Meet Our Expert

Chris Enroth is a horticulture educator with the University of Illinois Extension Service.

Jeff Lowenfels is the author of Teaming with Microbes: The Organic Gardener's Guide to the Soil Food Web.

What Is Tilling?

Tilling is the practice of physically turning soil to prepare it for planting or to cultivate between rows to reduce weed pressure. In a garden, rototillers are commonly used to turn the soil and to incorporate any amendments to a depth of about 4 to 6 inches. The broad fork, a big garden fork with very heavy tines that sink into and lift soil, is another tool that's used to turn soil.

Although tilling helps reduce weeds in the short term, it can also create weed problems. “Tilling soil brings weed seeds to the surface, often creating higher weed pressure in the garden," says Chris Enroth, horticulture educator with the University of Illinois Extension Service. "By keeping the tiller in the shed, you may have fewer weeds to battle during the summer."

Another problem is that repeated tilling over time tends to compact the soil, especially the layer right under the tilled soil.

What Is the No-Tilling Method?

Tilling churns up the top several inches of soil, which displaces soil organisms and breaks up soil aggregates. By contrast, the no-till method minimizes the disruption of the soil. Beneficial organisms in the top couple of inches of soil—fungi, bacteria, earthworms, and more—remain in their preferred zones to do the important work of breaking down organic matter, releasing nutrients, and aerating the soil.

“The bacteria and fungi are working all the time, so benefits start immediately,” says Jeff Lowenfels, author of Teaming with Microbes: The Organic Gardener's Guide to the Soil Food Web.

To establish a no-till garden in your yard, cover the area with a heavy wood mulch or plastic to kill the vegetation that is commonly part of the lawn. Do this during the fall so that by spring, your garden bed will be ready to plant without needing to be tilled.

When to Till Your Soil

Incorporating organic materials. “If you have the need to incorporate organics quickly, rototilling is the way with clay soil,” says Lowenfels. This is usually best done in the fall.

Compacted soil and compost. Adding compost while tilling helps improve the soil's structure in a new bed. “When tilling compacted soil, gardeners often incorporate compost to help break up the clay structure,” says Enroth. “Other amendments can also be added when tilling, such as lime or sulfur for adjusting pH.” A soil test may indicate that certain nutrients are deficient in your soil. Incorporating them into the soil with a rototiller readily places them in the area where plant roots will find them.

Preparing a seedbed. “Tilling helps prepare a uniform seedbed,” says Enroth. This makes it easier to plant seeds directly in the soil. In a no-till system, there may be debris left from previous vegetation, which makes direct seeding more difficult.

Breaking down organic matter. “Tilling also introduces oxygen to the soil, which can jumpstart the breakdown of organic matter, which releases plant nutrients to the soil,” says Enroth. While helpful in the short term, repeated tilling can speed up decomposition to the point that carbon is released to the atmosphere, which harms the environment.

The bottom line is that while tilling may be helpful in certain situations, it's not always necessary. No-till or minimal-tilling practices mean less disturbance to the soil environment, which promotes beneficial organisms and reduces soil compaction.

Tips for Protecting Your Soil

Whether you are for or against tilling your garden, use these five tips to ensure your soil is healthy and ready for planting.

1. Don't Till Regularly

Frequent tilling can cause an impermeable layer or “plow pan” to develop. “The plow pan occurs directly under the tilled soil, as the tiller tines need to push on something to break apart the soil overhead," says Enroth. "The soil being pushed deeper in the ground can create a hard layer right under the more friable tilled soil." This hard layer inhibits both root penetration and water drainage.

2. Add Compost

As the organic matter decomposes, it releases substances that help create soil aggregates that improve drainage in a clay soil and water holding capacity of a sandy soil. You may need to till your bed initially to incorporate the organic matter into the upper several inches of soil.

3. Test Your Soil and Incorporate Amendments

You may need to add garden lime or sulfur to adjust the pH or replenish nutrients that may be deficient. Adding these in the fall allows them time to infiltrate the soil more effectively, and tilling them into the soil can more quickly improve your soil’s chemistry.

4. Grow a Cover Crop

Wind and rain can lead to soil erosion when the soil surface is left bare. Select a crop that will be killed by cold temperatures or mowing, such as Australian winter pea, fava beans, or crimson clover. Leave the roots in place because they will help prevent soil erosion and gradually break down, releasing nutrients for your plants.

5. Use Mulch During Growing Seasons

There are many benefits of using mulch. Mulch reduces weeds, maintains more consistent soil moisture and temperature, and helps prevent soil surface crusting. As it decomposes, mulch adds nutrients and improves the soil’s structure.