For the spring rice crop in this experiment, fifteen-day-old rice(Oryza sativa L. indica, cv. Khang Dan) seedlings from a nursery bedwere transplanted to the experimental plots on 23 February.Transplanting was performed with 2–3 seedlings per hill and with 20 cm 20 cm spacing between hills. The experiment was designed using a 2 4 factorial randomized complete block design with triplicates on a plot size 4 m 5 m each. The first factor was water management and the second factor was organic matter management. Permanent flooding (PF) was the first level within water management in which the water level was maintained at 3– 7 cm above the soil surface, starting from one week before transplanting until 15 days before harvest. The second level was a