Reducing Ammonia Emissions from Crop Production Systems

Crop Production

In crop production systems, ammonia most often originates from nitrogen fertilizer that is volatilized before it can be used by the crop. Most of the volatilized nitrogen is lost within the first 3 to 5 days after application. The best means of reducing ammonia emissions is to apply fertilizers in forms, at times, and by means that maximize the amount of nitrogen available to the crop. Some general management means for minimizing ammonia emissions from crop production systems include:

• Choose plant varieties with high nitrogen use efficiency and that are well suited to the soil type in which they will be planted.
• Apply nitrogen fertilizer based on soil tests (including deep-soil sampling for applicable crops) and reasonable, historically-based yield goals. Where possible, utilize variable- rate applications based on soil characteristics and historical yield data to ensure optimal use of all applied nitrogen.
• Utilize slow release forms of nitrogen fertilizer such as those containing a urease inhibitor or side-dress/fertigate nitrogen when possible throughout the growing season to improve nitrogen uptake.
• Where possible, place fertilizer as close to the root zone as possible. Avoid broadcast applications of unincorporated fertilizer.
• For nitrogen applications that cannot be immediately incorporated into the soil, utilize the least volatile fertilizer formulations based on soil pH, texture, and other field-specific factors.
• Utilize nitrification inhibitors as an additive to fertilizer applications where broadcast application methods are the only viable alternative, where volatile forms of nitrogen are required, and when warm, wet, or windy environmental conditions are imminent.
• Where possible, minimize the use of anhydrous ammonia. If anhydrous ammonia is used, special attention is needed to utilize injection methods that minimize volatilization and to avoid leaks in the delivery system.

When a warning is issued that an air mass in eastern Colorado is likely to move into RMNP and move nitrogen into the Park, some practices that may be employed to reduce emissions during a warning period include:

• When possible, delay fertilizer applications to the soil surface until the warning period expires.
• Delay staging of manure or compost to be applied to fields until the warning period expires. If not able to delay the operation, incorporate broadcast fertilizer or manure immediately after spreading.
• Utilize a nitrification inhibitor to reduce risk of volatilization if application cannot be re- scheduled.
• Avoid fertigation through sprinkler systems.