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How Do You Know Your Soil is Healthy?

How Do You Know Your Soil is Healthy?
County Extension agent explains how to improve soil health.

By Richard Halopka

What is soil health? From questions and conversations I have had during winter meetings and field days, people have many interpretations of soil health.To understand soil health here's a quick review of soil basics.

Soils are alive, dynamic, and always in a state of flux.

Soil encompasses three components: physical, chemical, and biological.

How Do You Know Your Soil is Healthy?

The physical component is comprised of four areas. Texture is the relative amount of clay, sand, and silt present in a soil. Structure is the general appearance of the soil related to shape, size, and pore space. Bulk density is the weight for a known volume of soil; as weight per volume increases compaction probably occurred. Color is related to parent material, organic matter present and erosion.   

The chemical component is pH and plant available nutrients in the soil. This chemical component is determined from a soil test.   

The biological component is the interaction between the living, the dead, and the very dead in soil. A teaspoon of soil has more life (living critters present) than the human population of the world. Soil critters require decaying residues (including other dead critters) and live roots to survive. Providing food and shelter will allow the biological component of soil to multiple and flourish. If a house is built for the biological component they will come and flourish.

First and foremost there is no silver bullet to improve soil health. Purchasing a product will not cure the effects from years of soil abuse. Soils are always in a state of flux. So is a soil balanced?  No, this term is used in a multitude of fashions generally related to products that can be purchased to correct or improve soil health. Products may be purchased to provide soil nutrients or improve the soil environment (lime for pH, organic or commercial fertilizers, compost, or manure).  The soil critters will mineralize nutrients from organic materials without the aid of a silver bullet.   

Soil health is a combination of good soil structure, availability of essential nutrients, and a diverse group of living critters. Currently there is no system in place to measure soil health, although a soil test can measure organic matter (OM), pH, and the present level of plant available nutrients.

Reducing soil erosion will improve soil health. Soil erosion will never be eliminated, but it can be reduced. Generally your valuable top soil is lost to soil erosion.

Francisco Arriaga, University of Wisconsin-Madison soil scientist, has determined it will require a minimum of 180 years to naturally reproduce 1 inch of topsoil. Topsoil that encompasses the area of one acre (43,560 square feet) at a depth of 1 inch weighs 164 tons. Arriaga says the value of soil lost from erosion at current fertilizer prices equals $8.80 per ton. An acceptable soil loss is 5 tons per acre. Visualize the thickness of a dime across one acre, that depth equals 5 tons per acre and a $44 per acre loss. If soil eroded at the depth of 1 inch across one acre the value of nutrients lost would be $1400 per acre and require 180 years to be restored. This is just the loss of nutrients and doesn't consider the loss of soil structure or soil biology.

The basics for improving soil health are providing food, shelter, and an environment that will allow the soil critters to multiple and flourish. Diverse rotations that include annual and perennial crops, plus the addition of cover crops will provide live roots in soil for a greater period of time. This will help stabilize soils preventing erosion and provide food for your soil critters.

Reducing tillage will improve soil structure and prevent reductions in your soil critter population. Residues will feed soil critters, protect the soil surface from rainfall impact, and improve water infiltration, slow water runoff, and moderate soil temperatures. Integrated pest management will reduce the use of pesticides. Pesticides may be used when an economical threshold is attained, protecting natural predators and your soil critters. Nutrient management will account for available on farm nutrient credits (manure and legume), potentially reducing purchased fertilizer.

Improving soil health is a journey not a destination and will require the due diligence of farmers for many years.

The goal is to leave the farm (soil) in a better condition than the day you began. 

Halopka is the Clark County Extension crops and soils agent.

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