Effects of tillage practices combined with mucuna fallow on soil erosion and water dynamics on Ishigaki Island, Japan

Abstract

This study was conducted on a sloping field at the Japan International Research Center for Agricultural Sciences, Okinawa Subtropical Station, Ishigaki Island, Okinawa Prefecture, Japan, to evaluate the effects of zero tillage farming combined with mucuna fallow as a cover crop on soil erosion and water dynamics. Two fallow systems (natural and mucuna) in combination with two soil tillage treatments (zero tillage and conventional tillage) were imposed on three sloping fields (2.0°, 3.5° and 5.0°). A sorghum crop (Sorghum bicolor (L) moench) was planted after the soil tillage treatment. Soil loss for zero tillage farming combined with mucuna fallow was equivalent to only 3% of that for the conventional tillage farming with natural fallow. Runoff water was also reduced by between 74% and 77% when compared with the conventional tillage system with natural fallow. These results indicate that zero tillage with mucuna fallow is a very effective measure for the control of soil erosion and water runoff. Moreover, this farming system improved water infiltration during both the fallow and the sorghum cropping periods. For the zero tillage plot, water loss as deep percolation increased 1.6-fold compared with that for the conventional farming under heavy rainfall conditions. It is expected that under less rainfall areas or seasons, the effects of zero tillage farming combined with the mucuna cover crop may be more pronounced on water runoff control and, therefore, may greatly improve soil water conditions.

Key words:

• cover crop
• deep percolation
• soil erosion
• water runoff
• zero tillage

ACKNOWLEDGMENTS

The authors wish to thank Dr K. Ozawa, Head of the Island Environment Management Laboratory (JIRCAS–Okinawa) for providing comprehensive support. Our thanks also go to the field and laboratory staff, Mr K. Yamato, Mr H. Ikema, Mr Y. Shikina and Mrs M. Shimabukuro. Finally, we acknowledge Dr R. Zougmoré, our fellow researcher from Burkina Faso, for corrections and advice on earlier versions of the manuscript.

Notes

Present address: Soil Research Institute, Academy Post Office, Kwadaso-Kumasi Ghana