EFE S. I.
AWARITEFE O. D.
ABSTRACT. Using multiple correlation analysis and student ‘t’test, the Agroclimate factors of Oil Palm production was examined for ten years periods. Result showed that Agroclimate factors (sunshine, temperature and rainfall) are highly correlated with oil palm yield. This is evident from a multiple correlation of 74%. It was also observed that oil palm yield is more in the dry season than in the wet season.
INTRODUCTION
Any agricultural system is a man-made ecosystem that depends on climate to function just like the natural ecosystem. The main climatic elements that affect crop production are solar radiation, temperature and moisture. These climatic parameters and other depend on them, largely determine the global distribution of crops yield and livestock (Ayoade, 1993). He stresses further that climate elements exert an influenced on all stages of the agricultural production chain, including land preparation, sowing, crop growth and management, harvesting, storage, transport and marketing. This view has earlier be noted by Oguntoyinbo (1983) when he attributed the donation of the cocoa and kola-nut belt in southwest, oil palm bush in southeast and the north south ridge of river Niger comprising area of groundnut, cotton and rice cultivation to these climate vagaries.

Get Help With Your Essay
If you need assistance with writing your essay, our professional essay writing service is here to help!
Essay Writing Service

However, climate influence on oil palm has attracted the attention of some scholars over the years. Amongst whom are Manning (1956), Broekman (1963), Oshodi (1966); and Hartley (1988). An examination of their views shows that Manning (1956), outlined the rainfall requirements of selected food and commercial crops grown in West Africa, and he opined that the mean annual rainfall for oil palm is between 1500— 3000mm in West African Countries. Devuyst (1963) correlated oil palm yield with the influence of rainfall alone; using the concept of useful rainfall. His work however showed a positive correlation. He regarded rainfall as the sole agent influencing oil palm yield, and consequently considers any yield maxima to originate in wet season. Broekman (1963) accepted the view of Devuyst but differs in his finding. He stressed that dry season rainfall is positively correlated with oil palm yield.
To him, it is reasonable to except that the amount of rainfall during the dry season will be of particular importance, as moisture is a limiting factor during this period. On the other hand, Oshodi (1966) computed the effective growth energy index for some selected crops in Nigeria. The index was however based on only temperature and rainfall. The Effective Growth Energy (E.G.E) for oil palm in Nigeria is 250-300°F. Harley (1988) stated that oil palm yields are correlated with dry season rainfall with measures of effective sunshine, which take into account the distribution of such rainfall in’ the dry season. It is clear from the foregoing that rainfall and temperature correlation with oil palm has been substantiated, however, the relationship between sunshine and oil palm yield, as well as the joint contribution of sunshine, rainfall and temperature, has not be substantiated. Similarly there are divergent views on the relationship between the seasons and oil palm yield.
Also, since the establishment of Nigeria Institute for Oil Palm Research (NIFOR) in 1939 there have been a relative neglect in the development of Agroclimatological Research Unit in the institute. While other research units (Agricultural Economics, Agricultural Engineering Research, Agronomy, Biochemistry, Chemistry, Extension and On-Farm Adaptive Research, Entomology, Plant Breeding, Plant Pathology, Plant Physiology and Statistics) have been developed. What exists in that unit is a dilapidated weather station where climate data’s are collected and never used for research purposes. So, the present study of Agroclimatic factors of oil palm yield in Nigeria is borne out of the desire not only to fill the above gaps, but to proffer useful suggestion that will guide both the oil palm farmers, and the NIFOR officials on the need to plan with the climate of the area. Therefore, the aim of the study is to examine the extent to which temperature, sunshine and rainfall correlate with oil palm yield.
STUDY AREA
The Nigeria Institute for Oil Palm Research (NIFOR) is located approximately 29km North West of Benin City, Edo State in Nigeria. It was established in 1939 as Oil Palm Research Station (OPRS) by Nigeria Department of Agriculture. It was taken over in 1951 as West Africa Institute for Oil Palm Research (WAJFOR) by West African Research Organization (WARO). This organ was dissolved in 1960 after independence, and the station was renamed Nigeria institute for Oil Palm Research (NIFOR) by Nigeria Institute Act No. 33 of 1964 mandate extend to Coconut, Raphia and Date palm research.
The soil in NIFOR is acid type of sand which is an important oil palm growing soil in Nigeria (Hartley, 1988). The soil are well drained and acidic with clay content in varying proportion at different depths. The soil are deficient in plant nutrient hence the great need for fertilizers application to cultivate palms in NIFOR. NIFOR belongs to the tropical equatorial climate belt of the world, and falls within the tropical rainforest belt of Nigeria. The region is characterized with high rainfall and temperature. Rainfall is over 2066mm per annum, and temperature of 30 – 33°C. Vegetation here is luxuriant type dense tropical rainforest, which comprises of evergreen trees such as mahogany, Walnut etc. The research institute today has sub-stations and experimental stations all over the country where crops are cultivated due to their different climatic requirements.
CONCEPTUAL ISSUES
The most important concept for this study is the concept of climate and agriculture relationship. This concept which have been adopted by Broekmans (1963); Devuyst (1963); Oguntoyinbo (1966); Hartley (1988); and Ayoade (1993) in similar studies. reveals much on how climatic parameters (rainfall, sunshine, temperature, evaporation etc) are closely interrelated in their influence to drops. Because of this crops/plants are grown in a climatic belt that is best suited for its growth. Thus all crops cannot thrives well in one climate region. For instance, oats and fruits are best grown in the Mediterranean climate while, root crops such as cassava thrives well in region of abundant rainfall and temperature (Neiwolt, 1982).
Similarly, since climate is one of the most important natural factors which controls the growth of plants, plant communities therefore undergo gradual changes. And this is because of its ability to cope with the prevailing climatic conditions and also to compete for resources of that environment. Hence, the type of plants/crops cultivated in an area is related to the climate. Also, the annual yield and profitability of farming are predicated on weather elements. In fact, in this part of Nigeria, climate vagaries disrupt the efficient practice of agriculture, and climatic fluctuation creates significant changes for agriculture produces. It is on this that the growth and yield of oil palm is based. Oil palm are found in region with moderate rainfall, high temperature and sunshine which enable the fruit to ripe (Hartley, 1988).
METHODS
The data used for this study were extracted from the archives of the Agrometerological and harvesting units of the Nigerian Institute for Oil Palm Research (NIFOR) Benin City. Monthly and annual temperature, rainfall and sunshine data were collected from the Agrometerological division, while the monthly and annual oil palm yield data were collected from the harvesting unit both data were collected for ten year periods. The choice often years was based on availability and consistency of data. The seasons were delineated using six months (April — October) as wet season and October — March as dry season. Reconnaissance survey was also conducted round the oil palm farms in the institute.
Multiple correlation analysis and students ‘t’tests were used to analyze the data. The multiple correlation analysis was used to ascertain the joint relationship between oil palm yield and rainfall, temperature and sunshine. Apart from the joint contribution of the climatic parameters to oil palm yield, it will also enable us to ascertain the individual contribution of sunshine, rainfall and temperature respectively to the oil palm yield (Ayeni, I Q94). Student ‘t’ test was used to determine the season with highest oil palm yield over the years: as well as to ascertain whether there is any significant difference in oil palm yield in the dry and wet season.
DISCUSSION OF THE RESULTS
The data collected from the study are presented and discussed in the table below.
Table 1: Annual Oil Palm Yield (tons): Temperature (°C) Sunshine (hours): and Rainfall (mm) from 1989— 1998.

Year

Oil palm yield (tons)

Temp. oC

Sunshine (H)

Rainfall (mm)

1989

4470.2

32 .2

179.1

173.2

1990

3907.4

31.8

173.8

160.7

1991

3250.7

31.4

168.0

173.2

1992

3201.1

31.2

159.9

132.9

1993

3245.3

32.0

153.0

175.1

1994

1631.9

30.6

133.0

208.9

1995

3810.9

31.9

144.6

167.3

1996

4961.1

30.0

124.7

188.9

1997

2983.2

32.8

114.6

142.2

1998

3176.6

31.9

119.5

130.5

X

3463.9

31.6

147.0

165.29

From Table 1 above, the mean annual oil palm yield is 3464 tons, temperature is 32°C; sunshine 147 hours and rainfall 165mm. This showed a high yield, high temperature and a high sunshine duration respectively. During this periods, the highest yield of 4961 tons was recorded in 1996, this was followed by 4470 tons in 1989, 39O7tonsinl99O;38lltonsinl995,325ltonsin 1991,3245tonsin1993,3201 tons in 1992, 3177 tons in 1998,2983 tons in 1997 and the lowest yield of 1632 tons was recorded in 1994. This shows that there is no definite pattern of oil palm yield rather the oil palm yield has being fluctuating over the year (See figure 1 below).
Temperature distribution during this period is generally high over the years, with the highest temperature of 32.8°C in 1997 and the lowest temperature being 30°C in 1996. However, there is a little variation in temperature over the years given a range of 2.8°C. Sunshine duration is also generally high during this period. This is evident from the mean of 147; and the highest and lowest sunshine duration of 179 in 1989 and 115 in 1997 respectively. Sunshine did not also follow a definite pattern as it varies with a range of 64 hours. Rainfall also fluctuates over this period of study.
Fig. 1 above revealed that the three parameters (temperature, sunshine and rainfall) and oil palm yield followed a similarly pattern. There was a sharp drop in oil palm yield in 1994 occasioned by a drop in all the weather parameters. This gives a rainfall range of 78mm. It is evident from the above, that temperature, sunshine and rainfall influences the oil palm yield. The high yield recorded over the years could be explained to the high temperature, sunshine and rainfall respectively that encouraged its growth, and the ripening of the oil palm fruits. The seasonal distribution of oil palm yield, temperature, sunshine and rainfall is another pointer to the fact that climatic element correlates with oil palm yield. This is illustrated in figure 1.
Figure 2 shows that oil palm yield, sunshine and temperature exhibits similar pattern of variation. Oil palm yields increases from 366 tons in January to 435 tons and 432 tons in March and April respectively. This being the months with the lowest oil palm yield, it then decreases from 288 tons to 186 tons in July and August, being the month with lowest palm yield. Thereafter it rises to 2112 in the month of October. Sunshine duration followed a similar pattern, the highest duration of sunshine were noticed during the dry seasons. This showed a duration of 201, 185 and 182 hours in the month of November, December and January respectively, while the lowest sunshine duration of 70, 87 and 97 hours was recorded in July, August and September being the period of wet seasons. Temperature also exhibits a similar pattern with oil palm yield and sunshine duration. Generally, temperature is higher in the dry season, than in the wet season. This is evident from temperature of 33.7°C, 34°C and 35°C recorded in the months of December; March and February; and 3 1°C, and 29°C in June, July August and September respectively.
Rainfall distribution over the years showed a direct opposite pattern to sunshine and temperature with the highest amount of 317mm, 312mm and 313mm recorded in the month of July, August and September respectively (see fig. 2). The lowest amount of rainfall (23 mm and 10mm) was recorded in January and December being the dry season in Nigeria. To ascertain whether there is significant difference in the seasonal variation in oil palm yield, the student ‘t’ test showed that there is significant difference between oil palm yields in the dry and wet season. This is evident from the calculated ‘t’ value of 7560, which is far higher than the critical table value of 2.0. at 0.05 significance level. This is another pointer to the above distributional pattern, which shows that the dry season recorded the highest oil palm yield than the wet season.
The effect of the climatic factor (temperature, sunshine duration and rainfall) on oil palm yield was also analyzed. Result showed that they jointly contributed 74% to oil palm yield. This is evident from the result of multiple correlation analysis of yield, sunshine, temperature and rainfall. Thus it can be deduced that sunshine, temperature and rainfall are significantly related with oil palm yield. The rest 26% could be explained by other factors such as edaphic factors, evapo-transpiration, pests, humidity and diseases, etc. The contributions of each climatic factors to oil palm yield was also shown from the multiple correlation result. The result showed that sunshine, temperature and rainfall contributed 70%, 25% and 5% respectively to oil palm yield during this period. From this analysis one could now say that sunshine exerts the highest influences of 70% on oil palm yield than the other factors. This is because, sunshine duration did not only aids in ripening of the oil palm fruits, but also generate photosynthesis, which is the main energy source of all plants. Temperature influence on oil palm yield is as a result of the high sunshine duration. Rainfall, however, has a little influence on oil palm yield most especially during the dry season when plants generally needs moisture in the soil for growth and general survival.
Apart from the Agroclimatic factors of oil palm yield, the field observation conducted round some farms in NIFOR, reveals that weeds as well as seasonal outbreaks of pests and diseases were prevalent in the farms. Oil palm yield lost caused by these factors may be considerable over the years. More so when the diseases are often weather related, either in terms of local weather conditions being unfavourable for its growth and development or in terms of the prevailing winds helping to import air-borne germs/ spores into a given areas. The pests and diseases were more during the dry season where rainfall is minimised.
CONCLUSION AND RECOMMENDATIONS
The study revealed that Agroclimatic factors (sunshine, temperature and rainfall) exert high influences on oil palm yield. 74% expansion of oil palm yield is attributed to these climate factors. The rest 26% is attributed to other factors such as edaphic factors, pests, diseases, weed, humidity, etc. Sunshine, however, exerted more influence on oil palm yield than rainfall and temperature. Similarly, oil palm yield is more in dry season than in wet season. And there is more prevalence of pest and diseases in oil palm farms during the dry season than in the wet season.
To improve oil palm yields and to eradicate pest and diseases there is the need for the fanners and NIFOR officials to plan with the climate of this prevailing environment. Thus, oil palm should be cultivated during the wet season because of availability of moisture for its growth, and harvesting during the dry season because of high sunshine for its ripening. The farms should be constantly cleared to eliminate weeds since they accelerate water loss by transpiration at the expense of the oil palm. There should be weekly or monthly routine check-up of the oil palm plantation, so that the affected stands can easily be treated with the necessary pesticides or insecticides. This will also lid p to prevent the spread of epidemic outbreak across the stands.
The use of fertilizer and irrigation system should be intensified than the present level of usage in NIFOR. The irrigation is highly needed in the early age of oil palm growth during the dry season. The Agroclimate unit of NIFOR should be upgraded to research division and the attached weather station should be well equipped with modem Agroclimatic facilities/equipment. This division when upgraded will play advisory roles on the effect of climate factors on the various crops that is cultivated by this institute.
REFERENCES
Ayeni B. (1994), Quantitative Method for Geography Students. Research Support Services. Ibadan, pp. 72 – 81.
Ayoade J. O. (1993), Introduction to Climatology for the Tropics. Spectrum book Ltd. Ibadan, pp. 204 – 220.
Broekmans A. (1963), Growth, Flowering and Yield of the Oil Palm in Nigeria. In West African Institute for Oil Palm Research No. 12.
Devuyst A. (1963), Annual Oil Palm Yield. West African Institute for Oil Palm Research, No. 12.
Hartley C. W. S. (1988), The Oil Palm Tropical Agricultural Series, Longman Group Ltd, London.
Manning H. L. (1956), The Statistical Assessment of Rainfall Probability and Its Application to Uganda Agriculture. Proceedings of Royal Society Series, pp. 144, 460 – 480.
Oguntoyinbo J. S. (1966), Climate and Mankind. Annual Lecture Series Presented to the University of Ibadan.
Oshodi F. R. (1966), Biometerological Studies of Nigerian Crops. Nig. Met. Services Lagos.
Nienwolt S. (1982), Tropical Climatology: An Introduction to the Climate of the Low Latitude. John Wiley and Sons. Ltd. Chichester.