Conservation tillage and soil health are practices and concepts that continue to influence production agriculture. In recent decades, many soil scientists have increasingly focused on soil as a “living system,” rather than emphasizing the physical and chemical properties of an inert growing medium. Researchers are discovering how important the contributions from soil microorganisms are to maintaining and improving crop production systems.
Healthy soil provides a beneficial environment for a vast diversity of beneficial microorganisms. Two concepts that are fundamental to improving and maintaining soil health are minimizing disturbance and maintaining plant growth for as much of the year as possible.
Guidance to avoid disturbance relates to the physical space occupied by soil microbes. One of the most beneficial results of a thriving soil microbial community is the development of soil aggregates. Aggregates are individual soil particles (sand, silt or clay) held together in a larger particle. Formation of aggregates increases pore spaces within the soil contributing to both improved water holding capacity and internal drainage. Enhanced pore spaces also improve the gas exchange and availability of oxygen within the soil. A group of soil fungi is responsible for the production of the “glue” that holds soil aggregates together. Although the attachments are not strong, left undisturbed the aggregates and resulting soil structure can remain intact and improve from one season to the next.
Plowing, disking, ripping, cultivating and tilling are all processes that have been used to manage soil and crop production. Research and experience have now demonstrated that those disturbance processes destroy soil aggregates, soil structure and microbial habitat. These mechanical processes have been used in conventional agriculture in preparation for planting and weed control.
Minimum-till, no-till and zero-till are terms applied to conservation tillage methods practiced to preserve soil structure, microbial habitat and contribute to improving soil health. Crop production acreage where conservation tillage is practiced increases every year.
The same concepts practiced by farmers for whom soil stewardship is a high priority can also be adopted by home gardeners. Garden writer Carlie Nardozzi coined the term “no dig gardening” to describe the concept of minimal soil disturbance applied to gardening in smaller spaces. He includes this in an overall intention of "gardening with nature." Researchers and farmers have learned that the “reference” for a healthy soil is most often a soil supporting a thriving stand of native plants that remain undisturbed. Many gardeners start each season by spading, tilling or otherwise cultivating the soil in preparation for planting. Such an annual disturbance breaks up soil aggregates that might have developed and breaks down soil structure.
Nardozzi suggests that, especially in raised beds, rather than tilling or spading, a layer of compost be added on top of the bed and be maintained through planting and not tilled in. At the end of the season, instead of cultivating to cover residue, he recommends pulling or chopping plants and laying them into a layer of residue to decompose and add to the compost and organic matter of the soil. One caution would be to be careful to remove any diseased tissue that might lead to pathogen over-wintering and infection the following year.
The soil health concept of maintaining plant growth would support following summer crops with cool-season plants for a fall garden. Cover crops, intended to grow through the winter would be an additional approach. Fall cover crops are often planted as a mixture of grass and broadleaf plants. Selection of species depends on particular needs or conditions of individual gardens. Cover crops address the management concepts of soil health by reducing soil disturbance, increasing the diversity of soil biology, maintaining a living root system, which is critical to support microorganisms and controlling erosion and compaction.
Cover crops may limit the initiation and spread of certain diseases and insects in the soil. Cover crops are primarily used to "rest" or leave a garden area open during non-production times. Therefore, they are most often planted in the fall. However, summer cover crops can be equally effective and can provide the same benefits as a fall cover crop.
UGA Extension Circular 1057 "Using Cover Crops in the Home Garden" provides additional guidance about the establishment and husbandry of cover crops.
Roger Gates is the agricultural and natural resources agent for University of Georgia Extension, Whitfield County. Contact him at firstname.lastname@example.org.