Rice cultivation contributes 11% of the global 308 Tg CH 4 anthropogenic emissions. The alternate wetting and drying (AWD) irrigation practice can conserve water while reducing CH 4 emissions through the deliberate, periodic introduction of aerobic soil conditions. This paper is the first to measure the impact of AWD on rice field CH 4 emissions using the eddy covariance (EC) method. This method provides continuous, direct observations over a larger footprint than in previous chamber-based approaches. Seasonal CH 4 emissions from a pair of adjacent, production-sized rice fields under delayed flood (DF) and AWD irrigation were compared from 2015 to 2017. Across the 2 fields and 3 years, cumulative CH 4 emissions in the production season were in the range of 7.1 to 31.7 kg CH 4 −C ha −1 for the AWD treatment and in the range of 75.7−141.6 kg CH 4 −C ha −1 for the DF treatments. Correcting for field-to-field differences in CH 4 production, the AWD practice reduced seasonal CH 4 emissions by 64.5 ± 2.5%. The AWD practice is increasingly implemented for water conservation in the mid-south region of the United States; however, based on this study, it also has great potential for reducing CH 4 emissions.

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The response of the mutual deliquescence relative humidity (MDRH) of several mixed salt systems to changes in mole ratio is presented here. The MDRH values of NH4Cl-NaCl, NH4Cl-(NH4)2SO4, and, for the first time, the NaCl-NaBr systems were acquired as a function of mole ratio. These changes were studied using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The MDRH values of 1:1 salt mixtures were consistently found to be lower than the values of the individual deliquescence relative humidity (iDRH) of NH4Cl-NaCl and NH4Cl-(NH4)2SO4. The exception was the MDRH of the NaCl-NaBr system, which was found to be higher than the iDRH of NaBr particles, but lower than the iDRH of NaCl particles. When the mole ratio of the mixed system was varied, the MDRH of the mixtures showed a slight dependence on the mole ratio.

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