Making A Transition To Biological / Sustainable / Organic AG: How To Observe And Document Your Progress

By Philip A. Wheeler, Ph.D.

The first step in the transition is to establish the existing mineral levels in your soil and determine their availability to your crop. This is best obtained by have two distinctive type of testing done.  The first test is the standard Cation Exchange Capacity or CEC, which measures the amount of major, minor and trace elements which are assumed to be agronomically available to growing crops. It is called a CEC test because it measures the capacity of the soil to hold and exchange positive, exchangeable mineral ions (cations).  This is usually related to the clay content as the clay has spaces in its lattice structure to hold calcium, magnesium and potassium for agronomic use.  Organic matter in the form of humus can also add to the holding capacity, but is usually more significant in muck soils.  The higher the CEC number, the greater the holding capacity.  A typical sandy soil might have a CEC of 5, a sandy loam could be around 8 and a clay loam might be 12.  There are very heavy mineral, clay soils in the US and foreign countries that can run 30-40 or higher.

We call the higher CEC numbers a “bigger bucket” because a high CEC means that more lbs. of minerals per acre are held for plant use.  The size of your “bucket” helps to determine how you will approach your conversion.  Low CEC soils have few reserves, so care must be taken to track and replace minerals on a more frequent basis.  It also means it is easier to balance ratios. A high CEC may indicate a situation where trying to bring up the mineral content to a specified level or trying to balance ratios would be cost prohibitive.  The better approach there is to do more activation to assure availability to the crop.  Most soils allow for both activities to be economically feasible, i.e. replace minerals and biologically activate them.

The second test is called a LaMotte extraction.  It uses a weaker pH extraction and is designed to simulate the action of plant organic acids extruded by the roots to etch minerals from your soil.  The LaMotte soil test numbers are assumed to be the plant available amounts of nutrients.  It is very common to find large discrepancies between the CEC numbers and the LaMotte numbers.  It is the most common to find this situation on standard chemical farms, but I frequently find the same situation on organic farms.  The organic farmer may have replaced the minerals, but he or she didn’t take deliberate steps to activate the existing microbes or add new ones necessary to make the minerals available to the crop.

Once we have both sets of test numbers, we can analyze the situation and begin to see where the shortages and overages are.  You can’t do a lot about CEC indicated overages of a mineral on an immediate basis, but you can activate other minerals that are considered suppressive to the excess one.  For instance, calcium will suppress potassium and potassium is excessively available in many soils.  The obvious way to deal with shortages is to apply the needed mineral in a form that will be biologically enhancing to the microbes and also be compatible with the overall soil situation.  Many times you can receive a second nutrient right along with the one you are looking for by choosing the appropriate material.  When you buy ammonium sulfate, you get nitrogen and sulfate sulfur, which is the usable form. When you buy gypsum, you are buying the prime nutrient, calcium, and again getting the all important sulfate form of sulfur.  When replacing trace minerals, it is usually more economical to buy the basic oxide or sulfate form, such as copper sulfate.  These will require bacterial activity and time to make them available, so sometimes it is a good idea to use a readily available chelate in the row and/ or foliar to replace a yield limiting shortage.  Some of the very low level requirement trace minerals such as chromium, molybdenum, nickel and selenium can be replaced by the use of natural fertilizer materials such as yeast, garlic, seaweed and fish.

The first mineral to consider replacing (or activating) is the calcium.  If you need to add calcium according to the CEC test, the usual rule of thumb is: use high calcium lime (calcium carbonate) if the pH is below 7 and use gypsum (calcium sulfate) if the pH is 7 or above.  I usually avoid the use of dolomite or Ag-lime as the magnesium content is too high.  Application of more than a ton or two of Ag-lime will usually upset the calcium-magnesium balance and can cause compaction problems and nitrogen release problems.  When you start adding carbohydrates to the soil in the form of sugar or molasses, the calcium usually is the first major mineral to show increases in availability.

The most important point concerning the availability of all the minerals is that you must stop the use of muriate of potash (KCl or 0-0-60) because it is almost 50 % by weight chlorine (the major component of bleach) and seriously affects the microorganisms in a soil.  Anhydrous ammonia should also be phased out of your program for the same reasons.

Replacing phosphorous is usually a more expensive process.  Regular fertilizer sources such as MAP or DAP do offer soluble, immediate use sources.  For long term building, natural hard rock and soft rock sources are more economical.  The important issue with phosphorous is making it available to your crop through biological activity.  Many CEC soil tests show large quantities to the point of overages, but the farmer still has to add phosphorous in the starter to avoid obvious phosphorous deficiencies in the spring.  Molasses seems to be one of best materials to start activation of the bacteria that release phosphorous.

Another way to make phosphorous more available is to increase the amount of mycorrhizia present on the roots.  These root fungi attach/grow on and in the root surface and act as gateways for nutrients to move from soil to plant.  They are so efficient that they can relieve phosphorous deficiencies even in very low phosphorous soils.  Applications of muriate of potash and highly soluble phosphorous shut the mycorrhizia down.   The absence of mycorrhizia and other beneficial organisms on the roots is the main reason growers have so many problems with soil borne fungal diseases and have to apply costly fungicides.  Prevention by promotion of natural systems is always cheaper than chemical rescue.

Potassium is usually more than adequately available is chemically farmed soils.  If you do need to replace it, the use of sulfate of potash (0-0-50) is usually recommended instead of muriate of potash.  The sulfate form costs more per ton, but you can use less to get the same effect, you get the valuable sulfate sulfur along with it and you avoid the damaging chlorine.  Manure, compost, sawdust and ashes are also good sources of potassium.  The more calcium and other minerals become available, the less potassium is needed to make the system function.  (This also applies to nitrogen.)

Usually, magnesium just needs activating.  I like to use Epsom salts (magnesium sulfate) as a ground or foliar source to act as a stimulator of the magnesium already present in the soil.  It is available in most feed stores.  The adding or activating of calcium will also aid in the activation of magnesium.


By using the sources of mineral suggested above, you can cover the replacement needs for sulfur without having to buy it separately.  It is the most under-used of the six majors and the lack of it results in everything from weakened plants that are susceptible to insect attack to low RFV’s of the forages.  The forage may test high in protein, but part of the measurement includes free nitrates rather than amino acids of protein.


The ultimate goal of all the above-suggested practices is to have the LaMotte test numbers come up to the balanced CEC numbers. This would indicate that your plants have maximum access to the minerals stored in your soil and therefore, should perform with maximum efficiency relative to weather, plant populations, etc.  The ways to increase the efficiency even further relate to starters, side or top dressing and foliar feeding which will be the subjects of future articles.  One of the most frequent questions directed to me is: “If I am short of funds, should I put everything on a few acres or put less on more acres?”  There is no correct answer, but if fields aren’t performing, a small dose of minerals and activators may make a major difference in field/crop performance.


There is one final step that can be done after the selection of proposed inputs.  After analyzing the data from the two types of tests, one can check whether or not your choice of materials and activators matches the reality of the situation.  One can’t expect the grower to conduct 2-3 years of field trials just to find out that gypsum or corn sugar or whatever is good for his soil.  In living systems (plant, animal, big or small) there is the concept of resonance.  The more a living organism can resonate with its surrounding energy patterns, the longer it can live.  Obviously, elephants and turtles do this, as they are long-lived mammals.  To verify the choices for soil additives, it is important that we establish that the proposed input will resonate with the entire soil or soil/plant living system.  This can be done electronically by placing the soil sample and the proposed input into an electronic energy-measuring device.  If a proposed input does not raise the energy of the soil system a significant amount, than the proposed input is rejected for use at the present time.  That same input may be tried and used the next season as the soil goes through stages of recovery.  This assures that the grower is only purchasing and applying materials that have a good chance of producing a return on investment.


Monitoring of the whole recovery/transition process is important.  A grower may observe any of the following: insects starting to eat broad leaf weeds instead of the economic crop; brix and RFV rising in the crop; soil structural and water retention changes; improved animal performance and health; increased plant growth with less nitrogen required; less disease pressure on plants; frost resistance and so forth.  Be sure to observe in the field.  Don’t wait to just measure pounds of gain, because the best fertilizer in the wold is the footprint of the grower in the field.  Good Grazing!