The major soil types in the study area are Luvisols (73.23%) and
Lithosol (13.86 %) with 2:1 minerals that expand (swell) when wet, and shrink when dry, i.e., plastic characteristic.
The substrate is an acidicline to acidiphile superficial
lithosol, sandy gravel with a silty-sandy interstitial matrix.
99[grados]37' W, foret tropicale caducifoliee,
lithosol sur lutites, 3.X.1994, J.-N.
Soils are a
lithosol of limestone origin, with moderate to steep slopes.
Soil order (2) N Depth TOC Clay Silt Total P cm mg [kg.sup.-1] g [kg.sup.-1] Vertisol (1%) 16 13.1 12.3 374 238 368 Cambisol (4%) 13 12.4 12.2 295 212 301 Luvisol (13%) 47 13.7 11.8 176 258 235
Lithosol (19%) 45 17.6 10.4 132 250 239 Latosol (21%) 41 15.6 9.7 250 130 173 Argisol (15%) 90 15.3 8.9 147 157 167 Planosol (4%) 68 18.2 7.4 105 188 162 Regolithic 20 16.5 4.9 37 105 99 neosol (4%) Weighted 340 15.9 9.3 163 189 196 average (3) 1) Source: Jacomine et al.
When
Lithosol soils are dominant in a district, farmers tend to choose mixed rainfed farms more often but when Vertisol soils are dominant, farmers choose mixed irrigated farms less often.
Lithosol terrain is composed of rocky soils overlaying basalt bedrock, sparse vegetation and reduced growth forms of the dominant plant species: stiff sage (Artemisia rigida) and thyme leaf buckwheat (Eriogonum thymoides).
Local soils have been classified as
lithosol, and vegetation as forest fragments dominated by pine and oak (INEGI, 2000).
Such steps are made of a small outcrop of densely fissured hard rock, a small cliff as tall as the hard rock is thick, and a fiat area with shallow, stony Brown
Lithosol (Dan et al., 1975; Danin et al., 1975) in place of the soft rock layer.
Approximately 70% of the ground surface is unvegetated; the soil is a
lithosol, pH 6.9-8.0, developed over limestone, and organic matter is present mostly under Dryas mats.
The parent material of the soil along the slopes is of Eolian origin enriched by weathering of the parent rock, The soil is classified as a Brown
Lithosol.