ABSTRACT
This study was carried out with the aim of assessing the rattle tree (Albizia lebbeck) effects on soil properties and Irish potato (Solanum tuberosum) productivity on the Jos Plateau, Nigeria.
In carrying out the , a randomized complete block design (RCBD) was employed consisting of five and three replicates.
The five treatments applied were as follows: Treatment 1 (T1): Irish potato planted in the alley (space) between A. lebbeck tree rows without green manure; T2: Potato planted without A. lebbeck tree rows but with its green manure application, two weeks before planting of potato at 5 ton/ha; T3:
Potato planted in the alley of A. lebbeck tree rows with its green manure (as mulch) at 5 ton/ha; T4: Potato planted in the alley of A. lebbeck tree rows at 10 ton/ha and T0: Potato planted without A. lebbeck green manure and tree rows as control.
Plot size was 3 m x 2 m (6 m2) in form flat bed. Apart from T3 with the green manure as mulch on the plot, the green manure applied to other treatments was ploughed with the soil. Green manure application was done two weeks before planting of potato and A. lebbeck seedlings were planted one week prior to planting of potato.
The field experiment lasted for three years (2004 – 2006) and both rainy and dry cropping seasons were carried out.
The observations made include significant effect (P < 0.01) of the treatments, blocks, seasons and treatment x season (interaction) on the growth parameters (seedlings’ emergence percentage, plant height, leaf count and collar girth) and yield indices [tuber count (P < 0.05) and tuber weight (P < 0.01)].
T4 which had the highest level of green application (10 t/ha) with A. lebbeck tree rows emerged as the most effective treatment in terms of growth performance and optimal mean yield (10.24 t/ha). From the five cropping seasons, the mean yield from dry season harvests (7.89 t/ha) was higher than those of rainy season (7.73 t/ha).
The independent variables (collar girth, leaf count and plant height) showed positive correlation with the dependent variable (Irish potato yield) while stem count had a negative with yield.
Very importantly leaf count and collar girth were the two determinants of yields (of this bertita variety of Irish potato) from this study.
They accounted for 61.6 – 91.3% of the variation in yield (R2 = 0.616 – 0.913). Similarly, improvement on soil nutrient status and significant effect of treatments and blocks on some soil properties such as available phosphorus (P) (at 0 -10 cm depth) and potassium (K) (0 – 10 cm and 10 – 25 cm depths) at P < 0.05 were observed.
However, only block effect was recorded on pH and Mg and there was a general decrease in the organic matter, total nitrogen (TN), calcium (Ca), sodium (Na), exchangeable acidity and effective cation exchange capacity (ECEC) after planting.
This could probably due to leaching, absorption by the crops and crop removal. Thus, it could be inferred that the green manure (at 10 ton / ha) and tree rows of A. lebbeck can improve soil nutrient status and productivity of this crop.
Also, sustainable production of Irish potato without the use of nitrogenous / inorganic fertilizer under this agroforestry system is feasible on the Jos Plateau.
TABLE OF CONTENTS
TITLE………………………………………………………………….. i
DECLARATION………………………………………………………. ii
CERTIFICATION……………………………………………………… iii
ACKNOWLEDGEMENT……………………………………………… iv
DEDICATION………………………………………………………….. vii
TABLE OF CONTENTS……………………………………………….. viii
LIST OF TABLES………………………………………………………. xv
LIST OF FIGURES……………………………………………………… xvii
LIST OF PLATES……………………………………………………….. xix
LIST OF APPENDICES…………………………………………………. xx
ABSTRACT……………………………………………………………… xxvii
CHAPTER ONE INTRODUCTION
1.1 BACKGROUND TO THE STUDY PROBLEM……………… 1
1.2 THE STUDY PROBLEM……………………………………… 5
1.3 OBJECTIVES OF THE STUDY………………………………. 8
1.4 THE STUDY SCOPE…………………………………………… 8
1.5 JUSTIFICATION OF THE STUDY…………………………… 9
1.6 RELEVANCE OF THE STUDY TO ENVIRONMENTAL
AND RESOURCE PLANNING………………………………… 11
1.7 PRACTICAL IMPLICATIONS OF THE STUDY……………… 12
CHAPTER TWO LITERATURE REVIEW
2.1 THEORETICAL BACKGROUND…………………………… 13
2.1.1 Agroforestry System…………………………………………… 13
2.1.2 Origin…………………………………………………………… 17
2.1.3 Objectives / Benefits of Agroforestry………………………….. 18
2.1.4 Classification of Agroforestry Systems………………………… 21
2.1.5 Types of Agroforestry Systems………………………………… 23
2.1.6 Multipurpose Tree Species (MPTS)……………………………. 32
2.1.7 Effects of Trees on Soil Properties and Crop Yield……………. 34
2.1.8 Tree – Crop Interface…………………………………………… 37
2.2 SPECIFIC CASE STUDIES……………………………………. 39
2.2.1 Nodulation / Nitrogen Fixation in Nitrogen Fixing Trees (NFT) With Emphasis on Albizia lebbeck… 39
2.2.2 Effects of Green Manure on Soil Properties and Crop Yield…… 42
2.3 RATTLE TREE (ALBIZI A LEBBECK BENTH)………………. 44
2.3.1 Origin and Botany………………………………………………. 44
2.3.2 Environmental Requirements of Rattle Tree……………………. 47
2.3.3 Plant Establishment …………………………………………….. 47
2.3.4 Foliage Yield of the Rattle Tree…………………………………. 48
2.3.5 Uses of the Rattle Tree…………………………………………… 48
2.3.6 Pest and Diseases………………………………………………… 51
2.4 IRISH POTATO…………………………………………………. 51
2.4.1 Origin, Distribution and Varieties………………………………… 51
2.4.2 Botany…………………………………………………………… 53
2.4.3 Soil Requirements and Cultivation Conditions…………………. 55
2.4.4 Planting Procedure………………………………………………. 56
2.4.5 Irrigation Practices………………………………………………. 58
2.4.6 Harvesting, Handling and Yield………………………………… 58
2.4.7 Uses……………………………………………………………… 59
2.4.8 Pests and Diseases of Irish Potato ……………………………… 60
2.5 DEDUCTIONS FROM THE LITERATURE REVIEW………… 62
CHAPTER THREE MATERIALS AND METHOD
3.1 THE STUDY AREA…………… 63
3.1.1 Location………… 63
3.1.2 Climate…………. 66
3.1.3 Geology………… 69
3.1.4 Soils…………….. 70
3.1.5 Relief and Geomorphology of the Jos Plateau……………………. 73
3.1.6 Vegetation………………………………………………………… 76
3.1.7 Agricultural Land Use on the Plateau / Study Site……………….. 78
3.1.8 Population and Economic Activities of the People in the Study Area….. 80
3.2 METHOD……… 81
3.2.1 Experimental Design…………… 81
3.2.2 Statistical Models…… 82
3.2.3 Assumptions……………… 83
3.2.4 Hypotheses………….. 84
3.2.5 Raising of Abizia lebbeck Seedlings……………………………… 87
3.2.6 Digging of Soil Profile Pit………………………………………… 87
3.2.7 Site Clearing, Land Preparation and Plot Layout………………… 87
3.2.8 Pre-Experimental Soil Analysis…………………………………… 88
3.2.9 Establishment of Albizia lebbeck Tree Rows……………………… 90
3.2.10 Green Manure Application ………………………………………. 91
3.2.11 Planting of the Irish Potato Tubers ……………………………….. 92
3.2.12 Tending Operations (Management/Cultural Practices)…………… 95
3.2.13 Water Requirement of the Crop (Potato)…………………………. 96
3.3 PARAMETERS INVESTIGATED………………………………. 97
3.3.1 Growth Parameters of the Potato…………………………………. 97
3.3.2 Yield Parameters of the Potato…………………………………… 97
3.3.3 Physical and Chemical Soil Properties…………………………… 98
3.4 POST EXPERIMENTAL SOIL SAMPLE ANALYSIS………… 98
3.5 DATA COLLECTION…………………………………………… 98
3.6 METHODS OF DATA ANALYSIS……………………………… 98
3.6.1 Analysis of Variance Technique…………………………………. 98
3.6.2 Simple Bivariate Correlation and Regression Analyses ………… 100
3.6.3 Multiple Correlation and Regression Analyses………………….. 101
CHAPTER FOUR RESULTS
4.1 SEEDLINGS’ EMERGENCE……. 103
4.2 PLANT HEIGHT…. 104
4.3 LEAF COUNT……. 107
4.4 STEM COUNT………. 109
4.5 COLLAR GIRTH………. 110
4.6 TUBER COUNT…….. 113
4.7 TUBER YIELD……… 115
4.8 RELATIONSHIPS BETWEEN THE GROWTH PARAMETERS AND CROP YIELD……. 121
4.9 INCIDENCE OF BACTERIAL WILT/BACTERIAL SOFT ROT…… 134
4.10 ALBIZIA LEBBECK TREE ROWS AFTER FINAL HARVEST OF THE POTATO CROPS… 138
4.11 SOIL PROFILE………… 138
4.11.1 Morphplogical and Physical Properties… 138
4.11.2 Chemical Properties……… 142
4.12 PRE AND POST EXPERIMENTAL SOIL SAMPLE ANALYSES….. 142
4.12.1 Physical Properties…………………………………………………. 142
4.12.2 Chemical Properties………………………………………………… 146
4.13 MINERAL CONTENT ANALYSIS OF THE POTATO AND ALBIZIA LEBBECK LEAVES… 157
CHAPTER FIVE DISCUSSION
5.1 SEEDLINGS’ EMERGENCE……………………………………… 160
5.2 GROWTH PARAMETERS………………………………………… 161
5.3 YIELD PARAMETERS OF THE POTATO CROPS……………… 163
5.4 INTER-RELATIONSHIPS OF GROWTH PARAMETERS AND CROP YIELD… 165
5.5 INFLUENCE OF PESTS AND DISEASES………………………… 168
5.6 SOIL PROFILE……………………………………………………… 169
5.6.1 Physical Properties………………………………………………… 169
5.6.2 Chemical properties ………………………………………………. 170
5.7 PARTICLE SIZE DISTRIBUTION OF THE EXPERIMENTAL SOIL SAMPLES (BEFORE AND AFTER PLANTING)… 172
5.8 CHEMICAL PROPERTIES OF THE SOIL SAMPLES BEFORE AND AFTER PLANTING… 173
5.9 MINERAL CONTENT ANALYSIS OF THE POTATO (LEAVES AND TUBERS) AND ALBIZIA LEBBECK LEAVES…… 179
CHAPTER SIX SUMMARY, CONCLUSION AND RECOMMENDATIONS
6.1 SUMMARY……………………………………………………… 181
6.2 CONCLUSION…………………………………………………… 187
6.3 RECOMMENDATIONS…………………………………………. 188
6.3 CONTRIBUTION TO KNOWLEDGE…………………………… 190
REFERENCES…………………………………………………… 191
APPENDICES……………………………………………………. 209
INTRODUCTION
1.1 Background to the Study Problem
Trees play some vital roles in improving the nutrient status of soils in the forest and savanna ecosystems.
The non-nitrogen fixing trees augment soil fertility through erosion control, addition of organic matter (by means of litter deposition, especially the deciduous and semi-deciduous ones),
water conservation, protection of water catchment areas and creation of balanced micro- climatic conditions within an ecosystem.
The nitrogen fixing trees (NFT) have an edge over the non-nitrogen fixing ones in the sphere of nitrogen fixation due to the presence of Rhizobium bacteria in their root nodules or ability of some NFT to nodulate with the ubiquitous Bradyrhizobium in th1e soil thereby increasing the nitrogen status of the soil.
Trees and certain agronomic crops are parts of the components of agroforestry system and the former (trees) through some of their activities enhance the productivity of the latter (crops). Forest tree species, right from time immemorial are often left on agricultural farmlands in scattered manner.
They are later utilized by farmers for various purposes (such as timber, fuel wood, fodder/forage, gum, tannins, fencing poles, stakes and medicinal uses among others) in addition to their (trees’) roles in soil conservation in modern agroforestry systems.
REFERENCES
Adebagbo, C.A. (1997). Local Community Participation in Private Farm Forestry and Shelterbelt Scheme for Combating Desert Encroachment. Proceedings of the 25th Annual Conference of the Forestry Association of Nigeria (FAN) In E.A. Oduwaiye, P. C. Obiaga and J. E. Abu (eds.). Ibadan, Oyo State Nigeria 22nd – 26th Sept., 1997 pp. 113-114.
Adepetu, A.A. (1986). Agricultural Practices and Adjustment in the Region JPERDP Final Report. Chapter 20. Dept. of Geography, University of Durham. pp 341-355.
Adepetu, J.A.; Obi O and Aduayi, E.A. (1979). Changes in Soil Fertility Under Continuous Cultivation and Fertilization in South Western Nigeria. Nigeria Jour. of Agric. Sc. I (1) pp. 15-20.
Ajaegbu, H.I; Adeputu, A.A; Ajakpo, J.E.; Ihemegbulem, V.C. Jumbo, S.E. Olaniyan, J.A; OKechukwu, G.C. and Schoeneich, K. (1992). Jos Plateau Environmental Resources Development Programme. Jos Plateau Environmental Excursion Guide. Department of Geography, University of Durham (U.K) and Department of Geography and Planning, University of Jos, (Nigeria) pp. 24-31.
Alasiri, K.O. (1997). Soil Management Strategies for Horticultural Crop Production in Nigeria. ISSN 0795-4123, Occasional Paper No. 38 NIHORT Ibadan, Nigeria. 1997 pp. 1-9.
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