Patterns and Controls of Nitrous Oxide Emissions from Waters Draining a Subtropical Agricultural Valley

Although nitrous oxide (N20) emission from agricultural runoff is thought to constitute a globally important source of this greenhouse gas, N20 flux from polluted aquatic systems is poorly understood and scarcely reported, especially in low-latitude (0-30 degree) regions where rapid agricultural intensification is occurring. We measured N20 emissions, dissolved N20 concentrations, and factors likely to control rates of N20 production in drainage canals receiving agricultural and mixed agricultural/urban inputs from the intensively farmed Yaqui Valley of Sonora, Mexico. Average per-area N20 flux is both purely agricultural and mixed urban/agricultural drainage systems (16.5 ng N20-N cm-2 ht-1) was high compared to other fresh water fulxes, and extreme values ranged up to 244.6 ng N20-N cm-2 hr-1.