Ammonia volatilization losses from a rice paddy with different irrigation and nitrogen managements

Ammonia volatilization (AV) is one of the main pathways of nitrogen (N) loss from a rice paddy, which results in low N use efficiency and many other environmental problems. To reveal AV losses from rice paddies with different combined irrigation and N managements, field experiments were conducted using site-specific nutrient management (SSNM), controlled released nitrogen management (CRN), and non-flooding controlled irrigation (NFI). The interactive effect of N management and irrigation management on AV losses is significant. N management is the dominant management factor of AV losses from a rice paddy. Weekly AV losses followed by fertilization comprise the majority of seasonal AV losses. Ammonium contents in surface water or top soil solutions determine the AV loss rate for both flooding irrigation (FI) and NFI paddies. Moreover, AV losses are less sensitive to surface ammonium nitrogen contents for the NFI paddy than that for the FI paddy. Shallower water condition in the NFI paddy immediately after fertilization may result in higher AV losses than that in the FI paddy in a short term during the first wet–dry cycle after fertilization. However, the following wet–dry cycles result in lower AV losses in most of the rice growth stages. Seasonal AV losses from the NFI paddy using farmers’ fertilization practice (FFP), SSNM, and CRN treatments were 125.27, 37.63, and 23.73 kg N ha−1, which account for 31.1%, 23.2%, and 13.2% of the seasonal N inputs, respectively. These results were reduced by 14.0%, −17.1%, and 28.7% compared with those from the FI paddy with the same N management. A combination of NFI and CRN is the optimal treatment, with the lowest AV losses and high potential in reducing nutrient leaching risks. Increasing the water depth and the duration of flooding for the first wet–dry cycle after fertilization is a promising measure to reduce AV losses and improve N use efficiency in an NFI paddy.