Flooded Fallow and Rice Effects on Histosol Organic Matter and Fertility.

Flooded fallow and rice fields both have the potential to substantially reduce the oxidation of soil organic matter (soil carbon), and its loss to the atmosphere as CO₂. However, prolonged flooding of a soil has the potential to produce methane (CH₄), a reduced carbon gas with a higher global warming potential than CO₂ (an equivalent amount of CH₄ will warm the globe 31 times more than CO₂). However, because rice plants transport oxygen to their roots where it may leach out into the soil, flooded rice is expected to produce significantly less CH₄ than flooded fallows due to an increase in soil redox potential. Measurements of soil carbon gas flux (CO₂ and CH₄) under flooded rice production, a direct measure of soil subsidence, have not been published from Histosols in south Florida. Additionally another important soil gas is nitrous oxide (N₂O). Nitrous oxide has a greater ability to warm the atmosphere than either CO₂ or CH₄, with a global warming potential 298 times that of CO₂. In general, highly organic soils have a greater potential to absorb N₂O than mineral soils due to their high carbon content. This project which is being conducted in lysimeters will identify the most effective water management technique that minimizes soil greenhouse gas emmisions and if planted with rice, still produces optimum rice yields.