limestone (60 % of the area), while the eastern part consists of claystone
(39 % of the area). The scientific soil map was based on 22 described and
analyzed soil profiles, plus 341 auger sampling. The WRB classification of soil
types found Alisols, Acrisols and Cambisols, covering 69 %, 21 % and 9 % of
the mapped area respectively.
Farmers distinguished four main soil types, namely Black, Red, Orange, and
Yellow soils. After further interviews and updates a final soil map was compiled
using the most important soil classes of Black, Hard Red and Soft Red soils,
Fig. 2.11 (a) Petrographic map of the Bor Krai research area in north-west Thailand, (b) the local
soil map, and (c) a soil map according to the WRB classification, all at the soil group level
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K. Stahr et al.