Soil Health
The USDA-NRCS defines soil health, also referred to as soil quality, as “the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans”. They further state that “this definition speaks to the importance of managing soils so they are sustainable for future generations”.
Understanding soil health involves assessing and managing a soil’s inherent properties of fertility, structure, microbial activity, etc. so that it functions to support optimal plant growth, both now and in the future. This means that changes in soil health must be constantly monitored so that soil is not degraded, and conversely is managed using a set of practices that are both sustainable and promote soil sustainability for the long term.
Soil is an ecosystem that not only holds and provides nutrients and water for plant growth, but also provides habitat for soil microbes that are an integral part of the soil’s interaction with plants that are growing in it. These microbes are key to decomposition of chemical and plant residues and resultant nutrient cycling, as well as integral to soil components that affect soil structure, aeration, porosity, and water holding capacity.
Microbial activity is an integral part of soil health. As stated in the overview of the USDA-NRCS soil biology primer, “The creatures living in the soil are critical to soil health. They affect soil structure and therefore soil erosion and water availability. They can protect crops from pests and diseases. They are central to decomposition and nutrient cycling and therefore affect plant growth and amounts of pollutants in the environment.” Other chapters of this primer give additional detail about the living component of soil and how it contributes to agricultural productivity and sustainability, and air and water quality.
A video presentation by soil microbiologist Dr. Sarah Hargreaves entitled “The Haney Soil Test and Nutrient Turnover“ (go to 20 min. into the video) gives a detailed discussion about the various types of soil microbes and how microbial activity is involved in mineralization and nutrient turnover in the soil. She discusses how the Haney Test (click here for article describing the test and here for the results of a study conducted to evaluate this enhanced soil testing method in crop fields) is used to measure microbial respiration, which can then be used as an indicator of soil health by determining the levels of naturally occurring nitrogen and other nutrients.
Dr. Hargreaves also discusses how the C:N ratio (carbon to nitrogen ratio) in the soil can be used to determine the “feed value” of a soil in relation to microbial needs and activity, and how this ratio can be affected by cropping systems and cover crops to provide a year-round supply of organic matter to feed microbes. For a summary of the major points in the video presentation compiled by Dr. Dan Davidson of DTN, click here. Click here for the website of a laboratory that conducts the Haney Test.
The Haney Test is touted to better measure the effects of cover crop and no-till practices on soil health. The test results can be used to develop a soil health calculation and suggest a cover crop mix that will give a better C:N ratio. The results can also be used to better understand and measure the contributions made by cover crops.
The USDA-NRCS has a playlist of videos that cover all aspects of soil health. Click here to access. The agency also has numerous articles on the various aspects of soil health. Mr. Ray Archuleta of the NRCS is a renowned and dynamic speaker who makes presentations on the many aspects of soil health and how modern agriculture can be better managed to facilitate its improvement and/or sustainability.
Composed by Larry G. Heatherly, Jan. 2016, larryheatherly@bellsouth.net