614 Cover Crop Emission Surprise
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#RealisticRegenAg | Cover crops might be giving off more greenhouse gases than bare ground. It's a surprise, for sure. It all comes down to how long they sit in cool and wet conditions. They pull up and hold onto more nitrogen than bare ground, however when they die they can give off much greater nitrous oxide emissions compared to a bare field. So check out the articles below and read any of the most interesting articles that you see.
In case you’re new here, let me introduce myself. I’m an author and independent agronomist from the Western Canadian Prairies specializing in climate-smart agriculture. I focus on scientifically proven practices that benefit the planet and, just as importantly, farmers' economic sustainability. Be sure to visit my website, www.plantsdigsoil.com, to learn about my book “Practical Regeneration” and for services I that I offer for farmers and agribusiness.
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So how was your season this year?
Do you think you could have done better?
Fall is a perfect time to start working together. We still have time to plan soil sampling and analyze results to evaluate this year's performance. I'm knowledgeable about all the funding programs available to growers in Alberta and beyond, so if you're considering new practices, we may be able to cover those costs and even include them in my consulting fees in your application.
613 Tight Soils – Sodacity, Salinity, and Alkali Explained
White patches in a field are often referred to as alkali patches. The underlying problem may be high pH – alkalinity – but the salt in and of itself is not at a high pH and therefore is not alkaline. When you see salt on the surface it is more properly called salinity. The reason for this is that alkalinity may or may not be there. If present it may be near the surface or it may be deeper down.
Compounding on this, alkalinity may not be present. Excess sodium cations – not excess sodium salts – could be the cause. Finally, just because you don’t see salt on the surface doesn’t mean salinity is not the problem. Regular soil testing helps to see these problems developing before they visibly manifest themselves.
Huge amounts of money are spent trying to fix these patches with products or practices that either don’t work or make it worse. Even if someone is not trying to fix it, they may be putting down fertilizer and seed every year with the hope of getting something, only to be disappointed at harvest time.
Digging deeper – literally – and doing the proper tests will help you diagnose and decide. In this episode I’ll give an overview of how I approach this and why it is critical you get solid advice from a Certified Crop Advisor (CCA) or Professional Agrologist (P.Ag) that truly understands this issue.
Greenhouse gas emissions and agriculture
I came across this resource while doing some other searching and it turned out to be a great primer on the subject. Of note: In 1990 they calculate Canadian agriculture was a net sink of CO2. This is likely due to the switch to no-till. However, they can’t say agriculture was a net sink until the 2000’s when land conversions slowed down enough. This great news, but there’s a catch. We’ll be at [a steady state in 2040, meaning we are probably already at peak sequestration. This highlights something few seem to recognize: You can’t just keep putting carbon in the soil. It’s a cycle. Eventually what goes in comes back out.
https://agriculture.canada.ca/en/environment/greenhouse-gases
How do cover crops impact nitrous oxide emissions?
And now to the article that I’m headlining the newsletter with. In the previous article, if you read the entire resource, you’ll find that all soils emit N20 (nitrous oxide). Special microbes that use nitrogen for energy let this go as a byproduct. In cool & wet conditions more of these bacteria take over. When any vegetation, including cover crops, has been killed and is laying fresh on top off, or in, the soil, these little guys thrive.
“The primary driver of nitrous oxide emissions from agricultural soils is denitrification, which is promoted by wet soils, ample available mineral nitrogen (e.g., nitrate), the presence of carbon sources, and freeze-thaw cycles. Cover crops influence each of these conditions. A 2014 meta-analysis found that cover crops decreased N2O emissions in 40% of studies and increased them in the other 60%.”
“A recent study [in Ontario] compared a three-crop rotation with cover crops to a two-crop rotation without cover crops. The researchers, led by Dr. Claudia Wagner-Riddle, uncovered that a four-way cover crop mixture (cereal rye, crimson clover, oats, and daikon radish) seeded after winter wheat lowered emissions during the non-growing season relative to soybean stubble (Figure 1). The cover crop lowered soil nitrate in the fall and better insulated soil against freeze-thaw events over winter. However, N2O emissions in corn the next growing season were higher – likely driven by carbon and nitrogen release from decomposing residues. Total emissions were greater with cover crops present.”
The article finishes with some recommendations for how to mitigate the effects. Unfortunately there isn’t much. Legumes seemed to emit more and even low biomass - in other words, not leaving a thick mat of decomposing biomass, didn’t help either. They are studying inhibitors - the same ones used with fertilizer - to see the effect. So far they only says they “show promise”.
https://fieldcropnews.com/2024/08/crop-report-week-of-august-19-2024/
Treatments cut N2O emissions in winter wheat
Speaking of inhibitors, a new study shows that they work well in winter wheat production. In many systems they don’t pay but in winter wheat the nitrogen needs to be there in the fall and very early in the spring - prime times to lose nitrogen. However, a caution for those pencilling out the economics. They drop emissions of nitrous oxide, but the total pounds of nitrogen lost is in the single digits. It rarely pays for a farmer to use them unless there is a financial incentive.
https://www.producer.com/crops/treatments-cut-n2o-emissions-in-winter-wheat/
Cover crops pose challenge for Prairie farmers
This isn’t a knock-on-cover-crops episode but here’s another problem with them: They are hard to make work in the Prairies. New research is looking at how they could be inter-seeded with cash crops and survive the weed control sprays. Some are more tolerant than others and so they are hoping to find ones that are compatible with current systems.
“The team then studied weed pressure. The challenge was to find the “sweet spot” where weeds were controlled while keeping cover crops intact.”
“We’ve got to find this Goldilocks treatment that balances the time and space for cover crops to grow with our cash crops,” Lawley said, and find a cover crop that can best withstand weed treatments.”
https://www.producer.com/news/cover-crops-pose-challenge-for-prairie-farmers/
What Do Weeds Tell Us About Soil?
Have you heard that weeds can tell you what is lacking in your soil? I have heard this a lot, especially in organic circles. I’ve never heard it in academic talks. “A review published in 1977 had this to say, “The information on weed indicator species is poorly documented, much of it residing only in the minds of observant farmers and gardeners.” Sounds like reading the weeds is as reliable as reading the tea leaves. Robert Pavlis goes into much more detail in the article, as he always does. While he is focusing on the gardening world, much applies to the farming world.
https://www.gardenmyths.com/weeds-tell-us-about-soil/
What is the Climate Analogs Academy?
I recall when I was doing my master’s degree in the early 2000’s there was talk of collaboration with Russian farmers that farmed in very similar areas as the Prairies. Of course, we know that won’t be happening now. But what if there were areas where you could tap into research that farmers in similar climatic conditions were doing? You might find out quicker what new things to try. This could work if you are looking at present day or if you want to see what things might be like if climate change moves at the pace that is expected.
https://csanr.wsu.edu/what-is-the-climate-analogs-academy/
The Fertilizer Institute awards biostimulant certification to Valent BioSciences
It’s hard to tell if this is going to make a real difference, or it’s just a marketing scheme, but the idea of having biostimulants rated for efficacy could help bring some clarity to the market. In the very least, it should weed out the companies that out there just to make a quick buck.
Crushed glass replaces soil in this innovative approach to sustainable agriculture
And finally, an article that raises a lot of red flags for me. What happens to these glass particles in root crops? Embedded foreign material is a huge food safety concern for potatoes and anything where we eat something that is dug from the soil. Once this is applied to field, it’s there forever. You can’t pull this out. It is just in the pilot phase and it faces many barriers to commercialization, including cost and logistics, but still, I hope it is fully vetted before someone loses fields to production due to trying something innovative.