According to the United Nations soil system classification (fao-unesco system 1989), the main soil types in Laos are sandy soil, alluvial soil, gley soil, thin layer soil, coarse bone soil, rudiment soil, high activity strong acid soil, low activity strong acid soil, low activity leaching soil, saline soil, alkaline soil and high activity leaching soil. Among them, the distribution area of low activity strong acid soil is the largest, accounting for 48.94% of the land area of Laos; the second is high activity strong acid soil, accounting for 18.77%; the third is high activity leaching soil and rudimentary soil, accounting for 12.63% and 9.94% respectively.