




































American International Journal of Agricultural Studies  

Vol. 1, No. 1; 2018 

Published by American Center of Science and Education, USA 

 

16 

 

Rainfall Variation: Implication on Cocoa Yield in Ondo State, 

Nigeria 

 

DADA Emmanuel 

Department of Geography and Planning Sciences 

Adekunle Ajasin University 

Akungba-Akoko 

Ondo State, Nigeria. 

Email: vissitemma@gmail.com 

 

 

 

 

Received: November 7, 2018      Accepted: November 11, 2018           Online Published: November 17, 2018        

 

Abstract 

Cocoa is known as one of the notable cultivated cash crops of the tropical rainforest of the world that is rain 

dependent. The study examines the effect of rainfall variation on the yield of cocoa plantation in Ondo State, 

Nigeria. Data used for the study includes the rainfall data of 15 years from 2000 to 2014 collected from Ondo state 

agro climatological office as well as cocoa yield data for the same period of time from Ondo State ministry of 

agriculture and forest resources. Descriptive statistical method was employed to determine the relationship between 

both variables in which the result shows direct relationship between rainfall and cocoa yield. Results were presented 

using bar charts and line graph for the time series analysis of the variables. Linear regression statistical analysis was 

used to predict cocoa yield with certain amount of rainfall with the correlation coefficient ‘r’ value of 0.97 which 

implies that rainfall changes go a long way to determine the same variation trend in the cocoa yield. Though, not 

only the quantity of rainfall within the range of rainfall required for the growth of this crop affect the yield but its 

distribution. A little millimeter of rainfall above or below the required range of rain for cocoa plantation greatly 

affects cocoa yield.  

Keywords: cocoa yield, rainfall variation, relationship, Ondo State.  

1. Introduction 

Cocoa (Theobroma Cacao) is among the most important perennial crops in the world. It is a tropical lowland crop. 

Cocoa was a dominant foreign exchange earner in Nigeria from the early 1960s through the 1970s (Olujide and 

Adeogun, 2006). Historically, cocoa contributed average agricultural earning of 70.6% between 1971 and 1973, 

89.8% between 1976 and 1980, 84.6% between 1985 and 1987, 76.8% between 1986 and 1990, and 53.3% between 

1992 and 1996 respectively. This declining trend observed can be attributed to strong domination of Nigeria export 

earnings by crude oil and lots of other factors (Agboola, 2005). 

It became an important export crop in Southwestern Nigeria and other African countries including Ghana, Ivory 

Coast, Togo, etc. and attains its peak between 1954 and 1969. During these periods, cocoa became the second 

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largest and major source of foreign earner for Nigeria government. This crop provides job for large number of 

Nigerians and also source of raw material for beverages and chocolate industries (Hokona, 1994; Oyedele, 2007). 

According to Adegeye (2006), cocoa was first cultivated in the western region of Nigeria in 1890. It became 

prominence rapidly in Nigeria to the extent that Nigeria became the world cocoa second largest producer in 1965 

(Adegeye, 1996). Cocoa is produced in the tropical rainforests of Ondo, Osun, Ogun, Oyo, Ekiti, Edo, Delta, Cross-

Rivers, Akwa-Ibom and  Anambra states with the Ondo state as the largest cocoa producing state in Nigeria 

(Agegeye, 2006). Cocoa is grown in fourteen out of thirty-six states of Nigeria but mainly produced in the above 

stated states. It is well known that cocoa production is highly sensitive to changes in climate, from length and 

intensity of sunshine to rainfall and water application, soil condition and temperature due to evapotranspiration 

effect (Anim-kwapon & Frimpong, 2005). 

Climatic variation especially rainfall dynamics is one of the serious environmental challenges facing world 

agricultural productivity especially the perennial crops. The variation can be attributed to natural climatic cycle and 

majorly, human activities which adversely affect productivity especially in Africa as a result of poor technology 

(Ziervogel et al., 2006). Evidence from several researches revealed that climatic variation is a global issue, likewise 

its impacts but most adverse effects were majorly felt in the developing economies, especially those in Africa and 

Asia, due to low level of their coping capacities (Nwanfor, 2007; Jagtap, 2007).  As the planet warms, rainfall 

pattern deviates and result in extreme events such as drought, floods, forest fire etc. (Zoellick, 2009), this however 

causes poor and unpredictable yields, thereby making farmers more vulnerable, particularly in Africa (UNFCCC, 

2007). Larger proportion of African inhabitants are poor farmers and will mostly bear the brunt of crop failures, 

reduced agricultural productivity, hunger increase, malnutrition and prevalent of diseases (Zoellick, 2009). Findings 

by Jones and Thornton (2003)  shows that crop yield in Africa may fall by 10-20% by 2050 or even up to 50% due 

to climate change especially rainfall particularly in Africa that is predominantly practice rain-fed agriculture and 

hence fundamentally dependent on the vagaries of weather.    

 

Figure 1: Main Cocoa Producing States in Nigeria between 2006-2010 productions (000mt) (source: National 

Bureau of Statistics) 

As recorded by Food and Agriculture Organization of the United Nations (FAOSTAT 2012), Nigeria is the fourth 

leading exporter of cocoa in the world with Cote d’Ivoire as the first following by Indonesia and Ghana. Cocoa is 

the main agricultural export in Nigeria because it accounts for substantial quantity of the country total annual 

agricultural export contribution to the Gross Domestic (GDP) Export of Nigeria. However, production can be 



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increased if government make and implement decisive policy or measures that will enhance production and enlist 

Nigeria as the first or second cocoa producing and exporting country in the world.  

 

Figure 2: World top ten cocoa producing countries in 2010 (source: FAOSTAT) 

1.1 Climate Change and Cocoa Production 

It is well established that cocoa is highly sensitive to climatic variation from hour of sun, to rainfall and application 

of water, soil conditions and temperature due to effects on evapo-transpiration. Variation in climate could alter 

stages and rate of development of cocoa pests and pathogens, modify host resistance and result in changes in the 

physiology of host-pathogen/pests interaction. The most likely consequences depend on geographical distribution of 

host of pathogen, affect crop yields and crop loses which will impact socio-economic variables including farm 

income, livelihood and farm-level decision making. Hence, the need for an understanding of climatic variation 

impacts on cocoa production and the potential for adaptation to variation of climatic elements are essential. 

2. Material and Methods 

2.1 The Study Area 

The study area is cocoa plantation in Ondo State Nigeria. It lies within the central cocoa cultivation and forest belt of 

Southwestern Nigeria, which comprises of Ondo, Osun and Ekiti States. Ondo State is located in the geographical 

coordinates of 7
0
10

1
N and 5

0
5

1
E. It has the total land area of 15,500km

2
 (6,000sqm) (). And it share boundary with 

Ekiti, Kogi, Edo, Ogun and Osun states. 

 

2.1.1.   Climate 

 

The climate of Ondo state ranges from tropical wet- and- dry climate with mean annual rainfall of about 1500mm 

and 2000mm in the derived savanna and humid forest zones respectively (Adefolalu, 1997). The wet season starts in 

April and ends in October and dry season commences from November to March, though the average annual amount 

of rainfall mostly increased to 2500mm at the Sothern coast and can reduced to about 1220 mm in some years at the 

northern limit of the forest belt (Gilbert, 1969). The mean annual temperature is about 26.6
0c

 with the average yearly 



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humidity of 76.05%. The climate is monsoonal with a contrast between well-defined dry and wet seasons 

(Adebekun, 1978).  

2.1.2.   Geology and Soil 

Ondo state comprises of two distinct geological regions of sedimentary rocks in the Southern part and second is the 

pre-Cambrian Basement Complex rocks in the northern part of the state. The sedimentary rocks contain mainly post-

Cretaceous sediments and also the Abeokuta Formation of the Cretaceous. The basement complex rocks on the other 

hand contain the medium grained gneisses which are strongly foliated rocks occurring as an outcrops with 

alternating bands of dark and light minerals. The light bands color is rich in minerals such as feldspar and quartz and 

the dark colored bands are full of abundant biotic mica. A portion of the state in the northeast overlies the coarse 

grained granites and gneisses (A.J. Smyth, 1962). The soil ranges from medium –grained granitic rocks, medium-

grained gneisses and schist which support the development of low rainforest suitable for tree crops such as cocoa, 

kola, and oil-palm (Ekanade, 2007). The relief of Ondo state is dominated by the plain that rises gently from the 

coast northwards to the area of crystalline rock where icebergs rise above the surrounding plains (Adebekun, 1978).  

2.1.3.    Relief and Drainage 

The state composed of lowlands in the southern part and certain part in the central. And rugged hills with granitic 

outcrops dominate several places mostly in the northern part of the state. There is a rising of the land from the 

coastal area in the south i.e. less than 15 meters above sea level to the rugged hills of the north eastern area of Akoko 

region. The notable hills in Ondo state are found at Idanre and Akoko areas of the state which rise beyond 250 

meters above the sea level (Adebekun, 1978). The geomorphological units of the creek and riverine portions of the 

state contain sand ridges, lagoons, swamp flats, creeks and distributaries of the western Niger Delta (Online Nigeria 

Community Portal, 2013)/ www.onlinenigeria.com. The major rivers found in Ondo state include: Owena, Oluwa, 

Oni, Ogbese and Ose and their drainage system characterize with basement complex rocks. 

2.1.4.   Vegetation 

The southern and central parts of the state contains natural vegetation of high forest rich in  various hardwood for 

timber such as Melicia excels, Antaris Africana, Iroko, Obeche, Wawa, Terminalia superba, Lophira procera etc. 

But in the northern part are found the woody savanna and grassland such as Blighia sapida and Parkia biglobosa 

which dominate the Akoko area (Online Nigeria Community Portal, 2013). The swamp flats are the area of fresh 

water swamp forests dominated the interior and the units of mangrove vegetation near the coast. Worthy of notice in 

the state vegetation is the prevalence of tree crops plantation such as cocoa, kola,   coffee, rubber, oil palms and 

citrus with cocoa being the most vital tree crops in the state. Ondo state falls within the evergreen tropical rainforest, 

a transitional zone between the fresh-water swamps along the coast and Guinea Savanna belt in the north (Ekanade, 

1990).  

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Figure 3: Map of Nigeria showing Ondo State 

2.1.  Data Sources 

The study makes use of both primary and secondary data sources. The primary data used in this study was obtained 

through researcher field survey, focused group discussion and other means of social survey to access information 

about cocoa farmers perception on how rainfall variation over the years affect their yields and the coping strategies 

they have adopted over time. The secondary data for this research includes rainfall and cocoa yield data obtained 

from Agroclimatology department of ministry of Agriculture, Akure, Ondo State. 

2.2.  Data Analysis 

The data rainfall and cocoa yield data collected were analysed using both descriptive and inferential statistics. The 

descriptive statistics involved the used of table and simple percentage while the result were presented with bar charts 

and line graph to reveal the relationship between mean annual rainfall from year 2000 to 2014 and the yield of cocoa 

plantation recorded in tons during these same years. Regression inferential statistics was employed to predict the 

cocoa yield as a result of rainfall variation as the most unstable climate parameter in the study area.  

3. Result and Discussion 

The outcome of the analysis of the rainfall and cocoa yield data are presented and discussed in this section. The 

results of the descriptive analyses made in the survey were presented with bar charts and line graph to show or 

reveal how the independent variable (rainfall) determine the performance of dependent variable (cocoa yield). 

 



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Figure 4: Rainfall distribution between 2000 and 2014 

The rainfall bar graph above depicts the distribution of rainfall in the study area between 2000 and 2014 with the 

highest average annual rainfall of 1826.2 mm recorded in the year 2011 and lowest mean annual rainfall of 1169.1 

mm recorded in the year 2003. The variation in the mean annual rainfall recorded in the study area can be attributed 

to climate change which is a global phenomenon. However, the amount of rainfall does not necessarily determine 

the yield but the distribution of rainfall once the amount of rainfall is up to the minimum amount (1450mm) requires 

for the survival of cocoa plantation.  

 

Figure 5: Cocoa yield between 2000 and 2014 



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Yield of cocoa plantation is a function of a lot of factors ranging from natural factors such   rainfall, temperature, 

soil etc. to human induced factors such as constant treatment of the plantation with insecticide, pesticide and 

herbicide to prevent attack from diseases, the application of fertilizer, taken care of the plantation environment 

against unwanted weed and some other factors. Thus, most of these favorable factors for the better yield of cocoa are    

available in the study area. Hence, for the purpose of this research, rainfall as a very unstable climatic parameter was 

considered for the yield of this plantation in the study area. Gradual increase was   observed from the cocoa yield 

graph though not on a regular basis and interval based on various factors some of which was stated above. This 

gradual increased in the yield justified the result of an increase in the area of land occupied by cocoa plantation in 

Ondo state as an outcome of the detected change that took place in this plantation during the investigated period of 

this research. The lowest yield was recorded in the year 2003 with 45203 tons of   cocoa and the highest in 2014 

with 79210 tons which can be traced to impact of rainfall.   

 

Figure 6: Rainfall and Cocoa yield graph. 

The above graph reflects the relationship between rainfall variability and cocoa yields between 2000 and 2014. It 

can be deducted from the graph that yield is highly dependent on rainfall but not at the same proportion. The highest 

quantity of cocoa yield was recorded in 2014 with 79210 tons of cocoa and 1782.12 mm of rainfall during that same 

year. And the lowest yield was in 2003 with 45203 tons of cocoa and mean annual rainfall of 1169.8 mm, the 

reduction in the cocoa yield in this year can be attributed to shortage of rainfall which was actually below the 

minimum amount of rainfall required for the growth of cocoa crop. As noted by International Cocoa Organization 

(ICO 2010), cocoa required at least 1450 mm of rainfall to thrive very well. It is very obvious from this graph that 

the quantity of yield is a function of availability of     adequate rainfall, though there was a lot of variation between 

the yield and rainfall whereby the rainfall was high but low yield was recorded which can be attributed to the 

distribution pattern of rainfall. The 2008 witnessed increase in rainfall with 1681.38 mm compare to 2005 with 

1496.8 mm but more yield was recorded in 2005 than 2008, in this case emphases on the     distribution of rainfall 

cannot be ignored i.e. when rainfall is high during the flowering period of cocoa it will reduce the yield because 



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some of the flowers would have been removed by rainfall. However in comparing the yield and rainfall, distribution 

and period of rainfall are very important factors to consider. Generally, it can be deducted from this analysis that 

rainfall is a very important parameter that led to increase in the area cover by cocoa plantation as the change that 

took place in cocoa plantation class of the land cover of Ondo state. Therefore, there is a strong correlation or 

relationship between gradual increases in rainfall and increased in the area of land covered by cocoa plantation in 

the study area within the investigated time of this research. 

3.1. Regression Model   

Regression model was employed as an inferential statistical approach to measured how important rainfall as the 

most unstable climatic parameter determine the cocoa yield. In this regards, rainfall is independent variable while 

cocoa yield was set as the dependent variable. 

The rainfall data from Ondo State agroclimatological station and cocoa yields from Ondo State ministry of 

agriculture and forest resources from year 2000 to 2014  was subjected to regression analysis in order to infer or 

drawn certain conclusion about how the rainfall flunctuation affected cocoa yields during the period of investigation. 

This is solved by applied the most widely measured of goodness fit equation line of y a bx   related to bivariate 

data express as:    1 1 n nx y x y , this is the sum of the square deviation about the line expressed as:    

       
2 2

1 1 2 2     –    .     . 
n

n ny a bx y a bx y a bx y a bx                         

These can be expressed by an equation of the form: 

0 1 2    .....    nY b bx b bx       

Where: 

        y = dependent variable 

        b0 = constant term 

        b1,2 = regression coefficient 

        ∑ = error term that can enter the model 

  

   2 2
*

x y
r xy

n

x y
x y

n n

 

 

 


 
   

The outcome of regression analysis reveals strong tied on how rainfall variation affect the cocoa yield as one of 

phenological factors that determine the cocoa yield.  The explanation from analysis depict y-dependent variable 

which represent the cocoa yield in tons in Ondo state from year 2000 to year 2014 while the amount of rainfall 

measure in millimeter represent the indepent or explanatory variable depicted as’x‘. The result show very strong 



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relationship between rainfall and cocoa yield with 0.97 correlation coefficient result. This implies that the more the 

amount of rainfall recorded and well distributed within the range of amount of rainfall required for the growth of 

cocoa, the more the cocoa yield and the vice versa all other factors remain constant. This establishe the fact that few 

millimiter of rainfall deviation above or below the range of the required amount of rainfall for the growth of this 

crop is heinous to yield of this plantation. Hence, addiquate attention should be given to rainfall consideration for 

better cocoa yield in Ondo State because this parameter is the most unstable natural factor for cocoa raising in this 

region because this plantation is purely rainfed agriculture. 

 

4. Conclusion 

Cocoa farming is a typical rainfed agricultural practice that required high amount of rainfall with at least seven 

months of distribution which is a condition beyond the control of man. The variation in the amount and distribution 

of rainfall in the tropic has been greatly caused by antropogenic activities mostly deforestation as the situation is in 

the tropical rainforest region of Ondo State. The consequence of these human activities in this region have great 

impact on the yield of cocoa as the largest cocoa producing state in Nigeria (National Bureau of Statistics, 2011). 

Rainfall is considered as the most unstable climatic parameter and of course one of the most difficult humanly 

enhanced natural factors responsible for the growth of cocoa (Boyer, 1982). The more efforts government can put to 

control human activities especially deforestation in this region to stablize the amount and distribution of rainfall, this 

will go a long way to improve cocoa yield as the highest contributor of agricultural crop to Gross Domestic Product 

of Nigeria over time. The outcome of this research will be very useful for the decision maker in Ondo State to 

control human activities that reduce the mean annual rainfall and its distribution and also to increase its investment 

on this plantation to increase cocoa yield and thereby increase the revenue derive from this crop. 

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