Interaction of lime application and straw retention on ammonia emissions from a double-cropped rice field

Ammonia (NH3) emissions are an important pathway of nitrogen (N) losses in rice paddies. Lime application and straw retention are common practices to enhance soil fertility in acidic soils. However, the interaction of lime and straw application on NH3 emissions from paddies remain unclear. Here, a factorial experiment was employed to examine the interactive effects of slaked lime (i.e., Ca(OH)2) and straw retention on NH3 emissions and NH3 emission factors (EFs) in a double-cropped rice field. The results showed that compared to unlimed treatments, liming promoted NH3 emissions and EFs by 98.6% and 90.2% in the early rice growth season, respectively, with increases of 16.3% and 15.7% in the late rice growth season. Relative to straw removal, straw retention increased NH3 emissions by 52.8% in the early rice growth season but did not alter EFs, while reducing NH3 emissions by 9.9% and EFs by 25.7% in the late rice growth season. Liming interacted with straw retention to increase NH3 emissions and EFs in the early rice growth season. Under straw retention, liming promoted NH3 emissions by 147.7% and EFs by 148.3%, whereas liming raised NH3 emissions and EFs only by 45.3% and 45.5% under straw removal, respectively. Liming had no significant interactions with straw retention on NH3 emissions and EFs in the late rice growth season. It is likely that the decomposition extent of straw can alter the response of NH3 emissions to liming. Thus, NH3 emission inventories should take into account the interaction of liming and straw retention and its dependence on rice growth seasons in double-cropped rice systems with acidic soils.