The Organic Center and University of Maryland spotlight organic farming practices that provide the biggest bang to soil health

Even with good things, there is the best of the best. So it is with organic agriculture. Organic farming techniques have long been proven to help foster and restore soil health, replenish soil organic carbon and preserve underground biodiversity. And some organic strategies provide a bigger bang for soil health than others.

Now a new study conducted by the University of Maryland in collaboration with The Organic Center -- and supported by the GRO Organic research fund, Annie’s Homegrown of General Mills, and Patagonia -- provides a big-picture understanding of the organic techniques that have the most impact on soil health. The review of more than 150 studies from around the world on the benefits of organic farming to soil health and climate change mitigation illuminates specific organic farming practices that are the best of the best in supporting healthy soils. The Organic Center highlights the main findings in their latest report here.

The study, published in the scientific journal Organic Agriculture, identifies four practices that are the most critical to good soil health:

• Planting cover crops,
• Applying combinations of organic inputs,
• Increasing crop rotation diversity and length, and
• Conservation tillage.

“One of the strengths of organic is that it is always striving toward improvement. This project captures that spirit, because it leverages current research to better understand the practices within organic that maximize the benefits to soil health,” said Dr. Jessica Shade, Director of Science Programs for The Organic Center. “This scaffolding provides a useful roadmap on the most effective strategies that can be used by farmers – both organic and non-organic –to foster healthy soils, and on what areas that can be leveraged by research to support long-term agricultural sustainability across the board.”

Healthy soils are essential for resilient crop production and supporting the ecosystem. They retain water, support a diversity of organisms vital to decomposition and nutrient cycling, provide crops with essential nutrients and store away carbon, helping to mitigate global climate change. The growing demands for food, feed, fiber, and fuel cannot be met without healthy soils.

“Soils in the United States are being degraded by unsustainable agricultural practices, but techniques used by organic farmers can help stop soil health degradation, and even restore soil health in previously degraded soils,” said researcher and study author Dr. Kate Tully. “However, the specific impacts of organic practices on soil health are not well understood. This study compares strategies within organic systems to understand where the benefits from organic farming arise, and how they can be maximized.”

The best of the best

Researchers looked at data collected on organic soil-building strategies from around the world to pull out general themes of organic practices and the trends around which strategies have the biggest impacts on soil. They conducted a global, systematic review of the literature, including all studies that compared practices within organic farming systems.

Four key organic practices emerged as being the most critical for soil health:

Planting cover crops

Cover crops are grown to benefit the soil rather than harvest income. They protect against soil erosion, nutrient losses, and provide many other agroecosystem benefits. In organic systems, they control weeds and are often a critical source of nutrients for cash crops through nitrogen fixation and green manure. Many studies show that cover crops enhance soil health overall, and that roll-killed cover crops suppress weeds better than disking.

Applying combinations of organic inputs

The use of synthetic nutrients is banned for use on organic farms, so organic farmers rely on naturally occurring fertilizers such as compost and manure for enhancing nutrient content in soils. When farmers apply several organic fertilizers throughout the growing season, they can boost soil health when compared to relying on a single type of organic fertilizer. The use of organic inputs has been shown to increase soil carbon sequestration, which helps to mitigate climate change by locking away carbon that could otherwise act as a greenhouse gas in the atmosphere.

Increasing rotation diversity and length

Crop rotation is a critical component of maintaining healthy soils. Different crops break pest and weed cycles, help cycle nutrients, and reduce economic risks associated with single cropping strategies. Organic farms tend to have longer crop rotations than conventional farms, which leads to higher on-farm diversity. Diversity in rotations is key to enhancing soil health, especially when it comes to including perennials such as alfalfa.

Conservation tillage

Tillage on organic farms is sometimes used to control weeds, but frequent tillage can destroy soil structure and lead to soil organic carbon loss. However, there is growing interest in organic strategies to reduce tillage and increase soil carbon. The challenge in organic is that reducing tillage can sometimes cut yields. Different methods of tillage, such as “vertical tillage” or “strip-tillage,” can maximize both yields and carbon storage.

The Organic Center is a small organization achieving big results. For more information on The Organic Center and the (in)credible science behind organic, visit www.organic-center.org.

The Organic Center's mission is to convene credible, evidence-based science on the health and environmental benefits of organic food and farming and to communicate the findings to the public. The Center is an independent non-profit 501(c)(3) research and education organization operating under the administrative auspices of the Organic Trade Association.