Building Richness in Soil With Cover Crops

Cover crops are an important resource for many landscapers and farmers, who use the protective layers to build nutrients in the soil in place of synthetic or animal-based fertilizers. Cover crops enrich soil in many ways, including providing a healthier environment for the microbes that are so essential to growing nutritious plant varieties.

As Susan Fisk of the Soil Science Society of America has observed: “Soil is a living, dynamic substance, and the microbial life within it is crucial to providing plant life with the food they need to grow. The microbes can be bacteria or fungi, but both need space — the pores — for a good living environment.”

The Rodale Institute in eastern Pennsylvania has been studying this issue for more than three decades. In North America’s longest-running comparative study of organic and conventional techniques, Rodale analyzed the methods, philosophies and results of successful farming operations.

Rodale’s key findings include: “Organic yields match conventional yields. Organic outperforms conventional in years of drought. Organic farming systems build rather than deplete soil organic matter, making it a more sustainable system. Organic farming uses 45% less energy and is more efficient. Conventional systems produce 40% more greenhouse gasses. Organic farming systems are more profitable than conventional.” Significantly, Rodale also discovered: “Soil health in the organic systems has increased over time while the conventional systems remain essentially unchanged. One measure of soil health is the amount of carbon contained in the soil. Carbon performs many crucial functions such as acting as a reservoir of plant nutrients, binding soil particles together, maintaining soil temperature, providing a food source for microbes, binding heavy metals and pesticides, influencing water holding capacity and aeration, and more.”

This same issue has been studied for decades by researchers at the W. K. Kellogg Biological Station at Michigan State University. In their ongoing study they have proven the many benefits to soil of cover crops, including:

Improved soil quality. Greater soil biota activity, more complex soil structure, better soil aggregation, infiltration and bulk density. Soil structure is evaluated based on the intricacies and patterns of its pores. When soil is more complex and varied in its structure, beneficial microbes thrive, enriching the soil.

Erosion mitigation. Cover crops protect against water and wind erosion.

Weed control. Shade and plant cover help prevent germination of weeds. In addition, healthy soil grows healthy plants that are better able to fight off weeds, without the constant application of chemical herbicides.

Insect management. Healthier soil and crops lead to greater biodiversity, including insects that control pests, such as the Trichograma wasp that feeds on the European corn borer.

Examples of the cover crops recommended by the Kellogg researchers include: clovers, oilseed radish, winter wheat, buckwheat, Oriental mustard, cowpea, Austrian winter pea, hairy vetch, sorghum sudangrass and medics.

Medics are just one example of the incredible variety of cover crops. There are more than 35 species of this particular legume. Nature has given landscapers, gardeners and farmers much to work with — and so much to rediscover.