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How can you use soil test results? You could ask Mulder.
We have learned a lot about plant and soil science in recent decades, but there is a chart that gives us some insight into how the minerals used by plants as food might interact.
Before we learn how to use this chart, let’s review soil pH and nutrient absorption.
The 20 or so minerals used by plants as food are found in soil as ions. Ions are atoms and molecules that have either a positive or negative charge. These cations and anions, respectively, attach themselves to water molecules and are pulled into the plant by root hairs. The ability of a plant to pull those nutrients in depends largely on soil pH.
Soil pH ranges from 0 to 14, with lower numbers indicating acidity and higher numbers indicating alkalinity. Using the chart below, you can see that more nutrients are available, and there is greater microbial activity, when soil pH is between 6.0 and 7.0. Most plants can survive in soil pH from 5.2 to 7.8, but the narrower range allows plants to thrive. As anions and cations are pulled out of the soil, the soil pH changes, ever so slightly. This is why too much or too little of certain minerals in the soil may interfere with nutrient availability. This is where Mulder’s Chart comes in.
How to use Mulder’s Chart
Looking at Mulder's Chart, you can see 11 essential plant nutrients and micronutrients arranged around a circle. Solid and dotted lines connect the nutrients, with arrows heading one way or the other. Solid lines indicate an “antagonistic” relationship, which means high levels of one nutrient leads to a problem absorbing the nutrient being pointed to, while dotted lines indicate a “synergistic” relationship.
For example, according to Mulder’s Chart, high levels of nitrogen may reduce a plant’s ability to absorb boron, copper, and potash, as seen by the solid lines pointing from nitrogen toward the other nutrients. In the same way, high levels of nitrogen may stimulate magnesium uptake, and high levels of molybdenum might stimulate plants into absorbing more nitrogen, as seen by the dotted “synergistic” lines. Like most things in life, though, it isn’t really that simple.
Until you have a soil test from a reputable laboratory, you cannot know what is in your soil. Soil test results provide an amazing snapshot of what is really going on “down there”. Your soil test results will include individual measurements of several plant nutrients, as well as a cation exchange capacity rating, which describes a soil's ability to hold nutrients.
According to Linda Chalker-Scott, associate professor of horticulture and extension specialist at Washington State University, “It makes sense from a strictly chemical point of view, but soils are also biological. Plants exude organic acids from their roots. Mycorrhizae can mobilize "immobile" nutrients. I find these types of charts way too simplistic for real world conditions.”
While there is certainly a limit to its usefulness, I do encourage you to apply Mulder’s Chart to your soil test results and compare those results to what you are seeing in your garden. It may give you an idea of where problems may be occurring, or it might just be a fun way to review your soil test.
1/2/2019 04:08:46 pm
Because I'm typically reticent about reading things I deem to be too specific, I would ordinarily steer away from this, but because past experience with your posts are so helpful/informative, I'm now digging (pun intended) into this one as well. Thanks.
8/1/2019 02:00:54 pm
8/2/2019 07:19:35 am
10/26/2019 12:22:43 pm
"Garardus Johannes Mulder was a chemist who lived in the 1800s"
10/27/2019 05:03:23 am
Argh! You caught an error! And thank you!
It’s a very helpful blog. I got lots of information from this blog.
11/4/2021 03:41:09 am
There are no arrows on the red (antagonistic) lines on your Mulder's chart. That seems to imply the antagonism is in both directions with all connected elements. This is not so in other versions of the chart that I have found. Also, there are no arrows on the stimulation/synergistic lines.
11/10/2021 08:00:37 am
Thank you, Rob.
11/10/2021 08:32:12 am
Scratch that. Draw a better image.
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