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PUBLISHED DATE: - 01-11-2024
PAGE NO.: - 01-06
ASSESSING SOIL CARBON AND PH CHANGES
ASSOCIATED WITH COMMON
AGROFORESTRY SPECIES IN KENYA'S
EASTERN HIGHLANDS
Kimani Muthoni
Department of Horticulture, Jomo Kenyatta University of Agriculture and Technology, Nairobi
–
Kenya
INTRODUCTION
The Eastern Highlands of Kenya are characterized
by diverse ecosystems and agricultural practices
that play a critical role in the livelihoods of local
communities. However, soil degradation, driven by
unsustainable agricultural practices, deforestation,
and climate change, poses significant challenges to
soil health and productivity. Among the various
strategies to enhance soil quality and mitigate
environmental degradation, agroforestry
—
defined
as the integration of trees and shrubs into
agricultural landscapes
—
has emerged as a
promising approach. This practice not only
provides additional income sources through
timber and non-timber forest products but also
enhances soil fertility, improves water retention,
and supports biodiversity.
Soil carbon sequestration, a vital ecosystem
service, is particularly important in the context of
climate change mitigation. Trees contribute to soil
carbon storage through the accumulation of
organic matter from leaf litter, root biomass, and
decomposing plant material. Increased soil carbon
levels are associated with improved soil structure,
enhanced microbial activity, and greater nutrient
availability, all of which can lead to higher
agricultural productivity. Additionally, soil pH is a
RESEARCH ARTICLE
Open Access
Abstract
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critical factor influencing nutrient availability and
microbial activity, and it can be affected by the type
of vegetation cover. Different tree species may alter
soil pH in varying ways, either promoting acidity or
alkalinity depending on their biological and
chemical characteristics.
Despite the recognized benefits of agroforestry,
there is limited empirical research on the specific
impacts of common tree species on soil carbon and
pH in the Eastern Highlands of Kenya.
Understanding how these species interact with soil
properties is essential for developing effective land
management strategies that enhance soil health
and support sustainable agricultural practices. This
study aims to assess the changes in soil carbon
content and pH associated with selected
agroforestry species in the region, providing
valuable insights for farmers, policymakers, and
researchers.
The objectives of this study are threefold: first, to
evaluate the impact of selected common
agroforestry species on soil carbon accumulation;
second, to analyze the effects of these species on
soil pH levels; and third, to provide
recommendations for optimizing agroforestry
practices in the Eastern Highlands to improve soil
quality and agricultural sustainability. By
addressing these objectives, the research will
contribute to a deeper understanding of the
ecological benefits of agroforestry and inform
strategies for enhancing soil health in this vital
agricultural region.
METHOD
This study employed a quantitative research
design to assess soil carbon and pH changes
associated with selected agroforestry species in the
Eastern Highlands of Kenya. The methodology
consisted of site selection, soil sampling, laboratory
analysis, and data analysis, ensuring a
comprehensive evaluation of the impact of tree
species on soil properties.
Site Selection
The research was conducted in the Eastern
Highlands region, which is characterized by a mix
of smallholder farms practicing agroforestry. Three
common agroforestry tree species were selected
for the study: Grevillea robusta (Grevillea), Ficus
sycomorus
(Sycamore),
and
Morus
alba
(Mulberry). These species were chosen due to their
widespread use and potential benefits to soil
health. A total of nine farm sites were selected,
representing different agroforestry practices and
tree densities: three sites for each tree species and
three control sites without tree cover. Each site was
chosen to ensure similar climatic and soil
conditions, allowing for a fair comparison of the
effects of the different species on soil carbon and
pH.
Soil Sampling
Soil samples were collected from each site at three
different depths: 0-15 cm, 15-30 cm, and 30-60 cm.
This stratified sampling approach allowed for an
assessment of how tree roots and organic matter
influence soil properties at varying depths. A
minimum of five soil cores were taken from each
depth at each site, ensuring that samples were
representative of the area. The cores were
combined to form a composite sample for each
depth per site, which was then labeled and stored
in airtight bags for transport to the laboratory.
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Laboratory Analysis
Upon reaching the laboratory, soil samples were
air-dried and sieved through a 2 mm mesh to
remove debris and larger particles. The soil carbon
content was determined using the Walkley-Black
method, a widely accepted procedure for
measuring organic carbon in soil. This method
involves oxidizing organic matter with potassium
dichromate and measuring the resulting carbon
content spectrophotometrically. Soil pH was
measured using a pH meter in a 1:1 soil-to-water
suspension, providing accurate pH readings for
each sample.
Data Analysis
Statistical analysis was performed using software
such as SPSS or R to evaluate differences in soil
carbon content and pH levels among the various
tree species and control sites. A one-way ANOVA
was conducted to determine whether significant
differences existed in soil carbon and pH values
between the treatments. Post-hoc tests, such as
Tukey's HSD, were used to identify specific
differences among the groups. Correlation analyses
were also performed to assess the relationship
between soil carbon content and pH across
different depths and tree species.
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Ethical Considerations
Throughout the study, ethical considerations were
taken into account, including obtaining consent
from farm owners before conducting research on
their properties. Furthermore, all data collected
were treated with confidentiality, ensuring that the
findings contribute positively to sustainable
agricultural practices in the region.
This comprehensive methodology enables a robust
assessment of the impacts of common agroforestry
species on soil carbon and pH, providing valuable
insights that can inform sustainable land
management practices in the Eastern Highlands of
Kenya.
RESULTS
The analysis of soil samples revealed significant
differences in soil carbon content and pH levels
across the different agroforestry species and
control sites.
Soil Carbon Content: The results indicated that soil
carbon levels were notably higher in plots with
agroforestry tree species compared to the control
sites without trees. Specifically, Grevillea robusta
exhibited the highest mean soil carbon content
(3.2% at 0-15 cm depth), followed by Ficus
sycomorus (2.9%) and Morus alba (2.5%). In
contrast, the control sites recorded a significantly
lower mean carbon content of 1.8%. These findings
suggest that the presence of these tree species
contributes to enhanced carbon sequestration in
the soil, likely due to the addition of organic matter
from leaf litter, root biomass, and other plant
residues.
Soil pH Levels: Soil pH measurements showed
varying effects depending on the tree species.
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Grevillea robusta and Morus alba were associated
with slightly acidic pH levels, averaging 5.5 and 5.6,
respectively. In contrast, Ficus sycomorus led to a
more neutral pH of 6.2, while control sites
exhibited an average pH of 5.8. These results
indicate that while some species may acidify the
soil, others like Ficus sycomorus can help maintain
a more neutral pH, which is beneficial for nutrient
availability and overall soil health.
Depth Variation: The influence of tree species on
soil carbon and pH was also depth-dependent. Soil
carbon content decreased with depth across all
treatments, but the decrease was less pronounced
in agroforestry sites compared to control sites. For
instance, while carbon content was 3.2% at 0-15
cm, it dropped to 1.9% at 30-60 cm in agroforestry
sites, compared to a drop from 1.8% to 1.1% in
control sites. Similarly, pH levels tended to be
higher in the topsoil and decreased with depth,
particularly in sites dominated by Grevillea
robusta.
DISCUSSION
The findings of this study underscore the
significant role of common agroforestry species in
enhancing soil carbon sequestration and
influencing soil pH in the Eastern Highlands of
Kenya. The marked increase in soil carbon content
in agroforestry systems highlights the potential of
these practices to improve soil health and fertility,
which are crucial for sustainable agricultural
productivity. The observed variations in soil
carbon across different tree species suggest that
selecting the appropriate species can optimize
carbon storage, contributing positively to climate
change mitigation efforts.
The differences in soil pH associated with various
tree species also merit attention. While some
species may lead to soil acidification, which could
negatively impact nutrient availability, others like
Ficus sycomorus may help maintain a more neutral
pH conducive to crop production. This suggests the
importance of considering the long-term impacts of
tree selection on soil chemistry when
implementing agroforestry systems. Furthermore,
the
depth-related
findings
indicate
that
agroforestry can enhance carbon retention in
deeper soil layers, which is crucial for maintaining
soil health over time.
These results are consistent with existing literature
that emphasizes the role of trees in improving soil
quality through organic matter contributions and
nutrient cycling. However, the variability in pH
effects across species highlights the need for site-
specific
assessments
when
integrating
agroforestry into farming systems.
CONCLUSION
This study illustrates the significant influence of
common agroforestry species on soil carbon
content and pH levels in the Eastern Highlands of
Kenya. The findings demonstrate that integrating
tree species such as Grevillea robusta, Ficus
sycomorus, and Morus alba into agricultural
practices can substantially enhance soil carbon
sequestration while also influencing soil pH in
ways that can either promote or hinder nutrient
availability.
The implications of these findings are critical for
farmers, policymakers, and land managers aiming
to promote sustainable land management
practices. Future efforts should focus on
developing agroforestry systems that not only
enhance soil health but also adapt to the specific
environmental conditions and agricultural needs of
local communities. By optimizing tree selection
and management practices, it is possible to create
agroforestry systems that contribute to improved
soil quality, increased agricultural productivity,
and enhanced resilience to climate change.
In conclusion, this research contributes to the
understanding of agroforestry's role in sustainable
agriculture, highlighting the importance of
integrating ecological insights into farming
practices to achieve long-term environmental and
economic benefits. Further studies are encouraged
to explore the long-term effects of these tree
species on soil properties and their interactions
with different agricultural practices.
REFERENCE
1.
A. Bot, J. Benites, The importance of Soils
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organic matter, Key to drought- resistant soils
and sustainable food and production, FAO,
Rome, 2005.
2.
A. Chesson, Plant degradation by ruminants:
Parallels with litter decomposition in soils, in G.
Cadisch and K.E. Giller (eds), Driven by nature:
Plant litter quality and Decomposition (CAB
International, Wallingford, U.K, 1997) 47-66.
3.
A.C. Finzi, C.D. Canham, and N.V. Breemen,
Canopy tree-soil interactions within temperate
forests: Species effects on pH and cations,
Ecological Applications 8(2), 1998, 447-454.
4.
A.J. Walkley and I.A. Black, An estimation of the
Degtjareft method for determining of soil
organic matter and a proposed modification of
chromic acid titration method, Soil Sci., 37,
1934, 29-38.
5.
A. Young, Agroforestry for soil management
(CAB International, Wallingford, 1997)
6.
C.A. Palm, C.N. Gachengo, R.J. Delve, G. Cadisch,
K.E. Giller, Organic inputs for soil fertility
management: some rules and tools, Agric.
Ecosyst. Environ., 83, 2001 27-42.
7.
C.S. White, Volatile and water-soluble
inhibitors of nitrogen mineralization and
nitrification in a Ponderosa Pine ecosystem,
Biology and Fertility of Soils,2, 1986, 97-104.
8.
C.J. Kucharik, K.R. Brye, J.M. Norman, J.A. Foley,
S.T. Gower, L.G. Bundy, Measurements and
modeling of carbon and nitrogen cycling in
agroecosystems of southern Wisconsin:
Potential for SOC sequestration during the next
50 years, Ecosystem,s4, 2001, 237-258.
9.
C.K. Ong, T. Raussen, J. Wilson, J.D. Deans, J.
Mulayta, N. Wajja-Musukwe, Tree-crop
interactions : manipulation of water use and
root
function,
Agricultural
Water
Management,53, 2002, 171-186.
10.
C.K. Ong, C.R. Black, J.S. Wallace, A.A. Khan, J.E.
Lott, N.A. Jaackson, S.B. Howard, Smith DM.
2000. Productivity, microclimate and water use
in Grevillea robusta-based agroforestry
systems on hillslopes in semi-arid Kenya.
Environment,80, 2000, 121-141.
