ABSTRACT

This study was carried out in Uyo, Akwa Ibom state between January and April 2017, in order to assess the effect of variations in rainfall and temperature as affecting microbial population under three cropping systems. Soil samples were randomly collected under mixed cropping (MC) plot, sole cropping (SC) plot and uncultivated (UC) plot at auger depth of 0-20 cm. Thermometer was used to measure soil temperature in 0 C at 20 cm depth. While steel rain gauges calibrated in (mm), installed 30 cm above the ground were used for rainfall measurements. The soil samples were analysed in the laboratory for physico-chemical properties and microbial species and population determinate in Cfu/g of wet soil. The results of the soil analysis, rainfall and temperature data were summarized statistically and significant means separated, using Duncan Multiple Range Test at (p‹0.05) level.  The results showed that for the three systems, increase in rainfall caused sand, silt, VMC, organic carbon, acidity, total nitrogen and microorganisms to increase. The reverse was observed for bulk density and clay. Mean rainfall varied from 11.80 mm (MC plot) and 11.50mm (SC plot) to 11.27 mm (UC plot). Uncultivated plot recorded maximum temperature value of 31.50 0C, while minimum value of 26.00 0 C was recorded in MC plot. Total of nineteen microorganisms were isolated from the three systems. Bacteria and fungi counts varied significantly in the soils. Mean value for bacterial population at MC plot (7.99 x 107 Cfu/g) was significantly higher than that of SC (6.35 x 107 Cfu/g) and UC (5.13 x 107 Cfu/g) plots. In the same trend, fungal count was highest in MC plot with mean value of 10.28 x 106 Cfu/g and lowest in UC plot with mean value of 4.25 x 106 Cfu/g. Microorganisms recorded highest numbers in April and least in February. Microbial population correlated positively with sand, silt, VMC, organic carbon, total nitrogen but negatively with bulk density and clay fractions. While rainfall related positively but not significantly with microbial population, soil temperature correlated negatively with microbial populations. Results also showed that soil moisture at field capacity, temperature range of (25- 30 0 C) and soil fertility were established as optimum for increased microbial population, whereas the decrease was attributed to increase in temperature, soil compaction and high bulk density. In conclusion, the variations in rainfall and temperature favoured mixed cropping system than other systems and increase bacterial more than fungal microbial populations.

TABLE OF CONTENTS

TITLE                                                                                                                  PAGE

Cover page                  -           -           -           -           -           -           -           -           i

Certification                -           -           -           -           -           -           -           -           ii

Dedication                  -           -           -           -           -           -           -           -           iii

Acknowledgements    -           -           -           -           -           -           -           -           iv

Abstracts                     -           -           -           -           -           -           -           -           v

Table of contents        -           -           -           -           -           -           -           -           v

List of Figures             -           -           -           -           -           -           -           -           ix

List of Tables              -           -           -           -           -           -           -           -           x

List of appendixes      -           -           -           -           -           -           -           -           xi

CHAPTER ONE

1.0       Introduction    -           -           -           -           -           -           -           -           1

1.1              Background to the study        -           -           -           -           -           -           1

1.2              Significance of the study        -           -           -           -           -           -           3

1.3              Aim and Objectives of the study        -           -           -           -            -          4

1.3.1        Aim of the study                     -           -           -           -           -           -           4

1.3.2        Objectives of the study           -           -           -           -           -           -           4

CHAPTER TWO

2.0       Literature review      -           -           -           -           -           -           -           5

2.1       Precipitation and Rainfall       -           -           -           -           -           -           5

2.2       Temperature                -           -           -           -           -           -           -           6

2.3       Soil moisture               -           -           -           -           -           -           -           6

2.4       Soil microorganisms    -           -           -           -           -           -           -           7

2.4.1    Bacteria           -           -           -           -           -           -           -           -           7

2.4.2    Fungi              -           -           -           -           -           -           -           -           7

2.5       Soil physico-chemical properties         -           -           -           -           -           8

2.5.1    Texture                        -           -           -           -           -           -           -           -           8

2.5.1    Bulk density    -           -           -           -           -           -           -           -           8

2.5.1    Porosity           -           -           -           -           -           -           -           -           8

2.5.1    Chemical properties     -           -           -           -           -           -           -           8

2.6      Response microbes to changes rainfall and moisture content  -          -           9

2.6      Response microbes to changes in temperature -           -           -           11

2.8     Temperature and Rainfall on Soil-Plant- Microbial Interactions          -           12

CHAPTER THREE

3.0       Materials and Methods         -           -           -           -           -           -           15

3.1       Description of the study areas                        -           -           -           -           -           15

3.1.1    Locations        -           -           -           -           -           -           -           -           15

3.1.2    Climate            -           -           -           -           -           -           -           -          15

3.1.3    Geology          -           -           -           -           -           -           -           -           16

 3.1.4     Vegetation      -           -           -           -           -           -           -           -           16

3.2       Field study method    -           -           -           -           -           -           -           18

3.3       Laboratory analysis  -           -           -           -           -           -           -           19

3.3.1    Particle Size Analysis  -           -           -           -           -           -           -           19

3.3.2    Bulk Density   -           -           -           -           -           -           -           -           19

3.3.3    Total Porosity  -           -           -           -           -           -           -           -           19

3.3.4    Gravimetric and Volumetric moisture content           -           -           -           20

3.3.5    Soil pH           -           -           -           -           -           -           -           -           20

3.3.6    Total Nitrogen             -           -           -           -           -           -           -           20

3.3.7    Organic Carbon and Matter    -           -           -           -           -           -           20

3.3.8    Available Phosphorus             -           -           -           -           -           -           21

3.4       Microbiological Analysis       -           -           -           -           -           -           21

3.4.1    Isolation of microorganisms    -           -           -           -           -           -           21

3.4.2    Sub-culturing of Bacteria                    -           -           -           -           -           21

3.4.3    Characterization and Identification    -           -           -           -           -           22

3.5