Predicting Ammonia Loss from Surface Applied Manure.

The land application of manure is the largest source of ammonia (NH₃) emissions from farms.  A need exists to minimize these NH₃ losses to enhance crop yields and reduce environmental degradation.  Few management strategies however, are available to reduce these losses.  Due to the complexity of the NH₃ volatilization process these possible strategies can not be extended across a wide range of conditions.  A well tested and accurate simulation model however, can overcome this challenge. 

The Volt’Air simulation model was utilized to estimate NH₃ volatilization from manure spreading for various manure spreading considerations under a range of atmospheric conditions typically encountered in Eastern Canada.  Considerations included: (i) soil liming, (ii) time of day of manure spreading, (iii) rainfall (timing and amount) and (iv) manure incorporation (timing, depth and manure coverage area).

Results demonstrated that liming to increase pH by increments of 0.1 (up to a 1.5 total increase) resulted in enhanced NH₃ emissions by 3.3 kg ha^-1.  Delaying manure spreading by 1 h reduced NH₃ losses by 1.5 kg ha^-1.  Rainfall (10 mm) at least 20 h after manure application reduced losses, with increased reductions at higher rainfall amounts.  Incorporation soon (1 h) after application is best for NH₃ mitigation.  Increasing the depth of incorporation by 5 cm reduced NH₃ emissions by 4.4 kg ha^-1.  Increasing the area of manure covered by 10% reduced losses by ~2 kg ha^-1.