Abstract
<h2>Summary</h2> Cropland ammonia volatilization (<i>V</i><sub>NH3,AG</sub>) is a major pathway of agricultural nitrogen loss. It remains unclear, however, how climate warming and human intervention (e.g., agricultural management) will affect <i>V</i><sub>NH3,AG</sub>. Here, we use a fully coupled agroecosystem/chemical transport model and multiple climate projections to quantify the changes in climate-induced <i>V</i><sub>NH3,AG</sub> over the US. We show that climate change under an intensely warming scenario will increase <i>V</i><sub>NH3,AG</sub> by 81% (95% confidence interval, 69%–92%) from 2010 to 2100. The increase in <i>V</i><sub>NH3,AG</sub> will cause a 10% loss of nitrogen applied, decrease crop yields by 540 Gg-N year<sup>−1</sup>, increase atmospheric burden of ammonia/ammonium by 18%, and increase ammonia/ammonium deposition to sensitive ecosystems by 14%. We have found that combining climate-adaptive agricultural practices with feasible mitigation measures can fully offset the warming-induced increase in <i>V</i><sub>NH3,AG</sub>, saving 13% of applied nitrogen, increasing yields by 735 Gg-N year<sup>−1</sup>, and providing net benefits for air quality and ecosystem health.
Highlights
FEST-C_EPIC–CMAQ_BIDI estimates a 20% increase in VNH3,AG between the two years that is solely caused by changes in meteorology
The contribution can be up to 90% in certain areas of the Midwest. This analysis highlights the important role of VNH3,AG leading to the observed NH3 pulse in 2012 and supports the suitability of FEST-C_EPIC–CMAQ_BIDI in capturing the NH3 air-surface dynamics in response to climate change
The analyses consistently show the effect of management practices on VNH3,AG suppression in FEST-C_EPIC–CMAQ_BIDI and imply that the climate dependency of VNH3,AG described by RFMC is close to a scenario where fixed management practices are adopted irrespective of changing climate
Summary
Ammonia (NH3) in the air is the key constituent controlling and stabilizing aerosol acidity[1,2,3] and is a major contributor to secondary aerosol that has adverse impacts on human health and climate.[3,4,5,6] Excessive NH3 deposition is harmful to sensitive ecosystems as it causes soil acidification, eutrophication, and biodiversity loss.[7,8,9,10,11] Globally, approximately 43% of the atmospheric NH3 emission is attributed to volatilization from soils and plants over fertilized agricultural land (VNH3,AG)[12] due to the application of synthetic fertilizer and manure (agricultural land here refers to the cultivated land used for growing crops, hay, and pasture; VNH3,AG in this study denotes the NH3 volatilization from application of fertilizer and manure; VNH3,AG does not includes other livestock management processes except land application of manure). Applied worldwide is lost via VNH3,AG with important consequences for the global N cycle.[13,14,15]. VNH3,AG may increase as climate warms[12,16,17,18,19] because warmer conditions are thermodynamically favorable for increased NH3 release from multiple surface layers (e.g., soil and stomatal and moisture layers on the leaf cuticle) regulated.
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