Comparison of greenhouse gas emissions of chemical fertilizer types in China's crop production

Increasing awareness of climate change and food security has spawned an interest in low-carbon agriculture, an important aspect of which is the reduction of greenhouse gas emissions. As the largest source of agricultural emissions is fertilizer application, using a different type of fertilizer may help to mitigate greenhouse gas emissions from agriculture systems. The objectives of this study were to report a basic estimate of agricultural inputs and greenhouse gas emissions of crop production using national statistical data available for the period of 1993–2007, to compare the quantities of greenhouse gas emissions from different fertilizer types (per unit of N, P2O5, and K2O), to identify fertilizer types with the lowest emissions and the lowest costs, and to quantify the emissions gap between the lowest and actual emission scenarios, which will provide critical information for pursuing low-carbon agriculture in the future. According to available data, the use of all agricultural inputs increased during 1993–2012, resulting in an increase in not only yield but also in total greenhouse gas emissions from crop production. Not considering direct N2O emissions from the field, fertilizer-induced emissions accounted for up to 47.71% of the total greenhouse gas emissions from crop production. Therefore, lowering fertilizer-induced emissions is a priority measure that will result in low-carbon agriculture. Furthermore, ammonium bicarbonate, calcium superphosphate, and potassium chloride were found to be fertilizers with the lowest greenhouse gas emissions, and adoption of these fertilizers would result in a 49.15% reduction in fertilizer-induced emissions. This finding indicates that the judicious choice of fertilizer type would contribute to reducing greenhouse gas emissions in intensive production systems in China. Accordingly, utilizing ammonium bicarbonate, calcium superphosphate, and potassium chloride would be beneficial for greenhouse gas emission reduction and could be adopted as a good practice of low-carbon agriculture in China. This study highlights that changing to an appropriate fertilizer type could be an efficient option for mitigating greenhouse gas emissions in crop production in China.