I’ve had permission to share share information from a revised nitrogen management NebGuide from Ferguson, et. al that will soon be available. For those applying pre-plant nitrogen, a reminder to consider only applying a base rate of nitrogen (70-100 lb N/ac) this fall or spring pre-plant and apply the rest in season using a technology like Sentinel Fertigation. As these excerpts show, while good strides have been made, in general, we have opportunity to reduce nitrogen application rates.

“A recent survey in Nebraska found that 45% of farmers apply all N in early spring (33% pre-plant and 12% at planting), 14% in the fall, 12% during the growing season, and 29% use split application (Balboa 2023). The survey also found corn producers applying an average of 169 lb N/acre, with 80% using soil lab recommendations and 67% relying on personal experience/intuition. More advanced N recommendation tools generally had low adoption (crop models 23%, sensor-based algorithms 11%, and other digital tools 11%), indicating there is potential for growth in the use of these tools.”

Nitrogen Use Efficiency (NUE) is a measurement of how many pounds of fertilizer were used to obtain the grain yield in bushels. “Fertilizer N application by corn producers in Nebraska has gradually reduced over the past 50 years from around 1.7 lb fertilizer N/bu corn grain in 1965 to around 0.8 lb fertilizer N/bu corn grain in 2021. This is a tremendous improvement in fertilizer use efficiency, resulting in increased profit for Nebraska farmers and reduced environmental impact. Unfortunately, there continues to be significant areas of Nebraska with groundwater nitrate-N in excess of the EPA drinking water standard of 10 ppm.”

“In much of Nebraska, this trend for continuing increase in groundwater nitrate-N levels is partially due to the transit time of nitrate through the vadose zone. Due to the depth of the aquifer, nitrate entering the aquifer may have leached from the root zone several years to several decades ago and does not reflect current crop management practices. However, areas of the state with shallow aquifers also continue to see increasing groundwater nitrate concentrations (Juntakut et al., 2019), suggesting that more should be done to reduce nitrate loss from commercial fertilizers. Research at UNL in collaboration with NRDs calculated the partial N balance (difference between N inputs and grain N removal) across corn producers over several years as a proxy of N losses to the environment (Tenorio et al., 2021). About 70% of corn producers had a surplus N balance, indicating that N inputs were higher than N removal with grain. Corn producers with a large surplus of N were consistently over-applying N over the years.”

The “average grower fertilizer N application was around 0.8-0.9 lb fertilizer N/bu corn grain from 2000-2021. This lack of further reduction in N application per bushel raises the question of whether we’ve reached a limit to improving nitrogen use efficiency (NUE), or if broad adoption of different practices is needed to further improve NUE.”

“Nitrogen exists in many organic and inorganic forms in soil which are highly influenced by weather – particularly rainfall and temperature. Nitrogen is subject to loss from the soil via leaching and gaseous emissions (N₂O and NH₃). Consequently, our ability to predict N dynamics in soil, and availability of N from soil and fertilizer to the crop, is dependent on our ability to predict weather. Until we can perfectly predict weather, we cannot perfectly predict N availability to a crop…we believe that reactive management, applying most of the N fertilizer during the growing season, and basing the application rate on crop N status, can increase NUE for most growers, particularly for irrigated fields capable of fertigation.” For perspective, our on-farm research producers using Sentinel Fertigation had NUE ranging from 0.35-0.8. The goal would be an average of 0.5-0.7/year. I realize it’s hard to imagine that type of NUE, but our research keeps proving it is possible without hurting yields, with timely in-season N applications. It would also require time for a large infrastructure change for more in-season N to occur.

Reminders: Dec. 3: Cash Lease Workshop in York from 10:30 a.m.-2 p.m. (no charge and meal included thanks to Farmer’s National) on Dec. 3 at the 4-H Bldg. in York. RSVP: 402-362-5508.
Also Dr. Kohl is at the Bruning Opera House at 1 p.m. on Dec. 3 (no charge).

Dec. 5 is the Transition to Organic Workshop at ENREEC near Mead. No charge, RSVP and info. at: https://extension.unl.edu/statewide/enreec/2024-transition-to-organic-farming-conference/

Virtual Trade Show Webinar for Beef Producers at 7 p.m. each evening. Dec. 5: Water Monitoring Solutions and Dec. 9: Virtual Fencing. Register at: https://go.unl.edu/BeefTech.