Think Ahead to get Nitrogen Timing and Rates Right in 2021
Your corn fields are counting on you to provide the crop with nitrogen at the right time, right rate, right place and with the right product. What you did this past fall, what you’re doing this spring and the plans you’re making for the summer will make a huge difference in the combine at the end of the year.
“If adding nitrogen to a field was an efficient system and one unit of N applied went right into the crop, we wouldn’t have much of a conversation,” says Jeff Divan, farmer in Thompson, Iowa and senior manager of sales agronomy for Sound Agriculture. “When you apply nitrogen, 30% to 50% of that product can be lost due to environmental factors, so there’s a lot of opportunity to hone this process in financially and limit those environmental loss factors.”
The fight against nitrogen loss is ongoing. Learn more about evaluating your current soil composition, starting the crop and finishing the crop.
Establish the baseline
“Like choosing the right hybrid, N rates have the potential to make big differences on the bottom line — both yield and ROI,” says Ken Ferrie, Farm Journal Field Agronomist in a recent Boots in the Field podcast. “We know the corn plant is going to pick up somewhere between 1.4 lb. and 1.6 lb. of N per bushel. Some growers want to use the same N rate on all farms, no matter what the yield goal or planting population — I wish it were that easy.”
Don’t just assume you know what nitrogen is available in the soil. Each crop takes nutrients, residue and other ground cover all impact how you start each season.
“In the early season we need to be looking at soil temperature, soil moisture, content and figure out our goal for the year so when the combine rolls through we know if it’s been a successful season,” says Erich Eller, owner of ForeFront Ag Solutions. “Then, look at the weather. Right now, we’re six or seven inches of rain behind normal—is that pattern going to stay for the 2021 crop?”
For farmers who fall-apply nitrogen, lack of some rain might actually lead to less denitrification. However, a dry season might change your overall yield potential and goals, which impacts nitrogen needs, for example.
Eller recommends farmers get a soil nitrogen test at the beginning of the season to better inform decisions. A PSNT or ISNT test – either one – is what he suggests.
“Really look at it and ask, in order to finish the season at my yield goal, where do I need to be?” Eller says. If you use split applications, think about when the crop will respond to nitrogen the most when planning each application pass, rate and product.
When it comes to the nitrogen product you use, consider how it will respond to your soil types, timing, weather patterns and other uncontrollable factors. It’s different for every field and will take research to nail.
“For example, in my area when it’s early side dress I still like anhydrous,” Eller says. “We’re heavy clay and get a lot of ponding and anhydrous is nice because it’s stable. Early season I like urea because, chances are, you’re going to catch a rain.”
Monitor in season
Part of being responsive in-season is knowing what’s actually happening in your fields. There are a number of apps that can help provide estimates – but nothing beats boot-in-the-field investigation when you have concerns.
“One thing we recommend is putting a reference strip in each field that can be monitored aerially and in-field,” says Courtney Arnall, CEO of Ninja Ag. “There are two kinds: you can apply no nitrogen to a small area in the field, or you add a strip where an additional 40 to 50 pounds is added. Reference strips enable a line of communication from the field to the agronomist or grower. Weather is something we can’t control, but we can control how we manage a field’s fertility.
“Reference strips are a good foundation when building a fertility management plan. It can be easily built upon to build a more robust strategy while at the same time simplifying application timing. It’s a simple practice that provides and in-season visual of how nitrogen is moving in the soil,” she adds.
Apps and reference strips aren’t an end-all solution, you’ll still need to get more specific estimates about what’s going on in the field. Plus, you know large rain events and other factors can impact nitrogen availability, use that information to time scouting and if you should consider tissue samples.
“Don’t just rely on imagery alone,” Eller says. “For example, in 2020 we saw a yellowing spot in a field and in this case, it was potassium deficiency. Thing is that the soil had plenty of potassium, but it was compacted and the root system never really took off. So, even if we had put more potassium on the ground it wouldn’t have been taken up by the plant. We did a foliar feed instead.”
Use the tools you have available to home in on scouting, but don’t ignore the need to physically get in the field and diagnose what’s going on.
Consider unique field needs
It’s not just the soil composition you need to mind, the hybrid you choose impacts when and how nitrogen is absorbed into the plant. For example, Ferrie tested nitrogen timing, rate and placement in 2020 on two different hybrid types, a “D” hybrid and a “L1L2” hybrid. The D hybrid needs nitrogen during grain fill to max out yields, while the L1L2 needs nitrogen fromV6 to early dough.
The yield results for these hybrids varied greatly based on when the nitrogen product was applied. For this reason, and to get the most bang for your buck on nitrogen, talk to seed providers to find out what timing works best for the products on your fields.
“Being short on N will clip your yields more than any other nutrient,” Ferrie advises. “Before you make big changes to your N rate, do your homework.”