Soil Health

“Feed the soil, not the plant” is a common expression among growers who understand that soil health is the foundation for sustainable farming. Healthy soil is rich in organic matter and alive with biological activity. Typical characteristics of fertile soil include:

• drains well and warms quickly to allow for better plant growth during cool, wet periods
• stores moisture in order to provide a reservoir of water during droughts
• resists erosion and nutrient loss during heavy rains
• contains and supports diverse populations of soil organisms and microorganisms to increase the availability of soil nutrients, improve nutrient uptake by plants, and build plant resistance to pathogens above and below the surface of the soil
• surface doesn’t crust when dry, leading to better seed germination, easier cultivation and
  greater infiltration of air and water

All of these soil qualities directly reduce the need for expensive inputs while increasing production yield. As a result, healthy soil is a significant factor in the overall success and sustainability of any farm operation.

First Step to Healthy Soil: Know Your Soil

The soil on every farm is unique. Look carefully at your soil to determine its texture, structure, level of biological activity and nutrient content. Texture is determined by the proportion of sand, silt and clay present in the soil. Structure, or tilth, indicates how well the sand, silt, and clay particles hold together to form aggregates. Aggregates are held together in part by humus or decomposed organic matter. Soil aggregates help increase air and water infiltration and reduce soil erosion. Organic matter is critical to the creation of healthy soil. Without it, soil will lack the living community of biological organisms that help form humus, release soil nutrients, and create channels for air and water movement throughout the soil.

Using Soil Tests to Assess Chemical and Biological Properties

Begin the soil building process with a soil test. These tests assess soil texture, micro and macro-nutrient levels, cation exchange capacity, pH, and organic matter content. A soil test is performed by public and private laboratories; check with your local extension agent for testing facilities in your area. Although soil tests reveal a detailed picture of soil characteristics and composition, they also provide an accurate assessment of soil pH levels. Controlling and adjusting pH levels is critical for meeting the growing needs of different crops. Generally, a slightly acidic to neutral soil is desired. When optimal pH balance is achieved, the availability of desired nutrients increases and levels of micro-nutrients toxic to most plants decreases. A soil test is often required for organic certification.

Different Soils Require Different Soil Building Strategies

To build healthy soil you must increase the amount of organic matter, rectify any pH problems and manage soil nutrient levels. Building healthy soil involves a variety of strategies such as:

• planting cover crops to prevent soil erosion and/or plowing them into the soil as green manure
• applying manure or composted manure
• using mulch to control weeds, retain moisture and build organic matter
• fallowing ground
• planting crops along contours or on terraces
• practicing crop rotation
• using lime to balance acidic soils
• adding various soil amendments, such as bone meal, greensand, and biodynamic preparations
• reducing tillage

Key Resources for Soil Health in Organic Agriculture

• Appropriate Technology Transfer for Rural Areas (ATTRA): Free publications. Available by
  request at 800.346.9140 or on their website, www.attra.ncat.org
• Organic Materials Review Institute (OMRI): www.omri.org, 541.343.7600
• Alternative Farming Systems Information Center, National Agriculture Library: www.nal.usda.gov/afsic, 301.504.6559
• Building Capacity in Organic Agriculture Resource Manual, Second Edition, Georgia
  Organics, Inc., September 2003. www.georgiaorganics.org, 678.702.0400
• Building Soils for Better Crops. Fred Magdoff and Harold van Es. Sustainable Agriculture
  Network. 2000.
• Fertile Soil. Robert Parnes. Ag Access Corporation. 1993
• Soil Biology Primer. Elaine Ingham, A.R. Moldenke, and C.A. Edwards. Soil and Water
  Conservation Society. 2000. www.swcs.org.