What agronomic efficiency for fertilizer N is achievable?
• The agronomic efficiency of fertilizer N (AEN) is the increase in yield per unit of fertilizer N applied. Experiences in Asia indicate that an AEN of 25 is often achievable in the tropics with good crop management in high-yielding seasons, and an AEN of 18 to 20 is achievable in the tropics with good management in low-yielding seasons. An AEN of 15 is a realistic target for environments where existing fertilizer N management practices are very inefficient with AEN in farmers fields of about 10 or less.
