Role of Organic and Conservation Agriculture in Ammonia Emissions and Crop Productivity in China

There
is an increasing food demand with growing population and
limited land for agriculture. Conventional agriculture with nitrogen
(N) fertilizer applications, however, is a key source of ammonia (NH3) emissions that cause severe haze pollution and impair human
health. Organic and conservation agricultural (OCA) practices are
thereby recommended to address these dual challenges; however, whether
OCA provides cobenefits for both air quality and crop productivity
is controversial. Here, we perform a meta-analysis and machine learning
algorithm with data from China, a global hotspot for agricultural
NH3 emissions, to quantify the effects of OCA on NH3 emissions, crop yields and nitrogen use efficiency (NUE).
We find that the effects of OCA depend on soil and climate conditions,
and the 40–60% substitution of synthetic fertilizers with livestock
manure achieves the maximum cobenefits of enhanced crop production
and reduced NH3 emissions. Model forecasts further suggest
that the appropriate application of livestock manure, straw return,
and no-till could increase grain production up to 59.7 million metric
tons (100% of straw return) and reduce maximum US$2.7 billion (60%
substitution with livestock manure) in damage costs to human health
from NH3 emissions by 2030. Our findings provide data-driven
pathways and options for achieving multiple sustainable development
goals and improving food systems and air quality in China.