Chromatography: Writing Color
23 January 2023
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In winter, we take time to go inside and integrate experiences from the season. This week, the KYR team gave our soil the same opportunity.
Using the Pfeiffer Paper Chromatography method we developed images of the soil separated into its components. This method begins with dissolving a small amount of soil from each sample in sodium hydroxide and inducing a type of centrifugal force by mixing it over the course of several hours. These stratified soil samples are then leached into special filter paper that has been impregnated with silver nitrate.
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Here, the different particles are absorbed at differing speeds, some stretching toward the edges of the paper, others depositing at shorter distances along the way. Over the next two weeks as these chromas develop, beautiful mandala-like images become increasingly pronounced, offering holistic and integrated information about the soil's health and yield-production.
How does this relatively esoteric/subjective soil assessment method compare to laboratory analytics on samples? While a chroma won't offer you exact levels of NPK, minerals, organic matter, or pH, it will give insight into the highly variable interplays that thees elements can produce.
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For example, a low-yielding plot of land can have a soil profile and analytics quite close to a significantly higher-yielding plot. Without expensive and intensive testing on soil throughout the season, it is difficult to regularly look at soil structure, humus formation and condition, yields, germinating quality of the seeds, and protein quality. With this method of centrifuging the soil, we obtain a qualitative portrayal of the life in the soil -- how the soil's structure, minerals, proteins, and enzymes interact to support crop health and biological functions.
In this letter, we'll take a look at the chromatography process, but stay tuned for next week where we'll look at how to interpret our results!
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- Make a 1% solution of sodium hydroxide in distilled water. Make enough to have 50ml per sample.
- Using a mortar and pestle, grind up 5 grams of soil from each sample and place in clean beakers. Be sure that each sample has had enough time to completely dry out, as moisture will skew the results. Now woul
 d also be a good time to label the beakers according to the soil sample.
- Solubilize the soil in 50ml of sodium hydroxide solution (1%). The particle suspension process should be spaced out over at least 5 hours, mixing once initially. We swirl ours seven times clockwise, seven counter clockwise, then seven clockwise again constituting one "mix". After letting them sit for half an hour, mix again. Repeat after 1 hour, and again after 2 hours [from the last mix, not the initial one]. After this mix, let sit for three hours. In between mixes, do the following:
- Prepare Whatman no. 4 filter papers by using a compass to mark the center point and drawing concentric dashes at the radial distances of 1.5" and 2.375". Label each filter with the soil sample you will apply to it. Besides a location code, we also label ours with the dates, biodynamic times (flower, fruit, root, leaf), and moon phase & astrological symbol for both the day of collection and the day of processing.
- Use another filter paper to make wicks by cutting it into 3/4" squares and rolling them into cylinders. Make enough wicks to have 2 for each chroma.
- Poke h
 oles through the center of your filters, just enough to fit the wick through.
- Make a .5% solution of silver nitrate and distilled water.
- Put one wick through each chroma and set in a Petrie dish with a small amount of the silver nitrate solution pipetted in. Allow the solution to wick through the chroma up to the first line from the center and quickly tran
 sfer to a completely dark space to dry.
- **Goofs: if exposed to light, the silver nitrate will eventually develop, affecting the chroma. You want it to develop while the soil solution is soaked through it, so be sure to keep it hidden from light until then.
- After the soil has sat for the final three hours, place another wick in each dried filter. Pipette a small amount of supernatant off the top of the solution into a clean Petrie
 dish and place the wicked chroma into it to soak up to the second line.
- Hang on a line with light exposure to dry and develop there
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