Improved Estimates of Ammonia Emissions from Global Croplands

Reducing ammonia (NH3)
volatilization from croplands
while satisfying the food demand is strategically required to mitigate
haze pollution. However, the global pattern of NH3 volatilization
remains uncertain, primarily because of the episodic nature of NH3 volatilization rates and the high variation of fertilization
practices. Here, we improve a global estimate of crop-specific NH3 emissions at a high spatial resolution using an updated data-driven
model with a survey-based dataset of the fertilization scheme. Our
estimate of the globally averaged volatilization rate (12.6% ±
2.1%) is in line with previous data-driven studies (13.7 ± 3.1%)
but results in one-quarter lower emissions than process-based models
(16.5 ± 3.1%). The associated global emissions are estimated
at 14.4 ± 2.3 Tg N, with more than 50% of the total stemming
from three stable crops or 12.2% of global harvested areas. Nearly
three-quarters of global cropland-NH3 emissions could be
reduced by improving fertilization schemes (right rate, right type,
and right placement). A small proportion (20%) of global harvested
areas, primarily located in China, India, and Pakistan, accounts for
64% of abatement potentials. Our findings provide a critical reference
guide for the future abatement strategy design when considering locations
and crop types.