By James Hoorman, Hoorman Soil Health Services
USDA-NRCS (Natural Resource Conservation Service) is promoting farmers to adapt a soil health management plan for their farms. NRCS defines soil health as “the continued capacity of a soil to function as a vital living ecosystem that sustains plants, animals, and humans.” There are several key concepts. First, soil is alive and teaming with soil microbes and other biological life (earthworms, mites, springtails, etc.). Second, soil has many functions that are critical to our life.
Key essential soil functions include: 1) regulating water, 2) sustaining plant and animal life, 3) filtering and buffering potential pollutants, 4) cycling soil nutrients and 5) providing physical stability and support. Soil microbes mediate about 90% of all soil functions. Microbes process all soil carbon and even breakdown rocks to make plant nutrients available. Also, soil microbes are the end-product of most soil organic matter (SOM). Dead microbes become the long-term SOM.
Soils help control (regulate) where rain, snow, and irrigation water end up; how it flows; and where and how much is stored in the soil. All plants, animals and humans rely on soil to survive, because that is where our food is produced. Soil also filters and buffers many potential pollutants (fertilizer, manure, pesticides, sludge) that are applied to it. Soil organic matter (SOM) is made of around 50-58% carbon which helps soils accomplish many of these functions.
Soil also stores and recycles soil nutrients to keep plants healthy. Soil also provides physical stability and support for tractors to farm it; or for people to build homes, businesses, highways etc. For farmers wanting government assistance for conservation projects, a soil health management plan may be required.
USDA-NRCS are concerned about what happens to soils when they are cultivated or tilled for long periods of time. First, the tillage causes a rise in carbon dioxide from the soil into the atmosphere and a loss of SOM. Carbon dioxide is a greenhouse gas which, from the government’s perspective, leads to climate change. Tilled soils tend to have lower water infiltration, more nutrient runoff, tends to erode, have less biological life, and decreased biodiversity. Bare soil has higher soil temperatures, more soil compaction, less nutrient efficiency, and less resilience to bad weather and pests. In sum, bare soils tend to be described as being naked, run a fever (have a hotter soil temperature in summer, colder in winter), and are thirsty (soils crust, water runs off, soil holds less water for biological life).
Farmers often till the soil to control weeds and pests. However, tillage buries weed seed and preserves them. Tillage allows soils to dry out in the Spring, so the soil warms up. Every tillage pass loses 0.5-1.0 acre inch of water. However, tillage causes soils to stay wet due to soil compaction, so water can not drain away easily or on the reverse side, the loss in SOM means tilled soils hold less water in a dry summer. Well aerated, well aggregated soils with live roots allow cold winter water to drain away while holding more soil water for a dry summer. Tillage allows good seed-to-soil contact but well aggregated soils high in SOM do the same.
In the next few years, there are going to be many advances in biologicals to promote and maintain higher crop yields. Many companies are now researching and promoting microbial products that improve soil functions. Some biologicals make nitrogen and phosphorus more available and increase nutrient cycling and nutrient efficiency. Others add soil carbon (SOM) which improves soil aggregation (good soil tilth) for improved water control (less runoff, higher water infiltration, more soil water storage). Keeping carbon in the soil, helps reduce the impacts of climate change and allows soils to filter and buffer potential pollutants. Biologicals are also being developed to speed up residue decomposition. Ideally, 80% of the crop residue should be decomposed by next spring if your soil is healthy.
In a soil health management plan, USDA-NRCS emphasize four main core soil health principles. First, minimize disturbance as much as possible. That includes reducing or eliminating tillage, preventing over grazing on grazed land, and over applying nutrients and pesticides. Second maximize a living cover, whether that be surface residue or live plants to protect the soil from wind and water erosion. Third, maximize live roots by keeping the soil covered with live plants year-round. Either plant cover crops after the main crop or plant perennials (hay, pasture, etc). The fourth principle is to maximize biodiversity. Increase or lengthen your crop rotation to add more crops or even add livestock to improve soil biodiversity. Creating a soil health management plan is not only profitable, its good for the environment.