Manage Nutrients to Turn the Tide on Encroaching Regulations

01:03PM Oct 19, 2017
A series of strip trials comparing soil beneath a cover crop to an adjacent strip with no cover crop is revealing increases in microbial activity, water soluble carbon, water infiltration and carbon to nitrogen ratio.
( Farm Journal )

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.”