How much? How deep? How soon? These are just a few questions that strip-tillers contemplate before making fall fertilizer applications.
Regional variables and personal preferences can contribute to the scope of a fall fertility program, but post-harvest applications can help keep soils well-fed throughout the winter and primed for getting plants off to a strong start in spring.
But as the potential of stricter fall fertilizer regulations loom, strip-tillers and industry experts offer their best tips for efficient and economic fall nutrient applications.
1. Don’t Do What You’ve Always Done. Andy Thompson, Niota, Ill., farmer and territory manager for Yetter Mfg. Co., suggests a flexible fall nutrient application strategy has merit. “A ‘Do what you’ve always done’ mentality isn’t a good approach, because without a doubt, strip-tillers can reduce their waste with the right practices,” he says. “In Western Illinois, we used to apply 200-220 pounds per acre of anhydrous in the fall. Now, we’re down to applying 100-150 pounds and sidedressing the remainder, sometimes 25 units and sometimes 75, depending on the field and yield potential.
“That also allows us to then react a little to a tissue sample, see what nutrients are available and make sure we’re not wasting money on nitrogen applications that aren’t needed.”
2. Use Anhydrous Wisely. There are differing takes on the value of fall-applied anhydrous, but there’s little argument about it being the most affordable source of nitrogen (N). If applied correctly, it can help minimize nutrient losses during winter because of the chemical composition of the fertilizer, says Nick Jensen, president of Thurston Mfg.
“For fall strip-tillers who are dual-applying dry fertilizer for phosphorus (P) and potassium (K) and anhydrous for N, anhydrous should be placed 6-8 inches deep, most likely with a shank or a mole knife that has an 1½-inch foot on it,” Jensen says. “Because when you stir those soil molecules up, you’re freeing additional water molecules up for that anhydrous ammonia to attach to, which is exactly what it seeks out to find.”
3. Get a Sample Size. Soil testing and sampling can produce variable and even inconclusive results. But they’re still a good tool to assess nutrient needs. “We look at recent soil sample results to determine if we need to address a nutrient deficiency,” says Le Roy, N.Y., strip-tiller Donn Branton. “Why spend the money if it is not justified?”
In the past, Branton has pulled soil samples using 1-acre grids, by soil types and, more recently, by management zones based on soil types and topography. He’s constantly considering which approach may work best.
“We don’t believe in over-applying a nutrient to offset loss that can occur between application and crop usage,” he says. “Just to say something is done does not always mean it was done in the proper or best way possible.”
4. Hurry Up and Wait. Strip-tillers are often anxious to get strips built soon after harvest, but have to be patient enough to avoid making fertilizer applications in fields that are too wet, or too dry.
“I don’t like to strip-till into conditions that are too dry or too wet because it doesn’t make the ideal strip,” says Aric Homola with Midwest Ag Services LLC, a custom strip-till and application company based in Lake Norden, S.D.
He recommends using a strip-till rig that can accommodate less-than-ideal field conditions and extend the application window for banded fall fertilizer applications. “We include a fair amount of N stabilizer to help combat loss when temperatures are around 50 degrees, but the later it gets in the fall, the less we apply.”
5. Stabilize Your Soil. To minimize N loss, fall fertilizer applications are best made in soils colder than 50 F. Using an N stabilizer can minimize leaching.
“Once that soil temperature is at 50 degrees or below, it really slows down the microbes that would take ammonia and convert it to the nitrate form, which is the form we are all worried about leaching,” Jensen says. “Whereas anhydrous ammonia (NH3) is what is injected in to the ground, it is quickly converted into ammonium (NH4+) once it comes into contact with water molecules in the soil.
“This ammonium is stable in the ground when the ground temperature is below 50 degrees. As the ground warms up above 50 degrees, microbes convert the NH4+ into nitrate (NO3-), which is the form that has the potential to be lost due to leaching in wet conditions. If it sits in the ground all winter as an ammonia, you really don’t have a whole lot of risk losing N. It’s when those microbes start working on it and turning it into nitrate that we really have trouble.”
6. Be Mindful of Holding Capacity. Knowing the right amount of fertilizer to apply in fall is another precaution to avoiding costly loss. With application of P and K, because it moves slowly through the soil profile, placing it 4-8 inches deep keeps it well-preserved until spring, says Anthony Montag, with Montag Mfg.
But there is more concern about N loss, and knowing how much N soils can hold will help prevent leaching and over-application.
“How many times at the National Strip-Tillage Conference did we hear people getting by with 0.7, 0.9 or 0.9 units of N per bushel?” Montag says. “And were out there applying 200 units of N in the fall, then have to come back and sidedress because we know we lost it.
“It’s important to know our cap on the cation exchange capacity of our soils. When were loading our soils up with N in the fall beyond their capacity to hold nutrients, we’re just setting ourselves up for fall leaching process. That’s where a split-application or ESN product is valuable, so you can boost your N utilization level. It’s not a matter of putting on more dollars of N, but putting on smarter N.”
7. Protection by Injection. Denitrification and volatilization are references strip-tillers prefer to avoid using when discussing their fall fertility program. Jensen says there are two things farmers can to do make their program “bulletproof” against volatilization. “One is injection of that fertilizer. And the other is a ½ inch of rain within 24 hours,” he says. “We can control one of those, which is why we like to see N injected.
“If we’re going to try and maximize our N-use efficiency, apply a base N in the fall — maybe 30-50% of your total complement for the year of the N product,” says Jensen. “Then coming back with some starter on the planter, and then doing a sidedress injection operation around V6 stage if you really have a good crop. Then if you feel like it’s going to increase your N use efficiency, come back in that V10 to V12 stage with some sort of application, with a sprayer and a coulter or another type of application that would top that off to top out your yield.”