Sisomphone Southavong, Preston T R and Ngo Van Man 2011 Effect of Soil Amender (Biochar or Charcoal) and Biodigester Effluent on Growth of Water Spinach. Workshop on Reducing Greenhouse Gas Emissions from Livestock and Soils (Editors: Reg Preston and Sisomphone Southavong). National Institute of Animal Science, Hanoi, 14-15 November 2011. httm://www.mekarn.org/workshops/GHG-CC/sisom.htm