Plant Nutrition

Plant Nutrition, Chemistry, and Mulder’s Chart

Nutrient chemistry is a complex subject that stymies most of us.  Just keeping track of the nutrients that healthy soil requires and healthy plants need is often a headache-inducing situation.  Some helpful tips can be used by the average hobby gardener to shed some light on this rather esoteric science.

Mulder’s Chart

Thanks to a German chemist who lived in the 1800s, we have a tool that can make understanding the complex interactions of common elements in the soil much easier.  Soil science and chemistry have come a long way since Mulder fashioned his chart, and we have learned a lot more about plant and soil nutrition, but at its core, Mulder’s Chart is still a useful tool as long as we recognize its limitations.

How Things Work

We need to understand a little about what is going on at the molecular level in our soil and plants.  The elements that we consider to be the most important to soil and plant nutrition exist in the soil as ions.  Ions are the atoms of the element having either a negative or positive charge.  Respectively, these are called cations (+) and anions (-).  Because of their charge, they attach themselves to water molecules, which is the transport vehicle that allows the plant to pull in these nutrients.  The pH of the soil determines, to a large extent, how effectively the plant can make this happen.

Plant Nutrition - pH and nutrient availability

Here is the Catch 22

Normal pH is 7.0.  pH can range from 0 to 14.  The lower the number, the more acid the soil.  The higher the number, the more alkaline the soil.  When the pH is between 6.0 and 7.0, you generally find the greatest amount of microbial activity in the soil.  Plants can usually survive in soils with a pH as low as 5.8 or as high as 7.6.  Here is the kicker.   As the plant pulls the cations and anions from the soil, the pH changes ever so slightly.  This infinitesimal change is why too much or too little of some minerals can interfere with the nutrient flow and availability.

Enter Mulder’s Chart.

Mulder’s Chart lists the 11 most essential nutrients and micro-nutrients in a circular format.  Dotted lines and solid lines connect the different elements.  Each line has at least one arrow pointing own way or the other.  Solid lines indicate an “antagonism.”  A high level of an antagonistic mineral will lead to a problem with the plant being able to absorb the nutrient to which the arrow points.  (See Attachment 1)

A dotted line indicates that the two minerals share a “synergistic.” relationship.  Synergistically connected elements work together to enhance the plant’s ability to absorb the elements.  Hence, if one of the elements is in short supply, the plant may have a problem making use of the other element.

Let’s Look at an Example.

If we look at Mulder’s chart, we can see that Nitrogen at high levels can reduce a plant’s ability to absorb Boron, Copper, and Potash.   The solid lines connecting Nitrogen to these three elements tell us this antagonistic relationship.  Looking at the green lines, we can see that high levels of Nitrogen may stimulate the uptake of Magnesium. 

It seems simple enough.  But, like most things in life, it is not as simple as Mulder would have us believe.

The Realities

Without a soil test from a reputable lab, using Mulder’s Chart for more than a conversation is a risky business.   It is hard to build a firm thesis until you have a reliable starting point.  Find a lab that will give you not only the available amounts of each element, but also the total organic matter available in the soil.

The other problem with relying strictly on Mulder’s Chart and lab results from soil tests is the sheer complexity of what is happening in the soil.  Plants exude complex chemical compounds from their roots that can change the soil chemistry.  Mycorrhizae fungi exude chemicals that can mobilize elements that may test as immobile in the lab. 

On the other hand, applying Occam’s Razor to problems often yields surprisingly good results.  Using Mulder’s Chart and a recent soil sample may give you insight into what is happening with your soil and plants.  Combine this with the other telltale signs plants give when they are stressed, and you may have a good tool to understand what is happening, or not happening, below the surface.

plant nutrition - mulders chart

Links and Resources

For more information about organic gardening, lifestyles, and living, visit our website at West Texas Organic Gardening.

If you found the information here helpful, you might also find these articles on our website of interest.

Organic Growing Myths

Toss Your Tiller


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