摘要 : The effects of gypsum and phosphogypsum on methane and nitrous oxide evolution and on 15N and 226Ra uptake by rice were determined. Gypsum and phosphogypsum at 2.5, 5.0 and 10.0 tons/ha and 15N labelled urea (150 kg N/ha) were app... 展开 The effects of gypsum and phosphogypsum on methane and nitrous oxide evolution and on 15N and 226Ra uptake by rice were determined. Gypsum and phosphogypsum at 2.5, 5.0 and 10.0 tons/ha and 15N labelled urea (150 kg N/ha) were applied pre-flood to experimental plots drill-seeded with rice cv. cypress, in Louisiana, USA. Methane and nitrous oxide were measured twice a week over the main cropping season. Plant samples were collected at harvest and 15N uptake and 226Ra activity measured. Three rates of gypsum reduced methane evolution 49, 52 and 66%, respectively, compared with control plots. Phosphogypsum (2.5, 5.0 and 10.0 tons/ha) decreased emissions of methane 47, 46 and 51%, respectively, over the 84-day study. Nitrous oxide fluxes were low (10-29 g/ha per day) and only detected from control plots on two sampling dates. The assimilation of applied 15N in grain collected from gypsum plots was significantly higher compared with control and phosphogypsum treatments. The measured grain 226Ra activities were low and averaged 0.518 Bq/kg for phosphogypsum compared with a control plot activity of 0.222 Bq/kg. 收起