2017-09-13 / Opinion

In My Opinion

There’s more to dirt than meets the eye

What makes up dirt? Seems like a simple question however it can get really complicated. Let’s start with the basis for dirt, often referred to as the soil texture. There are three components: sand, silt, and clay. These components mixed together at certain ratios will have different physical properties from the others. A quick Google images search for “soil texture triangle” will give some context. To add some perspective imagine the sand particles as beach balls, silt as soft balls, and clay as marbles. Now imagine filling a room with just beach balls, soft balls, marbles, or a mixture of them. There will be air gaps between all of them but the amount of air between clay particles is significantly smaller then that of sand and so through covalent bonds clay has a greater capacity to hold more water whereas water can pass through sand much quicker. Soil is like a sponge: too much water and the excess won’t be absorbed, maximum soil capacity; if you were to squeeze the sponge till no more water comes out of it still it is wet just as you cannot squeeze any more water out, just as neither can a plant absorb the last bit of water out of the soil as the covalent bonds are too strong, mostly in heavy clay soils.

Speaking of water, that is how plants take up nutrients. The nutrients in the soil get caught in the water, absorbed through the roots, and distributed throughout the plant. And so without water plants have great difficulty taking up nutrients, and they could become malnourished.

Organic matter, in the soil, consists of living or dead plant material (i.e. roots and previous year’s crop residue) and dead animal material (e.g. animal excrement). Organic matter is what holds nutrients in the soil as well as increasing water infiltration, holding water, and even helps to reduce soil compaction through better soil structure. More research is coming out all the time about organic material and how important it is, and what we as farmers can do to sustain and even increase organic material in the soil. One way to do this is through cover crops, although every farm is different and not every cover crop is suitable for every farm operation. On my own farm we use either radish alone or with Crimson Clover. After some manure is applied to wheat stubble and worked in we plant these, not only to build organic matter. The radishes we plant are called tillage radishes; they put on deep roots and help break up compaction in the soil and they also soak up nutrients in the soil and hold them so that they are still available for next year’s crop. The Crimson Clover is what’s known as a legume plant, meaning they are able to fix their own nitrogen, adding nitrogen to the soil that will be saved by the radishes for next year. Adding nitrogen and holding that and other valuable nutrients means farmers don’t have to add as much fertilizer. No-till is another way that some farmers manage their soil health. As implied, no-till farmers don’t use tillage equipment on their farms. Less soil disruption means better soil structure, infiltration, and a healthier micro biome. (Side note: there are more bacteria in a handful of dirt than humans on Earth!)

Then we can’t forget that soil is arguably very much alive. Not just with earthworms (which are great for the soil even though they are an invasive species to North America) there are also nematodes and bacteria. Like so many things there are good and bad bacteria and nematodes, some help plants grow and even help gather nutrients for the plant while others feed of the plant and can infect the plant with diseases.

There’s a lot to know about dirt and everything that happens in the soil. And while this barely scratches the surface, pun fully intended, I hope this was insightful.

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