No-Tillage and Manure Effects on Soil Erosion, Carbon and Nitrogen Dynamics in Sugarcane Field in Okinawa, Japan.

Soil erosion and nutrients runoff have led to agricultural and environmental problems throughout the world. Not only on-site effect of decreasing soil fertility, but also various ecosystems have been damaged due to oversupply of sediment and nutrients from agricultural zones. Therefore effective soil management which can reduce sediment yield and nutrients runoff in the farmland are necessary. In this study, a field observation was conducted to confirm the effect of no-tillage farming and manure application. Study field was a sugarcane field in Okinawa, Japan. The field was divided into four plots, conventional tillage or no-tillage with fertilizer or manure application. In these plots, sediment, organic carbon, and nitrogen surface runoff and nitrogen leaching were measured. We also measured CO₂ efflux from soil surface and soil organic carbon content to confirm the carbon dynamics. Sediment runoff at the no-tillage plot was quite smaller than the conventional tillage plot. POC runoff showed the same trend with the sediment runoff. CO₂ emission at the no-tillage plot was also smaller due to lower surface soil temperature because surface soil was covered with residue at the no-tillage plot. Soil organic carbon content was increased or maintained under the no-tillage and/or manure condition. The leaching of nitrate nitrogen was greater than the nitrogen surface runoff. The leaching of nitrogen at the no-tillage plot was smaller than the conventional tillage plot. There was not obvious difference about the leaching between fertilizer and manure. These observed results support the combination of no-tillage and manure application farming is one of the best management practices for reducing sediment and nitrogen runoff and for storage of organic carbon in soil.