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Soil is a limited resource. Using soils must be considered to maintain sustainable. Soil management may affect both soil properties and crop yield. The purpose of the research is to study the effect of land use patterns and topography on soil fertility in Thung Yai watershed, Songkhla province. Land use patterns were as follows, (1) the para rubber plantation area with slope range 0-8 %, (2) the para rubber plantation area with slope range 8-16 %, (3) the para rubber agroforest area with slope range 8-16 %, (4) the para rubber agroforest area with slope range 16-30 %, (5) the orchard plantation area with slope range 16-30 %, and (6) the forest area with slope range more than 30 %. Soil sampling was taken from topsoil 0-15 cm. All the soil samples were analyzed for some important chemical properties in the soil. The obtained soil information was used to evaluate soil fertility status. The result reveals that soil texture of all the topsoils was sandy loam. Soil pH varied from strongly acid to very strongly acid (5.35-5.03, soil : water = 1 : 5), organic matter (OM) as 3.44-21.16 g/kg, available P as 2.20-5.40 mg/kg, exchangeable K as 78.00-152.10 cmol/kg, CEC as 3.16-11.58 cmol/kg, and %BS as 10.41-36.20. The soil fertility status assessment in Thung Yai watershed shows that the para rubber plantation area with slope range 8-16 % has a low level, while other land use patterns have moderate soil fertility status level.
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