How Does Tilling Affect The Soil?

It’s a question that crops and gardeners alike have pondered for centuries. And it’s one that has been hotly debated by scientists as well — and not just on how much we should be tilling our soils. Tilling is also an issue of timing. Some farmers believe that too-frequent tills are bad for their soil, while others say they help build up nutrients.

The truth likely lies somewhere in between those extremes. But before you decide whether or not to till your own plot, let us explain what exactly happens when you turn over the topsoil with a spade or hoe.

What happens when we till?

When people talk about tilling, they’re usually referring to turning over the surface layers of the soil (which makes up 0.1 percent) to break down any hard objects like rocks and clods. This process creates more room for air pockets and allows water, fertilizer and other natural materials to reach plants better. In short, good tilling improves drainage and nutrient availability.
“Good tilling involves removing stones, sticks and roots,” says Tom Lusk, owner of The Organic Gardener based out of Northampton, Massachusetts. “This loosens up the soil so that plant roots will grow deeper into the ground.”

Bad tilling, however, refers to the practice of using a rototiller or cultivator instead of manual tools to do this job. Rototillers use rotating blades attached to two pairs of handles at right angles to each other. They move back and forth across the ground, breaking up the top layer of soil to create deep holes called trenches. These trenches allow rainwater to drop straight through to the subsoil where it can soak in without running off elsewhere. Cultivators work similarly but don’t rotate. Instead, long metal blades push horizontally against the earth.

Both methods make a big difference depending on which way you look at them. If done correctly, tilling can improve aeration and circulation within the soil. However, if it’s overdone, it could actually rob moisture from the root zone. So how much is enough? That depends on many factors including climate, type of crop grown, depth of the soil and even local weather patterns. On average, most experts recommend no more than four times per year, though there are some who advocate for daily tilling during certain growing seasons.

While most agree that tilling helps drain excess moisture, there’s still disagreement about its overall effects on the soil itself. Let’s take a closer look at both sides.

Benefits of tilling
If you’ve ever tried to pull weeds after planting seeds directly into dirt, then you know firsthand that tilled soil holds onto moisture longer. It seems counterintuitive because all that churned stuff might seem like nothing more than loose soil particles being thrown around. How is that helping anything?
In reality, tilling breaks apart the soil’s structure, creating channels for water, oxygen and nutrients to flow freely throughout the entire root system. When that happens, the plant becomes healthier and stronger. A healthy root system means bigger flowers and higher yields.

Another benefit of regular tilling comes from the fact that the soil warms up faster and stays warmer longer once it hits temperatures above 64 degrees Fahrenheit. Warmer soil equals less stress on plants due to fluctuations in temperature. It also gives them time to cool down naturally overnight, rather than waiting until morning hours when frost may set in.
But perhaps the biggest reason why tilling matters is its ability to increase organic matter. By adding plenty of compost and manure, it increases the amount of humus in the soil. Humic substances are known to boost disease resistance, add nitrogen, strengthen cell walls and enhance the uptake of minerals such as phosphorus. All of these benefits translate into increased yield and healthiness of vegetables, fruits and herbs.

And speaking of diseases…the presence of lots of bacteria and fungi in unbroken dirt promotes the development of spores, which provide cover for pests and pathogens. Without proper cultivation, they end up infecting new shoots and leaves along with affected areas. Tilling gets rid of those unwanted guests, allowing fresh growth free of infection.
So now that we understand how tilling works, let’s consider the flip side. What are its downsides?

Negatives of tilling

One major factor that keeps many growers away from tilling altogether is erosion. Since tilling removes protective mulch, bare patches tend to develop. Any heavy rainfall combined with windy conditions results in serious loss of valuable topsoil. Even small amounts of runoff can cause problems. Mulches hold in moisture, reducing the risk of erosion significantly.
Additionally, tilling disrupts the soil’s fragile balance of microorganisms and worms. Healthy populations of microbes decompose dead cells and recycle nutrients back into the soil. Worms eat fallen bits of vegetation and poop out tiny pellets full of nutrients. Both groups play crucial roles in keeping the soil fertile and building strong microbial colonies capable of fighting off harmful invaders. With constant disturbance, they lose their jobs.

Finally, there’s compaction. After covering the surface with mulch, the soil loses its fluffy texture. As it turns over, compacted dirt takes on a harder consistency. Compacted soil lacks pores and therefore doesn’t absorb water very efficiently. Its dryness contributes to drought conditions and prevents important organisms from doing their jobs.
Some argue that tilling isn’t always necessary. Not true! You’ll need to cultivate every couple of years regardless of whether you live in a wetter part of the country or in a hot desert region. Plus, since tilling only affects the uppermost inch or two of the soil, it won’t solve drainage issues brought on by clayey soil. For example, if you find yourself knee-deep in mud during rainy spells, tilling won’t fix your problem unless you dig under the muck and replace the lost topsoil.
On the bright side, there are ways to minimize the negative aspects of tilling while maximizing the positives. One solution is to cultivate regularly but spread out the workload among multiple passes. Start the first pass by walking backward diagonally behind rows of seedlings to loosen up the soil. Then walk forward again to prepare beds for transplanting. Repeat this pattern until everything looks sufficiently moist. Finally, walk backwards to finish cultivating the rows.

A similar strategy applies to draining excess moisture. During periods of intense rain, wait until nighttime to begin digging trenches for drains. Walk slowly downward parallel to the row direction, leaving space between the lines. Next, walk upward alongside the trench to fill in the gaps and smooth things out. Now repeat this method on the opposite half of the field until all plots are drained properly.
Lastly, never apply pesticides or fertilizers immediately following a tilling session. Doing so would kill beneficial microbes and leave your veggies vulnerable to fungal infections. Instead, wait 24 hours, or ideally 48, before returning to your fields.
Now that we’ve covered the pros and cons of tilling, here’s one final piece of advice: Never try to tackle your lawn at the same time. While tilling is essential for vegetable gardens, it can destroy grasses’ shallow roots and deplete them of vital moisture. To keep your turf green in summertime, follow the same practices described previously. Just remember that frequent tilling will eventually lead to larger patches of bare dirt.

How often to till the garden soil?

For best results, it’s recommended to plan your tilling schedule according to your specific needs. Vegetable gardens require more intensive maintenance than grassy lawns. Depending on location, climate, soil composition and other factors, different techniques will prove more effective.
Once you decide on a routine, start practicing early spring. Do a trial run to see how frequently you want to till, and adjust accordingly. If possible, consult local agricultural extension agents for recommendations tailored specifically to your area.
Tom Lusk, owner of The Organic Garden, believes that a weekly regime is ideal for maintaining vegetable gardens. He recommends starting the week prior to planting with light tilling sessions lasting roughly 30 minutes apiece. Keep the frequency low and gradually increase it toward the end of the season. Ideally, he suggests dividing your garden into three sections, with one section getting attention twice per month and another receiving care once per month.
As far as grass goes, Lusk advises his clients to give their lawns a break every few weeks. If you notice spots going brown, then it’s probably time to get rid of the sod and reseed. Otherwise, avoid any kind of chemical treatments and simply focus on watering and mowing.

With regards to tilling schedules, Mark Steenbock, founder of Urban Gardens Organized, says there really aren’t strict rules. Many people prefer to save their main tilling efforts for late winter or early spring. Others choose to devote weekends exclusively to working in their yard. Still others put aside a portion of their annual budget for gardening supplies and hire someone else to handle the rest.
Whatever approach you go with, remember that it’s ultimately up to you and your personal preferences. No single method will work perfectly for everyone. Take advantage of information available online, ask questions of friends, and always pay close attention to environmental changes.

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