EFFECT OF LABLAB (Lablab purpureus L.) GREEN MANURE ON POPULATION OF PATHOGENIC AND NON-PATHOGENIC SOIL MICROORGANISMS AND BEAN (Phaseolus vulgaris L.) CROP ESTABLISHMENT OLIVER OTIENO OKUMU (BSc. Agriculture, Msc, Crop Protection, University of Nairobi) A THESIS SUBMITTED IN FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF DOCTOR OF PHILOSOPHY IN CROP PROTECTION FACULTY OF AGRICULTURE DEPARTMENT OF PLANT SCIENCE AND CROP PROTECTION UNIVERSITY OF NAIROBI 2018 DECLARATION ii DECLARATION OF ORIGINALITY Name of Student ……………………………………………………………………………. Registration Number ……………………………………………………………………………. College ……………………………………………………………………………. Faculty/ School/ Institute ………………………………………………………………………… Department ……………………………………………………………………………. Course Name ……………………………………………………………………………. Title of Work …………………………………………………………………………… Declaration 1. I understand what plagiarism is and I am aware of the University’s policy. 2. I declare that this thesis is my original work and has not been submitted for examination, award of a degree or publication. Where other peoples work, or my own work has been used, this has properly been acknowledged and referenced in accordance with the University of Nairobi’s requirements. 3. I have not sought or used the services of any professional agencies to produce this work. 4. I have not allowed, and shall not allow anyone to copy my work with the intention of passing it off as his or her own work. 5. I understand that any false claim in respect of this work shall result in disciplinary action, in accordance with University Plagiarism Policy. Signature …………………………………. Date ……………………………............. iii DEDICATION This thesis is dedicated to the memory of my late father, Herrington Okumu Onyuna, for his pioneering spirit, my dearest mother Julian Akoth Alolo, my beloved wife Susan Awino Wego and daughter Julie Lauren for their persistence in the face of adversity, and their belief in the value of higher education. iv ACKNOWLEDGEMENTS This research was made possible by the financial support from the McKnight Foundation under the project ―Multipurpose legumes and management strategies for reinvigorating and maintaining the health and productivity of smallholder mixed farming systems‖ and the Technical support by the Kenya Agricultural and Livestock Research Organization (KALRO) Kibos Centre, Kisumu I wish to express my sincere gratitude to Prof James W. Muthomi, my principal supervisor for his enormous encouragement, patience, constructive scholarly criticism and professional help throughout the project. I am also thankful to my supervisors’ Prof. Rama D. Narla, Prof; I could feel your persistent struggle when you constantly encouraged me to ensure the project was done, Prof John H. Nderitu and Dr. John Ojiem for their valuable suggestions and discussions along the completion of this project. Many thanks are also extended to Dr. Julie Lauren whose advice were instrumental in understanding the concept of this project I would also like to acknowledge the technical assistance of Simon Kamwana and James Nyongesa as well as the help of fellow PhD candidates Samuel Aringo Were and Luiza Munyua. Many thanks also to Technologists from the Department of Plant Science and Crop Protection, University of Nairobi for sharing their expertise and knowledge in the laboratory. I would also like to acknowledge my wife Susan Awino Wego and Daughter Julie Lauren you are my pillars of support, strength and inspiration. To my mum, I would not have successfully accomplished the project without your help and encouragements. You have sacrificed everything for my better future and I really wish to live to your expectations to my very best. To each one, I am very grateful. Above all and most importantly, I thank the Almighty God for His grace and favor for the wonderful opportunity I had at the University of Nairobi v ABBREVIATIONS AEZ Agro-ecological zone AG Anastomosis group ALS Angular leaf spot ANOVA Analysis of Variance AUDPC Area under Disease Progress curve BCMV Bean Common Mosaic Virus C Carbon CBB Common bacterial blight cfu Colony Forming Units DAP Diamonium Phosphate FAO Food and Agriculture Organization of the United Nations FAOSTAT Food and Agriculture Organization Corporate Statistical Database GLP2 Grain Legume Program Two Ha Hectare K Potassium KALRO Kenya Agricultural and Livestock Research Organization Kg Kilogram KK8 Kakamega eight MGT Mean Germination Time ml Milliliters MLP Multipurpose Legume Project N Nitrogen NaCl Sodium Chloride vi NARL National Agricultural Research Laboratories P Phosphorus PGPR Growth-promoting Rhizobacteria Ppm Parts per million SPSS Statistical Product and Service solutions UNESCO United Nations Education, Scientific and Cultural Organization WHC Water Holding Capacity vii TABLE OF CONTENTS DECLARATION .................................................................................................................................... ii DECLARATION OF ORIGINALITY .................................................................................................. iii DEDICATION ....................................................................................................................................... iv ACKNOWLEDGEMENTS .................................................................................................................... v ABBREVIATIONS ............................................................................................................................... vi TABLE OF CONTENTS ..................................................................................................................... viii LIST OF TABLES ............................................................................................................................... xiii LIST OF FIGURES .............................................................................................................................. xv GENERAL ABSTRACT ..................................................................................................................... xvi CHAPTER ONE: INTRODUCTION .................................................................................................... 1 1.1 Background information ............................................................................................................ 1 1.2 Problem statement ..................................................................................................................... 2 1.3 Justification of the study ............................................................................................................ 4 1.4 Study objectives ........................................................................................................................ 4 1.5 Hypothesis ................................................................................................................................. 5 CHAPTER TWO: LITERATURE REVIEW ......................................................................................... 6 2.1 Importance of common bean ..................................................................................................... 6 2.2 Production of common beans in Kenya .................................................................................... 6 2.3 Constraints to common bean production ................................................................................... 7 2.4 Root rots of common bean ........................................................................................................ 9 2.5 Factors affecting population of microorganisms in the soil .................................................... 12 2.6 Interactions among soil microorganisms and their effect on plant health ............................... 13 2.7 Factors affecting crop emergence and crop establishment ...................................................... 15 2.8 Lablab leguminous crop .......................................................................................................... 17 2.9 Application and decomposition of green manure .................................................................... 18 2.10 Factors affecting decomposition of organic matter in the soil .............................................. 19 2.11 Effect of green manure on soil characteristics ...................................................................... 21 2.12 Use of green manure in the management of soil fertility and soilborne diseases ................. 22 2.13 Mechanisms involved in management of soilborne diseases by use of green manure .................................................................................................................................. 24 viii 2.14 Potential limitations of green manure to crop production ..................................................... 26 CHAPTER THREE .............................................................................................................................. 28 EFFECT OF LABLAB (Lablab purpureus L.) GREEN MANURE ON POPULATION OF SOIL MICROORGANISMS AND ESTABLISHMENT OF COMMON BEAN (Phaseolus vulgaris L.) ............................................................................................................................................ 28 3.1 Abstract ................................................................................................................................... 28 3.2 Introduction ............................................................................................................................