Narrowing the agronomic yield gap with improved nitrogen use efficiency: a modeling approach.

Area of Science:

• Agricultural Science
• Agronomy
• Environmental Science

Background:

• Improving nitrogen use efficiency (NUE) in cereals is crucial for sustainable agriculture.
• Current understanding of NUE is limited by a lack of reliable on-farm data, with research station data often overestimating agronomic NUE (AE(N)).

Purpose of the Study:

• To determine the variability and causes of AE(N) across an agricultural region.
• To compare on-farm AE(N) with research station data in an irrigated wheat system.

Main Methods:

• Utilized the WNMM agroecosystem simulation model.
• Simulated AE(N), yield, gaseous N emissions, and nitrate leaching across 80 farmers' fields in the Yaqui Valley, Mexico.
• Compared simulated on-farm data with trials at the International Wheat and Maize Improvement Center (CIMMYT).

Main Results:

• Simulated on-farm AE(N) in the Yaqui Valley was highly variable and 44% lower than at CIMMYT for similar N fertilization rates.
• Variability in residual soil nitrogen supply was the primary driver of AE(N) variation.
• Improved split application of N fertilizer nearly doubled AE(N), increased profitability, and decreased N pollution.

Conclusions:

• On-farm AE(N) achievement is significantly lower and more variable than typically reported from research stations.
• Optimizing nitrogen fertilizer management, particularly split applications, offers substantial improvements in AE(N), profitability, and environmental outcomes.
• Site-specific nitrogen management technologies hold potential for even greater gains by directly measuring soil N supply and plant N demand.