Climate change may interact with nitrogen fertilizer management leading to different ammonia loss in China’s croplands

Abstract

Despite research into the response of ammonia (NH3) volatilization in farmland to various meteorological factors, the potential impact of future climate change on NH3 volatilization is not fully understood. Based on a database consisting of 1063 observations across China, nonlinear NH3 models considering crop type, meteorological, soil and management variables were established via four machine learning methods, including support vector machine, multi‐layer perceptron, gradient boosting machine and random forest (RF). The RF model had the highest R2 of 0.76 and the lowest RMSE of 0.82 kg NH3‐N ha−1, showing the best simulation capability. Results of model importance indicated that NH3 volatilization was mainly controlled by total input of N fertilizer, followed by meteorological factors, human managements and soil characteristics. The NH3 emissions of China's cereal production (paddy rice, wheat and maize) in 2018 was estimated to be 3.3 Mt NH3‐N. By 2050, NH3 volatilization will increase by 23.1−32.0% under different climate change scenarios (Representative Concentration Pathways, RCPs), and climate change will have the greatest impact on NH3 volatilization in the Yangtze river agro‐region of China due to high warming effects. However, the potential increase in NH3 volatilization under future climate change can be mitigated by 26.1−47.5% through various N fertilizer management optimization options.

Global benefits of non‐continuous flooding to reduce greenhouse gases and irrigation water use without rice yield penalty

“…Four RF models were used to identify explanatory variables that are most important to variations in global effects of non-continuous flooding practices on CH 4 emissions, N 2 O emissions, IRR, and rice yield, respectively. Similar models have been widely used for relative importance assessment (Xu et al, 2021), by measuring the increase in the out-of-bag (OOB) error when the variable was randomly permuted, while keeping all the other variables unchanged. The larger the increase in the OOB error the more important is the role of the corresponding variable.…”

“…Its built‐in variable importance assessment and error monitoring makes it robust in identifying the functional form of the relationships and provided more accurate predictions (Yin et al, 2021). It can also capture complex nonlinear relationships between predictors and outputs, and its predictive power in representing climatic or management effects has been demonstrated in a wide range of studies, with the advantage of higher computational efficiency and being robust to overfitting and noise data (Liu et al, 2019a; Terrer et al, 2019; Xu et al, 2021; Yang et al, 2021).…”

Adaptation Strategy Can Ensure Seed and Food Production With Improving Water and Nitrogen Use Efficiency Under Climate Change

“…The persistent yield gap between potential and actual yield is an important issue to be solved for global food production, especially in low‐ and middle‐inputs regions (Ray et al., 2012). Adaptation strategies, like optimized irrigation and N fertilization strategies, determine the potential for closing yield gaps, increasing yield and resource use efficiency, and reducing agricultural pollution (Horton et al., 2021; Liu, Yang, Folberth, et al., 2018; Xu et al., 2021).…”

“…Adaptation strategies have been proven to be effective to increase both crop yield and resource use efficiency in changing environments (Lee et al., 2014; Xu et al., 2021). Previous studies, based on statistics, field experiments, and modelling, have shown that regulated deficit irrigation could achieve the win‐win of crop yield and irrigation water productivity (WP I ) (Du et al., 2015; Kang et al., 2017; Mansouri‐Far et al., 2010).…”

Nitrogen dynamics in the Critical Zones of China

“…Moreover, the effects of climate change on N dynamics in CZs should also be considered. Drought and rising temperatures during crop growth periods would lead to increased ammonia volatilization on national scales and different responses on regional scales (Xu et al, 2021). Moreover, the impact of climate change on microbial communities and functions in CZs should also be evaluated.…”