What does chemically treated soil look like on a microscopic level?

On a recent trip to Guatemala to check in with our farmer partner Manuel, we also took the opportunity to gather soil samples from two areas. The first area is where we have been working with Manuel to incorporate a long-term agroecological system with his coffee plants. The other area is from an adjoining parcel of coffee grown in the conventional, chemical-based way.

Unfortunately, decades of intensive chemical use on the mountainside where we are working has turned large swaths of the native soil into little more than sand. This loose dirt lacks any ability to hold water or store carbon or nutrients. Therefore, when used for planting coffee or other crops, it must be heavily dosed with further chemical inputs for anything to grow.

These bean plants in the foreground reveal the predominant state of soil conditions in the area— essentially just sand.

This sad state of affairs is of course the reason we wanted to work here. We wanted to prove that agriculture can provide a regenerative function, not just a destructive one, and we wanted to contribute to conserving this beautiful place.

However, most of the work Manuel has done over the past year consisted of starting on long-term interventions, such as introducing terraces and planting shade, fruit, and nitrogen-fixing trees and shrubs. We were curious to see how much any of that work contributed to the overall health of the soil at this stage.

First, we dug up a sample from an adjoining plot where no regenerative practices has been introduced, then we pulled a sample from a nearby spot where Manuel had been introducing agroecological practices, including one application of a manure tea earlier that year.

That afternoon we put the samples under a microscope to see if there was any difference.

Depleted Soils

Let’s first look at the control sample: the soil that has suffered years of chemical abuse.

There’s not a lot going on in this soil. The sharply-edged objects in the picture are mineral particles— pieces of sand, silt, and clay. The brown lump in the bottom left-hand corner is likely a piece of organic matter, but it is the lone example in this view.

The tiny white dots are bacteria. They account for the only life present in this soil sample. We can see that the field is not especially dense with bacteria, and also that there is only one size and shape of bacteria present, in this case, cocci bacteria.

It isn’t possible to determine individual species of bacteria from this level of microscopy. However, bacteria come in all shapes and sizes. Based on the fact that there is only one morphological type of bacteria present, it is clear that there is a lack of diversity of bacteria as well.

Year 0 soil

I was curious to see how much, if any, effect Manuel’s efforts over the past year had had. Our mission is to make regenerative farming accessible to the average smallholder farmer, and that kind of process doesn’t happen overnight. So, what did we find?

This field shows that there has indeed been a change in the soil. The fuzzy-edged lumps in this image are bits of organic matter, and compared to the first image, it is clear that there has been an increase of this kind of material. This is good news because organic matter in soil provides a food source for microorganisms and also represents a level of carbon sequestration, since the material is carbon-based.

This other, rather poorly captured image shows that the quantity of cocci bacteria has clearly improved. However, there hasn’t been an increase in the number of different species of bacteria yet.

The living soil

One thing these still images don’t capture is the living nature of the soil. Even in the most depleted soils, the few remaining bacteria are buzzing in place. Here is a clip from the depleted, chemically treated soil:

One or two tiny bacteria are swimming around here, but overall, this soil is pretty lifeless.

Here is a clip of the soil where we have been implementing regenerative agriculture:

We still have a long way to go, but it is certainly a bit more lively. For reference, and as a sneak peak for my next post, this is where we are headed: