Rice residue management effects on greenhouse gas emissions and air pollutants on smallholder farms in southern Vietnam

Vietnam is a major producer and exporter of rice globally, and approximately 47 million tonnes of rice residue is produced annually. Rice residues are an economically valuable natural resource and a primary source of organic matter and nutrients for rice production, and recycling them enhances soil fertility. The prevailing practice for disposal of rice straw in the Vietnamese Mekong Delta is open burning, which causes the emission of greenhouse gases (GHG) and soil degradation. However, the suitable strategy for rice residue management practices on smallholder farms and their impact on GHG emissions and air pollution have not been intensively investigated. A study was conducted to quantify the amount of GHG and air pollutants emissions from paddy rice fields under four (4) community–based crop–residue management approach in southern Vietnam. The four management practices are (1) field burning of rice–residues, (2) field burning of rice stubble, (3) soil incorporation of rice–residues, and (4) use of rice-residues as fodder for shifting rice and fish culture. The findings showed that practices 1 and 2 release the largest quantities of GHGs and air pollutants like particulate matter of 2.5 μm and 10 μm, black carbon, carbon monoxide, sulfur dioxide, nitrogen oxides, ammonia, and non–methane volatile organic carbon to the atmosphere. The practices not only result in environmental pollution through the emission of GHGs that caused global warming but also results in the loss of valuable nutrients such as organic carbon, nitrogen, phosphorus, potassium, and sulphur. Moreover, practices 3 and 4 resulted in improved nutrient management and reduced air pollutants, suggesting that these practices can maintain soil fertility while significantly lowering GHG emissions. The results demonstrate that avoiding open–field burning of rice residues has the potential to promote more sustainable rice production, reduce air pollutants, and mitigate climate change.