Soil organic carbon (SOC) plays a significant role in soil fertility. Changes in SOC are associated with carbon input from organic materials. This study was conducted to assess the organic carbon dynamics of lowland soil from first to sixth cropping. A lowland area devoted to rice production under different production systems in six (6) successive croppings was evaluated. Results revealed that SOC changes with cropping. The second cropping generally showed higher SOC than the rest of the cropping period. In the sixth cropping, SOC in all production systems was comparable. The results suggest that organic amendments can be a good substitute for inorganic fertilizers in improving soil fertility aside from producing safe food to eat.