Ferrie: Farmer Asks How to Use Red Clover as a Cover to Reduce Nitrogen Rates and Costs
In this week’s Boots In The Field report, Farm Journal Field Agronomist Ken Ferrie answers several questions from a farmer based in southwest Ontario, Canada, who had participated in Ferrie’s Beyond The Basics agronomic series.
All three of the farmer’s questions focused around the topic of nitrogen (N) use, with regard to using it in conjunction with red clover. The farmer says he typically broadcasts red clover on his winter wheat in the spring, lets it grow after wheat harvest, then kills the red clover in the fall and tills it into the soil.
Following are the specific questions the farmer asked and how Ferrie responded. You can also listen to this Boots In The Field podcast in its entirety here.
Q: How much nitrogen can I expect from red clover the following year, and when will it become available?
A: “Red clover has a 14 to one carbon nitrogen ratio, which means it will decompose and recycle quicker than soybean stubble, which has a 30 to one carbon nitrogen ratio,” Ferrie says. “That means recycling will happen quickly in the spring when things warm up. Based on our plots here in Illinois, a good stand of red clover should give you between 50 and 100 pounds of nitrogen, and I would use 75 pounds as a rule of thumb.”
Q: The second question the grower asks has to do with him wanting to try some reduced N rates this spring to assess what the red clover is supplying for next year's nitrogen. The farmer’s question is, should he reduce the preplant 28% N application that gets worked in after spraying, or should he reduce the sidedress pass?
A: Ferrie says the answer depends on a couple of things – how much you're already putting down in the preplant versus the sidedress application and how much volunteer wheat or grasses are in the red clover cover.
“It’s not uncommon to have a good mixture of volunteer wheat and red clover when we interseed like that from volunteer wheat,” Ferrie says. “By October, this wheat typically has some good size to it. So it's probably at that 60 to one or higher carbon-to-nitrogen ratio. Chiseling this cover in will speed up its decay, and the nitrogen in the red clover will be available earlier in the season. But, if there's a lot of volunteer wheat in this mix, it will take longer to decay and will cause a large carbon penalty in the spring and could slow down next year's crop.”
“In either case, I would plan to pull the rate back in the sidedress nitrogen,” Ferrie says. “This keeps the N rate high early in the season when that crop's trying to get established and it's ready to go into the rapid growth stage. Sidedress nitrogen should be N that your crop needs in July and August. I would pull in-season nitrate tests before sidedressing to kind of help you answer the "so what" question at the end. I would also recommend multiple rates in the sidedress applications – a low, medium and high rate – so you can kind of build yourself a response curve. One additional note, N plots can mess with moisture and test weight. So I recommend you use a scale cart this fall to get accurate numbers. Yield monitors do struggle in this area.”
A third question the farmer asked had to do with nitrogen stabilizers. The grower wanted to know if Ferrie and his agronomic team at Crop-Tech Consulting have done any work using stabilizers to lower the N rate and, therefore, lower input costs.
Q: The specific question is, could we reduce the rate of N with a stabilizer and cut our costs?
A: “To answer this, we first must make sure we're using the right stabilizer,” Ferrie says. “A urease inhibitor is used to stop urea from volatilizing off the surface. When you work your N in right away, your urea will not volatilize. Urease inhibitors are for no-tillers or people who let their surface-applied N set for long periods before incorporating it.
“Being that you're incorporating your preplant N, I would use a nitrification inhibitor, one that slows down the process of making nitrates that can leach away. In your situation, though, unless you're in highly leachable soils, it might be hard to get a financial ROI out of your spring inhibitors by lowering the N rates. Because you are splitting your N program up with different timings and different rates and the addition of red clover, you're (already) in a 4R format when it comes to N,” Ferrie notes.
“Can you reduce your N rate with the use of a stabilizer? It's possible. But with today's N prices, if we take the money spent on spring stabilizers and invested in more N, more times than not more N wins in our plot trials. Now, if your goal is to reduce your nitrogen footprint and be safer on the environment, then using a stabilizer and lowering your N rate may give you a better true ROI, even if it doesn't give you a better financial ROI.
“You guys know how we talk about our ROIs, right? Financial ROI is what we can prove on paper as far as profit. So, we have a lot of data here at Crop-Tech that says starter fertilizer has a strong financial ROI. But for some growers, the hassle of using starter is just too much and it's not worth using, and that's their true ROI. It’s the same case here. If stewardship of your nitrogen is what's really at the forefront for you, then your true ROI may suggest that this process is better off even if it's not financially better off. Now, in some cases, there are programs that will pay to do the same thing, helping you to bring your true ROI and your financial ROI closer together. So, watching for those programs might be another way to handle this.”
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