ABSTRACT
Five experiments: leaf litter production, leaf litter decomposition,
quantity of precipitation pathways, nutrient cycling of leaf litter and of
precipitation pathways, and maize production were conducted in 2016 and 2017 in
Diospyros crassiflora plantation in the
Humid Forest Research Station, Forestry Research Institute of Nigeria (FRIN),
Okwuta-Ibeku, Umuahia, Abia State, Nigeria. A randomised complete block design
(RCBD) was used to study the leaf litterfall of Diospyros crassiflora in the D.
crassiflora plantation. A 2 x 6 and a 2 x 7 factorial experiment each in
RCBD were also conducted in 2016 and 2017 respectively to study the bi-weekly
decomposition rates of D. crassiflora in
the nursery unit of FRIN. A 3 x 9 x
2 factorial experiment in RCBD was also used to
study the quantity of water and nutrient cycling contents of three precipitation
pathways overtime in the D. crassiflora plantation.
A 3 x 3 factorial experiment in RCBD was used to determine the effect of
organic and inorganic fertilizer rates on the growth and yield of Zea mays in a 4 and 5 years old D. crassiflora plantation in 2016 and in
2017, respectively. Result showed that, the dry season months of November-
March had leaf litter production of 11.58 – 7.48 kg ha-1 in 2016 and
22.70 -16.10 kg ha-1 in 2017 which were significantly higher than
the rainy season months of April-October of 1.98 - 6.03 kg ha-1 in
2016 and 4.80 - 13.00 kg ha-1 in 2017. Total leaf litter
decomposition (100%) rates of soil surface-placed and soil-incorporated modes
were obtained at the 12thand 14th weeks after leaf litter
placement in 2016 and 2017 respectively. The results of nutrient contents in
the leaf litters in 2016 and 2017 were statistically similar for both macro and
micro-elements (N, P, K, Ca, Na, Mg, Fe, Org. M., Org. C, pH and Pb). In terms
of the precipitation pathways stemflow and rainfall had significantly the
highest and the least water quantities, respectively. Stemflow pathway in 2016
and 2017 had the highest (p ≤ 0.05) nutrient concentrations of calcium (Ca),
potassium (K), magnesium (Mg), chlorine (Cl), iron (Fe), lead (Pb) and
tetraphosphate. Application of inorganic (NPK 15:15:15) and organic (poultry
manure) fertilizer at 0.00kg, 250.00kg, 500.00kg and 0.00t, 2.00t and 4.00t rates in 2016 and 2017 improved and increased
the growth attributes of maize in D.
crassiflora plantation. The results of the various rates of fertilizer (F),
poultry manure (P) and the fertilizers x poultry manure treatment combinations
were not significantly different from each other within the period of study in
terms of maize yield attributes. In conclusion, agriculturists,
environmentalists and foresters are encouraged to adopt D. crassiflora species in
their farming system and plantation establishment because of its values in
mineral nutrients. The leaf litter of D.
crassiflora should be utilized as one
of the main sources of organic manure due to its fast rate of decomposition and
consequently its high mineral contents that could be deposited in the soil.
TABLE ON CONTENTS
Title page i
Certification ii
Declaration iii
Dedication iv
Acknowledgement v
Table of
Contents vi
List of Tables
xiii
List of
Figures xvii
List of Plates xviii
List of
Acronyms and Abbreviations
xix
Abstract xxi
CHAPTER 1
1.0
INTRODUCTION
1.1 Background Information 1
1.2 Statement
of the Problem 5
1.3 Objectives
of the Study 6
1.4 Justification
of the Study 7
1.5 Scope
of the Study 8
CHAPTER 2
2.0 LITERATURE REVIEW
2.1 Leaf litter Production 10
2.1.1 Types and sources of leaf litter 11
2.1.2 Seasonality of leaf litter production 12
2.1.3 Pattern of leaf litter production 13
2.1.4 Causes
of leaf litter production 14
2.1.4.1 Defoliation 14
2.1.4.2 Climate change 15
2.1.4.3
Physical disturbance to forest 16
2.1.4.4 Stand
structure and changes in stand community structure 16
2.1.4.5 Mechanism of leaf abscission and leaf
senescence 17
2.1.4.6
Water stress 18
2.1.5
Uses of leaf litter production 20
2.1.5.1 Restoration
of land degraded site/erosion 21
2.1.5.2 Uses of leaf litter production on growth
performance of forest species 21
2.1.6 Types of nutrients disposed 25
2.2 Leaf Litter Decomposition 26
2.2.1 Decomposition methods 30
2.2.2 Nutrient
cycling via litterfall 31
2.2.3 Nutrient
cycling via leaf litter decomposition 32
2.2.4 Nutrient contents 33
2.3 Nutrient
Accretion to the Soil 35
2.3.1 Nutrient accretion through litterfall 35
2.3.2 Nutrient accretion via stemflow and
throughfall 36
2.3.3 Morphological
characteristics influencing stemflow 38
2.3.4 Nutrient
cycling through incipient precipitation, stemflow and 39
throughfall
2.3.5 Nutrient cycling via rainfall (incipient
precipitation) 41
2.4 Agroforestry System 42
2.4.1 Classification of
agroforestry systems and practices 44
2.4.2 Roles
of agroforestry in forest management and carbon cycle 47
2.4.3 Provision of healthy forest
ecosystem 49
2.4.4 Socio-economic benefits 50
2.4.5 Application of fertilizers on arable crop production in
agroforestry 51
ecosystem
2.4.6 Effect of organic fertilizers on arable crop production in
agroforestry 52
ecosystem
2.4.7 Effect of inorganic fertilizer on crop production in agroforestry
ecosystem 54
2.4.8 Combination of inorganic fertilizers and organic
fertilizers/manures 55
2.4.9 Plant species used in agroforestry
ecosystems 56
2.5 Description of the Study Tree Species (Diospyros crassiflora) 62
2.5.1 Local names
of the plant in various parts of the world 65
2.5.2 Propagation of Diospyros crassiflora 68
2.5.3 Management of Diospyros crassiflora 69
2.5.4 Importance
of Diospyros crassiflor 69
2.6 Origin
of Maize (Zea mays L.) 71
2.6.1 Ecology of
maize 72
2.6.2 Utilization
of maize 73
CHAPTER 3
3.0 MATERIALS AND METHODS
3.1 Study Location 75
3.2 Methodology 79
3.2.1 Stand structure of Diospyros
crassiflora plantation 79
at Okwuta-Ibeku, Umuahia, Nigeria
3.2.1.1 Observation of the flowering and fruiting of Diospyros crassiflora 80
for the 2016 and 2017 study
periods.
3.2.2 Experiment 1: Leaf litterfall studies of D. crassiflora in 2016 and 2017 82
3.3.3 Experiment 2:
leaf litter decomposition studies 84
3.2.3.1 Leaf litter placement methods 84
3.2. 3.1a. Surface-placed leaf
litter 84
3.2.3.1b Soil-incorporated leaf litter study 85
3.2.4 Experiment 3: Nutrient cycling through precipitation pathways at 88
Okwuta-Ibeku, Umuahia
3.2.4 Experiment 4: Maize (var. OBA- super) production in D. crassiflora 90
based agroforestry ecosystem in
Okwuta- Ibeku, Umumahia,
Abia State.
3. 2.4.1 Growth characteristics of maize plants 91
3.2.4.2 Yield
characteristics of maize plants in D.
crassiflora agroforestry 94
ecosystem
3.2.5.1 Litter half-life and full-life estimations 97
3.2.5.2 Litter
turnover coefficient 97
3.2.5.3 Relative leaf litter disappearance rate (% day -1
sampling interval-1) 98
3.2.6 Physico-chemical analysis of leaf litter
nutrient contents 98
3.2.7 Nutrient analysis of rainfall (incipient precipitation),
throughfall and 99
stemflow
3.5 Statistical analysis and computation procedures 101
CHAPTER 4
4.0 RESULTS AND DISCUSSION
4.1 Results 102
4.1.1 Leaf
litterfall of Diospyros crassiflora 102
4.1.2 Leaf Litter Decomposition Rates of Diospyros crassiflora 105
4.1.2.1 Cumulative leaf litter
decomposition rates in 2016 and 2017 105
4
.1.2.2 Relative decay rates (% day -1) for soil incorporated and
soil 107
surface placed leaf litters in 2016
and 2017
4.1.2.3 Regression equation parameters, observed leaf litter
decomposition 110
rates, expected times for 100%
(full life) and 50% (half life) leaf litter
decomposition and the correlation
coefficients of the two leaf litter
placement modes of Diospyros crassiflora leaf litter in
2016 and 2017
in Umuahia, Nigeria
112
crassiflora
plantation.
4.1.3.2
Phophorus (P) (mg l-1) contents of the leaf litter of Diospyros 114
crassiflora
plantation.
4.1.3.3
Potassium (K) (mg l-1) contents of the leaf litter of Diospyros 115
crassiflora
in a plantation.
4.1.3.4
Sodium (Na) (mg l-1) contents of the leaf litter of Diospyros 117
crassiflora
plantation.
4.1.3.5 Calcium (Ca) (mg l-1) contents of the
leaf litter of Diospyros 119
crassiflora in a plantation. 4.3.6 Magnesium (Mg) (mg l-1)
contents
of the leaf litter of Diospyros crassiflora in a plantation.
4.1.3.6 Magnesium (Mg) (mg l-1) contents of the leaf litter
of Diospyros 121
crassiflora in a plantation.
4.1.3.7 Chlorine (Cl) contents of the leaf litter of Diospyros crassiflora 123
plantation at Umuahia, Nigeria
4.1.3.8 Organic Matter (Org. M) (mg l-1) contents of the leaf
litter of 125
Diospyros
crassiflora plantation at Umuahia, Nigeria
4.1.3.9 Organic
Carbon (Org. C) (mg l-1) contents of the leaf litter of 127
Diospyros
crassiflora in a plantation at Umuahia, Nigeria
4.1.3.10
Iron (Fe) (mg l-1) contents of the leaf litter of Diospyros crassiflora 129
in a plantation at Umuahia, Nigeria
4.1.3.11pH values contents of the leaf litter of Diospyros crassiflora in a 130
plantation at Umuahia, Nigeria
4.1.3.12 Cadmium (Cd) (mg l-1) contents of the leaf litter of Diospyros 132
crassiflora in a plantation at Umuahia, Nigeria.
4.1.3.13 Lead
(Pb) (mg l-1) contents of the leaf litter of Diospyros crassiflora 133
in a plantation at Umuahia,
Nigeria
4.1.4: Nutrient
Cycling Through Precipitation Pathways: Rainfall, 135
Stemflow and Throughfall
4.1.4.1 Quantity of water (mm) overtime (months) of various
precipitation 135
pathways in D. crassiflora Plantation in Umuahia, Nigeria in 2016
and 2017
4.1.4.1a Nitrate (mg l-1) contents of water of
precipitation pathways over time 138
(month) (March – November) in
2016 and 2017 at Diospyros crassiflora
plantation in Umuahia, Nigeria.
4.1.4.1b Nitrate (mg l-1)
contents of three precipitation pathways in 2016 and 139
2017 at Diospyros crassiflora plantation, Umuahia, Nigeria.
4.1.4.1c Nitrate (mg l -1) contents of water of
various precipitation pathways 140
over time (months) in Diospyros crassoflora plantation, in Umuahia,
Nigeria.
4...4.1d
Nitrate contents (mg l-1) of treatment interactions of three 141
Precipitation pathways overtime
(months) in the two study periods
(Years) in 2016 and 2017 at
Umuahia, Nigeria
4.1.4.2a Tetraphosphate (mg l-1) contents of
water of precipitation pathways 142
over time (month) (March –
November) in 2016 and 2017 at Diospyros
crassiflora plantation in Umuahia, Nigeria.
4.1.4.2b Tetraphosphate contents (mg l-1) of
three precipitation pathways in 144 2016 and 2017at Diospyros crassiflora
plantation, Umuahia, Nigeria.
4.1.5.2cTetraphosphate contents (mg l-1) of water
of three precipitation 145
pathways over time (months) in Diospyros crassiflora plantation,
in Umuahia, Nigeria.
4.1.5.2d Tetraphosphate contents (mg l-1) of
treatment interactions of three 147 Precipitation pathways overtime (9 months)
in the two study periods
(Years) in 2016 and 2017 at
Umuahia, Nigeria
4.1.4.3a Potassium (K) (mg l-1) contents of water
of precipitation pathways 149
over time (months)
(March–November) in 2016 and 2017 at Diospyros
crassiflora plantation in Umuahia, Nigeria.
4.1.4.3b Potassium (mg l-1) contents in three
Precipitation pathways in 2016 151
and 2017 at Diospyros crassiflora plantation in Umuahia, Nigeria
4.1.4.3c Potassium (K) (mg l-1) contents of water
of three precipitation pathways 152
overtime (months) in Diospyros crassoflora plantation, in Umuahia,
Nigeria.
4.1.4.3d Potassium (K) (mg l -1) contents of
treatment interactions of three 153
Precipitation pathways overtime
(9 months) in the two study periods
(Years) in 2016 and 2017 at
Umuahia, Nigeria.
4.1.4.4a Sodium (Na) (mg l-1) contents of water
of precipitation pathways 155
over time (months) (March –
November) in 2016 and 2017 at
Diospyros crassiflora in
Umuahia, Nigeria
4.1.4.4b Sodium (Na) (mg l-1) contents of three
precipitation pathways in 2016 156
and 2017 at Diospyros crassiflora
plantation, Umuahia, Nigeria.
4.1.4.4c Sodium (Na) (mg l-1) contents of water
of various precipitation 157
pathways over time (months) in Diospyros crassiflora plantation,
in Umuahia, Nigeria.
4.1.4.4d Sodium (Na) (mg l -1) contents in three
Precipitation pathways 159 overtime (months) in the two study periods
(Years) in 2016 and 2017
at Umuahia, Nigeria
4.1.4.5a Calcium (Ca) (mg l-1)
contents of water of precipitation pathways 161
over time
(months) (March–November) in 2016 and 2017 at Diospyros crassiflora plantation in Umuahia, Nigeria.
4.1.4.5b Calcium (mg l-1) contents in three
Precipitation pathways in 2016 and 162
2017 at Diospyros crassiflora plantation in Umuahia, Nigeria
4.1.4.5c Calcium (Ca) (mg l -1) contents of water
of various precipitation 163
pathways over time (months) in Diospyros crassiflora plantation in
Umuahia, Nigeria.
4.1.4.5d Calcium (Ca) contents (mg l -1) of
treatment interactions of three 164
Precipitation pathways overtime
(months) in two study periods (Years)
in 2016 and 2017 at Umuahia,
Nigeria
4.1.4.6a Magnesium (mg l-1) contents of
precipitation pathways over time 166
(months) (March–November) in 2016
and 2017 at Diospyros
crassiflora plantation in Umuahia, Nigeria.
4.1.4.6b Magnesium (Mg) (mg l-1) contents of
three Precipitation pathways in 167
2016 and 2017 at Diospyros crassiflora plantation in
Umuahia, Nigeria
4.1.4.6c Magnesium (Mg) contents (mg l-1) of
three precipitation pathways 168
over time (months) in a Diospyros crassiflora plantation in
Umuahia,
Nigeria.
4.1.4.6d
Magnesium (Mg) contents (mg l-1) of treatment interactions of three 170
Precipitation pathways overtime (9
months) in the two study periods
(Years) in 2016 and 2017 in D. crassiflora in Umuahia, Nigeria
4.1.4.7a
Chlorine (Cl) contents of water of three precipitation pathways over 171
time (9 months) (March–November)
in 2016 and 2017 at Diospyros
crassiflora plantation in Umuahia, Nigeria.
4.1.4.7b Chlorine (Cl) (mg l-1) contents of three
precipitation pathways in 2016 173
and 2017 in Diospyros crassiflora
plantation, Umuahia, Nigeria.
4.14.7c Chlorine (Cl) (mg l-1) contents of water
of various precipitation 174
pathways over time (months) in Diospyros crassoflora plantation,
in Umuahia, Nigeria.
4.1.4.7d Chlorine (Cl) (mg l-1) contents of
treatment interactions of three 175
Precipitation pathways overtime
(9 months) in the two study periods
years in 2016 and 2017 in Diospyros crassiflora in Umuahia,
Nigeria
4.1.4.8a: Iron (Fe) contents (mg l-1) of water of
precipitation pathways over time 177
(9 month) (March–November) in
2016 and 2017 in Diospyros crassiflora
plantation in Umuahia, Nigeria.
4.1.4.8b:Iron (Fe) (mg l-1)
contents in three precipitation pathways in 2016 and 179
2017 at Diospyros crassiflora agroforestry ecosystem in Umuahia,
Nigeria.
4.1.4.8c Iron (Fe) (mg l -1) contents of water of
three precipitation pathways 180
overtime (months) in Diospyros crassiflora plantation in 2016
and
2017 at Umuahia, Nigeria.
4.1.4.8d Iron (Fe) contents (mg l-1) of treatment
interactions of three 182
Precipitation pathways overtime (9
months) in the two study periods
(Years) in 2016 and 2017 at Umuahia,
Nigeria
4.1.4.9a pH values of water of precipitation pathways over
time (month) 183
(March–November) in 2016 and 2017
at Diospyros crassiflora
plantation in Umuahia, Nigeria.
March – 186
November) in 2016 and 2017 at
Umuahia, Nigeria
4.1.4.9d pH values in three Precipitation pathways overtime
(9 months) in 187
two study Years (2016 and 2017)
at Umuahia, Nigeria
4.1.4.10a Lead (Pb) (mg l-1) contents
precipitation pathways (March–November) 189
in 2016 and 2017 at Diospyros crassiflora plantation in
Umuahia, Nigeria
4.1.4.10b Lead (Pb) (mg l-1)
contents of three Precipitation pathways in 2016 and 190
2017 in Diospyros crassiflora plantation at Umuahia, Nigeria.
4.1.4.10c Lead (mg l -1) contents of three
Precipitation pathways March- 191
November) in 2016 2017 in Diospyros crassoflora plantation, in
Umuahia, Nigeria.
4.1.4.10d Lead (mg l-1)
contents in three Precipitation pathways overtime 192
(9 months) in the two study periods (Years) in
2016 and 2017 at
Umuahia, Nigeria
4.1.1.5 Maize Production in D. crassiflora Based Agroforestry
Ecosystem 193
in Umuahia
4.1.5.1 Plant parameters {plant
height (cm), plant diameter (cm), crown 193
diameter
(cm) and crown depth (cm)} of Diospyros
crassiflora
agroforestry
ecosystem in December, 2015, 2016 and 2017.
4.1.5.2 Physico-chemical properties of soil and poultry
manure samples 194
before and after experiment in Diospyros crassiflora agroforestry
ecosystem in 2016 and 2017 at
Umuahia, Nigeria
4.1.5.3 Effect of inorganic
fertilizer (NPK 15:15:15) and poultry manure 196
on plant
height (m) of maize (Zea mays L.) in 2016 and 2017 in a
Diospyros crassiflora ecosystem
4.1.5.4 Effect of inorganic
fertilizer (NPK 15: 15: 15) and poultry manure 198
rates on leaf
number of maize (Zea mays L.) in 2016 and 2017 in a
Diospyros crassiflora agroforestry ecosystem
4.1.5.5 Effect of inorganic
fertilizer (NPK 15:15:15) and poultry manure 201
on plant
diameter (cm) of maize (Zea mays L.) in 2016 and 2017 in a
Diospyros crassiflora agroforestry ecosystem
4.1.5.6 Effect of
inorganic (NPK 15:15:15) and poultry manure fertilizer rates 204
on the number of sub-tassels and
length of main tassels (cm) of maize
(Zea mays L.) in 2016 and
2017 in Diospyros crassiflora agroforestry
ecosystem
4.1.6. Yield Characteristics of Maize Plants in D. crassiflora
agroforestry 206
Ecosystem
4.1.6.1 Effect
of inorganic fertilizer (NPK 15:15:15) and poultry manure 206
rates on number of cobs per plant,
number of seeds per cob and
diameter of ears per cob (mm) of maize (Zea
mays L. ) at the 12th weeks
after planting in 2016 and 2017 in Diospyros
crassiflora agroforestry
ecosystem
4.1.6.2 Effect
of inorganic (NPK 15:15:15) and poultry manure fertilizer 208
rates on diameter of cobs (mm),
kernel depth (cm) and length of ears
(cm) of maize (Zea mays L.) at 12th
weeks after planting in 2016 and 2017.
4.1.6.3 Effect
of inorganic fertilizer (NPK 15:15:15) and poultry manure 210
fertilizer rates on number of roots,
roots length (cm) and roots depth (cm)
of maize (Zea mays L.) at 12th week after
planting in 2016 and 2017 in
Diospyros crassiflora agroforestry ecosystem
4.1.6.4 Effect of inorganic
fertilizer (NPK 15:15:15) and poultry manure rates 213
on
dry weights of cobs (kg) and dry weight of roots (kg) of maize
(Zea
mays L.) in 2016 and 2017 in Dioaspyros crassiflora agroforestry
ecosystem
4.2.7 Discussion 215
4.1.7.1 Leaf litter fall of Diospyros crassiflora 215
4.1.7.2 Cumulative Leaf
Litter Decompostion Rates 217
4.1.7.3 Relative decay/disappearance
rates 219
4.1.7.4 Regression equation parameters, observed leaf litter
decomposition 220
rates, expected times for 100%
(full life) and 50% (half life) losses
and te correlation coefficients
of the two leaf litter placement modes
of Diospyros crassiflora leaf litter in 2016 and 2017 in Umuahia,
Nigeria
4.1.7.5 Quantity of
water and nutrient cycling through precipitation pathways 222
4.1.7.6 Maize production in D. crassiflora based agroforestry ecosystem in 225
Umuahia
CHAPTER 5
5.0 CONCLUSION
AND RECOMMENDATIONS
5.1 Conclusion 229
5.1 Recommendations 230
References
LIST OF TABLES
2.1.5.2: Beneficial effects of
tree based agroforestry system 23
2.4.9a: Preferred agroforestry species in Nigeria 59
2.4.9b: Preferred agroforestry species in Cameroon 60
2.4.9c: Preferred agroforestry species in Ghana 61
3.0: Monthly
climatic variables in 2016 and 2017 at the study site in 77
the
humid forest research station, Forestry Research Institute
of
Nigeria (FRIN), Umuahia, Nigeria
4.1.1: Mean
monthly leaf litter production of Diospyros
crassiflora 104
plantation in 2016 and 2017 at
Umuahia, Nigeria
4.1.2.1: Leaf litter decomposition percentages of Diospyros crassiflora at 106
two leaf
litter placement methods over period (weeks after
leaf litter
placement) in 2016 and 2017
4.1.2.2: Relative decay rates (% day -1) for soil
incorporated and surface 109
placed leaf
litter in 2016 and 2017
4.1.2.3: Regression equation
parameters observed leaf litter decomposition 111
rates, expected times for 100% (full
life) and 50% (half life) losses
and the correlation coefficients of
two leaf litter placement
modes of Diospyros crassiflora leaf litter in 2016 and 2017 in
Umuahia, Nigeria
4.1.3.1: Nitrogen
(N) (mg l-1) contents of the leaf litter of Diospyros 113
crassiflora in a plantation
4.1.3.2: Phosphorus (P) (mg l-1)
contents of the leaf litter of Diospyros 114 crassiflora
in a plantation.
4.1.3.3: Potassium (K) (mg l-1)
contents of the leaf litter of Diospyros 116
crassiflora in a plantaion
4.1.3.4:
Sodium (Na) (mg l-1) contents of the leaf litter of Diospyros 118
crassiflora in a plantation.
4.1.3.5: Calcium (Ca) (mg l-1)
contents of the leaf litter of Diospyros 120
crassiflora in a plantation.
4.1.3.6: Magnesium (Mg) (mg l-1)
contents of the leaf litter of Diospyros 122
crassiflora plantation at Umuahia,
Nigeria
4.1.3.7: Chlorine (Cl) (mg l-1)
contents of the leaf litter of Diospyros 124
crassiflora in a plantation at Umuahia,
Nigeria.
4.1.3.8: Organic Matter (Org. M)
contents of the leaf litter of Diospyros 126
crassiflora in a plantation at Umuahia,
Nigeria.
4.1.3.9: Organic Carbon (Org. C)
(mg l-1) contents of the leaf litter of 128
Diospyros
crassiflora in a plantation at Umuahia, Nigeria.
4.1.3.10:
Iron (Fe) (mg l-1) contents of the leaf litter of Diospyros crassiflora in 129
a plantation at Umuahia, Nigeria
4.1.3.11: pH-value contents of
the leaf litter of Diospyros crassiflora
in 131
a plantation
at Umuahia, Nigeria
4.1.3.12: Cadmium (Cd) (mg l-1)
contents of the leaf litter of Diospyros 132
crassiflora in a plantation at Umuahia,
Nigeria
4.1.3.13 Lead
(Pb) (mg l-1) contents of the leaf litter of Diospyros crassiflora in a 134
plantation at Umuahia, Nigeria
4.1.4.1: Quantity
of water (mm) overtime (months) of various precipitation 137
pathways in D. crassiflora plantation in Umuahia, Nigeria in 2016 and
2017.
4.1.4.1a: Nitrate (mg l-1) contents
of water of precipitation pathways over time 138
(month)
(March–November) in 2016 and 2017 at Diospyros
crassiflora
plantation in
Umuahia, Nigeria
4.1.4.1c:
Nitrate (mg l -1) contents of water of various precipitation
pathways 140
overtime (months) in Diospyros crassoflora plantation, in Umuahia, Nigeria.
4.1.4.1d:Nitrate contents of
treatment interactions of three precipitation 141
pathways overtime (months) in the
two study periods (Years) in
2016 and 2017 at Umuahia, Nigeria
4.1.4.2a: Tetraphosphate (mg l-1)
contents of water of precipitation pathways over 143
time (month)
(March – November) in 2016 and 2017 at Diospyros
crassiflora plantation in Umuahia,
Nigeria. and 2017 in Diospyros crassiflora plantation in Umuahia, Nigeria.
4.1.4.2c: Tetraphosphate (mg l -1) contents of water of various precipitation 146
pathways over
time (months) in Diospyros crassoflora plantation, in
Umuahia,
Nigeria.
4.1.4.2d: Tetraphosphate (mg l -1)
contents of treatment interactions of three 148
Precipitation
pathways overtime (9 months) in the two study periods
(Years) in
2016 and 2017 at Umuahia, Nigeria
4.1.4.3a: Potassium (K) (mg l-1)
contents of water of precipitation pathways over 150
time (month)
(March – November) in 2016 and 2017 at Diospyros
crassiflora plantation in Umuahia,
Nigeria.
and 2017 at Diospyros crassiflora plantation in Umuahia, Nigeria
4.1.4.3c: Potassium (K) (mg l -1)
contents of water of three precipitation 152
pathways over
time (months) in Diospyros crassoflora plantation, in
Umuahia,
Nigeria.
4.1.4.3d: Potassium (K) (mg l -1)
content of treatment interactions of three 154
Precipitation
pathways overtime (months) in the two study periods
(Years) in
2016 and 2017 at Umuahia, Nigeria.
4.1.4.4a: Sodium (Na) (mgl-1)
contents of water of precipitation pathways over 155
time (months)
(March – November) in 2016 and 2017 at Diospyros
crassiflora in Umuahia, Nigeria 2016 and 2017at Diospyros crassiflora plantation, Umuahia, Nigeria.
4.1.4.4c: Sodium (Na) (mg l -1) contents of water of various precipitation 158
pathways over
time (months) in Diospyros crassoflora plantation, in
Umuahia,
Nigeria.
4.1.4.4d: Sodium (Na) (mg l -1)
contents in three Precipitation pathways overtime 160
(months) in
the two study periods (Years) in 2016 and 2017 at
Umuahia,
Nigeria.
4.1.4.5a:
Calcium (Ca) (mg l-1) contents of precipitation pathways over time 161
(month) (March–November) in 2016 and 2017 at Diospyros
crassiflora plantation in Umuahia,
Nigeria.
4.1.4.5b:
Calcium (mg l-1) contents in three Precipitation pathways in 2016 162
and 2017 at Diospyros crassiflora
plantation in Umuahia, Nigeria
4.1.4.5c: Calcium (Ca) (mg l -1)
contents of water of various precipitation 163
pathways over time (months) in Diospyros crassiflora plantation in
Umuahia,
Nigeria.
4.1.4.5d: Calcium (Ca) contents
(mg l -1) in three Precipitation pathways 165
over time (months) in the two study
periods (Years) in 2016 and 2017 at
Umuahia,
Nigeria.
4.1.4.6c:Magnesium (mg l -1)
contents of water of various precipitation pathways 169
overtime
(months) in a Diospyros crassiflora
plantation in Umuahia,
Nigeria.
4.1.4.6d: Magnesium (mg l-1)
in three Precipitation pathways overtime (months) 170
in the two
study periods (Years) in 2016 and 2017 at Umuahia, Nigeria.
4.1.4.7a Chlorine (Cl) contents
of water of three precipitation pathways over time 172
(9 month)
(March–November) in 2016 and 2017 at Diospyros
crassiflora
plantation in
Umuahia, Nigeria.
tion 174
pathways over
time (9 months) in Diospyros crassoflora
plantation, in
Umuahia, Nigeria.
4.1.4.8a: Iron (Fe) contents (mg
l-1) of precipitation pathways over time (months) 178
(March–November)
in 2016 and 2017 in Diospyros crassiflora
plantation
in Umuahia,
Nigeria.
time 181
(months) in Diospyros crassiflora plantation in 2016
and 2017 at
Umuahia,
Nigeria.
4.1.4.8d Iron (Fe) contents (mg l-1)
of treatment interactions of three Precipitation 182
pathways
overtime (9 months) in the two study periods (Years) in 2016
and 2017 at
Umuahia, Nigeria
4.1.4.9a: pH values of water of
precipitation pathways over time 184
(months:
March–November) in 2016 and 2017 at Diospyros
crassiflora
plantation in
Umuahia, Nigeria.
months: 186
March-November)
in 2016 and 2017 at Umuahia, Nigeria.
4.1.4.9d pH values in three
Precipitation pathways overtime (9 months) in 188
two study
Years (2016 and 2017) at Umuahia, Nigeria
4.1.4.10a Lead (Pb) (mg l-1)
contents precipitation pathways 189
(March–November)
in 2016 and 2017
at Diospyros
crassiflora plantation in Umuahia, Nigeria 190
4.1.4.10b
Lead (Pb) (mg l-1) contents of three Precipitation pathways in 2016
and 2017 in Diospyros crassiflora
plantation at Umuahia, Nigeria.
4.1.4.10c Lead (mg l -1)
contents of three Precipitation pathways March- 191
November) in
2016 2017 in Diospyros crassoflora plantation, in
Umuahia,
Nigeria.
4.1.4.10d Lead (mg l-1)
contents in three Precipitation pathways overtime 192
(9 months) in
the two study periods (Years) in 2016 and 2017 at
Umuahia,
Nigeria
4.1.5.1 Plant parameters {plant
height (cm), plant diameter (cm), crown diameter 193
(cm) and crown
depth (cm)} of Diospyros crassiflora agroforestry
ecosystem in
December, 2015, 2016 and 2017.
4.1.5.2 Physico-chemical
properties of soil and poultry manure samples before 195
and after
experiment in Diospyros crassiflora agroforestry ecosystem in
2016 and 2017
at Umuahia, Nigeria
4.1.5.3 Effect of inorganic
fertilizer (NPK 15:15:15) and poultry manure on plant 197
height (m) of maize
(Zea mays L.) in 2016 and 2017 in
a Diospyros
crassiflora ecosystem
4.1.5.4 Effect of inorganic fertilizer (NPK 15: 15: 15) and poultry
manure 200
rates on leaf
number of maize (Zea mays L.) in 2016 and 2017 in a
Diospyros crassiflora agroforestry ecosystem
4.1.5.5 Effect of inorganic
fertilizer (NPK 15:15:15) and poultry manure on 203
plant diameter
(cm) of maize (Zea mays L.) in 2016 and 2017 in a
Diospyros crassiflora agroforestry ecosystem
4.1.5.6 Effect of inorganic (NPK 15:15:15) and poultry manure fertilizer
rates 205
on the number
of sub-tassels and length of main tassels (cm) of
maize (Zea mays
L.) in 2016 and 2017 in Diospyros
crassiflora
agroforestry
ecosystem
4.1.6.1 Effect of inorganic
fertilizer (NPK 15:15:15) and poultry manure rates 207
on number of
cobs per plant, number of seeds per cob and diameter of
ears per cob
(mm) of maize (Zea mays L.) at the 12th weeks after planting
in 2016 and
2017 in Diospyros crassiflora agroforestry ecosystem
4.1.6.2 Effect of inorganic (NPK 15:15:15) and poultry manure
fertilizer rates on 209
diameter of
cobs (mm), kernel depth (cm) and length of ears (cm) of
maize (Zea mays
L.) at 12th weeks after planting in 2016 and 2017.
4.1.6.3 Effect of inorganic
fertilizer (NPK 15:15:15) and poultry manure 212
fertilizer
rates on number of roots, roots length (cm) and roots depth
(cm) of maize (Zea mays
L.) at 12th week after planting in 2016 and
2017 in Diospyros crassiflora agroforestry ecosystem
4.1.6.4 Effect of inorganic
fertilizer (NPK 15:15:15) and poultry manure 214
rates on dry
weights of cobs (kg) and dry weight of roots (kg) of maize
(Zea mays
L.) in 2016 and 2017 in Dioaspyros
crassiflora
agroforestry
ecosystem
LIST OF FIGURES
3.1.1: Map of Abia State, Nigeria and the Study Site
at Okwuta-Ibeku, 78
Umuahiain Umuahia North Local Government Area (L.G.A.).
LIST OF PLATES
1a: Determination of plant height 81
1b: Determination of plant diameter
81
1c: Determination of crown diameter 81
1d: Determination of crown depth 81
2a: Clearing of experimental
site 83
2b: Prepared litter trays 83
2c: Litters in tray 83
3a: Filling of polypots 87 3b: Arrangement of polypots 87
3c: Watering of Polypots 87
3d: Extraction of leaf litter 87
4a: Litter tray and containers for stenflow and throughfall 89
4b: Connecting hose to species for stem flow 89
4c: Measurement of stemflow 89
4d: Samples of incipient precipitation pathways for analysis 89
5a: D. crassiflora
plantation 92
5b: Demarcation and pegging of plots 92
5c: Planting of Zea mays
(maize) 92
5d: Zea mays at 6 weeks 92
6a: Data collection of maize height using
100cm wooden ruler 93
6b: Measurement of length of the main tassel 93
6c: Counting of sub- tassels 93
7a: Counting of roots 96
7b: Measurement of ear length
96
7c: Measurement ear diameter 96
7d: Counting of seeds per cob 96
7e: Weighing of cobs 96
LIST OF ACRONYMS AND ABBREVIATIONS
AAS: Atomic Absorption
Spectrophotometer
AgNO3: Silver Nitric
iii Oxide
AOAC: Association of Official
Analytical Chemists
APHA: America Public Health
Association
Aug.: August
BS%: Base Saturations Percentage
C: Carbon
C mol kg-1: Concentration of mole per kilogram
Ca: Calcium
CEC: Cation Exchange Capacity
Cm: Centimetre
CNREM: College of Natural
Resources and Environmental Management
CO: Carbon ii Oxide
CO2: Carbon iv Oxide
DBH: Diameter Breast Height
DEC.: December
D. crassiflora:Diospyroscrassiflora
EA: Exchangeable acidity
ECEC: Effective cation exchange
capacity
EDTA: Ethylene diaminetetra-acetic
F- LSD: Fisher`s Least Significant Difference
FMANR: Federal Ministry of
Agriculture and Natural Resources
FOREM: Forestry and Environmental Management
FRIN: Forestry Research Institute of Nigeria
FWTA: Flora of West Tropical Africa
g: gram
gkg-1: gram per
kilogram
HOD: Head of Department
H2SO4:
Tetraoxosulphate vi oxide
HCl: Hydrochloric acid
ICRAF: International Centre for Research and
Agroforestry
IF: Inorganic Fertilizer
IF + PM: Inorganic Fertilizer +
Poultry Manure
IPCC: Intergovernmental Panel on
Climate Change
K: Potassium
M x P: Month x Precipitation
Mg: Magnesium
MOUAU: Michael Okpara University of
Agriculture, Umudike
MPTs: Multi-Purpose Tree Species
N: Nitrogen
NEARLS: National Agricultural
Extension and Research Liaison Services
NH4: Ammonium
NO3: Nitrate Oxide
NPK: Nitrogen, Phosphorus,
Potassium
NRCRI: National Root Crops
Research Institute
NS: Not significant
Org. C: Organic Carbon
Org. M: Organic matter
P: Phosphorus
PGS: Post Graduate School
pH: Hydrogen ion concentration
PM: Poultry Manure
PPM: Parts per million
Prec.: Precipitation pathway
RCBD: Randomised Complete Block
Design
SOM –C: Soil Organic
Matter Carbon
TEM: Terrestrial Ecosystem Model
WALP: Weeks after litter
placement
WAP: Weeks after planting
CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND INFORMATION
Ajah (2006) noted that transformation and
movement of materials within soil organic matter pools is a process influenced
by climatic factors (rainfall, temperature, sunshine, relative humidity and
wind), soil type, vegetation and soil organisms. It is possible to trace the cyclic movement of these essential
chemical elements through the biosphere towards determing the interdependencies
that exist among them. The cycles involve both physical (dissolution,
precipitation, volatization and fixation) and chemical (synthesis, degradation
and oxidation-reduction). Forests improve the microclimate by reducing
the change caused by wind, protecting soil against erosion and restoring soil
productivity. Tree crops result in significant improvement in soil fertility
through the addition of plant litter, nutrient cycling, biological nitrogen
fixation, permeability, and water holding capacity, aggregate stability and
soil temperature regimes (Aluko, 2001). Deforestation results in changing the
status of the forest soil. In tropical rain forests, multi-purpose tree species
(MPTs) are found to exert considerable influence on soil properties (Lal et
al., 1975).
Lal et al. (1975)
stated that soil nutrient status could be improved through nutrient
cycling in terms of litterfall, litter decomposition and mineralization. This
phenomenon cannot occur without forest cover. Forests, especially protected, ones
ensure environmental sustainability and conserve biological resources for
future generations (Thies and Pfeil, 2004).
Increasing human population places greater demand on
forests for wood and non- wood resources which consequently results to rapid
decline in the existing forest estates (Ogbonna and Nzegbule, 2010). Otorokpo (2012) noted that due to increasing
pressure, bush fallow periods are short and soil fertility is highly reduced. Low
crop yields are obtained when food crops are planted on farmlands with reduced
soil fertility, continuous cropping and low organic matter contents. The key
component of shifting cultivation system is the recycling of plant nutrients
through the addition of above and below ground biomass of the fallow vegetation
(Otorokpo, 2012). Bush fallow system in the tropics accumulates large biomass
and enriches soil fertility. Nwoboshi, (1975) explained that for optimal
growth, plant requires essential nutrient elements such as potassium (K), magnesium
(Mg) and calcium (Ca). The fertility and productivity of the soil depend partly
on the soil’s capacity to hold these cations on particles of soil and to
exchange them from hydrogen and other ions obtained from the soil or plant
roots. The property that enables the soil to perform this unique function is
the cation exchange capacity (CEC) (Nwoboshi, 1975). Several studies have been
carried out to quantify the rate of leaf litter decomposition which is a major
pathway for the transfer of organic matter and nutrients in the soil within the
forest ecosystemsAccording to Liebig`s law of the minimum, nutrient that can
limit plant growth is an essential plant nutrient, especially if the plant
cannot complete its full life cycle without it (Foster and Bahatti, 2006). There
are two groups of nutrient elements, namely: (a) major, essential or macro-
nutrients and (b) minor, non- essential or micro-nutrients. This classification
is due to their relative abundance and usefulness in plants.
According to Otorokpo (2012) and Tisdale et al. (2003) macro- nutrients can be
broken into two more groups, namely: primary and secondary nutrients. The
primary macro- nutrients are: nitrogen (N), phosphorus (P), potassium (K),
whereas the secondary macro-nutrients are: calcium (Ca), sulphur (S) and
magnesium (Mg) (Foster and Bhatti, 2006; Evans, 1992; Ken, 1986).
Tisdale et al.
(2003) reported that macro-nutrients are consumed in large quantities and are
present in plant tissues in quantities ranging from 0.2% to 4.0% on a dry
weight content. These primary macro-nutrients are often lacking in the soil
mainly because plants use large quantities of these macronutrients for their
growth and survival. Secondary macro nutrients which are always enough in the
soil do not always require fertilizer application.
Micro-nutrients {chlorine (Cl), manganese (Mn), boron
(Bo), iron (Fe), copper (Cu), molybdenum (Mo), and zinc (Zn)} are those
essential elements that plants need for growth but in relatively small
quantities. Organic matters are excellent ways of supplying micro-nutrients to
the soil. According to Tisdale et al.
(2003), micronutrients are present in plant tissues in quantities that are
measured in parts per million (ppm), and range from 5 to 200ppm or that are
less than 0.02% of their dry weights. Evans (1992) observed that green plants
obtain essential elements from the soil through their roots and from the air
through their leaves.
Leaf litter is important in forest ecology because it helps
to return nutrients to the soil through nutrient recycling and consequently,
maintains soil fertility (Nzegbule and Mbakwe, 2001). Decomposition of leaf
litter is the major source of nutrients in forest ecosystems. Litterfall
undergoes microbial decomposition; organically bound nutrients are released as
free ions to the soil and are consequently made available for plant uptake
(Okeke and Omaliko, 1992). The organic matter serves as nutrient source for the
release of nutrient elements. Organic matter enhances the release of nutrients
in the forest ecosystem, thus preventing loss of nutrients from the ecosystem.
Naturally, leaf litter helps to improve the soil structure, increase the water
holding capacity, conserve moisture content, reduce leaching and water infiltration in the
soil.
Efforts are, therefore, made to restore more
sustainable and productive land-use systems, such as agroforestry, for
increased crop and soil productivity per unit area on small farms and also to
maintain ecological balance on the long - term basis through the inclusion of
forest food species (Kang et al.,
1981). Agroforestry is defined as a multiple land use system in which woody
perennials are integrated with crops and animals simultaneously or sequentially
on the same land unit area, using management systems that are compatible with
the culture of the local people (Nair, 1989). Such woody perennials not only
raise the protein requirements of the rural populace but also contribute to
improving the physico-chemical conditions of the soil among other valuable
services rendered (Prassed et al.,
1985). Goor and Vari (1985) and Nair (1989) noted that soils under trees (woody
perennials) have high utilization capacity and infiltration rates and also
enhance the soil productivity.
There is therefore, the need to evaluate the
agroforestry utilization potentials of trees and shrubs with respect to: soil conservation and management, including
soil fertility enhancement. Okeke and Omaliko (1991) emphasized the importance of
utilizing agroforestry ecosystems for efficient and cheap forms of nutrient are
cycling with minimal dependence on costly fertilizers in a low-technology and
low- resource agriculture characteristic of many developing nations. This study
focuses on the leaf litter production, nutrient
cycling rates and growth performaance and yield parameters of photo-period insensitive
arable (Maize - Zea mays L) in Diospyros crassiflora (Hiern–FWTA)
Plantation in Okwuta-Ibeku, Umuahia, Abia State, Nigeria
1.2 STATEMENT OF THE PROBLEM
Litter fall, leaf litter decomposition and nutrient
cycling in tree species are continuous processes which are absolutely slow to
meet up with the short period of bush fallow system. The increasing human
population has placed greater demand on tropical forests for agricultural crops
and other tangible and non- tangible forest products. Okeke and Omaliko (1991)
noted that increase in human population in developing countries has contributed
to the reduction of fallow periods, declining soil fertility and low
productivity of plant products in terms of quality and quantity to sustain the
ever-growing population. Tropical forests accumulate huge quantities of
nutrients. The efficient cycling of nutrients from the soil to the biomass and
back to the soil enables tropical forests to grow on relatively infertile acid
soils of the humid tropics (Otorokpo, 2012). Unsustainable methods of
harvesting tangible and non- tangible forest products result in major
disruptions of nutrient cycling because large quantities of nutrients are
removed from the system.
Leaf litter production and nutrient cycling in bush
fallow systems are efficient and cheap means of nutrient cycling for crop
production with minimal dependence on costly fertilizers in a low technology and
low resources agriculture characteristic of many developing countries (Okeke
and Omaliko, 1991). Costly inorganic
fertilizers have some adverse effect on soil pH, nutrient mineralization and
crop production. Nutrient depletion can be offset by fertilizer application but
this sometimes results in increased population of ground waters and algal
blooms in streams (Otorokpo, 2012).
Soil fertility depletion is the fundamental
biophysical reason for the declining per capita food production in small holder
farms in Africa (Sanchez et al., 1995). Sanchez and Palm (1996) reported
that agricultural system differs from natural systems in one fundamental
aspect. There is a net output of nutrients from the soil through harvesting of
crops. The nutrient removal can create net negative balances if nutrients are
not replaced (Otorokpo, 2012). Nair (1987, 1983,) advanced some hypotheses with
regards to the adverse effects of nutrient removal on soils of tree-based
systems in general and in agroforestry ecosystem, in particular. These include:
a. competition
for moisture and nutrients;
b. production
of growth inhibitors;
c. loss
of nutrients through tree harvesting;
d. possible
adverse effect on soil erosion.
With all these issues at stake, it is necessary to
determine the effective management of environment and soil fertility in order
to sustain adequate food and other forest products. Studies on leaf litter production and nutrient
cycling potentials of tree-based agroforestry systems are scarce. There is
equally lack of interest in Diospyros
crassiflora tree establishment, especially in monocultures despite its
commercial potentials. Presently, there is little or no information on leaf
litter production potentials of D.
crassiflora. Besides, there has been no research information on the
performance of arable crops, especially in D.
crassiflora- based agroforestry ecosystems.
1.3 OBJECTIVES OF THE STUDY
The broad
objective of this study is the assessment of the leaf litter production and
nutrient cycling of D. crassiflora in
an agroforestry ecosystem in Okwuta-Ibeku, Umuahia, Abia State, Nigeria.
The specific objectives of the study are to:
1
Estimate the leaf litter production rates of a 4
and 5 year - old Diospyros crassiflora in 2016 and 2017 respectively;
2
Determine the nutrient contents in the leaf
litter of D. crassiflora;
3
Assess the leaf litter decomposition rates of
D. crassiflora overtime (weeks after
litter placement – WALP);
4
Determine the total nutrient accretion of the
species to the soil through leaf litter production and also through
precipitation pathways;
5
Evaluate the growth and yield of maize in the
D. crassiflora-based agroforestry ecosystem using organic and inorganic
fertilizers.
1.4 JUSTIFICATION OF THE STUDY
As forest area in Nigeria is reduced annually and
soil nutrients status declining, there is need to determine an environmentally
friendly land-use system for agriculture, forestry and agroforestry. Crop
rotation, cover crops and natural based equipment are usually used to enhance
the soil fertility (Adegoke et al.,
2009). In the northern guinea savanna zone, preliminary investigation to assess
the effects of scattered farm trees on the yield of agricultural crops showed
that food crops like yam (Dioscorea rotundata) planted under light shade
of trees such as Mangifera indica (mango) or Accacia auriculiformis had 30% higher
yield than those planted in the open space (Adegbehim et al., 1990 ). This feature was due to tree
litterfall and nutrient cycling in the soil which enhanced the fertility of the
soil. Salami and Oluwole (2003) confirmed that the traditional agroforestry can
be better maintained in the tropical countries, such as Nigeria and Cameroon,
with different types of agroforestry systems to enhance soil fertility.
Farmers in Uroboland in the Niger Delta zone practise
integrated farming syetem that uses palm trees and some food crops to maintain
soil fertility (Aweto, 2000). Integrated farming system is a tool for
sustaining organic matter and nutrient build up in the soil and for improving
soil sustainability. The use of external inputs, such as fertilizers, is often
reduced by recycling of organic matter within the system (Okeke, 2010).
Shifting cultivation, bush fallow and alley cropping systems use deep rooted
trees and shrubs to recycle plant nutrients, thereby building up organic matter
(Nair, 1983; 1987).
Finally, Scherr (1991) emphasized the need for
studies to document basic potentials of trees and shrubs used in agroforestry.
This study emphasizes adoption of agroforestry development, especially with the
use of Diospyros crassiflora and
other arable food crops. The study also aims at determing the nutrient inputs
of D. crassiflora to the soil in
order to encourage farmers to embark on the establishment of D.crassiflora tree plantations, using
economically viable agroforestry land- use management systems. The results of
this study will also encourage greater production of D. crassiflora plantations and consequently, boast the health
status of the farmers via the medicinal values and industrial timber uses of
the species.
1.5 SCOPE OF THE STUDY
The study involved
leaf litter production and nutrient cycling in 1.5 hectare of four/five years
old Diospyros crassiflora plantation at the Humid Forest Research Station,
Forestry Research Institute of Nigeria (FRIN) in Okwuta Ibeku, Umuahia, Abia
State in 2016 and in 2017. The growth and performance of maize in the same
agroforestry farm was also determined or studied.
However, some
limitations encountered during the study are stated below:
a.
Time factor: More time is needed to gain a
better understanding on the variability and long-term trends in annual leaf
litterfall and leaf litter quality. A longer period is required to further
investigate the processes associated with the recycling of nutrients from leaf
litter decomposition through plantation uptake
b.
Lack of funds: This was another major constraint,
especially in the chemical analyses of soil and various leaf litter components.
The study was personally but not externally funded.
c.
Lacks of adequate equipment: Lack of adequate equipment
like oven, weighing and sensitive balances was difficult to come by. Permissions
were obtainedfor used of the equipment from Humid Forest Research Station,
Forestry Research Institute of Nigeria (FRIN) in Okwuta Ibeku, Umuahia, and
Soil Laboratory Unit of the National Root Crops Research Institute, Umudike,
all in Abia State, Nigeria.
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