Carbon Dioxide Emission from an Organically Amended Tropical Soil Under Various Tillage Practices.

This study examined carbon dioxide (CO₂) emission from a tropical soil (Waialua clay variant: Isohyperthermic Pachic Haplustolls) amended with organic compost (CP) and chicken manure (CM [Gallus domesticus]) under conventional (CT), residual (RT), and no tillage (NT). Measurements of CO₂ emission were made with CIRAS-1 Infrared Gas Analyzer during three growing seasons of a sweet corn (Zea mays L.) on a weekly or biweekly basis. The CO₂ flux data were analyzed using repeated measures of a split-plot design considering amendment type as the main plot and date of CO₂ measurement as sub-plot. Organic compost and CM amendments resulted in significantly high CO₂ emission compared with control treatments. Time after tillage significantly affected CO₂ emission, especially during warmer growing seasons, in interaction with amendment type. Soil surface disturbance during initial stage of growing season resulted in lesser CO₂ emission than continuous and frequent disturbances across the growing season. Therefore, CO₂ emission from soils under RT should be carefully assessed because the emission is correlated with the intensity and timing of soil surface disturbance. Maximum cumulative CO₂ emission (C_max), calculated from the Lineweaver–Burk transformation of the Michaelis–Menten equation, for NT was 81 and 41% less than those in CT and RT, respectively. Maximum cumulative CO₂ emission for RT was 68% less than that for CT (101 Mg CO₂ ha^–1). Carbon dioxide emission from Waialua soil tilled with ripper plow is in agreement with that from soils in the continental US tilled with chisel plow.