1. INFLUENCE OF SOIL MICROBES ON AGGREGATION AND ORGANIC
CARBON POOLS UNDER DIFFERENT LAND USES IN THE NORTHERN
GUINEA SAVANNA, NIGERIA
BY
Meshach Ufedo SALIFU
P16AGSS8014
SUPERVISORY COMMITTEE:
Dr. (Mrs) H.M LAWAL (Chairperson)
Prof. I.Y AMAPU (Member)
meshachsalifu@gmail.com
2. Land and Land-use
Soil organic matter
Soil microorganisms
2
Intraradical
Hypha
Root of
host plant
SOIL
Source: Reseacrhgate.net
INTRODUCTION
1
7. It is therefore of great necessity to assess the
soil for its microbial composition.
INTRODUCTION CONT’D
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8. PROBLEM STATEMENT
Increased emissions of greenhouse gases and
declining fertility in soils.
Availability of very little information
The functional importance of microbial diversity
Variability among land-uses 7
9. JUSTIFICATION
Microorganisms play vital role in keeping the soil
healthy.
Organic matter occupies a central role in agro-
ecosystem function.
Several studies on soil organic matter dynamics
only focused on its absolute amount.
8
10. JUSTIFICATION CONT…
The ability of microorganisms to improve soil
aggregation and carbon storage.
Variability among land uses.
9
11. MAIN OBJECTIVE
The goal of this research is to investigate the
relationship among soil microbes, aggregation and
organic carbon pools under different land uses of
agricultural importance.
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12. SPECIFIC OBJECTIVES
evaluate the effect of land use on diversity and
population of soil microbes in different soil
aggregate fractions.
evaluate the effect of land use on organic carbon
pools and aggregation
determine the relationship between organic carbon
pools and soil microbes. 11
13. SPECIFIC OBJECTIVES Cont..
determine the relationship between diversity of soil
microbes and soil aggregate stability.
determine the relationship between soil aggregate
stability and organic carbon pools under different
land uses.
12
14. DESCRIPTION OF SAMPLING SITES
Study Area: The research was conducted in the department of Soil Science and Microbiology of Ahmadu
Bello University, Zaria, Kaduna State, using soils that were collected from six different land uses within Kaduna
State.
Study Sites: The study sites includes the Afaka Forest Reserve located in Kaduna, the pasture fields of NAPRI
located in Zaria, Date palm plantation also located in Zaria, Continuously cultivated land of IAR field Zaria, a
grassland in Zaria and a fallow land in IAR fields Zaria, Kaduna State; all within the Northern Guinea Savanna
of Nigeria. The coordinates and the elevation of the locations were taken using a Global Positioning System
(GPS) during sampling.
Figure 1: Nigeria, showing Kaduna, Afaka Forest Reserve and Environs
Figure 1: Nigeria, showing Kaduna, Afaka Forest Reserve, Zaria and Environs
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16. SOIL SAMPLING & PREPARATION
disturbed from 20 points at 2 sampling depths
(0 – 5 and 5 - 20 cm) and un-disturbed cores; 3
from each point at 4 soil depths namely; 0 – 5, 5
– 10, 10 – 15 and 15 – 20 cm)
Air-dried and sieved through 5 mm mesh size
Air dried and passed through 2 mm sieve
Refrigerated at 4°C for microbial isolation and
characterization
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17. TREATMENT AND DESIGN
Treatment: The land-uses and aggregate
fractions served as treatments
Design: Randomized complete block design
(RCBD) 16
18. SOIL PARAMETERS MEASURED
Physical and Chemical Properties:
Particle Size Analysis (Gee and Or, 2002)
Bulk Density (Grossman and Reinsch, 2002)
Total porosity (Danielson and Sutherland, 1986)
Saturated hydraulic conductivity (Wosten et al.
(2001))
Soil pH (Rhoades, 1982)
Soil organic carbon (Pluske et al., 2019)
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19. SOIL PARAMETERS MEASURED
Physical and Chemical Properties Continued:
Particle Density (Flint, 2002)
Total Nitrogen (Bremner and Mulvaney, 1982)
Available Phosphorus (Bray and Kurtz, 1945; Murphy and Riley,
1962)
Exchangeable Bases and ECEC (Anderson and Ingram ,1993)
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20. SOIL PARAMETERS MEASURED
Aggregate Stability
By Wet Sieving method (Elliot, 1986)
By Dry sieving method (Kemper, 1986)
Sand free aggregates=
𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑎𝑔𝑔𝑟𝑒𝑔𝑎𝑡𝑒 𝑓𝑟𝑎𝑐𝑡𝑖𝑜𝑛−% 𝑠𝑎𝑛𝑑 𝑐𝑜𝑛𝑡𝑒𝑛𝑡
𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑏𝑢𝑙𝑘 𝑠𝑜𝑖𝑙−% 𝑠𝑎𝑛𝑑 𝑐𝑜𝑛𝑡𝑒𝑛𝑡
(Masri and Ryan, 2006; Lawal, 2013)
MWD mm= 𝑖=1
𝑛
𝑥𝑖𝑤𝑖
Where: xi = mean diameter of successive sieve
wi = proportional weight of sand free aggregates
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21. AGGREGATE STABILITY
Determined using these sieve sizes:
5 – 2 mm (Large macro-aggregates)
2 - 0.25 mm (Small macro-aggregates)
0.25 - 0.053 mm (Micro-aggregates)
< 0.053 mm (Silt-plus-clay aggregates)
Aggregates > 0.053 mm were corrected for sand
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22. SOIL PARAMETERS MEASURED
Carbon in Aggregates (Nelson and Sommers, 1982)
>250 µm (Labile/Active/Unprotected carbon)
>53 µm (Physically protected/intra-aggregate/Particulate carbon)
and <53 µm (Chemically protected/Humus carbon)
They were calculated as sand free carbon thus:
Sand free C fraction =
𝐶 𝑓𝑟𝑎𝑐𝑡𝑖𝑜𝑛
1− 𝑠𝑎𝑛𝑑 𝑝𝑟𝑜𝑝𝑜𝑟𝑡𝑖𝑜𝑛 𝑓𝑟𝑎𝑐𝑡𝑖𝑜𝑛
(Denef et al., 2001, Lawal, 2013)
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23. SOIL PARAMETERS MEASURED
Carbon in Aggregates:
Biochemically protected carbon (Non-hydrolysable/Recalcitrant
carbon) (Tan et al, 2004), Modified by Lawal et al.(2009; 2012)
Method: By Acid hydrolysis (HCl)
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24. SOIL PARAMETERS MEASURED
Soil microbiological properties
Soil microbial biomass carbon (by chloroform fumigation-extraction
method) (Okalebo et al., 2002)
Soil microbial biomass nitrogen
Isolation and Identification of bacteria (Gram, 1844; Bailey and Scott,
1966; Ruangpan and Tendecia, 2004) by spread plate technique
Colony forming unit was computed as thus: Total heterotrophic count
CFU/g (dryweight) =
𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑐𝑜𝑙𝑜𝑛𝑖𝑒𝑠 ∗𝑖𝑛𝑣𝑒𝑟𝑠𝑒 𝑜𝑓 𝑑𝑖𝑙𝑢𝑡𝑖𝑜𝑛 𝑓𝑎𝑐𝑡𝑜𝑟
𝑖𝑛𝑜𝑐𝑢𝑙𝑢𝑚 𝑠𝑖𝑧𝑒 (𝑚𝑙)
(Thaker, 2009)
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25. SOIL PARAMETERS MEASURED
Soil microbiological properties: Biochemical
Tests
Biochemical tests for bacteria after gram staining
and microscopy:
Urease, Catalase, Oxidase, Oxidation-
fermentation, Coagulase, Citrate utilization
Catalase, Indole, Methyl red-voges Proskauer,
Motility, Spore, DNAse,
Triple sugar iron test
Bacteria was identified using chart from Bergey’s
manual
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26. SOIL PARAMETERS MEASURED
Soil microbiological properties continuation
Isolation and Identification of Actinomycetes (Actinobacteria) (Sonia et al.,
2011; Xu et al., 2014; Anasuya et al., 2016) by spread plate technique
Biochemical tests for Actinobacteria
Casein hydrolysis, Citrate utilization, Catalase production, Hydrogen
sulphide production
Gelatin liquefaction, Urease production, Starch hydrolysis, Nitrate
reduction, Indole production, Methyl red and Vogues-Proskauer test
The microscopy of the isolates was performed and characteristics of
mycelium and spores types and numbers were recorded.
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27. SOIL PARAMETERS MEASURED
Soil microbiological properties continuation
Isolation and Identification of Fungi through plate culture (Singh
and Kapoor, 2010)) by spread plate technique
Saboraud dextrose agar slants were prepared and fungi sub-
cultured
Fungi was identified by microscopy and by the use of fungal ATLAS
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28. SOIL PARAMETERS MEASURED
Soil microbiological properties continuation
Determination of microbial population and diversity by;
Shannon-Wiener Index (Shannon and Weaver, 1949; Mette et al .2002)
Calculated as thus:
H = −
𝐼=1
𝑅
PlnP
where :
H = Shannon’s index, R = species richness (the number of different types of species that
are contained in a population often denoted as S), P= the proportion of characters
belonging to the ith type of letter in the population of interest. ln= natural logarithm
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29. SOIL PARAMETERS MEASURED
Soil microbiological properties continuation
Shannon-Wiener Index (Shannon and Weaver, 1949; Mette et al .2002)
• Species evenness: E =
𝑯
𝒍𝒏𝑺
where is species richness maximum,
this is also called Shannon’s equitability (EH =
𝑯
𝑯𝒎𝒂𝒙
),
Hmax = lnS (S -total number of species in the community).
• Shannon’s function (index) increases as diversity increases and vice- versa, meaning that high
value for Shannon Index (H) means high diversity, and low value for H means low diversity.
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30. SOIL PARAMETERS MEASURED
Determination of microbial population and diversity by;
Simpson Index (Edward, 1949)
• The index measures the degree of concentration when individuals are classified into
types, particular species
Calculated as thus:
• ⋏=
𝑖=1
𝑅
P squared
• Where: R= species richness, P = the proportion of characters belonging to the ith type
of letter in the population of interest. That is population of individuals belonging to the ith
species in the population set of interest.
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31. SOIL PARAMETERS MEASURED
Determination of microbial population and diversity by;
Simpson Index (Edward, 1949)
⋏ ≥ 1/R (0 – 1 = range). Simpson’s index is a similarity index, the higher the
value the lower the diversity of the population (1 – S).
• High value for Simpson’s index means lower diversity and lower value for
Simpson’s index means higher or greater diversity
• Zero (0) means no diversity 30
32. DATA ANALYSIS
Data Analysis (SAS 9.2, 2007)
Analysis of variance (ANOVA)
Correlation and Regression analysis (Steel
and Torrie, 1984)
Principal component analysis (SAS 9.2, 2007)
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55. CONCLUSION
The following conclusions are drawn from this study:
Fallow, forest and cereal pasture soils had higher
soil organic matter, microbes and carbon content in
different aggregates and aggregate stability.
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56. CONCLUSION
•Bacteria had more influence on soil aggregate
stability and organic carbon sequestration in the
different soil aggregates and bulk soil than fungi
and actinomycetes.
•The relative aggregating powers or abilities of soil
microbes are in this order; Bacteria > Fungi >
Actinomycetes.
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57. CONCLUSION
The micro aggregates and silt-plus clay aggregate
fractions were richer in bacteria possibly due to the
resilient nature of bacteria while the bulk soil and
small macro aggregate were the richest in fungal
communities.
Actinobacteria are the greatest influencers of the
recalcitrant carbon pool in soil.
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58. CONCLUSION
•There are strong relationships between unprotected
organic carbon which is labile, physically protected
carbon (PPOC), chemically protected (CPOC) and
Wet Mean weight diameter (MWDw) however,
PPOC and CPOC had greater influence on MWDw
than UPOC.
•There is a strong relationship between soil microbes
and aggregate stability. 57
59. RECOMMENDATION
From this study it is suggested that soil tillage be minimized by
practicing farmers while practices that improve soil organic
matter content should be employed or encouraged among
farmers in continuous cultivation practice.
It is also suggested that land-use management that promotes soil
organic matter and microbial buildup should be encouraged to
establish and maintain good soil health, crop productivity and
environmental wellbeing, since beneficial soil microbial
communities enhance suppression of soil borne pathogens in
agricultural soils.
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60. RECOMMENDATION
Generally, the growing of trees, shrubs and legumes will improve
the soil microbial population as their roots and nodules harbour
microbes or serve as habitat for soil microbes, their interaction
will improve the soil aggregate stability and organic carbon
storage and consequently soil fertility/quality.
It is also suggested and recommended that further studies be
carried out using more advanced methods so as to gain more
knowledge regarding soil microbes and their efficiency in soil
carbon sequestration and aggregate stabilization.
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62. PUBLICATION FROM RESEARCH
Lawal, H.M., Salifu, U.M., Amapu, I.Y., Atta, H.I. (2020).
Diversity of microbes in soil aggregates fractions under
different land uses in Northern Guinea Savanna, Nigeria.
FUDMA Journal of Sciences. Vol 4(2):510-518. DOI:
https://doi.org/10.33003/fjs-2020-0402-192
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63. SOIL PARAMETERS MEASURED
Soil microbiological properties
Colony forming unit was computed as thus: Total heterotrophic count
Colony forming unit per gram of bacteria or fungi = CPP × DF (Lawal, 2020)
Where:
CPP= average number of colonies per plate.
DF= dilution factor
WT= dry weight of soil
All results on colony forming unit per gram of soil microbes were expressed
on dry weight basis, after determining the gravimetric moisture content in
the soil.
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WT
