In the garden, most of the attention goes to the growth above the ground; the areas we are easily able to enjoy with our senses. Seasoned gardeners know it is what’s going on below that determines the quality of the resulting blooms and produce.
Tillage is the practice of mechanically digging into and turning the soil. Using a rototiller to mechanically work the soil can be an effective method for incorporating a cover crop, compost or other amendment into the soil in preparation for planting. It is common to till the soil to help break up the hard ground to create planter beds. While there are many practical reasons for tilling the soil, it comes with a cost.
Using machinery to break up the soil can negatively impact the physical soil structure. The soil aggregates (sand, silt, clay, organic matter) and the spaces between the aggregates contribute to the structure of the soil. The composition of these parts is important for many reasons including water holding capacity and to provide a habitat for microorganisms, known as the biological structure. Damaging the soil structure can increase runoff and erosion, washing away beneficial components of the soil and polluting the waterways. The biological structure is also damaged by mechanical tilling.
When tilling is required, using best practices can protect your soil. Till as late in the spring, or as close to planting, as possible. Tilling early and leaving soil exposed to the elements can cause compaction and cracking as the soil gets wet and then dries repeatedly.
Prior to tilling, ensure the soil is dry to the depth you plan to till, not just on the surface to reduce compaction. Only till to the necessary depth and limit the number of passes the rototiller runs over the soil to avoid excessively breaking down the soil structure.
Knowing the growth habits of the crops you intend to plant can inform what tilling depth is necessary. Crops such as potatoes, carrots and other root vegetables require a deeper, more thorough tilling to allow proper root development.
Crops that don’t require deep soil turning may benefit from a less intrusive cultivating. Cultivating can be done by hand or with a small machine and only works the soil a couple inches deep. This is particularly relevant for established garden beds where the soil has been tilled previously. A shallow cultivation with a long-handled garden hoe can be an effective way to remove newly established weeds without damaging the roots of nearby garden plants. Cultivating by lightly turning the soil with a broad fork in advance of planting allows young seedlings to emerge through the soil’s surface. Before applying fertilizer, a light cultivation can help the fertilizer reach the target area rather than washing away.
Planning for the off season is a proactive strategy for protecting the soil. Keeping the soil covered with a crop or other barrier reduces compaction and erosion and can return nutrients to the soil. Amending soil with organic matter is another great practice to preserve the soil structure and microorganism habitats. Nurturing the soil year-round is important for growing a healthy garden.
Cynthia Domenghini is an instructor and coordinator for K-State’s horticultural therapy online certificate program.