Abstract
Agricultural soil management may affect soil carbon storage. We predict soil carbon storage using the RothC model to determine the effects of cover crop and tillage system. The model used a customized version RothC improved model (Shirato, 2006) adjusted to Andisols. A long-term field experiment has been conducted in progress at the Field Science Center of Ibaraki University since 2002. This experiment combined three cover crop managements (fallow, hairy vetch and rye), three tillage systems (no-till, plowing and rotary) and two N fertilizations (100 kgN/ha for upland rice 20 kgN/ha for soybean, no fertilize) with four replications. Soil samples were collected at each depth (0-2.5, 2.5-7.5, 7.5-15 and 15-30 cm) twice a year. The RothC improved model has been applied to predict soil carbon storage based on the field data. The results of comparison between the actual data and the predictions of soil carbon storage indicate the model’s predictions were acceptable for notill and rotary not for plow system. Input organic matter was increased to incorporate in cover crop treatment. The model prediction suggests that rye cover crop will increase in soil carbon storage, and hairy vetch cover crop will be stable. On the other hands winter fallow will decrease soil carbon because there is very little plant residue incorporation in a year. These results strongly suggest that an appropriate farming system is necessary to maintain or improve soil carbon storage.
