A New Era of Nutrient Management

November 7, 2017 10:32 AM
Tile drainage ditch

If you think environmental regulation is not a real possibility, think again. The wheels leading to regulation turn slowly, says Farm Journal Field Agronomist Ken Ferrie, but they’re moving.

“The Clean Water Act has been on the books since 1972,” Ferrie says. “It has passed through various rewrites and revisions.”

As of now, EPA has charged states with reducing nitrogen (N) losses by 25% and phosphorus (P) losses by 15% in troubled watersheds by 2025. The end goal is to reduce the losses of both nutrients by 45%. For farmers in most states, the emphasis still is on voluntary measures.

“If farmers fail to achieve this goal, it’s possible regulations on fertilizer use could be the next step,” Ferrie says. “Municipalities are already regulated as to how much pollution they can discharge. So farmers are not being singled out—it’s a joint effort to reduce pollution and, if anything, farmers are being given more opportunity than cities to accomplish their goal voluntarily.”

Farmers needs to use the 4Rs—right nutrient, right time, right rate and right place—to prevent fertilizer from leaving their fields and protect water resources. In the process, they’ll lower production cost while increasing yield and profit.   

The 4Rs include a range of practices, some of which require more management than others. “But some of them are easy to adapt and should be common practices by everyone,” Ferrie says. “I call this shooting the slow rabbits first.”

When it comes to protecting water quality, N and P are two of the biggest concerns. The first step to keeping fertilizer in your fields and out of water supplies is to understand how nutrients are lost.

“Surface runoff and soil erosion account for the highest level of phosphorus loss from farm fields,” Ferrie says. “With nitrogen, loss occurs from volatility and denitrification, which release nitrogen into the atmosphere, and from leaching, in which nitrate is carried out of soil by water. When we reduce those losses, we increase nutrient availability to plants.”

With phosphorus, first steps involve controlling gully, sheet and rill erosion because phosphorus leaves fields attached to soil particles. “Erosion management is just another name for soil stewardship—preserving the health of soil so your kids and grandkids can farm it,” Ferrie says.

Preventing erosion might not require eliminating tillage. “However, we must be smarter about how we till,” Ferrie says. “Understand what tillage, if any, is best when and where to avoid creating erosion. In some fields, you may need to protect the tilled soil with a cover crop.

“Most farmers already have adopted systems that reduce erosion,” Ferrie adds. “But if you find yourself filling in gullies and ruts every season before you plant, that’s a sign you might be part of an environmental problem. Although abnormal rain at the wrong time can cause erosion, you should not have to address gullies and ruts every year.

“Another practice, or again a slow rabbit, as I like to call them, that should be common on all farms is basing all fertilizer applications, whether commercial fertilizer or manure, on a sound soil test,” Ferrie advises. “If you apply phosphorus to a soil that already tests high in P, you increase the risk of P leaving the field. And do not apply fertilizer or manure on frozen ground.”

While some N might be lost through soil erosion, most losses are associated with water leaching down through the soil profile or leaving the field through tile lines. “Water moves faster through coarse soils, such as sand and sandy loam, than it does through heavier soil, such as clay loam,” Ferrie explains. “The faster it flows, the easier it is to flush out the nutrients.

“So the first step to more efficient nitrogen use is to assess the risk of loss for every soil type you farm. On high-risk soils, adjust your application practices to reduce the risk.”

In today’s N planning, timing is as critical as equipment. “Think about when you are applying nitrogen and how much the weather influences nitrogen loss before plants have a chance to take it up,” Ferrie says.

Whether natural or man-caused, the climate seems to be changing. “South of Interstate 64 in Illinois and Indiana, most farmers don’t apply nitrogen in the fall because the soil stays warm too long,” Ferrie says. “Based on the past decade’s weather, these farmers fertilizer practices might need to move a tier or two north.  

“We can’t base nitrogen applications on the calendar anymore. We have to look at soil temperature and not apply until it stays below 50°F. Besides the environmental risk, applying nitrogen in the fall so plants can use it in June is a financial gamble. If weather conditions are perfect, you might not lose much; but if they aren’t, you can lose a lot. Often the loss occurs in the spring because of rain.

“All those factors make moving away from fall-applied nitrogen, in areas where fall weather stays warm, a slow rabbit,” Ferrie concludes.

While no-till, strip-till and vertical tillage prevent soil erosion, they can promote N loss if you fail to understand the effect on pH and residue. “Years ago, farmers would apply several tons of lime per acre and incorporate it through the soil profile with tillage,” Ferrie says. “But when you no longer incorporate, all that lime remaining on the surface creates a high-pH layer. That ties up available phosphorus and, more important, creates a risk of urea nitrogen volatility. With a high soil pH, nitrogen can volatilize in three hours.”

Even without high soil pH, residue on the soil surface increases the risk of N loss. “The urease enzyme, which drives volatility, is much higher in the crop residue than in the soil beneath it,” Ferrie says.

The solution is to apply less lime more frequently and use the correct stabilizer—a urease inhibitor to prevent volatilization. “And understand your nitrogen source,” Ferrie adds. “The more urea in your nitrogen fertilizer, the more risk of loss.”

Apply nutrients close to the time the crop will take them up to reduce the risk of loss. “We can no longer apply nitrogen in the fall and check the job off our list,” Ferrie says. “You need to know when plants take up nitrogen. You can find computer models on the internet that predict nitrogen uptake and use.”

Another way to think about N timing is that the closer to uptake you can apply N, the less chance plants will ever run short. “The key to high corn yield is to make sure plants never have a bad day,” Ferrie says.

The changes occurring in nutrient management symbolize a new era, when past practices no longer work. “To raise enough crops to feed nine billion people, we must consider the environmental aspect as well as the agronomic and economic,” Ferrie says. “If we don’t, there will be no way to avoid fertilizer regulations down the road.”

Six Steps to Efficient Nutrient Use

Preventing fertilizer from leaving your fields lowers production cost while increasing yield. Oh yes—it also protects water resources. Sure, you’ve heard the warnings before, but it can be overwhelming to put nutrient management practices into motion. Start with these six steps to address your environmental footprint:

1. Determine what type of tillage, if any, is best when and where to avoid creating erosion.

2. Base all fertilizer applications, whether commercial fertilizer or manure, on a sound soil test.

3. Assess the risk of nutrient loss for every soil type you farm.

4. Timing your nitrogen application is just as important as the equipment you use.

5. Apply less lime more often and use the correct stabilizer. Understand your nitrogen source, too.

6. Know when plants take up nitrogen and how much at critical growth stages.

Move Away From Fall-Applied Nitrogen

Farmers’ shift away from fall application of nitrogen for crops such as corn and sorghum is being reflected in changing retail practices, says Farm Journal Field Agronomist Ken Ferrie. “In my area of central Illinois, I know two fertilizer plants that have completely dropped anhydrous ammonia,” he says. “Their sales had shifted to spring application of nitrogen solution. While ammonia can be applied in the spring, farmers found it took up too much of their time when they needed to concentrate on planting, compared to nitrogen solution that can be applied as they plant or with herbicides.”

Traditionally, farmers have applied nitrogen in the fall because they feared they could not get over all their acres in the spring, especially if rainy weather set in. But that, like the climate that now keeps soil warm later into the fall, has changed, Ferrie says.

“When you consider all the options now available—spring preplant, with the planter, high-clearance, late-season application—you don’t need to bottleneck all your nitrogen into one time period,” Ferrie continues. “Worries about getting all your nitrogen applied in the spring really don’t reflect reality anymore. When I see farmers transition a few fields away from fall application, most of them soon decide they can do the same thing on their entire farm.”  

Price is not necessarily an obstacle to shifting away from fall application, Ferrie adds. “Some years, you can purchase liquid nitrogen fertilizer in the fall for application next spring cheaper than you can buy anhydrous ammonia for fall application,” Ferrie says. “Retailers can’t store large amounts of anhydrous ammonia; but they can buy nitrogen solution in large volume, store it in tanks and pass the savings on to their customers.”

Stabilizers Prevent Nitrogen Loss

The use of nitrogen stabilizers ranks alongside timing in efficient nitrogen management. “You must protect your nitrogen source,” says Farm Journal Field Agronomist Ken Ferrie. “Nitrogen stabilizers help prevent nitrogen from escaping before plants can use it.”

But you’ll need to spend some time learning about stabilizers and selecting the right one for your nitrogen source. “Nitrification inhibitors reduce denitrification and leaching, while urease inhibitors prevent surface-applied urea nitrogen from volatilizing into a gas and escaping into the atmosphere,” Ferrie explains. “Some products prevent both, by encapsulating nitrogen in a coating that keeps the nutrient stable until closer to plant uptake.

“Too often, I find growers using a nitrification inhibitor when they actually needed a urease inhibitor to keep surface-applied nitrogen from volatilizing. It’s easy to get confused about products, but it’s worth the effort to learn about them. The worst thing you can possibly do is to fall-apply nitrogen without a stabilizer and increase the rate to compensate for losses.”

Some farmers are reluctant to move away from fall-applied nitrogen simply because their present system has always produced a good crop, Ferrie says. “But a generation or two ago, we were growing 100 bu. to 150 bu. per acre corn. Today we apply enough nitrogen to grow 200 bu. to 250 bu. per acre. Simply because we are applying more nitrogen, our risk of loss is greater.”

While it might seem more efficient to use your labor force to run applicators in the fall, there might be a better way. “Consider all the costs of fall application, such as running the applicator and hauling the product to the field,” Ferrie advises. “If you apply nitrogen with your corn planter or herbicide application, field passes you will be making anyway, and eliminate the fall operation that increases your fertilizer efficiency.”


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