Journal of Experimental Agriculture International

42(5): 44-53, 2020; Article no.JEAI.57588 ISSN: 2457-0591 (Past name: American Journal of Experimental Agriculture, Past ISSN: 2231-0606)

Impact of Climate Change on Rainfall Distribution on Cassava Yield in Coastal and Upland Areas of ,

Isaiah A. I.1*, Yamusa A. M.2 and Odunze A. C.2

1Department of Soil Science, Faculty of Agriculture, Ahmadu Bello University, , Nigeria. 2Meteorological Unit, Department of Soil Science, Institute for Agricultural Research, Ahmadu Bello University, Zaria, Nigeria.

Authors’ contributions

This work was carried out in collaboration among all authors. Author IAI designed the study, performed the statistical analysis, wrote the protocol and wrote the first draft of the manuscript. Author YAM managed the analyses of the study. Author OAC managed the literature searches. All authors read and approved the final manuscript.

Article Information

DOI: 10.9734/JEAI/2020/v42i530517 Editor(s): (1) Dr. T. Muthukumar, Bharathiar University, India. Reviewers: (1) Dian Lourençoni, University of the San Francisco Valley, Brazil. (2) C. Hiambah, University of Buea, Cameroon. Complete Peer review History: http://www.sdiarticle4.com/review-history/57588

Received 28 March 2020 Accepted 03 June 2020 Original Research Article Published 20 June 2020

ABSTRACT

This study examined the implication of rainfall variability on cassava yield in selected coastal and upland areas of Akwa Ibom State, Nigeria. Thirty years daily rainfall data were collected from Nigeria Meteorological Agency (1989 – 2018); cassava yield data were also collected from Akwa Ibom State Ministry of Agriculture (1989 – 2018). Descriptive statistics was used to determine the average annual rainfall and cassava yield. Time series analysis were used to assess the relationship between rainfall and cassava yield. The result indicated an increase in rainfall trends in all areas with – r2 = 0.6631, Oron - r2 = 0.5329, Uyo - r2 = 0.4215 and - r2 = 0.4042. The result also showed an increase in yield of cassava in Uyo and Ikot Ekpene at r2 = 0.2436 and 0.4397 respectively; while its decreases in Eket and Oron at r2 = 0.0611 and 0.1159 respectively. This suggested that a high yield of cassava may be achieved only in the upland areas of Akwa Ibom State due to continuous increase in rainfall as a result of climate change.

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*Corresponding author: E-mail: [email protected];

Isaiah et al.; JEAI, 42(5): 44-53, 2020; Article no.JEAI.57588

Keywords: Climate change; cassava yield; rainfall variability; rainfall characteristics.

1. INTRODUCTION Rainfall is the most important factor for the proper and healthy production of crops [10]. Different studies have identified significant the Plants require huge quantities of soil moisture impact of climate change on rainfall variability in continuously during their life cycle. It deeply various countries of the world [1]. The climate impacts photosynthesis, respiration, absorption, change is the variation in the distribution of translocation and utilization of mineral nutrients, weather patterns (including rainfall, temperature) cell division and many other vital processes. It over an extended period of time, typically also affects evapotranspiration which is a joint decade. [2] reported global warming, increasing process of evaporation of water from the earth rainfall in rainforest areas and decreasing rainfall surface and plant surfaces and transpiration of in semi-arid areas of Nigeria due to climate water through the plant stems and tissues [11]. In change. Climate varies naturally on time scales, Akwa Ibom State, Agriculture is the main source from days, years to decades and centuries [3]. of livelihood of many households in Akwa Ibom Climate change and rainfall variability have State and it is characterized by subsistence become a major concern to farmers and other farming system. Farming activities solely individuals throughout the world in recent depends on rain. decades [4]. The distribution of the world’s rainfall is shifting due to climate changes and wet Therefore, the aim of this paper is to assess the areas may become wetter, dry areas drier, influence of rainfall distribution on cassava yield storms more intense, leading to more chaotic in Akwa Ibom State, Nigeria. weather around the world [5]. According to the Intergovernmental Panel on Climate Change [5], 2. MATERIALS AND METHODS an increase in average global rainfall will be mostly concentrated in rainforest zones and 2.1 Study Area other wet tropical areas due to change in climate resulting in variations in rainfall pattern and The study was conducted in Akwa Ibom State in atmospheric moisture content. four different locations in Akwa Ibom State two each in the coastal area (Eket and Oron) and Rainfall is the principal source of water to all upland area(Uyo and Ikot Ekpene), (Fig. 1). living things on the earth surface. It plays a crucial role in agriculture. Rainfall is the Akwa Ibom State lies in the coastal plain of deposition of atmospheric moisture on the soil South Eastern Nigeria, where sediments are surface in the form of liquid which is the principal supplied by Cross River, Qua Iboe River, Imo source of water for agricultural activities in the River and the Gulf of Guinea. Generally, the world [6]. All water sources at the earth surface; landscape of the state comprises of a low-lying such as ground water, surface wells, lakes, plain and riverine area, with an elevation of rivers, canal, oceans, streams, etc. are directly 185.32 meters above sea level [12]. Akwa Ibom influenced by rainfall. The distribution of rainfall State lies between latitude 04°56'23.06''N and varies from location to location due to climatic longitude 07°52'09.71''E. The State is bordered changes [7]. The variation in rainfall distribution on the East by , on the North affects sustainable agricultural development in and Northwest by Abia State, on the Southwest different countries of the world. by Rivers State and on the South by the Atlantic Ocean [12]. Climate change and agricultural production are interrelated processes that take place in a global The area has a humid tropical climate, dimension [8]. Despite the advancement in characterized by distinct wet and dry seasons. In science and technology that result in the the South and Central parts of the state (nearer production of improved crop varieties; adequate the coast), the wet season lasts for about 10 – 11 rainfall for crops remain key in months (February/March – mid November), but achieving sustainable crop production. towards the far north, it reduces to about nine Fluctuation in rainfall distribution possesses a months (i.e. March – October). The dry season great risk on the yield of crops. It influences the begins in mid – November and ends in February start of farming activities. Too much or too or March [12]. Annual rainfall amount varies from little rain is detrimental to the growth of plants 3,200 mm along the coast to 2,250 mm in the [9]. northern fringe. Temperature values are

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relatively high in Akwa Ibom State throughout the (i.e. coastal areas) were collected at Nigeria year with mean annual values varying between Meteorological Agency (NiMet), ; also 26 and 28°C. The months with highest cassava yield data were collected from temperatures include February and March (the Akwa Ibom State Ministry of Agriculture, Uyo period just before heavy rains), while July – for a period of 30 years (1988 - 2018) September have lowest temperatures (when respectively. heavy rains and cloud cover reduces insulation reaching the surface [13]. Also, relative humidity 2.3 Statistical Analysis remains at an average of 70 – 80 percent throughout the year. Average sunshine circulates Descriptive statistics were used to summarize to 1,450 hours per year and the annual the daily rainfall data into monthly, annual and evaporation rate range from 1,500 – 1800 mm decadal rainfall trends; as well as determining [11]. average cassava yield. Time series in Microsoft Excel version 16.0 was used to determine 2.2 Data Collection the relationship between rainfall and crops yield. Time series analysis is a statistical The daily rainfall data of Uyo and Ikot Ekpene technique that deals with series of data in (i.e. for upland areas) and that of Eket and Oron relation to time.

Fig. 1. Akwa Ibom state showing the study area

Table 1. Geographical characteristics of the weather stations

Location Latitude Longitude Elevation (m) Eket 04038'47.43''N 07 0 58'00.20''E 17.67 Oron 04048'27.24''N 08 0 15'00.52''E 30.16 Uyo 05030'45.36''N 07 0 55'56.16''E 54.23 Ikot Ekpene 05011'22.39''N 07 0 42'55.40''E 70.10 Source: NiMet, 2018

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3. RESULTS AND DISCUSSION starts from onset through cessation without stopping. 3.1 Distribution of Rainfall The result in Fig. 3 shows average annual Fig. 2 shows monthly rainfall distribution in decadal rainfall distribution. The decadal rainfall coastal (Eket and Oron) and upland (Uyo and in Eket, Oron, Uyo and Ikot Ekpene shows that Ikot Ekpene) areas. From Fig. 2, months of first decade record 2943.65 mm, 2830.48 mm, January and December recorded the least 2093.53 mm and 1752.52 mm respectively; amount of rainfall in coastal areas of Eket (i.e. second decade record 3138.46 mm, 2953.74 38.95 mm and 55.41 mm) and Oron (29.50 mm mm, 2166.85 mm and 1853 mm respectively; and 24.62 mm) respectively. and third decade record 3765.40 mm, 3500.34 mm, 2416.88 mm respectively. It indicated that a Moreover, in upland areas of Uyo, months of high amount of rainfall was recorded in the third January, February and December recorded the decade with Eket recording 3765.40 mm, while least amount of rainfall of 7.95 mm, 17.09 mm the least amount of rainfall was recorded in the and 12.29 mm respectively, while in Ikot Ekpene, first decade i.e. Ikot Ekpene with 2943.65 mm. months of January, February, November and The increase in the amount of rainfall from the December recorded least amount of rainfall of first decade to the third decade may be attributed 4.40 mm, 13.09 mm, 22.26 mm and 8.84 mm to change in the climate. It will result in the respectively. The highest amount of rainfall for degradation of the environment like erosion, coastal and upland areas was recorded in the flooding, etc. [5,17]. This reveals that the coastal month of July with 509.10 mm, 525.80 mm, areas of Eket and Oron will witness increase in 406.98 mm and 362.94 mm for Eket, Oron, Uyo environmental degradation like erosion, flooding, and Ikot Ekpene respectively. In both coastal and etc. due to the high amount of rainfall witnessed upland areas, there was an increase in the decade by decade compare to upland areas of amount of rainfall from January till July; decrease Uyo and Ikot Ekpene. This reveal that crops till it reaches December. production may be negatively affected in the coastal areas. The rainfall starts to stabilize for the cultivation of crops by February with 73.42 mm and 52.37 mm Fig. 4 show trends of annual rainfall in selected (i.e. Eket and Oron); while in the upland area of areas i.e. coastal areas (Eket and Oron) and Uyo and Ikot Ekpene, rainfall stabilizes for the upland areas (Uyo and Ikot Ekpene) of Akwa Ibom State. The figures shows significance cultivation of crops by March (111.34 mm and 2 52.37 mm) respectively. [14,15] stated that increase in annual rainfall in all areas. In Eket, r = 0.6631, and y = 59.702 + 2357.1; Oron, r2 = minimum monthly rainfall for the start of 2 cultivation of crops in rainforest zone should be 0.5329 and y = 34.417 + 2561.4; Uyo, r = 50 – 80 mm and semi-arid zone 80 – 100 mm 0.4215 and y = 22.289 + 1926.8; and Ikot Ekpene, r2 = 0.4042 and y = 28.86 + 1560.2; and above. This would enable crops to germinate 2 and establish well, except for drought tolerance (p>0.05). (Where r =rate of rainfall increase). crops. Therefore, Akwa Ibom which is a rainforest zone with over 2000 mm of annual These indicate that coastal areas experience the rainfall has recorded minimum rainfall highest amount of rainfall increase than upland requirement for the start of crops cultivation in areas. The variation in rainfall increase may be the months of February for coastal areas and attributed to proximity to water bodies March for upland areas over the study period. (continentality), climate change and topography Adequate rainfall for crops establishment is of the place [5,18,19]. In crops production, areas crucial in achieving high yield and productivity experiencing a high amount of rainfall more than since it helps in carrying-out different what a particular crop can tolerate will hinder the physiological and biochemical functions [16]. physiological and biochemical functions of the plant concern [20]. From the trends, it indicated that rainfall distribution in the areas follows a unimodal 3.2 Effect of Rainfall and Crops Yield pattern with the highest amount of rainfall recorded in the coastal areas of Eket and Oron. Figs. 5 – 8 show trends of rainfall and cassava That is, there is a single rainy season with yield. The trends indicates significance decrease highest rainfall (peak) amount occurring in a in yield of cassava in coastal areas of Eket at r2 = particular month (July). The seasonal rainfall 0.0611 and y = -0.0886x + 7.5549; Oron – r2 =

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0.1159 and y = -0.0778x + 5.9849; (p>0.05). cassava in Uyo and Ikot Ekpene may be due to Also, the trends show a significance increase in increase in annual rainfall. The average annual yield of cassava in upland areas of Uyo at r2 = rainfall recorded in Eket, Oron, Uyo and Ikot 0.2436 and y = 0.1412x + 5.2761; Ikot Ekpene – Ekpene was 3282.50 mm, 3094.84 mm, 2272.24 r2 = 0.4387 and y = 0.1207x; (p>0.05). Rainfall mm and 2007.49 mm respectively (Table 2). increase in all locations had similar pattern. The According to FAO [22], cassava required annual average yield recorded in Eket, Oron, Uyo and average rainfall of 1,200 – 2,200 mm. They also Ikot Ekpene was 5.83 mt/ha, 6.20 mt/ha, 11.50 noted that a higher yield of cassava was mt/ha and 10.21 mt/ha respectively (Table 2). It obtained with a high level of water supply; shows that only Uyo and Ikot Ekpene record the provided it is not above the requirement for yield that fall between the potential yields of 10 cassava and other tuber crops. Research by mt/ha and above predicted by National Root NRCRI [21] indicates that maximum cassava Crops Research Institute (NRCRI) [21] for yields are correlated with rainfall totalling different agro-ecological zones in Nigeria; under between 1600 - 1700 mm during the first to ninth the condition of adequate nutrients, rainfall and months after planting for cassava. The yields of other climatic variables, as well as good cassava increased six-fold when the quantity of varieties. The decrease in cassava yield in Eket water supplied matched the growth stage of the and Oron may be attributed to the increase in crop [23]. The result indicates that sustainable rainfall which provided more soil moisture than production of cassava may be feasible in upland the crop water requirement. Increase in yield of areas only.

Fig. 2. Monthly rainfall distribution for Eket, Oron, Uyo and Ikot Ekpene

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Fig. 3. Average annual decadal rainfall distribution in Eket, Oron, Uyo and Ikot Ekpene (1989 -2018)

Fig. 4. Annual rainfall of Eket, Oron, Uyo and Ikot Ekpene (1989-2018)

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Table 2. Rainfall distribution and cassava yield in Eket, Oron, Uyo and Ikot Ekpene

Location Eket Oron Uyo Ikot Ekpene Rainfall (mm) 3282.50 3094.84 2272.24 2007.49 Cassava (mt/ha) 5.83 6.20 11.50 10.21

Fig. 5. Trend of rainfall and cassava yield for Eket (1989 – 2018)

Fig. 6. Trend of rainfall and cassava yield for Oron (1989 – 2018)

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Fig. 7. Trend of rainfall and cassava yield for Uyo (1989 – 2018)

Fig. 8. Trend of rainfall and cassava yield for Ikot Ekpene

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