Should I till my garden?

Reconsidering my long held belief that tilling is bad for the garden.

Old-timers in my area tend to till their gardens. In fact, where I live, almost everyone tills their garden. i get it. Freshly plowed soil that is soft and supple is attractive, easy to plant in, and has been practiced for generations.

While in college, Morgan worked with an old-timer who grew vegetables to feed those in need. Here is a picture of her working a plow behind the tractor.

On the other end of the spectrum, lie the no-till gardeners. They propose that the recent breakthroughs in soil science highlight the role of microbes in the soil. Because tilling disrupts and destroys much of the microbial populations in a healthy soil, this group reasons that tilling should be avoided.

I lean towards the latter group but have since been re-evaluating.

Often times, my first advice to any aspiring gardener is to never till their garden and mulch heavily. This advice is born out of my agroecology philosophy: The soil-food-web, of which microbes play a vital and robust part, should be considered first when gardening, particularly when you are growing food to be consumed by humans.

It is true that tilling the soil destroys large portions of the soil-food-web. With that said, I think there are reasonable arguments in favor of soil cultivation. Not tilling, per se, but soil cultivation.

There have been multiple factors that have caused me to reconsider my no-till stance.

• My dad, who has gardened his whole life, was (and is) skeptical of “no-till”. He asked me: “if tilling is bad, then why, when soil in my yard gets disturbed, always turn out to be the greenest section of my yard once it grows back?”

• Annual plants, of which most vegetables are, prefer bacterial dominated soils. When soil is tilled, bacterial populations explode.

• Our friends and farming heroes over at Mountain Sun Farm in Menton Alabama, one of the few certified organic farms in Alabama, told us that cultivation and working the soil is an integral practice for their farm.

• I visited the country's first certified organic farm at UC Santa Cruz. I was shown research plots that showed the difference between no-till garden plots and garden plots that were tilled. The results were dramatic. And not in favor of no-till.

After considering this information and these experiences, I have decided

That I am still... a no-till, minimal cultivation, gardener evangelist.

Lets take a closer look at each of the above counter narratives and I’ll explain why none of these examples have caused me to change my belief or practices.

My Dad’s green lawn weeds.

So, my dad had a good point. Whenever you disturb a lawn, what grows back is often diverse and a healthy looking green. For example, whenever we trenched a line to put in a drainage pipe, the ground where the trench was lay visible in the yard over the next year. The plants were a darker shade of green and what grew back was a more diverse group of grasses and forbs.

Why is this?

In short, here is what happened: bacteria populations exploded when the soil was disturbed which caused a flush of nitrogen to be released (further explained below). The buried, dormant seeds in the soil found new life when exposed to sunlight, warmth, and water. Once sprouted, they found plentiful nitrogen in the soil and companion bacteria to further provide the needed nitrogen for lush, green growth.

When the soil was dug out, mixed up, and put back, much of the microbes (fungi, protozoa, nematodes) living in the soil were killed off. These dead microbes become food for the surviving bacteria still present in the soil, which causes their initial growth. The breaking up of soil particles also exposes microscopic pieces of organic material (think tiny bits of leaves, twigs, bugs) to be rapidly broken down, further feeding the bacterial population growth. In addition, the soil is aerated and infused with the oxygen needed for large populations of bacteria to thrive. When bacteria die, their bodies break down and release nitrogen which plants need to survive and thrive.

You might be wondering why this is a problem. For the trenched area in my yard, it is not. But in an agricultural system, where nutrient management is paramount, it is a major problem.

The bacteria in this scenario will eventually run out of surplus food and the populations will quickly die off, back to normal levels. The excess nitrogen will be used up by plants or leak out into the atmosphere. Now what? Each time I disturb the soil, I deplete the soil of its microbial populations, its organic matter (carbon) , and destroy its water retention capabilities.

The green flush is ephemeral. The damage to the soil-food-web is not.

Most vegetables prefer bacterially dominated soils.

I struggled when I learned this. Tillage promotes bacterial populations in the soil and releases nutrients in the soil for plants to uptake. This explains why vegetables often do well in tilled gardens. So, what gives?

Here is the deal: The positive effects of tilling do not outweigh their long-term negative consequences. So far, I have focused on how tillage negatively affects the soil-food-web. But the problems do not stop there.

Weeds. Almost everyone I know that has a garden and uses a tiller, can’t imagine not using a tiller. Why? How else would they deal with the weeds that overrun their garden each year? What they don’t realize is that tilling is making the problem worse! Here is why: Whenever weeds are tilled into the soil, the seeds on those plants are buried and seeds from previous tilling are brought up to the surface. It is a terrible cycle that can only be broken by stopping the tilling.

Another issue with tilling is the formation of a hardpan that develops after the repeated pounding of tiller tines. Tillers can only go so deep, and it is the area right beneath the tilled soil where the hardpan forms. In many cases, this hardpan will prevent water and even roots from penetrating it.

Lastly, tillage destroys a soil's structure. While freshly tilled soil is soft and crumbly, it won’t take long for it to become hard and compacted. The reason this happens is because the soil aggregates are destroyed during the tilling process. “Soil aggregate” is a fancy name for tiny clumps of stabilized soil that are bound together via multiple processes that include secretions from microbes, root exudates (or secretions), and via worms and other microarthropods that help form these clumps. The formation and preservation of aggregates is vital for soil structure, as it influences water infiltration, aeration, root penetration, and microbial activity.

So, yes, tilling does promote the release of nutrients and does promote a bacterially dominated soil, which most vegetables prefer, but the long-term damage to the soil is far worse than these short-term benefits.

Mountain Sun Farm

Morgan and I went to college with Brian and Liz, the fine folks who started Mountain Sun Farm. While we tried our hand at commercial growing and had to leave it behind, Liz and Bryan started and never stopped. They began shortly after college and have had a successful organic growing operation for 10+ years. This is an incredible feat and I take what they say with regards to growing food very seriously. So, when Liz told Morgan that tillage is a vital part of their growing operations, I paused and had to reevaluate my beliefs.

After much thought and consideration, here is where I landed: No-Till market farming at scale (3+ acres) is very difficult and likely impractical. This is because mechanization is necessary for efficient planting, weeding, and harvesting. While there are tractor implements that are designed and built especially for no-till operations, they are often very expensive and no-till management processes (at scale) can be difficult and risky.

Liz and Brian grow 6 acres of crops and use “farming methods (that) prioritize ecological diversity and improving soil quality through intensive cover cropping, promoting beneficial insects, (and) crop rotation.” Knowing how hard this work is and how difficult it is to make farming a viable economic enterprise, I have no shame calling them some of my heroes. Our society would do well to lift these type of small farmers up and support them wholeheartedly.

UC Santa Cruz No-Till Research

I recently had the chance to visit the UC Santa Cruz Center for Agroecology. While there, I toured their 30-acre organic farm – the first certified organic farm in the country. I was fortunate enough to get a tour from the center’s director who did his PhD research on no-till vs. Till operations, looking at how crop production was affected. He showed us a trial plot where he trialed the two methods side by side. The difference was stark. The sections that were not tilled were at best stunted and at worst barren. The tilled sections were growing as you’d expect. He mentioned the successful rise of no-till market farming but said that it was not sustainable due to the amount of compost that had to be used each year for fertility purposes.

Due to the nature of the tour and the fact that I was a part of a group, I was unable to ask many questions about his research and the methods he used. From what I did gather though, I learned that for the no-till portion of the research, no soil aeration was performed and no seed bed prep was performed. To me, this isn’t fair. I say this because seeds need a prepared seed bed (or at minimum a protected, moist environment, i.e. drilled into a cover crop) and compacted soils have to be aerated even in no-till operations. It is just a matter of how you do these things.

Part of the 30 acre organic farming operation at the UCSC Center for Agroecology.

As for their 30 acre farm, they definitely cultivate. I am not sure if they use a tiller, except for incorporating cover crops (like Mountain Sun Farm). Either way, I won’t be one to argue against their operations at scale. I’ll be the one taking notes.

Conclusion

For the home gardener and small-scale market farmer, I’d still encourage a no-till operation. In our home garden in town, we had practically no weeds, we had soft, friable soil year-round, and our plants thrived. Did I mention we dealt with practically no weeds? We mulched heavily with chopped leaves, aerated our soil with a broad fork and garden fork, added compost annually, and used a handheld garden cultivator to prepare seedbeds for cut greens and direct seeded crops. It’s simple and effective. Our soil was full of earthworms, we routinely had beneficial fungus growing on top of our soil, and our pest problems were minimal as was our weed problem. Because we kept our soil covered with chopped leaves, it stayed moist even on sunny, hot Alabama summer days.

A garden fork opening up the soil. Our no-till, weed free garden

Recently we moved. Back to the farm. Here I will be putting in a terraced family garden on a small hillside beside our house. Like I did at our last home, I will chronicle the journey here.