in respect of fertilizer use (for maize), with decreasing amounts used for Black, Red
and Yellow Soils.
Comparing farmers’ soil quality and soil fertility assessments with the scientific
data (see Fig. 2.10) often showed a match. At the bottom of the slopes, where soils
consist of sandy sediments; however, soil quality and infiltration was overestimated
by farmers and erosion on slopes was understated. In the case of Poor Red Soils
(catena 2 – upper part of the hill), farmers’ estimations based on their experience
were confirmed by soil analysis. The case of Black Soils estimated as good (fertile)
could be explained by the fact that high soil organic matter was associated with a
dark topsoil color by the farmers. The close correlation between soil organic matter
content (kg m
À2 ) and the sum of total nitrogen, S-value and available phosphorus in
Chieng Khoi (r
2
¼ 0.969), proved the high level of interrelationship between soil
organic matter, associated soil color and soil fertility, even if the calculated
regression line is only valid locally.
At the Bor Krai research site, Pang Ma Pha district, Mae Hong Son province
in north-west Thailand, both a local soil map and a scientific soil map were
created (Fig. 2.11b, c). The higher western parts of the area consist of Permian
Fig. 2.10 Summary results for soil profiles in Chieng Khoi, north-west Vietnam, with (a) cross
section of catenas 1 and 2, and sites 3 and 4, with recent land use and slope position: C cassava,
Mz maize, Ma mango, Fa fallow, Fo forest, P pines, T teak, HG Home garden, T top, uS upper
slope, mS middle slope, lS lower slope, bS basal slope, (b) the results based on local knowledge,
and (c) the results of a scientific investigation into soil quality, erosion and sedimentation hazards,
plus infiltration
2 Beyond the Horizons: Challenges and Prospects for Soil Science and Soil. . .
73
and Yellow Soils.
Comparing farmers’ soil quality and soil fertility assessments with the scientific
data (see Fig. 2.10) often showed a match. At the bottom of the slopes, where soils
consist of sandy sediments; however, soil quality and infiltration was overestimated
by farmers and erosion on slopes was understated. In the case of Poor Red Soils
(catena 2 – upper part of the hill), farmers’ estimations based on their experience
were confirmed by soil analysis. The case of Black Soils estimated as good (fertile)
could be explained by the fact that high soil organic matter was associated with a
dark topsoil color by the farmers. The close correlation between soil organic matter
content (kg m
À2 ) and the sum of total nitrogen, S-value and available phosphorus in
Chieng Khoi (r
2
¼ 0.969), proved the high level of interrelationship between soil
organic matter, associated soil color and soil fertility, even if the calculated
regression line is only valid locally.
At the Bor Krai research site, Pang Ma Pha district, Mae Hong Son province
in north-west Thailand, both a local soil map and a scientific soil map were
created (Fig. 2.11b, c). The higher western parts of the area consist of Permian
Fig. 2.10 Summary results for soil profiles in Chieng Khoi, north-west Vietnam, with (a) cross
section of catenas 1 and 2, and sites 3 and 4, with recent land use and slope position: C cassava,
Mz maize, Ma mango, Fa fallow, Fo forest, P pines, T teak, HG Home garden, T top, uS upper
slope, mS middle slope, lS lower slope, bS basal slope, (b) the results based on local knowledge,
and (c) the results of a scientific investigation into soil quality, erosion and sedimentation hazards,
plus infiltration
2 Beyond the Horizons: Challenges and Prospects for Soil Science and Soil. . .
73