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How Early Carbon Dioxide Readings Predict the Long-Term Health of Soil

Not all agricultural management practices have an immediate effect.

Apply fertilizer to a field, and it’s easy to imagine the effect on soil fertility, even without running an official nutrient test. But put on other amendments like compost or organic matter and the effect on the soil’s biology isn’t as easy to see, at least not until seasons later when crops flourish or suffer.

Now, ag-tech probes give farmers the rare chance to glimpse the future and find out what each addition of organic matter holds for their crops.

That’s because Teralytic probes can provide a reading of the carbon dioxide levels of soil. Carbon dioxide is a leading indicator, not just of next season’s yield but of long-term soil (and business) health, especially for farms dabbling in regenerative agriculture techniques. As microbes metabolize nutrients, they use up the carbon available in the organic matter; the bi-product is CO2.

Soil scientists have long removed samples from the fields and measured the vital nutrients before reporting back to farmers. This supplied important information to farmers about how to manage soil fertility and suggested how well a season’s crops might do before they were even sowed.

Seeing Microbes and Future Fertility

With immediate data available, farmers now have access to longer-term and more meaningful predictions about their crops.

The CO2 data from Teralytic's probes can indicate the level of microbial activity in the soil. In turn, that activity provides hints of the soil’s health for years, even decades, to come.

To understand why, consider the process by which soil microbes take existing compounds in the soil and turn them into soluble nutrients, which plants can take up and use for growth. After an addition of compost, soil has many new nutrients. The microbes in that soil metabolize them. The output is twofold: available nutrients and CO2. A healthy population of microbes can ensure that the nutrients in compost or other amendments will become nutrients available for plants to take up, both sooner and later, with each additional application of compost. Having this feedback is crucial for those who are making a transformation in their farming practices, like a signpost along an otherwise unknown way.

Take a farmer who is applying compost. Within an hour, at 6 inches below the surface in suitable conditions, the probe would sense a huge change in the amount of CO2, indicating that the microbes are starting to work. As microbes ingest and use the nutrients in the soil, they output CO2; meaning that a higher CO2 indicates more activity. Still, a high CO2 reading does not mean there’s suddenly available nitrogen in the soil.

For that to happen, those nutrients need to become accessible to plants. If nitrogen is unusable, you can keep adding and adding it without having much success.

With immediate data available, farmers now have access to longer-term and more meaningful predictions about their crops.

Here’s where the CO2 reading can give context to the nitrogen reading:

  1. The vitality of the microbial community gauges how adroitly the soil’s nutrients will dissolve at points in the future.

  2. Strong microbial activity combined with existing nitrogen can indicate both how much nitrogen is available now and how much might accessible to plants down the road.

Still, immediate activity isn’t always exactly what a farmer wants; if nutrients are too readily available, they can be leached from the soil if plants aren’t able to use them.

Microbes will keep on taking up the organic forms of the nutrients as needed and releasing them through waste in their inorganic form, whether or not plants are ready. A reading that shows an appropriate ratio of carbon to nitrogen or carbon to phosphorus indicates that nutrients from compost will be available to the plants as they grow in the future.

If, on the other hand, you don’t have a way to witness the microbes in action, you might inadvertently throw these ratios off with too much compost. In that way, the microbes act as a progress report for the otherwise invisible soil’s transformation, with carbon readings their external signal.

Customizing Standards

These early readings can help farmers set their own standards for nutrient management. Environmental factors, and cold, dry, saline, or acidic soil can affect the balance of a field and encourage the farmer to apply fertilizers or other amendments.

Another variable has to do with what additions farmers are making to the soil: Are they adding compost? Are they planting cover crops? Or are they applying nitrogen fertilizers? The management strategies used by farmers can have vastly different effects on the microbes in their soil.

Either way, if farmers see that carbon is taking off in their readings, they can adjust expectations and set appropriate standards for other indicators of soil health. That’s because they now know they’re fostering a microbial community that will be doing some of the work for them in the future.

Taking the Long View

Understanding the microbiology of soil by using CO2 readings from the probe invites farmers to implement management strategies for the long term. With additions of composts, cover crops, and other regenerative techniques, the baseline carbon dioxide level will likely improve over time—meaning that the microbial community is also thriving.

Worldwide, common intensive agriculture practices can make it appear that the only way to keep soil productive is through high inputs of nitrogen and phosphorus fertilizer, which are used 7 and 3.5 times more often than they were 60 years ago, according to a 2002 paper on the topic.

Such amendments can help farmers produce large yields in the short term. On a longer timeline, these amendments detract from soil quality and inhibit the natural processes that keep soil fertile. By taking the long view and turning to organic matter to supplement some percentage of their fertilizer, farmers can prevent soil from degrading. In the meantime, they can watch CO2 as a proxy for microbial activity, a leading indicator of soil’s future fertility and a reminder that soil is a dynamic system that can improve with the help of proper management.

Conclusion

A good read on soil provides actionable information for managing the nutrients and optimizing plant growth of crops. Yet not every indication in the data is about the present, or the next season. Looking at the CO2 reading and understanding that it can point to long-term soil health helps farmers make decisions about their fields for ongoing success.