Effect of substituting urea with grain-legume fixed N fertiliser on CO2 emissions, and of raising pH on N2O emissions. Wongan Hills, Western Australia, 2009-2011 [Theme 4: Soil Carbon in N2O emissions]

Grain production is a net producer of greenhouse gases (GHG) via fertiliser, herbicide and farm machinery usage. In south-western Australia, previous research demonstrated that applying N fertiliser as urea contributed ca. 80% to total on-farm emissions by emitting carbon dioxide (CO2) via urea hydrolysis, and nitrous oxide (N2O) via soil biological activity. This project will determine if on-farm CO2 emissions from urea can be decreased by substituting urea with grain-legume fixed N; and if on-farm N2O emissions can be decreased by raising soil pH (via liming). Nitrous oxide emissions will be measured on a sub-daily basis from lupin-wheat rotations (limed and unlimed) using soil chambers connected to a fully automated system that enables simultaneous determination of greenhouse gases (N2O, CH4, CO2). Research findings will equip grain producers with strategies to manage on-farm GHG emissions.

粮食生产通过化肥、除草剂及农用机械的使用，成为温室气体（GHG）的净排放源。在澳大利亚西南部，既往研究显示，以尿素形式施用氮肥时，其通过尿素水解过程排放二氧化碳（CO₂）、经由土壤生物活动排放一氧化二氮（N₂O），约占农场总排放量的80%。本项目旨在明确两大核心目标：一是以禾谷类-豆科作物固定的氮源替代尿素，能否降低尿素施用带来的农场内源二氧化碳排放；二是通过施用石灰调节土壤pH值，能否减少农场内源一氧化二氮排放。本研究将采用连接全自动监测系统的土壤气室，对施石灰与未施石灰的羽扇豆-小麦轮作田块开展亚日尺度的一氧化二氮排放监测，该系统可同步测定一氧化二氮、甲烷（CH₄）与二氧化碳三种温室气体。本项目的研究成果将为粮食生产者提供农场内温室气体排放的精细化管理策略。