CLIMATE AND SOIL FACTORS AFFECTING AMMONIA EMISSIONS FROM UREA AND DAIRY SLURRY APPLICATIONS ON ANDOSOLS

In Chile, agriculture and cattle production are important productive economic activities, accounting for 4.5% of Gross Domestic Product (GDP) along with the forestry sector. At a global level, it has been estimated that agricultural activities are the main source of ammonia (NH3) emissions to the atmosphere, being the application of nitrogen fertilizer to grasslands, either from organic or mineral origin, one of the most important sources of emission. NH3 emissions derived from losses of the applied nitrogen fertilizer have been linked to important environmental impacts. Nevertheless, despite the importance of these emissions, there are few published data regarding the factors affecting their generation from grasslands in southern Chile. Fertilization is a common practice in southern Chile, where most of agricultural production systems are based almost exclusively on the use of permanent grasslands as the main source of animal feeding throughout the year. The aim of this review was to analyze the factors that may affect NH3 emissions from urea and dairy slurry applications to permanent grasslands on Andosols of southern Chile. Results indicated that main factors that could affect the magnitude of N losses by NH3 volatilization are climate, grassland/soil conditions, and fertilizer management. Options to reduce NH3 emissions are available, improving the nitrogen use efficiency while minimizing the risk of environmental pollution.