INTRODUCTION:

Climatic variables govern to large extent the types of crop that may be grown in a given area at a given time. In spite of the recent technological and scientific advances, weather is still the most important variable in agricultural production. All aspects of agriculture – from sowing or planting to harvesting in the country depend directly or indirectly on the weather and climate. There is scarcely any aspect of agriculture in which weather does not play a vital role. Rainfall is undoubtedly the most important climatic variable with far-reaching influences on agriculture especially in the tropics (Adebayo 2010).

Ayoade (2002) pointed out that most of the problems facing agriculture and indeed crop production particularly in the tropics are climate related. According to him, agriculture is sensitive to weather and climates at all stages of production from land clearing and preparation, through crop growth and management to harvesting, storage, transportation and marketing of agricultural products. This means that weather and climates have a profound influence on all the stages of agricultural production in the tropics. Thus, climate variability, fluctuation and indeed climate change constitute major limiting factors in agricultural productivity in the region.

Climate conditions such as temperature, rainfall and sunshine significantly influences the groundnut production. Adequate rain fall well distributed during the growing season, especially during fruiting, is essential for maximum yield and quality of groundnut. Also, a minimum 100 days optimum temperature growing season is necessary for successful groundnut crop production. The favorable climate for groundnut is a well-distributed rainfall of at least 500mm during the crop-growing season, and with abundance of sunshine and relatively warm temperature. Temperature in the range of 25 to 30⁰C is optimum for plant development (Weiss, 2000).

According to (PROTA, 2009), climatic conditions such as temperature and rainfall significantly influence the groundnut production. Warm and most conditions are very favourable than cool and wet climate, which results in slow germination and seedling emergence, increasing the risk of seed rot and seedling diseases. Temperature is a major environmental factor that determines the rate of crop development. Temperatures above 35⁰C inhibit the growth of groundnut. Optimum mean daily temperature to grow is 30⁰C and growth ceases at 15⁰C. For rapid emergence, soil temperature above 21⁰C is needed. The optimum temperature for the most rapid germination and seedling development is about 30⁰C.

Groundnut is essentially a tropical plant and requires a long and warm growing season. The favorable climate for groundnut is a well-distributed rainfall of at least 500 mm during the crop-growing season, and with abundance of sunshine and relatively warm temperature. Temperature in the range of 25 to 30ºC is optimum for plant development (Weiss 2000).

Rainfall is the most significant climatic factor affecting groundnut production, as 70% of the crop area is under semi-arid tropics characterized by low and erratic rainfall. Low rainfall and prolonged dry spells during the crop growth period were reported to be main reasons for low average yields in several parts of Africa (Camberlin and Diop, 1999).

Results from a series of experiments at ICRISAT (1984) showed that early stress or lack of rainfall/soil moisture during 29-57 days after sowing (DAS) did not influence pod yield significantly, where as pod yields were increased by 150 kg/ha/cm of water applied during seed filling stage (93-113 DAS). Pod yield of groundnut and rainfall received during pod formation to maturity were positively correlated in a rainfed crop grown at semi-arid region of Andhra Pradesh in India (Subbaiah et al., 1974).

Analysis of the relationship between simulated groundnut yield and Climate in Ghana of western Africa showed that yield was predominantly influenced by rainfall from flowering to maturity. Water stress imposed during the flowering and pegging stages of JL-24 produced greatest reductions in pod yield followed by water stress at early and late pod stages (Christensen et al., 2004). Naveen et al. (1992) found that water stress imposed during the flowering and pegging stages of JL-24 produced greatest reductions in pod yield followed by water stress at early and late pod stages.

Higher temperature, promoted greater vegetative growth and higher photosynthesis in 3 genotypes of groundnut, but the reproductive growth was decreased, due to greater flower abortion and decreasing seed size (Talwar et al. 1999; Prasad et al., 2003). Karunakar et al. (2002) reported that yield attributes like number of effective pegs, developed pod numbers and pod dry weight per plant of groundnut grown under semi-arid tropical conditions of India were positively influenced by minimum temperature and relative humidity during the crop growing period.

MATERIALS AND METHODS:

Experimental Treatment and Design:

The treatment consists of three groundnut cultivars namely; Kampala, Kwachamba and Gargajiya. The selection of the groundnut cultivars was based on the fact that they are the commonly used varieties in the state as observed by AADP (2005). The three cultivars were obtained from AADP Yola, a recognized government agency responsible for the handling of agricultural seeds in the state.

An experimental farm with a total size of (20 x 20)m² was laid out in a Randomized Complete Block Design (RCBD). The experimental farm was established at the teaching and research farm of the Department of Crop Production and Horticulture, Modibbo Adama University of Technology, Yola. The three groundnut cultivars was planted at the same time on the farm at the onset of rain, and replicated three times with one seedling per stand. All inter-and intra-rows spacing of the crops was 75cm and 20cm apart for larger seeds (Kampala and Gargajiya). This gives plant population of 83200 plants per hectare for each of the two cultivars. Smaller seeds (kwachamba) were spaced at 75cm between rows and 15cm within rows given the plant population of 108800 plants per hectare. Each plotwas separated by 1.5m pathway between plots. The total number of plots per farm was nine containing three groundnut varieties replicated three times (i.e. 3 x 3 = 9).

Experimental Farm Management Practices:

Uniform cultural farm management practices were applied to the farm throughout the growing season. Farm was cleared, ploughed, harrowed and well leveled by tractor in order to get flat and fine tills before sowing so as to have easy and uniform seed germination (PROTA, 2009). The single superphosphate (SSP) fertilizer was applied before harrowing.

The seed cultivars were treated with a fungicide before sowing in order to control seedling diseases. Seed was sown on flat and level ground after the plots are marked out. Planting was commencing when the air and soil moisture conditions are suitable for seed germination. One seed was planted per stand (hole). Weeding frequency using hand hoe was maintained. The crop was thoroughly weeded within the first 45 days. Once the development of the ‘peg’ begins, earthling-up was kept to a minimum. Weeds at this stage were hand pulled. (PROTA, 2006).

Data Collection:

A sole crop of groundnut comprising three different varieties was grown on the farm under rainfed condition for one growing season (2013). Data that were collected include those determining the crop growth and yield such as soil data, climatic data and data on crop agronomy.

Soil samples to determine the physical characteristics and chemical compositions of the farm was collected and determined. The physical properties of soil include texture, colour and the water holding capacity of the soil. Chemical composition of soil include the nutrients components such as the total calcium (Ca%), available phosphorus, (P), available Potassium (K), organic carbon content and exchangeable cat ions such as Potassium (K⁺), Calcium (Ca⁺⁺), Magnesium (Mg⁺⁺) and Sodium (Na⁺). The soil sample collection procedure involved randomly digging of five holes on the farm using a soil-auger to the depth of 0-20cm and 20-40cm (expected depth the crop’s root can reach respectively).

Daily weather data on maximum and minimum temperature, soil temperature, rainfall, relative humidity and sunshine hours were collected and used for this study. These data were obtained from the metrological stations of the Modibbo Adama University of Technology, Yola.

Data on crop agronomy such as the crop growth and yield determining parameters was collected on the farms from continuous monitoring of the crop growth and yield throughout the growing season. Data on growth parameters such as plant height, number of leaves, number of branches and leaf area were taken from 3 weeks after sowing and at after every 10 days of interval to the harvest. In order to determine the effects of climate on the growth and yield, periodic measurement of 10 randomly selected plants from the net plots were made. The parameters measured include; Plant height, number of leaves, number of branches, leaf height, leaf length, leaf area and grain yield per plot.

Statistical Data Analysis:

Descriptive statistics such as mean and percentages were used to summarize the data collected from the field. Correlation analysis was used in this study to determine the relationships between climatic factors and growth, and yield of groundnut.

RESULTS AND DISCUSSIONS:

The analysis was carried out using SASS and SPSS statistical package with respect to the aim and objectives of the study, aspects of which includes; correlations between the climatic elements and, growth and yield of groundnut of the study area.

The Relationship between Climatic Elements and the Growth Parameters of Groundnut:

Correlation coefficients between climatic factors and the growth parameters of groundnut are presented in Table 1. The result of the bivariate correlation reveals the differences in the effect of each climatic variable on the groundnut growth parameters.

The result of the relationship between climatic elements and the groundnut growth parameters and yield reveals the following: Total rainfall was positively correlated with leaf length, leaf area at p = 0.01 and leaf height at p = 0.05. Other positive correlation values were recorded between rainfall and plant height (0.362), number of leaves (0.092), number of branches (0.090). Maximum temperature correlated negatively with plant height, leaf length, leaf height, leaf area at p = 0.01, and number of leaves, number of branches at p = 0.05. Minimum and soil temperature correlated negatively with all the growth parameters at p = 0.01. Sunshine has a negative correlation with plant height and leaf length at p = 0.01 as well as leaf height and leaf area at p = 0.05. Other positive correlation was observed between sunshine and number of leaves, number of branches at p = 0.05. Relative humidity was correlated positively with all the growth parameters at p = 0.01. This result indicates that, only relative humidity and rainfall are significant for groundnut vegetative growth (growth parameters). The interaction between humidity and water storage capacity of the soil will obviously be a major factor in determining weather-crop phonology is affected (PROTA, 2006), low humidity and high temperature results in excessive transpiration and water deficit in a plant resulting in abscission of buds, flowers and small fruits. A strong positive correlations was observed between the groundnut growth parameters and relative humidity in Yola indicating that the higher the relative humidity the higher the yield (Table 1).

Rainfall is the most significant climatic factor affecting groundnut production, as 70% of the crop area is under semi-arid tropics characterized by low and erratic rainfall. Low rainfall and prolonged dry spells during the crop growth period were reported to be main reasons for low average yields in most of the regions of Africa (Camberlin and Diop, 1999).

Table 1 Correlation Coefficients Of Climatic Elements With The Growth Parameters Of Groundnut

	Plant height	Number of leaves	Number of branches	Leaf length	Leaf height	Leaf area
Total rainfall	0.362	0.092	0.090	0.578**	0.439*	0.487**
Mean max. temp	-0.791**	-0.530*	-0.486*	-0.862**	-0.814**	-0.824**
Mean min. temp	-0.888**	-0.694**	-0.633**	-0.810**	-0.845**	-0.773**
Mean soil temp.	-0.828**	-0.603**	-0.547**	-0.782**	-0.781**	-0.734**
Mean sunshine	-0.497**	-0.380	-0.343	-0.473**	-0.474*	-0.508*
Mean humidity	0.922**	0.773**	0.695**	0.766**	0.859**	0.751**

*=Significant at 0.05

**=Significant at 0.01

The Relationship between Climatic Elements and the Yield of Groundnut at Different Phenological Stages.:

The result of the bivariate correlation between the observed climatic parameters and groundnut yield is presented in Table 2. The result reveals the differences in the effect of each climatic variable on groundnut yield at different phonological stages of growth. This shows the advantage of dividing the growing season in phonological stages as suggested by Olaniran and Babatolu (1987), Adebayo (1994) instead of using the simple growing season value in analyzing climate – crop yield relationship. This will also help in detecting the critical physiological stages for yield formation. Doorenbos and Kassam (1979) worked out stage wise water requirement as well as total water requirement of the crop. The water requirement of the crop ranged from 500 to 600mm for the total growing period (PROTA 2006). The growing period of the crop is divided into six stages. Climate yield correlations for each phonological stage are discussed below:-

Vegetative Growth:

From Table 2, rainfall and relative humidity correlated positively at p = 0.05 and 0.01 with groundnut yield at the vegetative growth stage. This signifies the importance of rainfall and humid environment during the vegetative growth stage. This finding agrees with the report of Camberlin and Diop (1999) that, low rainfall and prolonged dry spells during the crop growth period were reported to be main reasons for low average yields in several parts of Africa. Zeyong (1992) also reported that drought is the most important constraint to groundnut production in China, especially in parts of northern China where rainfall is less than 500 mm yr-1.

Table 2: Correlation Coefficient Of Climatic Elements With Groundnu Yield At Various Phonological Stages

	Planting – emergence	Vegetative growth	Flowering	Pegging	Pod development	Pod filling
Total rainfall	-0.640	0.769*	0.929**	0.946**	0.771*	0.758*
Mean max. temp	-0.332	0.151	0.989**	0.994**	-0.278	-0.692
Mean min. temp	-0.637	-0.781*	0.533	0.942**	0.019	-0.781*
Mean soil temp.	-0.405	-0.234	0.993**	0.989**	-0.126	-0.663
Mean sunshine	-0.451	0.151	0.227	-0.983**	0.188	-0.596
Mean humidity	-0.395	0.929**	-0.948**	-0.872**	-0.977**	0.654

*=Significant at 0.05

**=Significant at 0.01

Flowering:

The correlation coefficients result from Table 2 Showed that, rainfall, maximum temperature and soil temperature correlated positively with groundnut yield at flowering stage at 0.01 probability level. This signifies that, flowering is significantly influence by rainfall, consequently the higher the yield. This result confirm the assertion made by Christensen et al.,(2004) that, analysis of the relationship between simulated groundnut yield and climate in Ghana of West Africa showed that yield was predominantly influenced by rainfall from flowering to maturity. In the other hand relative humidity correlated negatively with yield at flowering stage at p = 0.01.

Pegging:

Rainfall, maximum temperature, minimum temperature and soil temperature, have positive correlation with groundnut yield during pegging at 0.01 probability level. But sunshine and humidity correlated negatively with yield during pegging at p = 0.01. This implies that, rainfall and temperature is importance for pegging and hence increases the yield. This result agrees with the finding of Naveeh et al., (1992) that, water stress imposed during the pegging stages of JL – 24 produced greatest reduction in pod yield. Talwaret et al.,(1999) ; Prasad et al., (2003) in contrast reported that, high air temperature reduced the proportion of flowers setting pegs. High soil temperature significantly reduced the production of pegs forming pods.

Pod Development:

The result from Table 2, shows that, rainfall significantly correlated positively with pod development at p = 0.05, while relative humidity significantly correlated negatively with groundnut yield during pod development at 0.05 probability level. This indicates that the rainfall at the range of 108.5 – 152.7mm is significant for pod development and the relative humidity at the range of 82.9 – 85.2% is insignificant for pod development. This result confirm the assertion made by Subbaiah et al., (1974) that, pod yield of groundnut and rainfall received during pod formation to maturity were positively correlated in a rainfed crop grown at semi arid region of Andha Pradesh in India.

Pod Filling:

Rainfall has positive correlation with groundnut yield during pod filling at 0.05 probability level, while minimum temperature correlated negatively with pod filling at p = 0.05. This signifies that, groundnut yield increases by increases in rainfall during pod filling. This result agrees with the work of; ICRISAT (1984) that, pod yields were increased by 150kg/hac/cm of water applied during seed filling stage (93 – 113DAS), and Karunakar et al.,(2002) that, yield attributes like number of effective pegs, pod development and pod dry weight per plant of groundnut grown under semi-arid tropical conditions of India were positively influenced by relative humidity during the crop growing period.

Summary:

This study examines the effect of climate on the growth and yield of groundnut in Yola. Especially, the assessment of the relationship between climatic elements (rainfall, maximum temperature, minimum temperature, soil temperature, sunshine and relative humidity) and, the growth and yield of groundnut

The study involved the growing of the three different groundnut cultivars namely: Kampala, Gargajiya and Kwachamba. These cultivars were grown on experimental farm located at Teaching and Research Farm of the Department of Crop Production and Horticulture, Modibbo Adama University of Technology Yola for the period of one growing season (2013).

The primary data collected includes; soil sample data, climatic data and data on crop agronomy. Soil data includes some of the basic components of soil such as the texture, organic carbon content and exchangeable cat ions. Percentage concentrations of these components were determined from the laboratory analysis of the soil. Climatic variables used in this study include, rainfall, maximum temperature, minimum temperature, soil temperature, sunshine and humidity. Data on such climatic elements were obtained from the meteorological station of Modibbo Adama University of Technology Yola. Data on crop agronomy such as the crop growth and yield parameters were collected on the farm from continuous monitoring of the crop growth and yield throughout the growing season.

Observations and measurements of the growth and yield parameters were carried out on farm spots assessments after 10 days of previous visit. Means and percentages of the climatic variables were obtained using simple statistical method. Correlation analysis was also used in this study to examine the relationship between the climatic factors and, the growth and yield of groundnut in Yola.

Correlation coefficients of climatic factors with the growth parameters and yield of groundnut cultivars show that, relative humidity was highly significantly correlated positively with all the growth parameters (vegetative growth) at P = 0.01. Rainfall also correlated positively with leaf length, leaf area at P = 0.01 and leaf height at p = 0.05. While temperature correlated significantly negatively with the growth parameters (vegetative growth) at P = 0.01. In order to achieve detailed studies and identify minute relationship, the growth cycle of groundnut was divided into six phonological stages. The mean values of the climatic variables associated with each stage were computed and analyzed using correlation analysis techniques. The correlation results of the climatic elements and yield of groundnut at various phonological stages shows that, at each stage one climatic variable stand out more pronounced on its effect at particular stage. Rainfall, maximum temperature and soil temperature correlated positively with yield at flowering and pegging stages at P = 0.01. Also rainfall correlated positively with yield at vegetative growth, pod development and pod filling stages at p = 0.05. Minimum temperature correlated positively with yield at pegging stage at p = 0.01, but correlated negatively with vegetative growth and podfilling at p =0.05 respectively. Sunshine correlated negatively with yield at pegging stage at p = 0.01. Relative humidity has positive correlation with yield at vegetative growth stage and negative correlation with flowering, pegging and pod development stages at 0.01 probability levels.

CONCLUSION:

The major conclusion from this study is as follows; humidity and rainfall are the climatic variables that mostly positively influenced the growth of groundnut, while temperature has a negative effect. At phonological stages of groundnut growth, rainfall was the most climatic variable that positively affects groundnut yield at from vegetative growth to podfilling. On the other hand, humidity mostly affects groundnut yield positively at vegetative growth and negatively at flowering, pegging and pod development stage. This indicates that, rainfall was the important climatic variable with far reaching influence on the growth and yield of groundnut in Yola.

RECOMMENDATIONS:

The following recommendations were proposed based on the finding:

1. To achieve better results from improved agricultural technology in groundnut production, the benefiting effects on growth and yield must be optimized as much as possible if not avoided. Thus, for Yola, the planting period of groundnut must be as soon as the antecedent moisture status of the soil is good for effective germination.

2. Seminars and workshops should be organized to give more orientation to farmers on the effects of climate on the growth and yield of groundnut.

3. Generally, adequate and reliable knowledge of local weather and climate is necessary as it will help farmers in the study area in planning their agricultural operations including what crops to plant and when to plant them in order to make the best of the climatic environment for crop production. Also, knowledge of weather forecast is necessary for farmers in the study area to take informed decisions to control pests and diseases and to minimize their damaging effects on crops.

4. Finally, there is the need for new genotypes, new groundnut varieties and improved cropping systems in study area to cope with the predicted negative effects of climate change on crop production in future in most part of the globe especially more pronounced in Sub Sahara Africa, Nigeria inclusive.

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Received on 12.06.2019 Accepted on 26.06.2019

Int. J. Tech. 2018; 9(1):20-26.

DOI: 10.5958/2231-3915.2019.00006.3