Community Agriculture Alliance: Soil health
August 28, 2014
Soil health — you may have heard this latest descriptor and wondered what it is. Hopefully, by now you are aware that soil is not just dirt. It's a complicated ecosystem that takes place beneath our feet to support the environment that we see above ground.
Plants often are portrayed as the one of the most important organisms in our ecosystem, but without good soil, there would be no plants. So while you may not consider soil as "pretty" as a plant, I would argue that it is more important.
A healthy soil consists of billions of micro-organisms and thousands of macro-organisms that all work together to better the soil.
Glomalin is a micro-organism that stores carbon in its protein and carbohydrate (glucose or sugar) subunits. Arbuscular mycorrhizal fungi, found living on plant roots around the world, appear to be the only producers of glomalin. The fungi use carbon from the plant to grow and make glomalin. In return, the fungi’s hair-like filaments, called hyphae, extend the reach of plant roots.
Hyphae function as pipes to funnel more water and nutrients — particularly phosphorus — to the plants. As a plant grows, the fungi move down the root and form new hyphae to colonize the growing roots. When hyphae higher up on the roots stop transporting nutrients, their protective glomalin sloughs off into the soil.
There it attaches to particles of minerals (sand, silt and clay) and organic matter, forming clumps. This type of soil structure is stable enough to resist wind and water erosion, but porous enough to let air, water and roots move through it.
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It also harbors more beneficial microbes, holds more water and helps the soil surface resist crusting.
Dig up a small plant and you will see the tiny particles of soil that are still clinging to the roots are being held by glomalin. It truly is a fascinating little specimen.
One of my all-time favorite macro-organisms of the soil is none other than the earthworm. Maybe this is due to my parents who made hunting and digging up night crawlers to fish with fun, but it's also because of what their presence in the soil means.
If you have worms, lots of worms, you have a healthy soil. Although earthworms derive their nutrition from micro-organisms, many more micro-organisms are present in their feces or casts than in the organic matter that they consume.
As organic matter passes through their intestines, it is fragmented and inoculated with micro-organisms. Increased microbial activity facilitates the cycling of nutrients from organic matter into forms readily taken up by plants. Earthworms increase infiltration by enhancing porosity as they move through the soil.
Some species make permanent burrows deep into the soil. These burrows can persist long after the inhabitant has died and can be a major conduit for soil drainage, particularly under heavy rainfall.
At the same time, the burrows minimize surface water erosion. The horizontal burrowing of other species in the top several inches of soil increases overall porosity and drainage.
By fragmenting organic matter and increasing soil porosity and aggregation, earthworms can significantly increase the water-holding capacity of soils.
The channels made by deep-burrowing earthworms are lined with readily available nutrients and make it easier for roots to penetrate deep into the soil.
Plant and crop residue are gradually buried by cast material deposited on the surface and as earthworms pull surface residue into their burrows. (Clive A. Edwards, Ohio State University).
Management of crops plays a huge role in soil health, as well. Traditional tillage kills important soil organisms so the less plowing and tillage, the healthier your soil.
Not only is no tilling important, but so is finding the right crops and crop rotation that will benefit the soil but still help the farmer put money in his pocket.
The goal is to find the right plants that help add all the nutrients back into the soil after the previous crop harvest so that no additional fertilizer is needed. If the right mix of plants is used, they also can prevent noxious weeds from invading, as well, therefore eliminating the need for herbicide.
Another key is using grazing in crop rotations. Livestock add essential nutrients back into the soil ecosystem faster than synthetic fertilizers.
So how does Northwest Colorado's soil health look?
Pretty good in some areas. Farmers and ranchers who have had ground in grass hay for decades and are responsible grazers of pastures and native rangeland have great soil health.
Their soil ecosystem is producing a high amount of soil organic matter and giving back to the soil just as much as they are taking from it.
Our old crop fields that were once in a wheat fallow rotation and have been planting back to grass have a less healthy soil ecosystem, but time will help with that as well as adding plant diversity which some landowners are doing.
Our least healthy areas are fields that still are being tilled. With increased knowledge, hopefully the soil health will increase, as well.
It's not a simple fix, and not only does a farmer have to make a dollar, he or she also has to feed the world.
The best thing about a farmer or a rancher is that almost all of them want to better the ground for future generations, and they want to be sustainable. These individuals have a work ethic that's a lost art, and they're inventive.
A farmer can fix just about anything, so I know that they will figure out what works for them and what will help their soil health.
Lori Jazwick is a district conservationist for Natural Resources Conservation Service.