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Healthy Soil is like a good chocolate cake. It should be soft and crumbly and it should smell great. Use your senses: You can see, feel, and even smell the difference between healthy and unhealthy soils. Grab a shovel. Take a walk in your fields. And get to know your soils.
Look
Start by looking at the surface of your fields. Is there residue? Growing plants? Earthworm middens? Residue and growing plants protect the soil surface from the impact of rain. Raindrops hit the ground as fast as 20 miles per hour and can dislodge soil particles 3-5 feet away. Surface crusting and sealing is caused by a breakdown of soil aggregates due to raindrop impacts which detach particles that fill soil pores. Excessive tillage and lack of residue can damage soil structure, leading to increased soil sealing and soil erosion associated with rain events.
These images were taken from adjacent fields, same soil types. The left has been in long-term no-till and cover crops. The middle is from the same spot with the residue pulled back – note the texture and abundance of earthworm middens. The right image has been managed in a more conventionally-tilled system without cover crops – note the shinier, sealed surface… and weeds.
Dig in. Highly aggregated soils—those granular, durable, distinct aggregates in the topsoil that leave large pore spaces between them—are soils with good tilth and good structure. An interconnected network of pores associated with crumbly, highly aggregated soils allows easy movement of both water and air through the soil and provides habitat for a multitude soil organisms. In fact, there are more organisms in a teaspoon of healthy soil than there are people on earth, but you don’t need a microscope to look for health – just look for living roots and earthworms.
These images were taken from the same fields as above. Not only can you see the difference in soil texture of the notill/cover cropped soils (left) vs. heavily tilled soils (right), there is an obvious difference in color, an indicator of organic matter.
Smell
Can your soils pass a sniff test? Soil should smell sweet and fresh. This is due in part to a compound known as geosmin, a metabolic by-product of certain actinobacteria. Geosmin is also responsible for the earthy taste of beets and is a strong contributor to the delicious smell of rain after a dry spell. If your soil smells sour, rotten... or maybe like a kitchen cleanser, it could be a sign of a soil that isn’t functioning well.
Even after 2-1/2 weeks after the last rainfall demonstration, the soil on the left – from a long-term no-till/cover cropped field – was moist and smelled sweet and fresh. The soil on the right – same soils, but heavily tilled – was crusted and smelled metallic and somewhat acrid.
Feel
Take the muddy boot challenge. After a rain events, even heavy ones, it’s generally possible to walk across fields of healthy soils without bogging down in mud. In dry seasons, healthier soils have more give, similar walking on a padded carpet, whereas unhealthy soils tend to feel something more akin to concrete.
Changing from leg muscles to using your arms and back, it should be relatively easy to push a shovel or tile probe into healthy soils, especially fields with a history of multi-species cover crops as demonstrated in this video:
Get your hands dirty. Healthier soils should crumble easily in your hands. A soil that is hard to break apart could be a result of a variety of factors: compaction, breakdown of soil aggregates and destabilized pore structure, and loss of soil-stabilizing exudates of living organisms.
Use your senses – and get a sense of your own soils’ health... And get started towards a soil that resembles a good chocolate cake.
