023 Cover Crop ROI
#RealisticRegenAg | Cover crops need to pay in the immediate, short, and long-term. Join me as I discuss how treating cover crops as another input on the farm that is expected to give results will pay now and in the future.
Transcript of Episode 023 of the Plants Dig Soil podcast – “Cover Crop ROI”
Hello! This is Scott Gillespie and welcome to the third season of Plants Dig Soil. In this podcast, you will learn how to think critically about regenerative practices as you work to incorporate them into your agricultural, horticultural, and home gardening systems.
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In early September I made the case for cover crops to an audience of potato growers from all over Canada; possibly from all over the world as, like most things today, it was online. I have found that creating presentations helps me to refine my thoughts on a particular subject and this one was no different. I really had to think through how it would make sense for a farm to use them.
At one point the idea of Return on Investment (ROI) came to me. I had heard a segment about it on Real Ag Radio one day this summer and that must be what came to mind as I started applying it to cover crops. I realized that there really is no reason to use them unless the farm expects to get a return on the money spent.
As I was thinking further, the return needs to come back to the farm as soon as possible. Cover crops are usually an investment in the following crop year so it is reasonable to expect that any money spent on them should return within a year. There is no reason to spend money just to have it come back so there should be a benefit back to you greater than if nothing was done.
In my talk with potato growers, I illustrated the concept with fungicide use. Even organic growers will likely have used an organic approved product. The Irish Potato Famine was caused by a disease called late blight. This disease is still around today and still just as deadly. It can take down a field in a matter of days if the conditions are perfect. After taking down the foliage and the stems it can move in the soil, infect the tubers, and destroy them as well.
On your farm, market garden, or home garden think about something you apply each year. Perhaps you could think of fertilizer or maybe compost or manure. It could be a particular herbicide, fungicide, or insecticide. It does not matter if you are organic or not. I am sure there is something you apply each year to your land. Maybe even think of the seeds you plant. How about we use that? Think of planting your cash crop.
If you do not plant anything you will get weeds. You may get something that the other creatures around you can eat but it is not something you can eat or can harvest and sell. If you plant something you will at least have something. You know from experience how many seeds to plant so think what happens when you plant the proper amount.
Now what happens if you plant too much? Too close of spacing for some plants, like carrots, means you do not get the size you want. Over seeding and then thinning can help to make up for some seeds not germinating or pests taking out some of them. However, there is a point when you are spending more than you are getting back. If you could have planted less and achieved the same final stand you spent more than you needed to.
Shifting back to cover crops if you can solve an immediate problem then you should get payback within the growing season. Holding onto soil and/or nutrients pays back right away.
Solving a short-term problem should still payback more than the money spent. Examples of short-term problems to solve include increasing water infiltration, increasing nutrient availability, and lowering pest pressures.
Long term problems to solve with cover crops can be hard to justify spending the money on right now as it could take decades to see the return. The two main problems to solve are increasing stable organic matter and increasing water holding capacity. The beauty of cover crops is that, unlike most inputs you apply to your farm, the benefits from immediate and short-term goals accrue to long term goals.
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Before moving on I want to make sure you have the link to the presentation that this podcast episode is based on. I had mentioned last month that I would be sure to put the link to the replay in and you will find it in the transcript[1]. The full title is “Are Cover Crops Worth the Work? – A Spud Smart Roundtable Webinar & Podcast” and you will be able to find it on spudsmart.com. I am coving the highlights in this episode but to dive deeper I encourage you to check it out.
I had also mentioned last month that I had recorded an episode for the Pulse School on RealAgriculture.com. That episode has now been posted and there will be a link for it in the transcript[2]. The full title of it is “Targeted cover crop use could reduce soil erosion.”
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For the remainder of this episode, I’m going to expand on the immediate, short, and long-term benefits of a cover crop. While listening, be thinking in Return on Investment (ROI) terms
I often say that holding onto your soil will always pay. While intuitively it makes sense that you do not let your soil blow or flow away, I want to make the case that there is a direct economic cost.
A few years ago, while out soil sampling, I saw some soil that had been blown into a ditch. There had been a wind event that had moved soil from a newly harvested potato field. I probed a bunch of spots in it and put in one of my bags. I had the lab determine the soil texture so that I had a scientific basis for classifying it. It was basically beach sand: Right on the line between a sandy loam and a loamy sand. It was 78% sand, 10% clay, and 12% silt.
In Southern Alberta we farm in a semi-arid area near the Rocky Mountains that gets very little rain. Our soils are called the brown soils because historically, and I am talking thousands of years, they do not produce a lot. Two percent organic matter is considered to be good in this area. I do not know what the native prairie would have been, but I know some grassland that had never been farmed and only had been grazed with cattle was 2.8% organic matter when I tested it. This blown beach-sand soil was 2.4% organic matter.
There was not much nitrogen in it, but that is to be expected as nitrogen gases off or leaches very easily. What was surprising was that the phosphorus was 164ppm or just over 300 lb/ac for every six inches of depth. Phosphorus is typically exceptionally low in our soils without a lot of manure or fertilizer over the years. We have naturally high potassium levels in our soils but even this was high at 820 ppm or over 1600 lb/ac. I will not go through the micronutrients but even all of them were above the critical numbers. Some were even in the moderate to high range.
When you hold onto soil you hold onto nutrients. We do not tend to be at excess moisture levels even with all the irrigation we use but if you regularly have water flowing through the profile you can also lose the mobile nutrients, such as nitrogen. To me, this is the best reason to grow a cover crop. Holding onto soil and nutrients. With current fertilizer prices this pays even more now.
Holding onto your soil is goal number one. Once you have achieved that you may want to move the next level and make some improvements to it. Three common goals are to increase water infiltration, increase nutrient availability, and to lower pest pressures.
Water infiltration may be increased within weeks of the cover crop being established but it’s more likely something that will gain over multiple cycles. Water infiltration is not the total amount that the soil can hold. This refers to how fast the water can move into the soil. When you have good infiltration, you can take in rainstorms quickly and have less run off. When irrigating you can put more water on at a time.
If you can grow a legume cover crop and incorporate or leave all of it in place you have a chance to increase the nitrogen content of the soil. For this to work it needs to grow long enough to grow significant biomass and it must have actively producing nodules. Phosphorus cannot be easily mined from a soil, no matter what the celebrity farmers say. Microbial mining of soil particles is a fact. However, the rate that it occurs at gives a fraction of what we export in crop off the land each year.
What we can tap into, and I think the “no fertilizer added” people are actually using, is the legacy phosphorus. Phosphorus fertilizer gets tied up quickly in the soil and is slowly released over the years and decades that follow. If a cover crop does the work to liberate this instead of your cash crop, and its decomposition coincides with your cash crop growth, you may be able to access this before it again gets tied up.
If you want to explore this more, I suggest you check out an episode from earlier in the season called “018 Three Pillars Propping Regen Ag”[3]. In it I go deeper into why I think microbial mining is not happening at the rate many claim it is and why I think legacy phosphorus is what they are actually accessing. There is nothing wrong with using this legacy phosphorus. You just need to understand that it is not sustainable as you will be mining your soils of nutrients in the long term.
Lowering pest pressure is the final of the short-term goals that I think cover crops should be used for. Herbicide tolerant weeds are a common reason that most farmers in the United States get into cover crops, and it is where they have the most success. By covering the land with the best species for the job they crowd out the undesirable species. It is not 100% control, but it may allow them to use the herbicides that they do have more effectively.
To get a farmer perspective on this I suggest you check two episodes of the Field Work podcast where they talk about the cotton industry and talk to a farmer using cover crops. One of the key takeaways I heard was to use the species that meets your goals. Adam Chappell tried diverse mixes of cover crops, but they did not achieve the goal of suppressing pigweed. Through trial and error, he learned what worked on his farm and what makes him money. He also dives into return on investment thinking for all areas of his farm. He has actually let go of land because he can be more profitable on the acres he does have. Bigger is not always better. The links will be in the transcript[4] [5] [6].
Insect and disease suppression is where I get the most excited in the potential of cover crops. Work in the Pacific Northwest of the United States over the last decade by farmers and researchers has shown that a green manure crop of mustard ahead of potatoes can decrease disease and increase yield. Specific varieties of mustard must be used, they must grow long enough to get big biomass, and they must be chopped and incorporated into the soil within minutes to have their effect. Growing a small crop, not incorporating it, or mixing in other species is not enough for the effect. Treating it like input and giving it all the attention that a cash crop gets pays you back.
I would like to put a caution out here that the research is only in its infancy. A particular cover crop may work in one agricultural region and not work in another. We must test them in our area in our conditions to determine if they are a fit. In the Spud Smart webinar there was a question at the end about conflicting results on a particular pest. Canadian research showed a particular cover crop species increased the pest whereas Dutch research showed the same cover crop decreased the pest. It is unclear why this is the case. The researchers are simply reporting what they are seeing. Farmers should be cautious before making big changes on their farms before the true impacts are known.
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To review, I have covered the immediate and the short-term goals you may be looking at when growing a cover crop. Focus on something that gives tangible results to your farm right now. Immediate goals such as holding onto your soil and/or nutrients defend your land. Short term goals such as increasing water infiltration, increasing nutrient availability, and decreasing pest pressure improve your soil.
That is where you spend your money and that is where you see your results. Unlike many things you spend money on for your farm if you keep up with defending and improving your land the benefits will accrue over time. These benefits may include increasing organic matter and increasing water holding capacity.
These goals are extremely hard to measure because of their long-term timeline. You may counter with the argument that organic matter goes up quickly in no-till and cover crop systems. However, you must dig deeper. Literally. Most studies only look at the top 5-15cm (2-6”). When researchers take the entire rooting zone into account (1-2 metres or approximately 3-6’) there is often no net difference.
It is hard to see how this can be, but I think part of it is that our time scales are too short. Soils take thousands of years to develop. Perhaps a two-year or ten-year study is not long enough. I have two entire episodes devoted to this with extensive references so I would encourage you to check them out. One is from last season: 013 Caution on Carbon Payments[7]. The other is from earlier this season: 019 Carbon in its Proper Place[8].
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Remember to get local advice before acting upon this information. If you do not know who to talk to, get a hold of me and I will help you find someone. If you are in my local area and need help, contact me. It is always free to chat. If we get to the point that the scope broadens to consulting work, we can work out a plan that fits your budget.
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If you are still listening, you are probably like me and like to know what the catch is. Why am I putting out this information for free? The reason is that I love to learn, and I love to share the information. My knowledge has been built up from experiences in my own garden, advising clients in my consulting business, and from reading the latest books and articles on agronomy and regenerative agriculture.
I have a B.Sc. (Agr.) with an agronomy focus and a M.Sc. with a focus on Plant Science. Beyond my formal education, I have attained, and maintained, my Certified Crop Advisor designation and am a member in good standing with the Alberta Institute of Agrologists.
Nearly everything I talk about is from free resources posted to university and research organization websites. Books that used to be hard to track down are available to buy or borrow for nearly anyone with an e-reader. The information is out there – sifting through it all is what takes the time.
I make my living entirely from consulting. I do not sell any products, software, or systems. I strive to be as independent and as unbiased as possible so I can provide the best advice to my clients and help as many people as possible move from conventional to regenerative agriculture.
[1] Spud Smart Magazine. Sep 9, 2021. “Are Cover Crops Worth the Work? – A Spud Smart Roundtable Webinar & Podcast.” https://spudsmart.com/are-cover-crops-worth-the-work-a-spud-smart-roundtable-webinar-podcast/
[2] Kara Oosterhuis. Real Agriculture. Sep 22, 2021. Pulse School: Targeted cover crop use could reduce soil erosion.
[3] Scott Gillespie. Plants Dig Soil. May 9, 2021. 018 Three Pillars Propping Regen Ag.
https://www.plantsdigsoil.com/podcast/018-three-pillars-propping-regen-ag
[4] Laurie Stern. Field Work Podcast. May 18, 2021. Can Cotton Drive American Ag Sustainability?
https://www.fieldworktalk.org/episode/2021/05/12/can-cotton-drive-american-ag-sustainability
[5] Laurie Stern. Field Work Podcast. May 18, 2021. How Conservation Saved a Cotton Farmer.
https://www.fieldworktalk.org/episode/2021/05/19/how-conservation-saved-a-cotton-farmer
[6] Scott Gillespie. Plants Dig Soil. Aug 30, 2021. 012 Simplicity in Cover Crop Mixes.
https://www.plantsdigsoil.com/podcast/012-simplicity-in-cover-crop-mixes
[7] Scott Gillespie. Plants Dig Soil. Sep 30, 2020. 013 Caution on Carbon Payments.
https://www.plantsdigsoil.com/podcast/013-caution-on-carbon-payments
[8] Scott Gillespie. Plants Dig Soil. Jun 5, 2021. 019 Carbon in its Proper Place.
https://www.plantsdigsoil.com/podcast/019-carbon-in-its-proper-place