Biochar amendment techniques for upland rice production in Northern Laos. 1. Soil physical properties, leaf SPAD and grain yield - Asai, Hidetoshi; Samson, Benjamin K.; Haefele, Stephan M.; Songyikhangsuthor, Khamdok; Homma, Koki; Kiyono, Yoshiyuki; Inoue, Yoshio; Shiraiwa, Tatsuhiko; Horie, Takeshi (Elsevier, 2009)