Advantages & Disadvantages of Tilling

Soil Improvement

• By loosening the soil, tilling improves drainage and makes it easier for roots to expand and absorb the water and nutrients needed for plants to grow. Tilling is often used to mix compost and other soil amendments into the soil, further improving growing conditions. Plus, tillers can be used to uproot small, weedy plants in preparation for planting. Finally, the loose soil created by tilling has larger spaces between soil particles, giving the soil a spongelike quality. This allows the soil to hold more water, nutrients and air -- three elements that are critical for plant health and vigor.

Possible Disadvantages

• Problems can arise when the the different layers of soil are mixed by a tiller. Topsoil -- characterized by a dark brown color and loose crumbly structure -- is what provides nutrients to plants, while subsoil is primarily for anchoring the roots. Mixing these layers means that nutrients may not be available in the shallow soil where the majority of plants' feeder roots are concentrated. Physically breaking and mixing the soil with a tiller can also disrupt the biological process carried out by microorganisms in soil. This process is responsible for converting organic matter into food available for plant uptake. There is also the potential for soil compaction to occur from repeated tilling, especially in the layer of soil scraped by the bottom of the tiller tines.

Best Tilling Practices

• Never till in excessively wet soil conditions, as compaction is likely to occur. If the soil forms a ball when squeezed in the palm of the hand, it it too wet for tilling. If it crumbles when squeezed, the moisture level is suitable for tilling. To avoid inverting the soil layers, it is better to remove the topsoil first and then loosen the subsoil with a tiller or digging fork. Then, return the topsoil to its original position, mixing it with compost and amendments in the process. Once the subsoil has been loosened in this way once, the topsoil can be worked lightly by hand each season before planting to minimize soil disturbance.

Complementary Approaches

• Plants can be used to accomplish some of the same goals as tilling. "Cover crops" are plants used to add organic matter to the soil, smother weed growth and improve soil texture. Some of these have strong, deep taproots that help to break up the subsoil and improve drainage. "Cover crops" are often planted in fall after the main growing season and include annuals, such as fava beans (Vicia faba), common vetch (Vicia sativa) and buckwheat (Fagopyrum esculentum). In addition, mulching is an effective technique to preserve and maintain soil fertility without tilling. Spreading a layer of leaves or other organic matter over the soil each fall prevents compaction of the soil surface and supplies a slow release of organic matter into the soil.