96-12 Influence of Variable Soil Carbon on CH4 and N2O Emissions from Rice Fields.
See more from this Division: ASA Section: Environmental QualitySee more from this Session: Greenhouse Gas Emissions from Agriculture: I
Monday, November 3, 2014: 4:00 PM
Long Beach Convention Center, Room 202A
Reclamation of the Sacramento-San Joaquin Delta’s peatlands provided fertile soils for agriculture, but resulted in the oxidation of peat soils, extensive greenhouse gas (GHG) emissions, and subsidence. Rice cultivation has been proposed as a regional solution to mitigate past agricultural impacts. Multiple factors are capable of influencing GHGs emissions. In the present study, we investigate the influence of nutrient management and soil carbon content to CH4 and N2O emissions from highly organic peat soils under rice cultivation. The experiment was conducted in rice fields at Twitchell Island, California and consisted of 4 soil carbon contents (6%, 11%, 18%, and 23%) in combination with 2 nitrogen fertilization rates (0 and 80 kg N ha-1 as urea). We determined CH4 and N2O emissions with a typical closed chamber method during the growing season of 2013. In general, N fertilization did not affect CH4 and N2O emissions regardless of soil C content, while both CH4 and N2O emissions varied considerably across the soil C gradient. CH4 emissions were generally higher from the 6% C field than others. CH4 emissions were maximal during the drainage event, averaging 48.3, 17.2, 5.2, and 11.4 mg CH4 hr-1 m-2 for 6%, 11%, 18%, and 23% C fields, respectively. N2O emissions were low during the flooding period and negative emissions were frequently observed in all fields, especially in the 23% C field, suggesting the consumption of N2O was greater than soils with lower carbon. High N2O emissions were observed in all fields right after the drainage, except for the 23% C field where the emission was largely negative. Our results suggested that, in addition to carbon quantity, soil carbon quality maybe also important in controlling the GHGs emissions. Furthermore, N management many not be as effective as water management to mitigate GHGs emissions from the rice fields with highly organic, but subsiding soils.
See more from this Division: ASA Section: Environmental QualitySee more from this Session: Greenhouse Gas Emissions from Agriculture: I