Soil health is the ability of the soil to produce safe and nutritious crops sustainably without degrading or affecting the environment negatively.
An example of a negative effect of an unhealthy soil is water erosion, which removes the fertile surface soil from the farm and deposits it in places where it is unwanted, such as in ditches, streams and irrigation canals.
Wind erosion is another common problem that we face in New Mexico, and with poor soil quality, the soil is easily blown away causing a lot of suspended particles in the air.
Poor soil quality is also a reason for decreasing productive capacity of some of the soils in the state. At times, the level of soil degradation can be so severe that high yields cannot be attained even by increasing farm inputs such as fertilizer, insecticides and herbicides.
With soil health, we are not just looking at the chemical aspect of the soil. In addition to the chemical, we are considering all aspects of the soil — which includes the biological and the physical. Chemical aspects of the soil have to do with issues relating to macronutrients such as nitrogen, phosphorus, potassium and micronutrients such as boron, zinc and copper. Other important measurements related to soil chemistry include soil reaction (pH), salinity and sodium content.
Although information on these chemical measurements we get from the standard soil test reports have proven very useful in production agriculture, there are other important soil attributes and functions that we need to manage in order to secure sustainable crop production and optimal yields. Many of the measurements related to the physical and biological aspects are not commonly considered in managing the soil.
Soil physical aspects, which include functions such as aeration, porosity, water infiltration, compaction and structure, need to be carefully managed for the soil to produce consistent and optimal yields.
Compaction within the plow layer, for example, will prevent roots from growing deeper into the soil, limiting the amount of water and nutrients available for crop uptake. Compaction can also cause water logging and surface runoff to happen faster in a field because the hard layer within the soil will restrict water movement down into the soil profile.
In addition, the role of soil biology in production agriculture has not been well addressed. Out of all the aspects of the soil, the biology is least well known. The biological functioning of the soil revolves around organic matter, which is often less than five percent of the soil, but exerts a tremendous influence on overall soil health.
The organic matter of soil consists of living, dead, decaying and decomposed substances of organic origin. Several groups of micro- and macro-organisms are involved in making sure that the soil is in good shape to provide adequate nutrition for plants. Important contributions of the soil biology include organic matter decomposition, nutrient cycling, mineralization, nitrogen fixation, nitrification, mychorrizal associations and many other useful functions that enhance crop growth and soil health.
Good organic matter management strategies normally benefit all the different aspects of the soil. For example, by adding organic matter such as manure or compost, you will not only stimulate soil biology, but the effects will also improve soil aggregation and infiltration (physical) and improved nutrient availability (chemical).
Managing soil health is more than just adding fertilizers to meet crop demands. It is a long term strategy which involves practices such as reducing unnecessary tillage, practicing good rotations, adding organic matter to the soil by means of increasing crop residues, and appropriate use of synthetic inputs (fertilizers and agro-chemicals) when needed.
John Idowu is a plant sciences extension agronomist for New Mexico State University. Contact him at 575-646-2571 or by email: email@example.com