Tips for Maximizing Nitrogen Efficiency
March 27, 2009
The roller coaster ride of fertilizer prices which began last summer has started to slow down, with prices for nitrogen and phosphorus near what they were a year ago, but perhaps 50% less than what they were mid to late summer of last year. While prices may be better for now, using fertilizer efficiently will help you reduce your input costs.
Following is a prioritized list of five things producers can do to maximize their nitrogen fertilizer dollar.
Figure 1. Use of anhydrous ammonia has dropped over the last decade in Nebraska as the use of UAN solution has increased.
Soil Test. Fertilizer recommendations based on accurate soil tests will insure that rates are as close as possible to the economic optimum. Current guidelines on soil testing are available in the NebGuide Guidelines for Soil Sampling (www.ianrpubs.unl.edu/sendIt/g1740.pdf) and the Extension Circular Soil Sampling for Precision Agriculture (www.ianrpubs.unl.edu/sendIt/ec154.pdf). Once soil test information is available, use the UNL Soil Test Web site (www.soiltest.unl.edu) to calculate economic optimum fertilizer rates.
- Delay Nitrogen Application. The longer nitrogen (N) is in the soil, the greater the potential for it to be lost — either by leaching, volatilization, or denitrification. Fertigation through center-pivot irrigation systems and sidedress application are both excellent ways to apply nitrogen for corn near the time of maximum crop uptake.
- Incorporate or Inject Fertilizer. Placing fertilizer below the soil surface increases the likelihood that it will be used efficiently. Broadcasting fertilizer on the soil surface or residue increases the potential for runoff, volatilization or immobilization of N. Injecting N fertilizer in a sub-surface band reduces fertilizer contact with soil, slowing the rate of conversion to the more leachable nitrate form.
- Carefully Choose N Fertilizer. There has been a trend in recent years in Nebraska for producers to use more UAN solution (Figure 1), due to its flexibility and convenience as a fertilizer. In 2008, about 57% of N sold in Nebraska was UAN solution; 30% was anhydrous ammonia, and only 10% was urea. However, anhydrous ammonia historically has been the least expensive fertilizer per pound of N. Because ammonia must be injected, it generally has less risk of loss from runoff, volatilization or other processes than urea or UAN solution. The fact that these sources can be surface-applied increases their loss risk relative to ammonia, though if applied below the soil surface, urea and UAN have basically the same efficiency as ammonia.
- Buy Some Insurance. Or at least products which help insure N availability. If broadcast application of urea or UAN solution fits best for your production system, the urease inhibitor Agrotain® can help reduce or eliminate the risk of ammonia volatilization to the atmosphere. For sandy soils where preplant anhydrous ammonia is applied, the nitrification inhibitor N-Serve® can reduce the risk of nitrate leaching. Both of these products can help preserve yield potential if environmental conditions are conducive to N loss.
Extension Soils Specialist