How And When To Till The Soil In Your Garden

A guide to tilling your garden plot.

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Warmer weather means spending more time outside. This means time for planning and preparing your garden space. But before you can begin sowing seeds or planting starters, such as strawberries, tomatoes, or sunflowers, you’ll need to make sure the soil is ready. One way to prepare the soil is by tilling. Tilling is when you turn over the soil and add amendments to get it ready for planting. But not every gardener agrees that tilling is the best method.

Garden tilling is the process of turning over the top layer of soil, breaking it up and adding air to the soil. “Tilling is a mechanical process that takes soil from below the ground and brings it up to the surface and breaks it up or loosens it” says Kim Roman, expert gardener for Square Foot Gardening 4 U, a online source for gardening classes, and author of How to Garden Indoors & Grow Your Own. “This will help the roots of your plants be able to move more easily through the soil.” Aerated soil helps plants receive all the different nutrients they need to grow.

Tilling can be done manually or with a motorized tiller, also called a roto-tiller. However, tilling can cause more harm to your soil than benefits, so you’ll want to consider whether it makes sense for your area and needs.

Tilling the soil isn’t something that should be done frequently, and there is controversy if it should be done at all. The truth is, tilling can be harmful to the soil. “If tilling is done too often, it can change the soil structure,” explains Angelo Randaci, Master Gardener and Horticulture Expert at Earth’s Ally. “This can cause soil runoff and erosion.”

Tilling can cause other problems, such as too many weeds in your garden plot. “Tilling is not just bad for the soil structure, the act of rototilling brings up soil from below and reactivates weed seeds,” explains Roman. Tilling can also hurt microorganisms that are fundamental for the soil. “Tilling disrupts the animal life in the soil such as worms and microorganisms that help provide soil health,” says Randaci. Tilling can create compaction further below the soil. “This is called a hard pan and this will make it difficult for roots to expand below the tilled depth,” says Randaci.

Manually tiling is often considered a better choice than using a rototiller but it’s also up for debate since it still affects the soil structure. Manually tilling requires a lot of physical labor. “Hand tilling is less invasive, but still disrupts the structure of the soil, and is a lot of hard work,” says Janet Sluis, Horticulturist and MS in horticulture, Curator, Sunset Plants.

Machine-powered tillers get a bad rap because of how they dig into the ground. “The reason rototillers can be problematic is because they are designed to dig deep into the ground and pulverize the soil structure, but there are other tools that are helpful for limiting the depth of your tillage,” explains Tools Product Manager, Jen Goff at Johnny's Selected Seeds. One alternative tool is a power harrow. “Power harrows are a common tool for reduced tillage because the blades are oriented vertically and do not work the soil as deep,” explains Goff.

Minimizing tilling of the soil has been shown to be better for the soil and microorganisms. “There is quite a bit of university research that suggests reducing tillage can be beneficial to your garden soils and reduce weed pressure by limiting the number of weed seeds brought up to the soil surface to germinate,” says Goff. “Reduced tillage can help maintain the soil structure and soil biology that supports crop health.”

The size of the garden and whether the soil is compacted or loose will help determine if you hand till or use a machine tiller. “Tilling (or manual double digging) is usually done if the soil is heavily compacted, for heavy clay soils, and when you want to add a lot of nutrients or other amendments into the soil, like for a vegetable garden,” shares Sluis.

Using a motorized tiller can save time and physical labor if you have a large area that has never been used before. “Rototillers can be very helpful for breaking new ground,” says Goff.

Typically tilling is best for big plots. According to Sluis, [Tilling is] usually reserved for very large spaces, or areas that have known soil problems that need to be addressed, [such as] standing water, compaction.”

If you do choose to till, it’s a good idea to conduct a soil test. “Contact your state’s extension service or look online for a university that runs soil tests for home gardeners,” explains Roman. A soil test will provide insight into what amendments your soil may need. “The test will also tell you what nutrients your soil is deficient in, and now is the time to add fertilizers and other trace minerals,” shares Roman. “Don’t add fertilizers, other than compost, unless you’ve run a soil test.”

Tilling a garden is typically done after the last frost, usually in early spring and sometimes in the fall, to prepare the soil for planting. “The garden can be tilled in the fall as part of the fall cleanup or anytime before planting,” says Randaci. Before you begin, you need to make sure the soil isn’t too dry or too wet.

Wet soil creates compaction. “Compaction doesn’t allow for air space between soil particles which is needed for your plant roots to breathe,” explains Roman. But if the soil is too dry, it can also create problems for the soil. “Tilling dry soil could pulverize the soil particles,” says Roman.

Wondering how to know if your soil is too wet or dry? You can do a quick check by picking up a handful of soil and creating a ball. “The simplest way I know to check for the right balance of moisture in your soil is to take a trowel and dig a handful of soil about 6” (15 cm) down,” says Roman. “Squeeze it into a ball about 2” (5 cm) across—if it doesn’t form a ball, then your soil is too dry, or too sandy.” She suggests watering the ground and waiting a couple days before testing again.

What about if it’s too wet? “If it doesn’t break up, or just splits in half, then it’s too wet,” says Roman. “If the soil is too wet, let it sit for 3+ days and test again.”

How do you know if the soil is okay to till? “Hold the ball in the palm of your hand and press your thumb to the center, says Roman. “If it breaks up nicely, then you should be able to till your soil.”

If the soil test shows you have a lot of clay, you can add amendments that will help loosen the soil, such as coco fiber or peat moss, shares Roman. “Soils with too much clay and too much sand can both be remedied by lots of good organic matter like compost,” she says.

There are other ways to prepare a garden bed for planting. Consider using a broad fork, which is a nomination of a shovel and rake. “It doesn’t really “till” but it aerates and minimally breaks the soil, explains Roman. “It’s a sturdy metal implement that looks like a large rake, usually 20” (50 cm) wide with about 5-8 long, thick tines.” Goff agrees and adds, “A broadfork and a good bed preparation rake can be plenty for the small market farm or home garden, as long as you are breaking up the compaction beneath the soil surface and creating a smooth bed top.”

Many times if a garden space has been planted year after year, you likely only need to add amendments, such as compost, which can be mixed in with a digging fork. “Just place a layer on top of the soil, and work a little into the soil with the fork,” says Sluis. “This does less damage to earth worms and overall soil structure.”