What are the physical and chemical dimensions of soil health?
by Juan Vicente Beneitez Lajas on 20/Jul/21
What is soil health?
The concept of soil health is broad and complex as it involves multiple elements and various approaches. In this post, we gather some of the key elements to take into account when exploring the topic of soil health. This glossary is a living body that we will continue to enrich with new and relevant terms in an attempt to shape a holistic vision of soil health in agriculture. Learn more about this all-important topic in our soil health glossary.
Dr. Nyle Brady and Dr. Brady both describe the seemingly interchangeable concepts of soil health and soil quality in the following way: "Although these terms are often used synonymously, they involve two distinct concepts. The soil health refers to self-regulation, stability, resilience, and lack of stress symptoms in a soil as an ecosystem. Soil health describes the biological integrity of the soil community-the balance among organisms within a soil and between soil organisms and their environment." Soil quality on the other hand, “is a term that we use when we talk about the physical attributes of soil. These attributes can all be influenced by management practices and have the capability to enhance or diminish soil health.” (1).
Although they are two distinct concepts, knowing that soil quality is the capacity of soil to function, and that it is “used to describe more complex soil characteristics such as soil organic matter, nutrient amounts, soil structure, etc... and have the capability to impact soil health,” (2) we can infer that soil quality has a direct effect on the overall health of soils.
Soil health depends on the physical, chemical and biological properties or composition of the soil, which are interrelated. Furthermore, soil health is the prerequisite for sustainable crop production (3). Understanding and improving these properties will result in improving the productive capacity of soil, along with boosting crop yield and quality. That said, soil health is directly affected by management practices as well, which plays an equally important role in the overall prognosis.
Physical components of soil quality are well-documented and comprise rocks and minerals which, over time, have broken down into small particles of sand, silt and clay (4). These physical properties of soil quality i.e. texture, bulk density, porosity and aggregate stability, are measured through generally simple, fast and cost effective methodologies. The structure of soil is described as “the arrangement of mineral particles and organic matter in the soil, and particularly the arrangement of pores among these particles...”(2). The granular structure of soil, as Cardoso et al. (2013) explains, “is considered the most suitable for plant growth, allowing for a better balance between macro and micropores, and consequently, between the air/water proportion” (4). Affected by organic matter, soil structure (which is the major soil physical attribute) consequently affects other physical characteristics such as porosity, bulk density, aeration, water infiltration and retention (8). And contrary to texture, soil structure can be substantially modified by soil management (9).
The chemical components of soil include water, the pH and nutrients which are the major compounds and key elements that influence the crop’s nutritional status (7). The amount of water and nutrients stored in soil and their availability to plants is a critical element impacting plant health and subsequently crop health. Physical properties of soil, which are correlated with water holding capacity, suggests that the chemical components are largely dependent on the soil physical components. “A soil with good structure will form stable aggregates that allow easy infiltration of rainwater. The soil aggregates will hold water, yet release the water for greater availability for plants” (5). In other words, organic matter present in soil readily absorbs water and holds it until needed by plant roots. The more organic matter present in soil, the greater ability the soil has to absorb rain water, thus as organic matter increases, the plant-available water also increases. According to Cardoso et al., “it has been estimated that for every 1% increase in soil organic matter, the plant-available water in the soil increases by more than 20,000 gallons per acre” (4).
Bottom line: Organic matter and nutrient levels are the main chemical attributes used in soil health assessment. And as the chemical attributes correlate with high yield crops, a negative or positive impact of these attributes can be easily interpreted, allowing efficient improvement of chemical status by liming and/or fertilization.
1: Curell, C. C., Gross, P. G., & Steinke, K. S. (2012, November 20). Soil health and soil quality. Https://Www.Canr.Msu.Edu/. https://www.canr.msu.edu/news/soil_health_and_soil_quality
2: Soil Basics. (n.d.). Https://Www.Soils.Org/. https://www.soils.org/about-soils/basics/
3: Sevanthi, A. M., Prakash, C., & Shanmugavadivel, P. (2019). Recent Progress in Rice Varietal Development for Abiotic Stress Tolerance. Advances in Rice Research for Abiotic Stress Tolerance, 47–68. https://doi.org/10.1016/b978-0-12-814332-2.00003-4
4: Cardoso, E. J. B. N., Vasconcellos, R. L. F., Bini, D., Miyauchi, M. Y. H., Santos, C. A. D., Alves, P. R. L., Paula, A. M. D., Nakatani, A. S., Pereira, J. D. M., & Nogueira, M. A. (2013). Soil health: looking for suitable indicators. What should be considered to assess the effects of use and management on soil health? Scientia Agricola, 70(4), 274–289. https://doi.org/10.1590/s0103-90162013000400009
5: Kime, L. (2021, July 18). Soil Quality Information. Penn State Extension. https://extension.psu.edu/soil-quality-information
6. Idowu, O. J., van Es, H. M., Abawi, G. S., Wolfe, D. W., Ball, J. I., Gugino, B. K., Moebius, B. N., Schindelbeck, R. R., & Bilgili, A. V. (2008). Farmer-oriented assessment of soil quality using field, laboratory, and VNIR spectroscopy methods. Plant and Soil, 307(1–2), 243–253. https://doi.org/10.1007/s11104-007-9521-0
7. Singh, B. & Schulze, D. G. (2015) Soil Minerals and Plant Nutrition. Nature Education Knowledge 6(1):1
8. Garcia, C., Nannipieri, P., & Hernandez, T. (2018). The Future of Soil Carbon: Its Conservation and Formation (1st ed.). Academic Press.
9. Team, F. (2016, February 24). Soil Structure and the Physical Fertility of Soil. Future Directions International. https://www.futuredirections.org.au/publication/soil-structure-and-the-physical-fertility-of-soil/
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