Soil health has been underestimated as a contributor to the overall health and yield potential of a crop, but it’s one of the most critical components to ensuring plants get the valuable nutrients they need to grow, especially early in the season.
Soil has been described by many words: dirty, static, lifeless; leading the public to think of soil as non-living and needing little inputs. But in reality soil is a complex environment vibrant with life. Soils are made up of four components: minerals, air, water, and organic matter. In most soils minerals represent around 45% of the total volume, water and air about 25% each, and organic matter from 2% to 5%. Billions of organisms live in the soil, including bacteria, fungi, nematodes and earthworms. In fact, 1 tablespoon of soil has more organisms in it than there are people on Earth, according to the USDA Natural Resources Conservation Service (NRCS).
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The organic soil component contains all the living creatures in the soil and the dead ones in various stages of decomposition. An acre of living soil can contain 900 pounds of earthworms, 2400 pounds of fungi, 1500 pounds of bacteria, 133 pounds of protozoa, 890 pounds of arthropods and algae, and even small mammals in some cases (1). Humus is the fraction of organic matter in the final stage of decomposition and serves as a reservoir of plant nutrients. Soil microorganisms are the invisible workforce contributing to soil health by enhancing organic matter decomposition and nutrient cycling. This process helps improve soil structure, which limits soil erosion, increases water availability and helps plants withstand challenging weather conditions more successfully. Viewing soil as a living ecosystem reflects a fundamental shift in the way farmers care for the land, said Nick Groeser, Ph.D., Director of Soil Health Partnership.
Healthy productive soil can help reduce input costs for farmers and they want to implement proven practices that fit their operation. Best-management practices to improve soil health include reduced tillage, increasing organic matter, introducing organic amendments, utilizing cover crops and increasing oxygen availability. Healthy soil leads to healthy roots and healthy plants, ultimately resulting in better yields and higher quality products for consumers.
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Limiting tillage practices provides benefits to the soil. A reduced tillage system has many advantages including soil conservation, reduced water runoff, increased water infiltration and long-term build-up of organic matter that keep nutrients available for use by growing plants. Healthy soil created by less tillage can also help buffer the crop against weather extremes, from drought to flooding, while offering an extra layer of protection from a variety of other biotic and abiotic stresses. This helps the crop maximize its genetic potential and provide growers the greatest return on their investment. Practices such as reduced tillage that can improve soil health also have the potential to improve water quality, according to Iowa State University Extension.
What started as a desire to cut his crop input costs turned into a quest for greater soil health – and higher yield potential – for Denny Winterboer, a corn and soybean grower from Milford, Iowa, who has been farming for 45 years. “I was tired of what tillage was costing me in terms of diesel fuel, “said Winterboer. “Less tillage was a big change for me, because I grew up with the plow. Not only has less tillage saved me money through less fuel usage, but it creates an environment that’s good for microbes and earthworms.”
Maintaining or building organic matter levels is critical to successful crop production. Dead plant material is the largest component of organic matter, followed by living plant tissue and soil-inhabiting microbes, animals and insects. Plant residue at the end of the crop season should be returned to the land to replace decomposition of material used throughout the growing season. Soil organic matter is the warehouse for several nutrients including: nitrogen, phosphorous, and sulphur. Nutrients stored in organic matter must be readied for plants through the activity of soil microorganisms. Organic matter improves soil tilth, aids in reducing compaction and surface crusting and increases water infiltration into the soil.
One means to build organic matter is planting cover crops on fallow land during the off-season. Cover crops can also suppress weeds, help break pest cycles, and through their pollen and nectar provide food sources for beneficial insects and honeybees. Cover crops cycle soil nutrients making them available to subsequent crops as the green manure decomposes. The addition of 1 percentage point of organic matter in the soil releases 20 to 30 pounds of nitrogen, 4.5 to 6.6 pounds of phosphorus and 2 to 3 pounds of sulfur per year. Appropriate mineral nutrition needs to be present for soil organisms and plants to prosper. As the focus turns to improving soil health, the consequence of increased levels of organic matter could result in a lower demand for synthetic fertilizers and less financial costs for the grower.
Soil health cannot be changed overnight, in fact it will take ~500 years to form 1 inch of topsoil, making it a very precious natural resource indeed (2). Healthy soil is critical to agriculture sustainability and for optimizing the land in cultivation for feeding and clothing the world population today and in the future. So next time you think about soil, think of it as the complex and living ecosystem it is rather than mere “dirt”.
- Pimentel, D. et al. 1995. Environmental and economic costs of soil erosion and conservation benefits. Science. Vol. 267, No. 24. p. 1117-1122.
- 10 Incredible Facts about Dirt; http://www.audubon.org/content/tern; Audubon Society.