The importance of soil biologySixty percent of all the world’s nutrients applied to fields never make it to the plants. That is an astonishing number, considering the cost of fertilizers. It is also worrisome considering that phosphorus is expected to run out in the next few decades, and nitrogen is not too far behind. So what is happening?
By: Kristine Larson, Agweek
Sixty percent of all the world’s nutrients applied to fields never make it to the plants. That is an astonishing number, considering the cost of fertilizers. It is also worrisome considering that phosphorus is expected to run out in the next few decades, and nitrogen is not too far behind. So what is happening?
Plants need biology in the soil to do its job before they can do theirs. Bacteria and fungi need to be present in soils to break down these valuable nutrients and convert them to a form the plants can uptake. It is the roots of the plants that provide the habitat for these microorganisms to live. Disturbing the root systems disturbs the biology. They starve to death without constant organic matter throughout the entire year. Diversity in the biology allows for resistance and resilience in the plants.
Different plants also have different nutrient needs. Grass crops such as wheat, barley and corn contain high amounts of carbon, but they require more nitrogen. Other plants fix nitrogen well such as broadleaf species like beans, peas and vetches. These different species contain microorganisms that are generalists, which can be found living in lots of different species, and specialists, which can only be found on specific species. Generalists and specialists all play key roles in the different nutrient cycles.
So where are all the nutrients going? A recent survey of more than 2,000 rivers and streams throughout the United States conducted by the Environmental Protection Agency found that 55 percent of them were in poor condition and a threat to aquatic habitat. Elevated levels of nutrients in these systems from farming practices, urban runoff and other human factors have caused eutrophication. Eutrophication leads to algae blooms that increase the water temperatures and lower the levels of dissolved oxygen. This is when we get fish kills. Eutrophication has increased so much that the Gulf of Mexico now has a “dead zone.”
Soil biology can help us with these issues. The microbes are able to convert the nutrients to make them available for plants, but they also are able to convert them to an immobile form. This immobile form ties up the nutrients in the soil instead of letting them leach into our waterways and acts as a reserve nutrient source if needed.
Any amount of disturbance disrupts the habitat of the biology living in our soils. A no-till system lessens this disturbance while leaving organic matter for it to feed. Incorporating cover crops provides diverse, living root systems for those generalists and specialists to harness and convert our precious nutrients.
We spend a lot of money trying to increase yields and produce high-quality food, but we do not have to. Nature figured this out a long time ago, and she does it for free if we will allow her. People need to set the stage, and let plants and soil do what they are meant to do.
Editor's Note: Larson is with the Grand Forks County Soil Conservation District.