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Electrical Conductivity: The Pulse of the Soil

Soil consultants have traditionally used electrical conductivity to measure salinity. Conductivity can tell us much more about the physical structure and health of the soil, though, and can help  indirectly measure crop productivity.

electrical conductivity - the pulse of the soilWhen we walk into our home on a dark night, the first thing we usually do is turn on the lights. With the flip of a switch we complete the electrical circuit, initiating the flow of electricity to the light bulb and illuminating our home.

In the human body, electricity controls the flow of blood from the heart to all the organs. In the same way that flipping a switch turns on a light, electrical signaling in the body tells the heart when and how often to contract and relax. These electrical signals can be altered by the intake of nutrients. For example, the intake of high-salt foods can lead to a higher pulse rate. A higher pulse rate forces the heart and other organs to have to work harder in order to function properly. This extra work certainly puts added stress on the body. In contrast, consuming a balanced form of energy can reduce the stress put upon the body.

Waking up in the morning and only consuming caffeine does not give you the same energy as waking up and eating a balanced breakfast. While both inputs may increase your readiness in the morning, they affect the human body in different ways physiologically. Inputs into any biological system, whether human, animal, plant, or soil, affect the system in unique ways.

Electrical Conductivity Measures Soil Energy

Albert Einstein theorized that all matter is energy and derived the famous formula, E=mc2. If all matter is equal – simply a form of energy – then, conceptually, the human system is no different than the soil/plant system. Furthermore, the concepts that we apply to our own physical health can be applied to soil and plant health.

Quantifying the human body’s energy level is done by monitoring pulse rate. For soil, the current energy level in the field or in the lab can be determined by measuring the soil electrical conductivity. Electrical conductivity is a direct measurement of energy flow in the soil system. And energy, measured in ergs (energy released per gram per second), is a function of the soil’s ion concentration, clay type, moisture content, porosity, salinity, and temperature.

As consultants and growers, we are focused on crop productivity. We often aim to maintain the nutrient or ion concentration in the soil solution that is best suited for the highest crop production.

This ion concentration is expressed by the quantity of ions surrounding the diffuse layer of the soil colloid and also by the soil’s moisture content. Electrical conductivity is a direct measurement of these factors and can be used in the field to tell us how much energy is available for plant growth.

It is important to note that natural fluctuations in electrical conductivity can occur. In the soil, the conductor of electrical current is water. As soil moisture changes due to dry periods and/or rainfall events, electrical conductivity can vary. Abiotic factors are variables in the accurate representation of the ion concentration in the soil solution.

However, overall, if the electrical conductivity (concentration of ions in the soil solution) is either too high or too low, it will be reflected in decreased crop productivity. From our experience, the majority of problems facing growers and consultants can be related to abnormal electrical conductivities.

Crop productivity is governed by three scientific disciplines: physics, chemistry, and biology. Explaining electrical conductivity on a chemical or biological level requires a much more lengthy and detailed explanation. Focusing on the physics of electrical conductivity by referring to it as energy brings simplicity to this complex topic.

Einstein taught us that an object’s mass is a function of energy. If you apply this concept to crop production, crops (mass) are simply an expression of energy. In order to produce mass (yield), energy is needed. For a plant to perform photosynthesis and to produce mass, an initial energy requirement must be met. This energy requirement comes largely from the electrical current in the soil. Soil electrical conductivity can thus be utilized as a direct measurement of energy and an indirect measurement of crop productivity.

Electrical Conductivity and Crop Productivity

Crop productivity can be simplified into two stages: growth and decomposition. We can discern that the growth stage of the plant life cycle has different energy requirements than the decomposition stage. The amount of energy needed to produce mass in the form of plant growth varies between 200 and 800 ergs. When the energy in the soil falls below or above these values for a prolonged period of time, the plant can no longer produce mass (growth) and decomposition will set in. Once plant tissue decomposition begins, disease and decay will follow. During the growth life cycle of the plant, energy must be present to produce mass (growth).

plant growth life cycle

During the growth life cycle of the plant, energy must be present to produce mass (growth).

In order to produce mass in the form of a nutrient-dense and healthy plant, the energy coming from the electrical conductivity of the soil must come from “good” sources. Electrical conductivity coming from biological activity, flocculation, soil moisture, and clean balanced nutrients (ions) can be considered “good” sources of energy. Electrical conductivity coming from salinity in the soil solution can be defined as a “bad” source of energy. “Bad” sources of energy will produce nutrient-poor, unhealthy, low-energy, and quickly-decomposable mass.

Nutrient-dense, healthy, high-energy plant mass is what we as consultants and growers should try to achieve. Yes, by using these “bad” sources of energy you can produce high quantities of mass (high yields). We see this year in, year out with the use of synthetic fertilizers.

However, if your goal is to produce high-quality, nutrient-dense, healthy plant mass, your energy source must come from “good” sources. Low-salt fertilizers, organic matter, biological amendments, cover cropping, and proper soil stewardship can provide your soil with “good” sources of energy. All of which indirectly restores your soil’s fertility for future generations.

If all matter is energy and all energy is matter, we as consultants and growers must begin to think in terms of energy.

In order for seeds to germinate, an energy requirement must be met. In order for plants to grow, an energy requirement must be met. In order for plants to reproduce, an energy requirement must be met. In order for plants to dry out and be harvested, an energy requirement must be met. In order for your soil to repair itself over winter, an energy requirement must be met. And in order for you to have read this article, an energy requirement was met.

By Glen Rabenberg & Christopher Kniffen. This article appeared in the April 2014 issue of Acres U.S.A.

Glen Rabenberg is the CEO and owner of Soil Works LLC. Soil Works LLC is home to Genesis Soil Rite Calcium, PhosRite, TestRite Labs, and GrowRite Greenhouse. Mr. Rabenberg extensively travels the world solving soil problems with a little bit of simplicity and the “rite” tools.

Christopher Kniffen is writer, public speaker, and manager of the research and development department of Soil Works LLC. For more information, Rabenberg and Kniffen can be reached at Soil Works LLC, 4200 W. 8th St., Yankton, SD 57078, 605-260-0784.

Resources:

Eigenberg, R.A., J.W. Doran, J.A. Nienaber, R.B. Ferguson, and B.L. Woodbury. “Electrical conductivity monitoring of soil condition and available N with animal manure and a cover crop.” Special issue on soil health as an indicator of sustainable management. Agric. Ecosyst. Environ.

Johnson, C.K., J.W. Doran, H.R. Duke, B.J. Wienhold, K. Eskridge, and J.F. Shanahan. 2001. “Field-scale electrical conductivity mapping for delineating soil condition.” Faculty Publications, Department of Statistics. Paper 9, digitalcommons.unl.edu/statisticsfacpub/9.

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McBride, R.A., A.M. Gordon, and S.C. Shrive. 1990. “Estimating forest soil quality from terrain measurements of apparent electrical conductivity.” Soil Sci. Soc. Am. J. 54:290-293.

McNeill, J.D. 1980. “Electrical conductivity of soils and rocks.” Tech. note TN-5. Geonics Ltd., Mississauga, ON, Canada.

Rhoades, J.D., N.A. Manteghi, P.J. Shouse, and W.J. Alves. 1989. “Soil electrical conductivity and soil salinity: new formulations and calibrations.” Soil Sci. Soc. Am. J. 53:433-439.

 

 

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