Nitrogen (N) fertilizers may be a limiting factor for corn production based on rising nitrogen fertilizer prices and other production input. There are a few things to consider with high N fertilizer prices: (a) apply nitrogen fertilizer at the right time, (2) add or treat urea-based fertilizers with a proven nitrogen stabilizer, and (3) apply the nitrogen fertilizer at the appropriate rate.

Apply at the right time

Preplant nitrogen application in corn is not recommended in Tennessee because of the length of time from application to when the corn plant will begin significant nitrogen uptake. One exception is the application of anhydrous ammonia with properly calibrated equipment. Corn plants take up little nitrogen (<12% of N uptake during the growing season) until V6 growth stage, with the most active period of nitrogen uptake occurring between V8 to V14. Hence, there is a greater risk for nitrogen loss via ammonia volatilization or nitrate leaching from preplant nitrogen.

Split application is recommended when nitrogen rates are greater than 120 lb N/A. A typical split management practice is to apply a third of the total intended nitrogen per acre at planting and sidedress the remaining nitrogen fertilizer between V4 to V6. Split application also provides flexibility to adjusting nitrogen rate during growing season as compared to just a single application at planting. Split-application of a third of the recommended nitrogen at planting and sidedressing the remaining nitrogen fertilizer provides greater yield than single application at planting.

Add a stabilizer

Urea-based fertilizers (Urea and urea ammonium nitrates) are relatively susceptible to volatilization losses compared to other nitrogen sources. Ammonia loss from surface applied urea without nitrogen stabilizer (120 lb N per acre) can be more than 20% of the sidedress nitrogen applied, which is equivalent to more than 24 lb of nitrogen per acre. Also, it is important to note that ammonia loss from urea is generally higher than UAN applied at the same rate. Surface-applied UAN (10.3 – 23.3% of sidedress N) tends to be more susceptible to ammonia volatilization loss compared to UAN dribble between rows. Treating or adding a nitrogen stabilizer to urea-based nitrogen fertilizers is recommended if at least ¼ inch of rainfall is not forecasted within two days after application. Proven nitrogen stabilizers can reduce ammonia volatilization, particularly under conditions favorable for ammonia loss. There are a myriad of nitrogen stabilizer products with different formulations and concentrations available on the market that claim to reduce nitrogen loss via ammonia loss and improve crop yield.

Apply at appropriate rate

Current nitrogen application rates for corn production should be based on realistic yield goals. Adjustments can be made based on past production records and Pre-Sidedress Nitrate Test (PSNT) results if applicable. In Tennessee, only the PSNT is calibrated for corn production, and is recommended only for producers using animal manure, poultry litter or biosolids. Another tool available for estimating corn nitrogen ate is the Nitrogen Rate Calculator at www.utcrops.com  which estimates economical nitrogen rate rather than highest yielding nitrogen rate, and is useful in years where fertilizer prices are very high or corn prices are very low. Recent studies across 10 trials in Tennessee showed that the Economic Optimum Nitrogen Rate for dryland corn was 170 lb N/A based on yield data.

Source: University of Tennessee Institute of Agriculture, which is solely responsible for the information provided and is wholly owned by the source. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset.