PRA (Chambers 1992), including: (1) semi-structured interviews, (2) group
discussions and (3) participatory mapping, all involving experienced local farmers.
Workshops were conducted across hamlets and communes in preparation for the
soil surveys (Clemens et al. 2010; Schuler et al. 2006; Schuler 2008). In 6 hamlets
in north-west Vietnam, those where scientific soil information already existed,
Hagel (2011) collected local soil information in order to compare local and scientific soil assessments, and to reveal knowledge flows within the hamlet and learn
about the impact of developments over recent decades, as well as the effects of land
use intensification on soils. To do this, Hagel split the farmers into two groups;
those below or above 45 years-old. Scientific soil knowledge was evaluated during
several surveys, with soil profiles described and classified according to FAO
guidelines (FAO 2006; IUSS Working Group WRB 2006). Chemical and physical
soil properties, as well their evaluation, were determined or estimated in accordance
with Schlichting et al. (1995) and FAO guidelines (FAO 2006). For the characterization of soil fertility stocks, total nitrogen content (Nt, in kg m
À2 ) and available
bases (S-value, in mol c m
À2 ) in the effective rooting space (ERS) were also
calculated according to FAO guidelines (FAO 2006).
2.4.2 Criteria for Local Soil Classification
In all the study villages, except Ban Huon, farmers classified soil types mainly on
the basis of color or color combinations (black, red, yellow, yellow-red, yellowblack), often combined with textural features (e.g., stony, sandy, and less often
clayey) or hardness, but seldom based on a soil quality assessment (poor or good)
(Table 2.5). The additional criteria identified depended on the different
environments. The use of color as the first criterion is very common among local
soil classifications (cf., Ettema 1994; Talawar and Rhoades 1998), with the comprehensive study on ethnopedology carried out by Barrera-Bassols and Zink (2003)
concluding that all the reviewed local soil classifications used color as a parameter,
because it is the most obvious and easily distinguishable soil property.
Using a quotient based on the number of criteria used to classify soils (1–9) and
the number of soil types in the villages (6–12) to measure the degree of differentiation, it can be seen that the Hmong in Vietnam used more attributes than the Thais
or the other ethnic groups in Thailand. In the ethnic Thai commune of Chieng Khoi
in Vietnam, the degree of differentiation was also high, probably due to the great
diversity of parent materials. In all the villages it was possible to collect information
about the topographic position of each soil, as well as the properties of each soil and
information about the level of susceptibility to hazards (an example is shown in
Table 2.6). Assessing soil quality changes over time was only possible after
lengthier discussions with the villagers and only after asking site specific questions.
The results showed that most sites have undergone soil quality changes recently,
especially soils in the higher and foot slope positions, which have been affected by
high levels of erosion and sedimentation.
66
K. Stahr et al.
discussions and (3) participatory mapping, all involving experienced local farmers.
Workshops were conducted across hamlets and communes in preparation for the
soil surveys (Clemens et al. 2010; Schuler et al. 2006; Schuler 2008). In 6 hamlets
in north-west Vietnam, those where scientific soil information already existed,
Hagel (2011) collected local soil information in order to compare local and scientific soil assessments, and to reveal knowledge flows within the hamlet and learn
about the impact of developments over recent decades, as well as the effects of land
use intensification on soils. To do this, Hagel split the farmers into two groups;
those below or above 45 years-old. Scientific soil knowledge was evaluated during
several surveys, with soil profiles described and classified according to FAO
guidelines (FAO 2006; IUSS Working Group WRB 2006). Chemical and physical
soil properties, as well their evaluation, were determined or estimated in accordance
with Schlichting et al. (1995) and FAO guidelines (FAO 2006). For the characterization of soil fertility stocks, total nitrogen content (Nt, in kg m
À2 ) and available
bases (S-value, in mol c m
À2 ) in the effective rooting space (ERS) were also
calculated according to FAO guidelines (FAO 2006).
2.4.2 Criteria for Local Soil Classification
In all the study villages, except Ban Huon, farmers classified soil types mainly on
the basis of color or color combinations (black, red, yellow, yellow-red, yellowblack), often combined with textural features (e.g., stony, sandy, and less often
clayey) or hardness, but seldom based on a soil quality assessment (poor or good)
(Table 2.5). The additional criteria identified depended on the different
environments. The use of color as the first criterion is very common among local
soil classifications (cf., Ettema 1994; Talawar and Rhoades 1998), with the comprehensive study on ethnopedology carried out by Barrera-Bassols and Zink (2003)
concluding that all the reviewed local soil classifications used color as a parameter,
because it is the most obvious and easily distinguishable soil property.
Using a quotient based on the number of criteria used to classify soils (1–9) and
the number of soil types in the villages (6–12) to measure the degree of differentiation, it can be seen that the Hmong in Vietnam used more attributes than the Thais
or the other ethnic groups in Thailand. In the ethnic Thai commune of Chieng Khoi
in Vietnam, the degree of differentiation was also high, probably due to the great
diversity of parent materials. In all the villages it was possible to collect information
about the topographic position of each soil, as well as the properties of each soil and
information about the level of susceptibility to hazards (an example is shown in
Table 2.6). Assessing soil quality changes over time was only possible after
lengthier discussions with the villagers and only after asking site specific questions.
The results showed that most sites have undergone soil quality changes recently,
especially soils in the higher and foot slope positions, which have been affected by
high levels of erosion and sedimentation.
66
K. Stahr et al.