ABSTRACT

A two-year field experiment was conducted at the National Root Crops Research Institute, Umudike situated in a rain forest agro-ecology in 2020 and 2021 cropping seasons to evaluate the effect of NPK-enriched rice mill waste forms for commercial root production of orange-fleshed sweet potato. Studies in both years were factorial and laid out in a Randomized Complete Block Design (RCBD) with three replications. The experiment involved the application of four levels of NPK 15:15:15 fertilizer at 0 kg/ha, 200 kg/ha, 400 kg/ha and 600 kg/ha, respectively. Rice mill waste involved its carbonized form at 0 t/ha and 5 t/ha and un-carbonized form at 0 t/ha and 10 t/ha respectively. On the average, rice mill waste forms increased the vine length, number of leaves per plant, number of branches per plant, stem girth, but had no significant effects on root yield components. The use of combined application of NPK 15:15:15 fertilizer at 400 kg/ha + 5 t/ha CRMW + 10 t/ha URMW proved satisfactory as total root yield (t/ha) seemed best in both 2020 and 2021 cropping seasons and therefore is recommended for orange-fleshed sweet potato production in Umudike, Abia State, Nigeria.

TABLE OF CONTENTS

Title page                                                                                           i

Declaration                                                                                        ii

Certification                                                                                       iii

Dedication                                                                                         iv

Acknowledgments                                                                                       v

Table of Contents                                                                              vi

List of Tables

Abstract

CHAPTER   1

INTRODUCTION

1.1 Background of the Study                                                                                     1

1.2 Statement of Problem                                                                                           2

1.3 Objectives of the Study                                                                                        4

1.4 Justification of the Study                                                                                     5

CHAPTER   2    

LITERATURE REVIEW

2.1 Origin and Distribution of Sweet Potato                                                              6

2.2 Botany of Sweet Potato                                                                                       6

2.2.1 Production and production regions                                                                   8

2.2.2 Soil and climatic requirement                                                                            9

2.2.3 Propagation                                                                                                        10

2.3 Economic Importance of Sweet Potato                                                                11

2.4 Concept of Integrated Nutrient Management                                                      12

2.5 Effects of Integrated Nutrient Management on Soil Properties.                          14

2.6 Effects of Integrated Nutrient Management on Crop Yield                                16

2.7 Effects of Integrated Nutrient Management on Yield of Sweet Potato              17

2.8 Effects of Mineral Fertilizer on Soil Chemical Properties                                    18

2.9 Effects of Mineral Fertilizer on Growth and Yield of Sweet Potato                   18

2.10 Effects of Organic Manure on Soil Chemical Properties                                    21

2.11 Effects of Organic Manure on Growth and Yield of Sweet Potato                  22

2.12 Nutrient Requirements of Sweet Potato                                                             24

CHAPTER   3

MATERIALS AND METHODS

3.1 Description of the Experimental Site                                                                    25

3.1.1 Location of the experiment                                                                                25

3.1.2 Rainfall                                                                                                              25

3.1.3 Temperature                                                                                                       26

3.1.4 Relative humidity                                                                                              26

3.1.5 Sunshine                                                                                                             26

3.1.6 Soils of the study area                                                                                       26

3.2 Field Experiment                                                                                                  29

3.2.1 Land preparation                                                                                                29       

3.2.2 Experimental design/treatment                                                                          29

3.2.3 Planting material                                                                                                29

3.2.4 Field maintenance                                                                                              30

3.3 Data Collection                                                                                                     30

3.4 Yield Parameters                                                                                                   30

3.5 Soil Analysis                                                                                                         31

3.6 Statistical Analysis                                                                                                32

CHAPTER   4    

RESULTS AND DISCUSSION

4.1 Physical and Chemical Properties of the Soil at the Experimental Site                34

4.2 Effect of NPK-enriched Rice Mill Waste Forms on the Growth and Yield of   38

Orange-fleshed Sweet Potato

4.2.1 Vine length                                                                                                        38       

4.2.2 Number of leaves                                                                                               44

4.2.3 Number of branches                                                                                           49

4.2.4 Stem girth                                                                                                          54

4.3 Effect of NPK-enriched Rice Mill Waste Forms on the Root Yield of Orange- 59

fleshed Sweet Potato

4.3.1 Total roots yield weight                                                                                     59

4.3.2 Marketable roots yield                                                                                       60

4.3.3 Unmarketable roots yield                                                                                   60

4.3.4 Number of marketable roots                                                                              61

4.3.5 Number of unmarketable roots                                                                          61

4.4 Discussion                                                                                                             75

CHAPTER   5    

CONCLUSION AND RECOMMENDATIONS

5.1 Conclusion                                                                                                            78

5.2 Recommendations                                                                                                            78

REFERENCES                                                                                                    80

APPENDICES                                                                                                     91

LIST OF TABLES

                                                                                                                                          Page

3.1       Agro-meteorological data of the study area in 2020 and 2021                           28 

4.1       Physical and chemical properties of soils of the experiment area                         36 

4.2       Chemical properties of the rice mill waste used in the experiment                       37 

4.3       Effect of NPK-enriched rice mill waste forms on the vine length                       40 

of orange-fleshed sweet potato in 2020 and 2021 cropping seasons

4.4       Interaction of NPK fertilizer × carbonized rice mill waste × un-carbonized  43       

rice mill waste effect on vine length of orange-fleshed sweet potato in

2020 and 2021 cropping seasons

4.5       Effect of NPK-enriched rice mill waste forms on the number of leaves per  45

plant of orange-fleshed sweet potato in 2020 and 2021 cropping seasons

4.6       Interaction of NPK fertilizer × carbonized rice mill waste × un-carbonized    48

rice mill  waste effect on number of leaves per plant of orange-fleshed

sweet potato in 2020 and 2021 cropping seasons

4.7       Effect of NPK-enriched rice mill waste forms on number of branches of       50

orange-fleshed sweet potato in 2020 and 2021 cropping seasons

4.8       Interaction of NPK fertilizer × carbonized rice mill waste × un-carbonized      53

rice mill waste effect on number of branches of orange-fleshed sweet potato

in 2020 and 2021 cropping seasons

4.9       Effect of NPK-enriched rice mill waste forms on stem girth of orange-                 55

           fleshed sweet potato in 2020 and 2021 cropping seasons

4.10     Interaction of NPK fertilizer × carbonized rice mill waste × un-carbonized      58

rice mill waste effect on stem girth of orange-fleshed sweet potato in

2020 and 2021 cropping seasons

4.11     Effect of NPK-enriched rice mill waste forms on root yield attributes                62

of orange-fleshed sweet potato in 2020 and 2021 cropping seasons

4.12     Interaction of NPK fertilizer × carbonized rice mill waste × un-carbonized    65

rice mill waste effects on yield and yield components of orange-fleshed

sweet potato in 2020 and 2021 cropping seasons

4.13     Combined analysis of variance of yield and yield attributes of orange-fleshed      68

sweet potato across the two years

4.14     Combined analysis of variance of interaction of NPK fertilizer × carbonized        71

 rice mill waste × un-carbonized rice mill waste effects on yield and yield components of orange-fleshed sweet potato across the two years

4.15    Correlation matrix of growth and yield components of sweet potato in 2020         74

and 2021 cropping seasons