© The Authors, 2025, Published by the Universidad del Zulia*Corresponding author: ana.gonzalez2@unipamplona.edu.co
Keywords:
Land use
Multivariate analysis
Soil degradation
Soil quality indicators
Soil characteristics under dierent crops in mountain environments in Pamplona, Norte de
Santander
Características edácas bajo diferentes cultivos en ambientes de montaña en Pamplona, Norte de
Santander, Colombia
Características do solo sob diferentes culturas em ambientes de montanha em Pamplona, Norte de
Santander, Colômbia
Ana Francisca González-Pedraza
1*
Steve Sandoval
2
Juan Carlos Escalante
3
Rev. Fac. Agron. (LUZ). 2025, 42(4): e254248
ISSN 2477-9407
DOI: https://doi.org/10.47280/RevFacAgron(LUZ).v42.n4.V
Crop production
Associate editor: Dr. Jorge Vilchez-Perozo
University of Zulia, Faculty of Agronomy
Bolivarian Republic of Venezuela
1
Facultad de Ciencias Agrarias, Universidad de Pamplona,
Pamplona, Norte de Santander, Colombia, Código postal:
543050.
2
Ingeniero Agrónomo independiente.
3
Tecnológico de Antioquia, Medellín, Colombia, Código
postal: 050036.
Received: 08-08-2025
Accepted: 26-09-2025
Published: 08-10-2025
Abstract
Agricultural intensication in mountain regions can alter soil
quality and compromise its ecosystem functionality. Accordingly,
this study evaluated the inuence of land use on the physical,
chemical, and biological properties of soils in agricultural and
forest systems located in the Monteadentro district, municipality of
Pamplona, Norte de Santander. During the 2019 rainy season, ve
land-use types were analyzed: strawberry, pea, tree tomato, pasture,
and natural forest. In 1,000 m² plots, composite soil samples were
collected at 0–10 cm depth to determine texture, volumetric water
content (VWC), bulk density (BD), pH, electrical conductivity
(EC), total organic carbon (TOC), and soil basal respiration (SBR).
Both univariate and multivariate statistical analyses were applied
(ANOVA, Kruskal–Wallis, correlations, and PCA). The results
showed that land use signicantly aected soil properties. Forest
soils exhibited more favorable conservation conditions, with higher
TOC content (2.8 %) and lower BD (0.7 g.cm
-3
), in contrast to
agricultural soils, which presented higher BD, lower VWC and
TOC, and higher SBR, likely associated with more labile organic
substrates and organic matter degradation. Principal Component
Analysis identied two main gradients: a physical–textural gradient
(clay, VWC, EC, sand) and a biochemical–structural gradient (silt,
pH, TOC, SBR), which dierentiated land-use systems according
to their degree of disturbance. These ndings emphasize the need
to implement conservation-oriented management strategies and
regular soil monitoring in order to preserve soil functionality in
mountain ecosystems.
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Rev. Fac. Agron. (LUZ). 2025, 42(4): e254248 October-December. ISSN 2477-9409.
2-7 |
Resumen
La intensicación agrícola en zonas de montaña puede alterar
la calidad del suelo y comprometer su funcionalidad ecosistémica.
En tal sentido, este estudio evaluó la inuencia del uso del suelo
sobre las propiedades físicas, químicas y biológicas en sistemas
agrícolas y forestales de montaña en la vereda Monteadentro,
municipio de Pamplona, Norte de Santander. Durante el período
de lluvias de 2019 se analizaron cinco tipos de utilización: fresa,
arveja, tomate de árbol, pasto y bosque natural. En parcelas de
1000 m² se recolectaron muestras compuestas de suelo a 0-10 cm
para determinar textura, humedad volumétrica (HV), densidad
aparente (Da), pH, conductividad eléctrica (CE), carbono orgánico
total (CO) y respiración basal (RB). Se aplicaron análisis estadísticos
univariados y multivariados (ANOVA, Kruskal-Wallis, correlaciones
y ACP). Los resultados evidenciaron que el tipo de utilización afectó
signicativamente las propiedades edácas. Los suelos bajo bosque
presentaron condiciones más favorables de conservación, con mayor
contenido de CO (2,8 %) y menor Da (0,7 g.cm
-3
), en contraste con
los suelos agrícolas, donde se registró mayor Da, menor HV y CO, y
mayor RB, posiblemente asociada a sustratos orgánicos más lábiles
y degradación de la materia orgánica. El análisis de componentes
principales permitió identicar dos gradientes: uno físico-textural
(arcilla, HV, CE, arena) y otro bioquímico físico (limo, pH, CO,
RB), los cuales diferenciaron los sistemas de uso según su grado
de perturbación. Estos resultados sugieren la necesidad de adoptar
estrategias de manejo conservacionista y monitoreo regular del suelo
para preservar su funcionalidad en ecosistemas de montaña.
Palabras clave: usos del suelo, análisis multivariado, degradación
edáca, indicadores de calidad del suelo.
Resumo
A intensicação agrícola em áreas de montanha pode alterar a
qualidade do solo e comprometer sua funcionalidade ecossistêmica.
Nesse sentido, este estudo avaliou a inuência do uso do solo sobre
as propriedades físicas, químicas e biológicas em sistemas agrícolas
e orestais de montanha na vereda Monteadentro, município de
Pamplona, Norte de Santander. Durante o período chuvoso de 2019
foram analisados cinco tipos de uso: morango, ervilha, tomate de
árvore, pastagem e oresta nativa. Em parcelas de 1.000 m² foram
coletadas amostras compostas de solo na profundidade de 0–10
cm para determinar textura, umidade volumétrica (UV), densidade
aparente (DA), pH, condutividade elétrica (CE), carbono orgânico
total (COT) e respiração basal (RB). Foram aplicadas análises
estatísticas univariadas e multivariadas (ANOVA, Kruskal–Wallis,
correlações e ACP). Os resultados evidenciaram que o tipo de uso
afetou signicativamente as propriedades edácas. Os solos sob
oresta apresentaram condições mais favoráveis de conservação,
com maior teor de COT (2,8 %) e menor DA (0,7 g.cm⁻³), em
contraste com os solos agrícolas, que apresentaram maior DA,
menor UV e COT, e maior RB, possivelmente associada a substratos
orgânicos mais lábeis e à degradação da matéria orgânica. A Análise
de Componentes Principais permitiu identicar dois gradientes: um
físico-textural (argila, UV, CE, areia) e outro bioquímico-físico (silte,
pH, COT, RB), os quais diferenciaram os sistemas de uso conforme
seu grau de perturbação. Esses resultados sugerem a necessidade de
adotar estratégias de manejo conservacionista e de monitoramento
regular do solo para preservar sua funcionalidade em ecossistemas
de montanha.
Palavras-chave: uso do solo, análise multivariada, degradação do
solo, indicadores de qualidade do solo.
Introduction
The mountain environments of the Andean regions of Colombia
exhibit distinctive edaphoclimatic conditions that favor diversied
agricultural systems, which are fundamental to ensuring food security
and promoting rural development. At elevations ranging from 2,000
to 3,600 m.a.s.l., small-scale family farming predominates, centered
on crops such as strawberry (Fragaria × ananassa Duchesne ex
Rozier), tree tomato (Solanum betaceum Cav.), and pea (Pisum
sativum L.), in addition to livestock systems sustained by Kikuyu
grass (Cenchrus clandestinus (Hochst. ex Chiov.) Morrone). In the
municipality of Pamplona, Norte de Santander, these systems play
a critical role in sustaining rural employment, securing household
income, and maintaining the continuity of the local agrarian fabric
(Villamizar et al., 2024).
However, inadequate practices, such as the intensive use of
agrochemicals and the limited adoption of conservation measures,
have triggered soil degradation processes. Local studies report high
acidity (pH 3.5–5.5), low biological activity, and nutrient deciencies
(P, Mg, S, Zn, and B), particularly in conventional agricultural
systems (Visconti-Moreno & Valenzuela-Balcázar, 2019), thereby
compromising productive sustainability (Rodríguez et al., 2024;
Flórez & Ochoa, 2022).
Considering these conditions, it is necessary to compare land-
use systems in order to determine their eects on soil structure,
fertility, and biological functioning. Multivariate characterization
based on physical, chemical, and biological indicators provides a
comprehensive framework for assessing soil quality and guiding
sustainable management strategies (Cruz et al., 2022). In this context,
the present study aimed to compare the physical, chemical, and
biological properties of soils under strawberry, tree tomato, pea, and
pasture cultivation with those of a natural forest in the Monteadentro
district (Pamplona), with the objective of generating technical
information to support the sustainability of mountain agroecosystems.
Materials and methods
Study area
The research was conducted in the Monteadentro district
(Pamplona, Norte de Santander), within the cold thermal belt (2,000–
3,000 m.a.s.l.) and the lower montane humid forest life zone. The
climate is classied as oceanic (Cfb), with a mean annual temperature
of 14.4 °C and an average annual precipitation of 1,863 mm,
concentrated mainly in April and October (Climate-Data.org, 2024).
The topography is characterized by steep slopes (>20 %), which
increase the risk of erosion (Villamizar et al., 2024; IGAC, 2012).
Inceptisols derived from the Durania Granite predominate, with a
sandy loam texture, slightly acidic pH (~6.0), and medium organic
carbon content (2.46 %). In agricultural areas, soil acidity increases
as a result of the intensive use of highly acidifying nitrogen fertilizers
(González-Pedraza et al., 2023; Visconti-Moreno & Valenzuela-
Balcázar, 2019; IGAC, 2012).
Research design
Five land-cover types were evaluated—strawberry (Fragaria ×
ananassa Duchesne ex Rozier), pea (Pisum sativum L.), tree tomato
(Solanum betaceum Cav.), kikuyu grass (Cenchrus clandestinus
(Hochst. ex Chiov.) Morrone), and natural forest—during the rainy
season of May 2019 in the Monteadentro district, municipality of
Pamplona (Norte de Santander), located between 2,506 and 2,533
m.a.s.l. The plots, situated in relatively close proximity (500–1,000
This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
González-Pedraza et al. Rev. Fac. Agron. (LUZ). 2025, 42(4): e254248
3-7 |
therefore analyzed using the Kruskal–Wallis test followed by Dunn’s
test with Bonferroni correction. Pearson correlation coecients were
calculated among continuous variables, and a Principal Component
Analysis (PCA) was performed on standardized data (z-scores),
retaining components with eigenvalues > 1 according to Kaiser’s
criterion. To facilitate interpretation, land-use centroids were
represented by the mean of their factorial coordinates (F1 and F2), so
that each system was summarized in a single central point, enabling
comparison and the identication of edaphic gradients. All statistical
analyses were conducted in R (version 4.3.1) (R Core Team, 2023).
Table 1. Methods used for the analysis of soil physical, chemical,
and biological properties.
Variable Method
Author /
Reference
Volumetric Water
Content (VWC)
Bouyoucos hydrometer
Gee & Bauder
(1986)
Soil Bulk Density (BD) Field measurement Gardner (1986)
pH / Electrical
Conductivity (EC)
Uhland core method
Blake & Hartge
(1986)
Total Organic Carbon
(TOC)
Potentiometric determination
in a 1:2 soil-to-water
suspension
Mclean (1982)
Soil Basal Respiration
(SBR)
Loss on ignition (LOI, 450 °C)
Westman et al.
(2006)
Volumetric Water
Content (VWC)
Static incubation with CO₂
titration
Alef & Nannipieri
(1995)
Results and discussion
Descriptive statistics of soil properties
Based on the exploratory analysis of soil variables (Table 2),
marked heterogeneity was observed across the dierent land uses.
The properties with the highest relative variability were SBR, TOC,
and VWC. Silt also exhibited high dispersion, whereas EC and clay
showed moderate variability. In contrast, pH and bulk density were
the most stable properties, reecting more homogeneous conditions
within the system.
Physical properties of soils
The comparison of soil textural fractions among the ve land-
use types revealed signicant dierences. Clay content was higher
in soils under pea and strawberry, whereas forest and tree tomato
recorded the lowest values; pasture fell within an intermediate range.
With respect to sand, higher proportions were observed in forest and
tree tomato, in contrast to strawberry and pea, which exhibited the
lowest percentages; pasture showed intermediate values. Silt was
more abundant in soils under pasture, followed by strawberry and pea,
with the lowest levels found in tree tomato and forest. Although soil
texture is a relatively stable property, these results indicate marked
granulometric variability associated with the spatial heterogeneity of
soils across land uses (Table 3).
The results of particle size distribution revealed variations among
land uses that, rather than being attributable to immediate agricultural
management, may be associated with topography, land-use history,
and geomorphological dynamics.
m apart), were selected to represent each land-cover system. In each
case, a 1,000 m² plot was delineated, with slopes of 17.3 % in pasture,
37 % in strawberry, 22 % in pea, 30 % in tree tomato, and 24 % in
forest. These plots were representative of the topographic conditions
of the study area, characterized by steep slope gradients (23–59 %)
that increase susceptibility to erosion (Villamizar et al., 2024; IGAC,
2012).
In addition to slope, the relative position of the plots within the
landscape was considered: pasture and pea were located on midslopes;
strawberry and tree tomato on upper slopes with greater exposure to
erosive processes; and forest on a steeper slope with a protective
function within the landform, following the geomorphological
classication criteria proposed by IGAC (2012).
From a geomorphological and geological perspective, the
municipality of Pamplona is situated in the Espíritu Santo
Valley, underlain by Quaternary uvio-lacustrine deposits that
unconformably overlie igneous bedrock (quartz monzonitic gneiss,
Ortoneis unit). The valley is tectonically controlled by the Pamplona
Fault and the Chitagá Fault System, which delineate geomorphic
units characterized by hills and ridges, associated with sedimentary
sequences such as Girón, Tibú–Mercedes, and Aguardiente. This
lithostructural conguration explains the marked topographic
variability and edaphic heterogeneity of the area (Moya-Gutiérrez et
al., 2020).
Crop management was carried out under a conventional approach,
with mechanical tillage and sprinkler irrigation. In strawberry,
certied varieties were used together with plastic mulching, chemical
and organic fertilization, chemical control of pests and weeds,
periodic pruning, and manual harvesting every two days, primarily
performed by family labor. In pea and tree tomato, soil preparation
was similar; fertilization combined chemical inputs with organic
amendments (vermicompost and manure), along with practices such
as early staking, manual weed control, constant irrigation, and both
chemical and physical phytosanitary management (González-Pedraza
et al., 2023).
In each plot, ve composite soil samples (0–10 cm) were
collected and treated as independent experimental units for the
analyses. This number of replicates ensured a balance between
statistical representativeness and logistical feasibility. Sampling from
the surface layer was justied by its concentration of ne roots, high
biological activity, and greater sensitivity to agricultural practices,
while also maintaining comparability between agricultural systems
and natural covers.
Laboratory analyse
Physical (3), chemical (1), and biological (2) properties were
evaluated using standardized methodologies widely recognized in the
scientic literature (Table 1). Samples were collected with an auger,
stored in 2-kg airtight plastic bags, properly labeled, and immediately
transported to the Agricultural Soils Laboratory at the University
of Pamplona for processing. Undisturbed samples for bulk density
determination were collected using cylinders measuring 10 cm in
height and 5 cm in diameter.
Statistical analysis
A one-way ANOVA (p < 0.05) was performed, with Tukey’s HSD
post hoc test applied after verifying normality (Shapiro–Wilk test) and
homogeneity of variances (Levene’s test). The variables VWC, EC,
sand, TOC, and SBR were log-transformed. However, TOC did not
meet the assumption of normality even after transformation and was
This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
Rev. Fac. Agron. (LUZ). 2025, 42(4): e254248 October-December. ISSN 2477-9409.
4-7 |
Table 2. Descriptive statistics of soil physical and chemical properties under dierent land uses.
N Mean Minimum Maximum Variance SD CV
VWC
25 23.8 4.5 53.9 126.7 11.3 47.3
EC
25 1.1 0.3 2.0 0.2 0.4 37.1
BD
25 0.9 0.4 1.2 0.0 0.2 20.5
Clay
25 29.9 13.1 47.1 87.5 9.4 31.3
Sand
25 51.4 32.5 76.7 196.0 14.0 27.2
Silt
25 18.6 6.8 37.4 72.8 8.5 45.8
pH
25 5.6 4.2 7.0 0.4 0.7 11.8
TOC
25 1.5 0.7 3.2 0.6 0.8 52.2
SBR
25 39.4 5.0 110.0 723.8 26.9 68.2
VWC: Volumetric water content (%); EC: Electrical conductivity (dS.m⁻¹); BD: Soil Bulk density (g.m⁻³); Clay (%); Sand (%); Silt (%); TOC: Total organic carbon (%); SBR: Soil basal respiration
(µg C–CO₂·100 g.24 h⁻¹). SD: Standard deviation; CV: Coecient of variation.
Regarding VWC, soils under pasture exhibited the highest
values (38.6 %), followed by strawberry and tree tomato, whereas
forest presented the lowest value (13.0 %). These dierences may be
associated with variations in vegetation cover and soil management.
With respect to BD, forest soils exhibited the lowest values (0.7
g.cm⁻³), indicating greater porosity, while cultivated soils (strawberry,
pea, and tree tomato) showed higher values, suggesting compaction
related to intensive agricultural practices (Table 4).
Although plastic mulching reduces evaporation, it can alter water
redistribution and promote subsurface compaction if not accompanied
by organic matter incorporation (Gao et al., 2019). In pea, also with
a clay loam texture, VWC was even lower, indicating reduced water
retention associated with intensive tillage and limited cover; although
BD was low, it may be masking subsurface compaction (Ewunetu et
al., 2025).
In tree tomato (sandy clay loam texture), VWC remained within the
expected range (20–30 %), and BD was lower than the typical values
(1.3–1.6 g.cm⁻³), reecting low compaction and good porosity, likely
favored by its perennial nature and reduced soil disturbance.
Table 3. Comparison of particle size distribution under dierent land uses.
Land Uses Clay CV Sand CV Silt CV Textural Class
Pasture 24.0±9.4c 23.3 47.5±9.2ac 19.4 28.6±6.2a 21.6 Loam
Strawberry 37.1±4.0ab 10.8 40.0±5.0a 12.6 23.0±1.9a 8.3 Clay loam
Pea 41.0±3.7a 9.1 39.3±6.8a 17.3 19.7±6.5ac 33.2 Clay loam
Tree tomato 27.4±6.5bc 23.9 63.3±5.7bc 8.9 9.4±2.8b 30.2 Sandy clay loam
Forest 20.2±5.9ac 29.3 67.2±11.6b 17.3 12.6±6.5bc 52.0 Sandy loam
Note. Mean values ± standard deviation followed by dierent letters indicate signicant dierences among land uses at p < 0.05 according to Tukey’s test. CV: Coecient of variation.
It is important to note that soil texture is a relatively stable edaphic
property, whose variability is primarily driven by erosive processes or
the intrinsic spatial heterogeneity of soils. In this regard, it should
be emphasized that the plots belong to the same physiographic
framework (Espíritu Santo Valley) but were located in contrasting
topographic positions (IGAC, 2012), which explains part of the
observed variation.
On upper and convex slopes (strawberry, 37 %; tree tomato,
30 %), runo promotes the selective removal of silt and clay. On
midslopes (pea, 22 %), in addition to reduced runo energy, partial
accumulation of materials transported from higher elevations may
occur, which also inuences particle size distribution. In forest soils
(24 %), dense vegetation cover and the natural dynamics of erosion
and deposition favor the retention of ne fractions, whereas in
pasture (17.3 %), compaction from livestock trampling induces the
redistribution of surface particles. Thus, dierences in slope position
and management practices account for the observed granulometric
variations (Villamizar et al., 2024; Moya-Gutiérrez et al., 2020).
Table 4. Comparison of soil physical parameters under dierent land uses.
Land Uses
Volumetric water content
(%)
CV
Soil bulk density
(g.cm
-3
)
CV
Pasture 38.6±14.0a 36.2 0.9±0.1ab 26.5
Strawberry 27.1±4.5a 16.5 1.0±0.1a 8.8
Pea 17.2±4.4a 25.7 1.0±0.1a 9.9
Tree tomato 22.9±2.7a 11.7 0.9±0.1ab 11.3
Forest 13.0±5.4b 41.4 0.7±0.2b 27.0
Note. Mean values ± standard deviation followed by dierent letters indicate signicant dierences among crops. CV: Coecient of variation.
This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
González-Pedraza et al. Rev. Fac. Agron. (LUZ). 2025, 42(4): e254248
5-7 |
In forest (sandy loam texture), VWC matched the reference range
for this texture (10–20 %), while BD was the lowest among all land
uses, well below the range for mineral soils (1.4–1.7 g.cm⁻³). This
highlights the positive inuence of litterfall and higher organic carbon
content on structural stability (Gao et al., 2019).
These results are consistent with the ndings of Huf dos Reis et al.
(2024), who demonstrated that volumetric water content at dierent
matric potentials can be predicted using pedotransfer functions (PTFs)
that incorporate texture, bulk density, and porosity. Consequently, soils
with higher clay content and greater organic matter inputs tend to retain
more water, whereas sandy soils exhibit lower values. The combination
of the identied textural classes and the specic management of each
land cover explains the observed dierences in BD, VWC, and porosity,
conrming the decisive role of land use and agricultural management
in shaping soil physical functionality.
Soil chemical and biological properties
Signicant dierences were observed in pH, EC, and TOC, whereas
SBR, although variable, did not dier signicantly among land uses.
Regarding pH, forest soils were signicantly less acidic than cultivated
soils, particularly strawberry and pasture, likely due to the use of
nitrogen fertilizers and the lower buering capacity of degraded soils.
Pea and tree tomato showed intermediate values, with no signicant
dierences compared to the other land uses, indicating greater pH
stability in these systems (Table 5).
With respect to EC, interpreted as an indirect indicator of the total
concentration of soluble salts in the soil solution rather than as a measure
of specic salts, higher values were observed in intensively managed
agricultural soils (pasture, strawberry, and tree tomato) compared with
pea and forest. This pattern suggests a potential accumulation of salts
derived from chemical fertilization and reduced drainage eciency.
TOC was highest in forest soils, reecting their ecological stability
and continuous organic matter accumulation. Agricultural soils showed
intermediate values, with no marked statistical dierences among
them, likely due to variability among replicates and heterogeneous
management practices. Although no signicant dierences were found
in SBR, high variability was observed across land uses, with the highest
value in strawberry and the lowest in tree tomato (Table 5).
Soil pH is a key regulator of chemical and biological processes,
including nutrient availability and microbial activity. Values below
5.5, such as those observed in soils under strawberry and pasture, can
induce Al³⁺ and Mn²⁺ toxicity and decrease the availability of basic
cations such as Ca²⁺ and Mg²⁺ (Mitsuta et al., 2025).
This pattern is consistent with the ndings of Visconti-Moreno &
Valenzuela-Balcázar (2019), who reported that the conversion of forest
to intensive agricultural systems in Norte de Santander leads to organic
carbon loss and reduced aggregate stability, both clear indicators of
physical and chemical degradation.
In contrast, forest soils exhibited pH values closer to the optimal
range (5.5–7.0), reecting lower disturbance and greater buering
capacity.
Although soil structure was not directly characterized in this study,
the more acidic pH and higher bulk density observed in strawberry and
pasture provide indirect evidence of soil deterioration, in contrast to the
more stable conditions recorded in forest soils.
Regarding total organic carbon (TOC), the highest content was
recorded in forest soils, associated with the continuous accumulation
of litterfall and roots, the absence of tillage, permanent cover, and a
cool–humid microclimate that slows organic matter decomposition
and favors stabilization (Gao et al., 2019). In contrast, agricultural
systems showed intermediate and variable values, inuenced by
tillage, trampling, residue removal, and erosion, which accelerate
mineralization, oxidation, and leaching of organic compounds.
These losses, which may reach 20–45 % following forest-to-crop
conversion, reduce soil structural integrity and its capacity for water
and nutrient retention (Singh et al., 2020).
The absence of clear statistical dierences among crops can be
attributed to heterogeneity in management practices and the eect
of slope topography, which intensies dierential carbon losses and
generates high variability among replicates. Recent studies agree that
land-use change and agricultural management are key drivers of soil
carbon dynamics, emphasizing that its stabilization largely depends
on the transformation of residues into microbial necromass and their
association with ne mineral fractions (Cotrufo et al., 2019).
With respect to SBR, although no statistical dierences were
detected among land uses, higher values were observed in soils
under strawberry, pasture, and pea, likely due to the input of labile
compounds such as crop residues (Singh et al., 2020). However,
elevated SBR does not necessarily indicate improved soil quality,
as it may reect rapid mineralization without long-term carbon
stabilization (Shi et al., 2025). In forest and tree tomato soils, lower
SBR suggests the predominance of complex organic compounds,
such as lignin and phenolics, which contribute to long-term carbon
sequestration (Almendros & González-Pérez, 2025). This aligns
with studies reporting higher respiration rates in grasslands due
to changes in substrate quality, temperature, and moisture, as well
as residues with low C/N ratios that stimulate microbial activity
(Pardo-Plaza et al., 2019).
Pearson correlation matrix for soil properties
The Pearson correlation matrix was evaluated to explore linear
relationships among soil physicochemical variables and to justify
the application of Principal Component Analysis (PCA). The results
revealed signicant associations among key variables, indicating
patterns of joint variation that support the multivariate approach.
Table 5. Comparison of soil chemical and biological parameters under dierent land uses.
Land Uses pH CV
Electrical conductivity
(dS.m
-1
)
CV
Total organic
carbon
(%)
CV
Soil basal respiration
(µg C-CO₂ 100 g.24 h
-1
).
CV
Pasture 5.2±0.3b 5.7 1.6±0.4a 24.6 1.3±0.4ab 29.1 48.1±32.3a 67.1
Strawberry 5.0±0.6b 11.8 1.3±0.2a 13.0 0.9±0.1b 7.4 56.0±25.3a 45.3
Pea 5.8±0.4ab 7.8 0.9±0.2b 23.7 1.1±0.3ab 24.0 48.3±35.2a 72.8
Tree tomato 5.8±0.5ab 8.1 1.2±0.1a 10.3 1.5±0.7ab 48.6 19.4±6.8a 35.3
Forest 6.4±0.5a 8.0 0.6±0.2b 27.2 2.8±0.4a 14.6 25.4±9.6a 37.8
Note. Mean values ± standard deviation followed by dierent letters indicate signicant dierences among crops. CV: Coecient of variation.
This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
Rev. Fac. Agron. (LUZ). 2025, 42(4): e254248 October-December. ISSN 2477-9409.
6-7 |
The very strong positive correlation between VWC and EC (r
= 0.97; p < 0.05) indicates that soils with higher water content also
exhibit higher concentrations of soluble salts. In strawberry, pea, and
tree tomato systems, where amendments such as poultry manure and
lime were applied, the increase in ions in solution may explain the
rise in EC under conditions of greater water retention. In contrast,
in pasture systems nutrients were mainly derived from grazing,
whereas in forest soils no external inputs were recorded. This result
is consistent with the ndings of Ylagan et al. (2023), who reported
that apparent electrical conductivity is strongly inuenced by soil
moisture and nutrient accumulation.
Other relevant, although not statistically signicant, relationships
included the negative correlation between BD and TOC, suggesting
that soils with higher organic matter content tend to exhibit more
porous structures. A positive association was also observed between
sand and TOC, possibly related to prole aeration and residue
decomposition. In contrast, SBR showed weak correlations with
the other variables, which may be attributed to its high sensitivity to
specic microenvironmental conditions.
Overall, the correlation patterns indicate the presence of latent
multivariate structures integrating soil physical, chemical, and
biological attributes. This provides strong support for the application
of PCA as an appropriate dimensionality-reduction technique,
facilitating the ordination of soil variables and the identication of
shared edaphic gradients across land-use systems.
Principal component analysis (PCA) of soil properties
The correlation matrix was analyzed using PCA, which identied
three components with eigenvalues greater than 1, together explaining
63.30 % of the total variance. The rst two components (PC1 and
PC2), which jointly explained 50.96 %, were retained for graphical
interpretation, according to Kaiser’s criterion and the scree plot
(Table 6).
Table 6. Eigenvalues, percentage of explained variance, and
cumulative variance for each principal component.
Component Eigenvalue
% of Variance
Explained
Cumulative
Variance (%)
1 3.3255 36.95 36.95
2 1.2611 14.01 50.96
3 1.1109 12.34 63.30
PC1 (36.95 %) represented a textural–hydric gradient, characterized
by strong positive loadings for clay content, volumetric water content
(VWC), and electrical conductivity (EC), and a negative loading
for sand. PC2 (14.01 %) captured a fertility–chemical stability axis,
primarily dened by silt, pH, and total organic carbon (TOC), with
soil basal respiration (SBR) also showing a positive contribution. In
contrast, bulk density (BD) was oriented in the opposite direction to
these variables, suggesting divergences in soil structural conditions and
biological quality (Table 7).
The biplot (Figure 1) corroborated these patterns, highlighting the
opposition between sand and the ne fractions (clay and silt), as well as
the positive association of volumetric water content (VWC) with electrical
conductivity (EC), in contrast to the inverse projection of bulk density
(BD). The clustering of silt, pH, and total organic carbon (TOC) reected
soils with higher fertility and greater stabilization of organic matter, while
soil basal respiration (SBR) also aligned positively with this axis.
Table 7. Factor loadings of the variables on the rst two principal
components.
Variable PC1 PC2
Volumetric water content 0.8387 -0.2816
Soil bulk density -0.3940 -0.2263
Clay 0.8496 0.1507
Sand -0.9300 -0.1432
Silt 0.1905 0.9494
pH 0.1943 0.9202
Total organic carbon (%) 0.1696 0.9136
Electrical conductivity (dS.m
-1
) 0.7868 -0.1945
Soil basal respiration (µg C–CO₂·100 g.24 h⁻¹) 0.1159 0.7834
The distribution of centroids further distinguished land uses:
forest and tree tomato systems were positioned in the quadrant linked
to improved fertility and structural stability; pasture occupied an
intermediate position, associated with moderate water retention and
compaction; whereas strawberry and pea systems were projected in
the opposite direction, indicating structural constraints and reduced
water retention capacity under intensive management.
Figure 1. Projection of the variables on the factorial plane dened
by the rst two principal components (PCA). VWC:
Volumetric water content; EC: Electrical conductivity; BD:
Soil Bulk density; TOC: Total organic carbon; SBR: Soil
basal respiration.
The PCA emphasized the pivotal role of soil texture as a
semi-permanent attribute regulating water dynamics and nutrient
availability. Intensive production systems, characterized by the
combined application of irrigation and fertilization, tended to foster
salt accumulation and compaction, whereas forest soils maintained
more stable conditions through leaching processes. Soils enriched in
This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
González-Pedraza et al. Rev. Fac. Agron. (LUZ). 2025, 42(4): e254248
7-7 |
ne fractions demonstrated a greater capacity for carbon retention
and pH buering, thereby enhancing microbial activity and structural
stability. In contrast, intensively managed agricultural systems
exhibited compaction and reduced aeration, which diminished
biological eciency and underscored their susceptibility to
degradation.
Conclusions
The study demonstrated that volumetric water content, electrical
conductivity, pH, total organic carbon, and basal respiration
are sensitive indicators of agricultural management, eectively
reecting the impacts of land use. Strawberry, pea, and tree tomato
systems exhibited signs of acidication, carbon depletion, and salt
accumulation, whereas pasture systems were characterized by
compaction and biological limitations. In contrast, natural forest
maintained more favorable conditions, serving as a benchmark for
soil stability and quality.
These ndings provide clear evidence that intensive land use
in mountain environments exacerbates the risk of soil degradation,
underscoring the importance of adopting conservation-oriented
strategies. Recommended practices include the correction of soil
acidity through amendments, the incorporation of stabilized organic
matter, the diversication of plant cover with legumes and agroforestry
systems, and the rationalization of chemical fertilization, all aimed at
enhancing the resilience and sustainability of agroecosystems.
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