Obalum, S. E., J. Oppong, J. C. Nwite, Y. Watanabe, M. M. Buri, C. A. Igwe, and T. Wakatsuki. 2012. “Long-Term Effects of Lowland Sawah System on Soil Physicochemical Properties and Rice Yield in Ashanti Region of Ghana”. Spanish Journal of Agricultural Research 10 (3), 838-48. https://doi.org/10.5424/sjar/2012103-566-11.