8.1.5. Humidity retention

The physical-chemical dynamics of this soil is controlled by the presence of allophane, caused by the alteration of volcanic ash; this component has an affinity for humus, and establishes

horizon (cm)

(0–5 cm) Oe

(5– 65 cm) A

(65– 80 cm) C

(80– 105 cm) Bb

(105– X cm) C1

Main characteristics

boundary

structure (loose)

clear and wavy boundary

Mattress of live and dead roots

A dark brown (7.5YR 3/2); sandy loam texture; structure: large, thin, and weak angular blocks; friable wet consistency; consistency in wet conditions: not plastic and not sticky; abundant macropores; abundant medium, thin, and thick roots; little macroorganism activity, positive reaction to NaF, pH 5.3; diffuse and wavy

Yellowish brown color (10YR 3/4); Tuff: without

Dark brown color (10YR 4/3); sandy texture; fine granular structure; weak, loose, moist consistency; consistency in wet condition: not plastic and not sticky; abundant macropores; scanty roots; positive reaction to NaF, pH 4.7;

Dark olive brown (2.5Y 3/3); sandy texture; without structure; coarse grain not consistent

The humus-allophane interaction gives the soil particular properties such as high porosity, high water retention, and high capacity for nutrient retention (CICA); however, most of the electrical charge is not available to retain nutrients at the soil pH; this load only appears when the pH rises, such as occurs when the floors are limed. The load, which depends on the pH, is called variable load (CICV) and is the one that is present in this soil. A feature that distinguishes soils of volcanic origin, due to the presence of allophane, is the low availability of phosphorus; however, the analytical results of this soil show average contents of this element,

The dark brown color of these soils is generated by the accumulation and high levels of MO in the first horizon resting on clear materials. The texture is sandy loam, while the laboratory

with it strong bonds that result in the accumulation of organic matter in the soil.

undoubtedly due to the presence of apatite in volcanic materials.

VS24262 Depth

100 Soil Moisture

8.1.4. Physical characteristics

Table 2. Profile no: VS24262 internal profile features.

Figure 1 illustrates the moisture contents (%) and the soil moisture tension (Bars), information that indicates that as the soil tension increases, the moisture content decreases and what is related in this measure when the tension is zero (0) the ground is at the point of saturation.

Such soil water behavior is evident for both horizons: A and Bb. The humidity retention is high at different stresses as a probable result of the presence of allophane and high levels of organic matter.


Table 4. Chemical properties VS24262.

8.1.5.1. Humidity threat

dense forest mainland).

626,831 m

moisture threat.

3

; this in sum equals 3,667,841 m

This measure is considered to be of great value in the study and in correspondence with the studied problematic as it is the mass removal of the soils; its meaning allows us to understand the capacity of these soils to retain water and to increase in volumetric and gravimetric terms the natural condition of the soil, that is, its volume of water content and its corresponding weight. The analysis starts from the consideration of the apparent density expressed in dry weight (1.05 and 1.01) and that allows to calculate the weight of a surface of soil (1 hectare). Determining its saturation point (80.35 and 41.38%) allows to quantify the water that can hold the soil in each horizon and that correspond to values of 3,041,010 and

Figure 1. Mosaic of soil profiles in pits for different cover systems and at different altitude ranges in volcanic soils in Colombia (secondary vegetation; pasture mosaic with natural spaces; weeds; weedy grasses; clean pastures; and high,

The Humidity of the Volcanic Soils and Their Impact on the Processes of Mass Removal in Colombia

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103

By virtue of the above findings, water or humidity threat allows us to suggest the potentiality of moisture retention at the time of sampling and the determination of the saturation

<sup>3</sup> of water per hectare in the investigation of

The Humidity of the Volcanic Soils and Their Impact on the Processes of Mass Removal in Colombia http://dx.doi.org/10.5772/intechopen.80399 103

Figure 1. Mosaic of soil profiles in pits for different cover systems and at different altitude ranges in volcanic soils in Colombia (secondary vegetation; pasture mosaic with natural spaces; weeds; weedy grasses; clean pastures; and high, dense forest mainland).

#### 8.1.5.1. Humidity threat

Id.

Height

pH Aluminum

Nitrogen

O.M cold

Phosphorus

Potassium

Calcium

Magnesium

Sodium

Sulfur

102 Soil Moisture

(cmol(+)/kg)

(mg/kg)

(cmol(+)/kg)

(cmol(+)/kg)

(cmol(+)/kg)

(mg/kg)

sample

SV24262-

2444

 5.3

A

SV24262-

2444

 4.7 0.2

0.54

 14.36

104

0.06

0.93

0.09

0.235

 8.32

Bb

Table 4.

Chemical properties VS24262.

(masl)

(cmol(+)/kg)

(%)

0.59

 16.46

22

0.05

1.43

0.14

0.319

 16.67

weather (%)

> This measure is considered to be of great value in the study and in correspondence with the studied problematic as it is the mass removal of the soils; its meaning allows us to understand the capacity of these soils to retain water and to increase in volumetric and gravimetric terms the natural condition of the soil, that is, its volume of water content and its corresponding weight. The analysis starts from the consideration of the apparent density expressed in dry weight (1.05 and 1.01) and that allows to calculate the weight of a surface of soil (1 hectare). Determining its saturation point (80.35 and 41.38%) allows to quantify the water that can hold the soil in each horizon and that correspond to values of 3,041,010 and 626,831 m<sup>3</sup> ; this in sum equals 3,667,841 m<sup>3</sup> of water per hectare in the investigation of moisture threat.

> By virtue of the above findings, water or humidity threat allows us to suggest the potentiality of moisture retention at the time of sampling and the determination of the saturation

9. Conclusions

the two.

Author details

References

the Andes; 1993

William Chavarriaga Montoya

University, Manizales, Caldas, Colombia

relative threat by mass movements.

the OM content and the degree of soil cover.

The high humidity retention or high levels of saturation at the different tensions were confirmed as fundamental detonators of the mass removal of the studied soils, as a consequence of the instability of soil aggregates to water, high porosity, and high hydraulic conductivity and their relation with the mineralogy of these soils of volcanic origin, the high rainfall regimes of the region, the altitudinal position, slopes or inclination of the terrain that condition a high

The Humidity of the Volcanic Soils and Their Impact on the Processes of Mass Removal in Colombia

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105

Inter-variable correlations were found that facilitate explaining the phenomenon of mass removal in the area, among them some of significant order referring to the association between the variable "Humidity-Threat" and the organic matter for all the coverages analyzed. There is

There is a significant and positive relationship between the stability of the soil structure with

It is possible to explain the variations in the stability of aggregates, by the combined action of OM content and the degree of soil cover; however, this last variable is the most significant of

The management of soils against mass removal should consult systems that involve minimal disturbance of the soil and the greatest possible protection through forest coverings, as ways to promote a stable structure and, consequently, promote the resistance of soils to water erosion.

a negative effect of intervention on forests on the stability of soil aggregates.

Address all correspondence to: william.chavarriaga@caldas.edu.co

face features of ashparticles. Nature. 1999;401(6754):688-690

Department of Rural and Natural Resources, Faculty of Agricultural Sciences, Caldas

[1] Arango JD. General characteristics and geotechnical behavior of volcanic ash in the Zona del Antiguo Caldas [master's thesis in Civil Engineering]. Bogotá, Colombia: University of

[2] Büttner R, Dellino P, Zinranowski B. Identifying magma-water interaction from the sur-

point for a soil that was not in rainy weather conditions. Such values constitute a powerful argument to estimate the extraordinary erosive capacity of the soil water storage and retention factor in the study and the increase of the soil susceptibility to the mass removals the pending factor is added to this, mountain relief, gravity, geomorphology, lack of protection of the soil of the natural or wooded vegetation cover and poor pasture management due to overgrazing.

In other words, the difference between the water retained to saturation and field capacity is the water that intervenes mainly in the phenomena of mass removals. Another implication is that: 3667.8 tons of water migrate from horizon A, toward C constituted by pyroclastics; there increases the speed of infiltration and in contact of moisture with the buried soil or horizon Bb the water hangs (drain hanging) thanks to the slope of the slope and the horizon becomes a plane of sliding.

The dispersion coefficients of 12.38% on average for the sampled horizons qualify the soil as stable. The variables DPM (weighted average diameter) with average value (5.22) as well as the state of aggregation (95.92%) allow one to assess the soil as very stable or in its defect state of very high aggregation (>90%). Conversely, the stability index < 1.0 warns of the presence of large aggregates that determine and indicate instability with aggregates greater than 5 mm, as confirmed by the DPM (5.22), and susceptibility to soil mass removals. Stability indexes greater than 1 would be ideal and would indicate predominance of intermediate aggregates well distributed in the soil. The usable humidity (12.8%) however for the soil is an average value of available water or useful water or vegetable water supply.

On the other hand, the saturated hydraulic conductivity (Ks) determined in the laboratory with values of 145.51 and 138.9 mm/h allows to identify the speed with which the water permeates the soil; therefore, it is a measure of the permeability as an intrinsic character of the soil. Such values indicate a very fast hydraulic conductivity and/or permeability.
