Corn+Soybean Digest

How To Penny-Pinch Nitrogen

Sound agronomic practices can save you more money than lower nitrogen (N) prices, says Dave Franzen, North Dakota State University soil specialist.

Franzen reviewed proven ways to use N more efficiently at a recent University of Minnesota Tillage Conference. They include:

  • Be sure to use the most recent maximum return to N recommendations from your university.

  • If you spring-apply urea or 28% N, incorporation is important to avoid having it volatilize to ammonia gas and CO2. Ammonia volatilization from urea is especially difficult to avoid in soil with a lot of residue, since residue hosts 100 times more urease enzyme as bare soil. Urease's activity produces volatilization. Finding a way to place urea beneath the soil surface is important to keep urea-N safe from early season losses.

    When spring urea or N solution is applied to moist, high-residue soil without rain, ammonia volatilization can steal 30-40% of it. You can lose 15% of your N in just one week in high-residue soils without incorporation, Franzen says, and one-third of your N in three weeks. As soil warms up, loss accelerates. Losses are less in dry or acidic soil.

  • Sidedressing is the most underused tool we have to increase N efficiency, Franzen says. “Sidedressing is most useful when you anticipate further decreases in N prices, leaching or early denitrification,” he adds.

  • A urease inhibitor makes economic sense when tillage will not occur within two days of urea application, or on alkaline or stubble-rich soils. Conversely, if tillage or rain will occur within two days, or you have acidic bare soils, it's less advisable, he adds.

  • Do not apply fall ammonia before the recommended start date for an area, and then only if morning soil temperatures begin to dip below 50°. Apply ammonia at least 5 in. deep. Shallow ammonia application is usually only about 90% efficient.

  • Don't apply fall N to soils prone to early season flooding.

  • Do not apply fall N to sandy loams or loamy sands or you will likely have big leaching problems in the spring.

  • When applying spring anhydrous ammonia, there's no safe interval between application and planting, so either control the pass or travel at an angle to the row to minimize crop damage.

In summary, “Know your soils; tailor your N source and timing to your soils, crop and labor; and communicate with your applicator,” Franzen says.

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