Denitrification Power of the Flooded Rungsit Very Acid Soil

Abstract

A study was conducted by addition of ammonium and nitrate fertilizers into the Rangsit very acid soil, the soil was flooded, the rice seedlings were transplanted, and denitrification activity including ammonium and nitrate contents were followed. Results revealed that denitrifying microorganisms, in both ammonium and nitrate fertilized soil, increased rapidly and reached their peaks approximately 3 to 4 weeks after submergence. Approximately 1/7 of the added ammonium was transformed to nitrate, of this 71 percent (or 10 percent of the ammonium nitrogen added) was lost via nitrification-denitrification sequence. Eighty four percent of nitrate (or 86 percent of the nitrate nitrogen added) was denitrified and lost from the nitrate-treated soil. The rice yield obtained from the ammonium treated soil was significantly higher than that nitrate treated soil.