Building Healthy Soil Communities: Evaluating Soil Texture

Well, it has been a couple weeks since my last farm blog. And writing about farming becomes as linear of a task as everything else that needs to be done on the farm. So, I will have to admit this blog is weather induced…..it’s raining outside.

Sweet spring rain turning into a tumultuous downpour that makes Oregon such a great place to love plants. If you live in Oregon, you know spring is for warm sunshine, sideways rain, hard hail, and a rainbow finale all within a five-minute span. Nature is exhilarating! And it is within these short windows that my long-term tasks are completed for future harvest success.

On our farm, we track seasonal phenology. This is the term for watching our natural cycles in a specific location, to make daily decisions. When making farming decisions, I consider things like average rainfall, mountain snowpack, relative humidity, prevailing winds, day length, sun exposure, and heat units influence each crop cycle.

Even before plants find their niche among our fields, the soil itself is our first foundation to build through careful observation. And spring is an important time to determine what is happening in the ground. One of my favorite farm tools is the soil auger. Here’s what my auger looks like.

I can easily plunge down 8, 10, 24 inches beneath the topsoil to observe where our over-wintering perennial roots thrive and see where our spring seedlings will soon be heading. It provides me with a full profile of our soil’s moisture and texture. Rubbing soil into a ribbon in the palm of my hands is a simple way to get familiar with the daily changes within each individual field. It’s important to evaluate the changing medium from winter to summer soil, like an artist mixes paint or a gourmet cook adds butter to a simmering sauté. The consistency has to be nearly perfect for the best results.

If the texture is too dry, topsoil can be lost in the wind. More specifically, clay colloids are blown away in the wind during dry conditions. A single clay colloid is the smallest particle of soil. Colloids are smaller than silt, smaller than sand. Think about going to the beach and picking up a single grain of sand. Colloids are two steps smaller than this. And when the soil gets too dry, these tiny pieces pick up and fly away in the wind.

And chemically speaking, clay particles have a negative charge while most plant nutrients hold a positive electrical charge. Quick lesson: opposites attract. And I want my soil attracting plant nutrients. Clay also has the ability to hold 2-3 times more water than sand or silt.

Therefore, if you were to collect dust that wind moves across a field and analyze it, you would find that it has the highest fertility of anywhere in the field. That’s right, the dust above the field is more fertile than the field itself. Unfortunately, this means that the most fertile part of the soil leaves first when there is wind and water erosion. These tiniest parts of clay hold nutrients, and they often concentrate in fertile low valleys.

The good news is that here in the Pacific Northwest, very dry conditions are typically not a problem. At least not until our late summer months. But at that time, our fields require protection using wind buffers, dense crops, and a vigorous stand of cover crop.

But here we are in spring. And the hot dry winds are still months away. Looking down at the soil in my auger, I’m more likely to see that the ground is too moist.

Matt with wet soilIf the texture is too moist, soil will smear like glue. This is a signal to patiently wait for early season sun-breaks and longer days. And in springtime Oregon, this may take a while. Especially in 2017, where our farm has recorded nearly 60” of annual rainfall, which is almost double our historical average!

The main problem with working in wet soil is compaction. Soil compaction is the compression of soil particles. Literally, it’s the soil getting pressed down into itself, resulting in a loss of soil structure, aggregate stability, and an overall reduction in soil porosity.

We strive for textbook soil, which is an ideal mix of 45% minerals, 5% organic matter, 25% air, and 25% water. However, working wet soil will drastically reduce air and water spaces. Reduction of available oxygen and water will begin to choke our microbial environment and aerobes cannot break down organic matter in a proper way. Nutrient and water holding capacities are drastically reduced, and the ensuing crops will suffer throughout the upcoming growing season.

So, practice patience.

Head into the greenhouse to sow more seeds. Make those outstanding repairs in the shop. Take a given moment to learn more. Even stop to write a blog piece or two. Realize nature does not operate according to our own schedule and working within the elements is the best reward of ecological farming!