An efficient sampling strategy for estimating methane emission from rice field

Rice fields are a major source of atmospheric methane. Evaluation of management strategies designed to reduce emissions while maintaining or enhancing yield requires data on fluxes from a range of ecosystems and climatic zones. Automated closed chamber systems are too expensive for this purpose everywhere, but analysis of the patterns of diel and seasonal flux variation reveal an optimal less-intensive sampling strategies for use with manually operated chambers. Such an analysis, presented here, suggests that sampling at 0600, 1200, and 1800 h is sufficient to capture most of the diel variation observed throughout the growing season, and that sampling is most important where fluxes are most variable, between flowering and harvest. For a typical 100-day growing season, fluxes should ideally be measured at around 10, 20, 30, 50, 70, 77, 84, 91, and 98 days after planting. The proposed sampling strategy considers seasonal variations in methane emission as influenced by temporal, spatial, and crop management related factors.