Looking to keep nitrates out of streams and rivers? Field nutrient management is a good place to start.
“Nitrogen (N) is a very difficult nutrient to manage because there are so many potential loss mechanisms,” says Peter Motavalli, professor in soil fertility and plant nutrition at the University of Missouri. He helps conduct research on new management practices to improve N use efficiency. “We want to get more of the N fertilizer we are putting down into the plant and not out into the environment. It makes sense economically, and it makes sense environmentally.”
There are a lot of potential fates for N, says Motavalli. Many aren’t good for production. Major loss processes include:
• Ammonia volatilization
• Runoff and erosion
• Nitrate leaching
The good news is tools including sensors, remote sensing, new software, and even drones are available to help farmers increase N efficiency.
It’s that technology that Chad Groenhagen, an Oregon, Illinois, farmer at Circle G Farms & Feedlots, has been using on his operation. The corn grower and livestock producer uses manure as his main nutrient source. He takes soil samples and closely monitors nutrient levels to assure that he isn’t applying excessive amounts; he only applies manure every four years.
He uses DuPont Pioneer’s Encirca to monitor his fertility program. “With Encirca, it’s been really easy to adapt how and when I apply nitrogen,” says Groenhagen.
Fields with no manure applications receive 70 pounds per acre of 32% liquid N preplant. Groenhagen then comes back to sidedress anhydrous ammonia between the V3 to V5 corn-growth stages. The sidedress rate ranges from 140 to 180 pounds per acre, depending on what the soil samples show is needed, says Groenhagen.
“The predictive part of Encirca takes 50 years of weather data and breaks down soils into their environment response units (ERUs),” he says. “It can show predictively where N will be used, when it’ll be used, and how much will be used through the 50-year weather average.”
The responsive part of Encirca allows Groenhagen to make relevant decisions throughout the season. His farm’s weather station allows him to monitor the current-time N levels in the field.
“As I get into the V8 to V10 crop stage, I can look at my N and decide if I need to hit a late N application or if I’m set,” says Groenhagen.
He’s seen the benefits of Encirca with his liquid manure program. “They take 12- and 24-inch core samples in the soil to ground-truth the model,” says Groenhagen. That’s the case even in fields that are one and two years removed from the liquid manure applications.
“I’m seeing the organic N release is still there. That’s something I hadn’t accounted for is still being released,” says Groenhagen. “It has allowed me to incorporate that into my N program, as well.”
Adjust Your Mind-Set
It’s a model of sustainability, he says. “You can see it coming in the future. These models and tools are going to become mandatory, and you’re going to have to justify every bit of N, phosphorus (P), and potassium (K) you put into an acre. Right now, I’m able to ground-truth that I’m not running out of N. I’ve learned that what occurs naturally is more than what I had previously accounted for,” explains Groenhagen.
Fertilize for the Current Crop
Nutrient efficiency allows Steve Anderson, Beaman, Iowa, to lessen his risk of nutrient loss. “I like to be insured against multiple risks,” he says.
That’s why he spoon-feeds N throughout the growing season. In addition, Anderson has moved to soil sampling every one to two years. The practice may cost him more in the short term, but it pays off for him in the long term.
“I’m putting fertilizer out there because I know that I need to,” says Anderson. He has two high-clearance sidedressing rigs. His primary system uses Y-Drops that allow him to place N at the base of the plants.
“Sidedressing is more efficient; there’s less risk of loss because I can put it into the plant as it uses it, instead of having to manage it sitting there until it’s used,” explains Anderson. He also utilizes AgLeader OptRx Crop Sensors, which use ultraviolet cameras to sense the N needs in the corn plants.
“It will variable-rate the N as I’m going through the field, according to plant needs,” says Anderson. “This year, some fields called for a lot more N than I was anticipating because of the heavy rains.”
That’s not usual for Anderson, but with exceedingly volatile weather, he wants to be prepared. “In an average year, I tend to save N compared with what I would’ve normally put down,” says Anderson. “In a year like this with excessive rainfall, it also puts on what the plant needs instead of me guessing what it needs.”
Build Soil Health to Get the Most Out of N
Dave Legvold, a farmer in Northfield, Minnesota, was an idealist when he started farming. He set out to treat the land ethically and gently, which he determined meant organic, no chemicals. That changed when he saw what he calls the soft underbelly of organic farming: the amount of tillage necessary to make the system work. Not able to stomach the amount of tillage necessary for him to successfully farm organically, he decided to turn to conventional farming.
Soon, the conservation-minded farmer started to focus on how to best build soil organic matter, how to place the correct rate of nutrients, and how to best prepare a seedbed.
The answer came in the form of a strip-tillage machine called the Soil Warrior. While he no-tills soybeans, the strip-till tool allows him to place the nutrients in the ground for corn, and he’s able to prep the seedbed without disturbing much of the soil, he says.
“There’s an Environmental Quality Incentives Program (EQIP) enhancement to my Conservation Stewardship Program (CSP) contract where you are paid a small amount for placing your P fertilizer at least 2 inches deep in the soil,” says Legvold. “This puts it right in the ground. It satisfies my objective of fertilizer efficiency and satisfies the USDA of doing something with the P besides broadcasting.
“I use the Iowa State N Calculator for a base point for N,” says Legvold. He also works with nearby St. Olaf College students. They come out to the farm and do in-season N sampling. He stays on top of the N needs, making sure to not overapply.
He never applies N in the fall. “I can’t go out in the fall and put out 200 pounds of N and expect it to be there in the spring,” he says.
Instead, he gives a 40-pound N credit from the previous soybean crop and comes in with the Soil Warrior to apply 40 pounds of N preplant.
Legvold is suspicious when he drives through the countryside and sees perfectly green cornfields. “There’s so much N present that all of those corn plants are green and happy,” says Legvold. “If I’m at maximum efficiency, there will be yellow spots in the field. I like to see a little yellow, and I can bring it up by sidedressing.”
That’s exactly what he does, usually going back to sidedress around 60 to 75 pounds of N per acre. Legvold will even run small research plots with the students applying extra pounds of N to evaluate the difference in yield.
It doesn’t stop there for Legvold. He believes in well-drained soils. However, he knows drainage can lead to N loss when excess moisture leaves the field. That’s why he’s investing in a water-management program. This system allows him to control the amount of water draining from his fields.
During the winter months, Legvold can stop the water from leaving his fields. In the spring, he can then drain excessive moisture to allow for fieldwork. He can hold back moisture as needed in the summer.
(Source – http://www.agriculture.com/crops/fertilizers/technology/stop-n-loss-befe-it-starts_175-ar50986)