Abstract
Application of nitrogen fertilizers for food crop production is the important source of atmospheric nitrous oxide (N2O). The direct measurements of N2O emissions under tropical environments where turnover of nitrogen is rapid are relatively rare, particularly in Southeast Asia. This study aims to measure the direct N2O emission from managed soil in Thailand. It was performed in a long–term experimental field (47 y) of cassava cultivation with different fertilizations; variations in chemicals (nitrogen [N], phosphorus [P], and potassium [K]) and organic (crop residue [CR] and compost [CP]) fertilizers. The application rate of N, P (P2O5), K (K2O), CR, and CP were 100, 50, 100, 6,250, and 18,750 kg ha-1. A closed chamber method was used to investigate the emissions for 400 d during November 2021 to December 2022. The results show that the application of N from both chemical and organic fertilizers were the key factor inducing a significant fraction of N2O emissions. The amount of N2O emissions during these measurement periods ranged from 0.84–3.37 kg N2O ha-1, its average was 2.21 kg N2O ha-1. The nutrients provision by fertilizers directly resulted in increased cassava yield production. It was observed that the application of NPK or NK produced the greater yield, and these were additionally enhanced when CR or CP was applied together. Long–term soil management influenced soil characteristics based on the properties of materials applied to the soil. High pH and C content in CP increased soil alkalinity and soil organic carbon (SOC) sequestration. High nutrients in fertilizers affected the greater soil nutrients accumulation. Soil management with NPK+CR appeared to be the most suitable in this study when considering among environment, food security, and SOC aspects.
