaknesses when compared to no-till practices.
Short term benefit, long term problems
Frequent and repeated tilling, such as that done seasonally to prepare the garden, can do a lot of damage to both the soil structure and to the Soil Food Web;- the complex biome of macro- and micro-organisms that help maintain healthy soils.
Tilling kills many macro-organisms such as earthworms and beetles. It damages micro-organisms by shredding fungal hyphae and exposing beneficial fungi and bacteria to the elements. Time can heal this wound, but it is a violence to the soil nonetheless.
Tilling at the same depth season after season can create a compacted layer of soil below the topsoil called hardpan. Hardpan forms where the tines strike their lowest depth over and over with each tilling. Over time this layer can become so compacted that it impedes drainage and root growth.
Upsetting Nature's Carbon Balance
Deep cultivation, that which results in the physical inversion of the soil, releases a large amount of CO2 quickly. In fact, plowing of virgin lands releases carbon that has been sequestered there for thousands of years.
Cover cropping is intended to sequester excess nitrogen and replace organic matter. But when it is turned over at the end of its season, it can also contribute to the release of excess CO2 during its accelerated decomposition. Undisturbed soils not only retain their sequestered carbon, they absorb 30% more CO2 than tilled land.
So, I shouldn't till?
You need to make the decision about which soil preparation technique is right for you. Don't let glossy ads in the back of gardening or homesteading magazines make your decision. And don't let alarmists or absolutists make it for you either. Make it based on what is right for you now, and right for your soil in the future.
What if I have a large garden?
This site is devoted to home gardening, so we are going to leave the topic of market gardens for another day, but there is a lot of reading available on this very subject.
Years ago I thought tilling was the only way to maintain my 1/2 acre vegetable garden. If I was going to do it all over again, I might have initially prepped that sandy soil with a tiller (it needed tons of compost worked in) but I would have maintained it with no-till practices from that point forward. A very large area can be prepped with absolutely no disturbance of the soil.
No-Till Practices
There are several ways to build garden beds that are considered no-till practices. Lasagna Gardening, Sheet Composting/Mulch Gardening, and building raised beds are popular and successful in our area. The Back to Eden method is also gaining ground.
A hybrid approach
I feel that seasonal tilling is generally NOT a healthy practice for soils. But a one-time deep tilling before, or as part of, bed preparation is perfectly fine. This one-time tilling can help to improve soil drainage, root out perennial weeds, and incorporate organic matter and amendments into the native soil to provide a good base for future years of no-till soil practices. This is sort of a "hybrid" method; tilling once, no-till from that point forward.
You can use your one-time tilling as your sole method of bed preparation, or you can do this to improve the native soil prior to building a raised bed with added bed mix on top of the tilled area. Tilling is not a necessity to raised bed building, but it is an option.
How to till for bed preparation
- Mow the area using a low setting and a mulching mower. We don't want to lose the organic matter, but we don't want long fibers tangling up the tines either.
- Water the area deeply at least two or three days before you till. Tilling wet soil can do such drastic damage that it will take years to recover. Tilling dry gumbo is torture. Find the happy medium.
- Make a first pass over the entire area using the tiller at the shallowest setting possible. The first pass will only barely scuff up the turf and weeds.
- Make another pass without adjusting the tines lower, but working at 90 degrees to your last pass.
- Adjust the tines to the next depth and repeat 3 & 4. You will do this as many times are required to eventually get to the full depth of the tines. If at any time the tiller bogs down or kicks, make a second set of passes without adjusting the tines lower. You cannot rush this process. Heavy clay soils take time to break up.
After this first tilling, wait a week or two. You will have brought hundreds of thousands of dormant weed seeds to the surface, and a few perennial weeds may have survived the tilling process. It is guaranteed that you will have triggered the survival mechanism of nut-sedge! You can till this spurt of regrowth under during the next step which is incorporating compost and amendments.
Amending soil properly when tilling
Most urban and suburban vegetable and ornamental gardens start out in what was once turf. Just consider this a blank slate, no matter how well it was cared for during its life as a lawn.
Add organic matter at a rate of about 25-30% by volume of soil. This translates to adding about 3" - 4" of organic matter on top of the bed and working it into about 10" - 12" of soil.
There is no easy short cut and no magic soil amendment that can take the place of good quality organic matter. Organic matter helps to improve both the physical and biological properties of soils when added in sufficient amounts, to sufficient depths, and with sufficient regularity. Organic matter improves the structure and aeration of clay soil and improves moisture and nutrient retention in sandy soil.
Much has been learned about the importance of the Soil Food Web. Organic matter is imperative to supporting the SFW in your own soils. There are a variety of organic materials that can be used depending on availability, preference and cost. The bottom line is, don’t short cut this part of bed preparation.
Compost is the best option overall. I am always asked about one form of compost or another - composted barks, leaf compost, mushroom compost, and composted manure. The best advice I can give you is to use the best you can afford. My preference is generally two-year old leaf mold compost from Nature's Way Resources.
Steer clear of working in peat moss. I still see this listed as a soil amendment, but it is pretty certain that those who support this have never gardened in clay gumbo soils. All I have to say about that is that clay, peat moss, and water make a pretty good adobe brick - 'nuff said?
Contrary to what you may have heard along the line, it is not necessary to add sand or gypsum. Neither improves the soil as well as organic matter, and both can cause other problems, so the expense and labor are not justified. The only time I suggest gypsum is if you are trying to correct a salinity issue, not for soil structure.
What else should I add?
Since you are doing this one-time tilling process for bed preparation, you can choose to add nutrients and supplements now so they can be incorporated with the final tilling passes. If you are tilling as an improved base, and will be building a raised bed on top of the base, wait to add nutrients and supplements into the top layer, but be sure to add the compost before you start building upwards.
The transition to no-till
After you have completed the one-time tilling process and built your beds, you will establish a no-till maintenance program for the duration. No-till gardening has some distinct advantages over tilling. They are heavily organic so they retain moisture well, reducing the need for supplemental water.
They are fantastic at suppressing weeds in four ways – the suffocation layer at the bottom, the mulch layer at the top, a rich fungal soil that is not as friendly to weed species, and the fact that dormant weed seeds are not repeatedly brought to the surface where they can germinate and grow.
There is a reduced need for fertilizers since you will be planting into a nutrient rich soil and there is less labor overall. Once the bed is established, it is very simple to maintain. The key to staying no-till is to maintain the “forest floor” – keeping a decomposing layer at all times on all types of no-till beds, and applying compost to raised no-till beds regularly.