How Long-Term Fertilization Affects Greenhouse Gas Emissions from Cassava Production？ | Newswise

Agriculture is a major source of greenhouse gas (GHG) emissions, especially in tropical regions. While the widespread use of chemical fertilizers has improved crop yields, it has also led to emissions of gases such as carbon dioxide (CO₂) and nitrous oxide (N₂O). With a global warming potential hundreds of times higher than that of CO₂, N₂O primarily originates from microbial transformations of nitrogen in soil. As a key global producer and exporter of cassava, Thailand’s GHG emissions from agricultural production have attracted significant attention. So, how do different fertilization methods impact GHG emissions in long-term cassava cultivation? Is it possible to reduce climate impacts while ensuring yields?

Based on a 47-year-long cassava field experiment in Rayong Province, Thailand, Dr. Patikorn SRIPHIROM from Silpakorn University, Dr. Amnat CHIDTHAISONG from King Mongkut’s University of Technology Thonburi, and their colleagues systematically compared the effects of multiple treatments—including no fertilization, mineral fertilizer alone, crop residue alone, and combinations of mineral fertilizers with organic amendments—on GHG emissions, soil properties, and cassava yields. The related research was published in Frontiers of Agricultural and Engineering (DOI: 10.15302/J-FASE-2025641).

The study found that inputs of organic carbon from crop residues (CR) and compost (CP) significantly increased soil CO₂ emissions, mainly due to enhanced microbial respiration driven by organic matter decomposition. Nitrogen application, whether from mineral or organic sources, significantly stimulated N₂O emissions. Notably, at equivalent nitrogen application rates, mineral nitrogen fertilizers induced higher N₂O emissions, with a mean emission factor (EF) of 0.75%, compared to 0.56% for the crop residue treatment. The research also indicated that long-term exclusive use of mineral fertilizers led to soil acidification and nutrient accumulation, while organic amendments effectively increased soil organic carbon (SOC) stocks, improved soil pH, and enhanced phosphorus and potassium availability.

Among all fertilization treatments, the combination of “NPK fertilizers + crop residues” resulted in the highest absolute GHG emissions. However, due to its significantly higher cassava yield, it ultimately achieved the lowest GHG emission intensity per unit yield. This outcome demonstrates that this fertilization strategy can more effectively control the climate impact per unit of output while maintaining high productivity.

Furthermore, microbial community analysis in the study revealed the underlying mechanisms of emissions: N₂O emissions are primarily associated with nitrification, with ammonia-oxidizing archaea (AOA) Nitrososphaera and ammonia-oxidizing bacteria (AOB) Nitrospira as key contributors. The average direct N₂O emission factor observed in the study was 0.68%, lower than the Intergovernmental Panel on Climate Change (IPCC) default value of 1%. This indicates that emission factors in specific regions may differ from global defaults, highlighting the importance of establishing localized emission estimation parameters.

This field study not only uncovers the long-term effects of different fertilization methods on GHG emissions but also provides practical directions for the sustainable management of cassava production in tropical regions. Overall, the combined use of mineral fertilizers and crop residues exhibits significant advantages in improving soil quality, maintaining high crop yields, and reducing carbon emissions per unit output, offering valuable insights for achieving agricultural green transformation.