ABSTRACT
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A survey experiment was conducted in twelve (12) out of the twenty three (23) Local Government Areas in Benue State. Semi structured copies of questionnaire were used for the study. The State was delineated into three zones (A, B and C) for purposes of convenience in the course of the study. Five (5) Local Government each from zone A and B and two (2) from zone C were chosen for the study. The selected Local Government areas were Katsina-Ala, Ushongo, Konshisha, Logo and Vandeikya which belong to zone A. The Local Government areas from zone B were Buruku, Gboko, Gwer-East, Gwer-west and Tarka while Oju and Otukpo Local Government areas were sampled from zone C. The disparity in number of Local Government areas among the three zones is because Zones A and B are much more involved in citrus production than zone C. In each of the LGAs, 15 famers were selected five (5) of which were small scale (< 1ha), middle scale (1–5ha) and large scale (> 5ha) famers respectively. Famers with orchard that measure less than 1 ha were considered small scale famers, those that measured between 1 and 5 ha were tagged middle scale famers while those having orchards in excess of 5 ha were considered large scale famers. Thus, a total of 180 farmers were sampled in the state. Furthermore, five (5) manure rates: control (no fertilizer application), 600kg/ha NPK 15:15:15, 10 t/ha poultry manure, 300kg/ha NPK 15:15:15 + 5 t/ha poultry manure and 600kg/ha NPK 15:15:15 + 20 t/ha Rice hull mulch, were evaluated in three orchards (Classified as well, fairly and poorly managed farms). Experiment was laid out in randomized complete block design (RCBD) replicated four times. Field data were collected on fruit yield parameters. Also, postharvest parameters of the fruits under ambient temperatures were measured. Furthermore, nutritional qualities of the juice extracted from the fruits were determined to elucidate the effects of the manure treatments. Survey data were analyzed with dispersion statistics and percentages. Analysis of variance (ANOVA) was performed on the field and laboratory data using  RCBD and completely randomized design (CRD) models, respectively. Significant means were separated with Fishers least significant difference at 5% probability level (F-LSD (0.05). All statistical analyses were performed using GENSTAT Discovery edition. The result of the survey indicated that majority of the farmers (66.7%) attained tertiary education at the age range of 31-40 years within family size of 6-10 individuals (44.4%). Orchard establishment was in May and June (77.8%), and about 51.1% farmers transplanted one year old seedlings. About 98% of the growers apply straight fertilizer. Manurial treatments increased the leaf-tissue concentration of N.P.K and Ca. The effect of second order interaction involving farm management, year of harvest and season on fruit yield (kg) per plant revealed that well managed orchard recorded highest fruit yield of 345kg per plant in the first season of the second year. First season harvests of the second year for both the fairly and poorly managed farms gave higher yield in their corresponding second seasons. The first order interaction of farm management and year of harvest significantly (p<0.05) influenced fruit weight loss over time. Relative to the non-fertilized plants, fruit rot was higher in fruits harvested from fertilized plants. Significant (p< 0.05) fertilizer effect was only recorded on fruit weight, fruit peel and residue weight after the third year of application. Application of 10 t/ha of poultry manure, in most cases gave the best fruit traits, highest fruit yield and lowest fruit weight loss, although, these were statistically similar to the other treatments. Nutritional qualities of juice were significantly (P< 0.05) influenced by farm management during each of the three years of evaluation. After one year of fertilizer treatment, well managed orchard had the highest ash, potassium, moisture, sodium, sugar, volume of fruits juice and vitamin C contents in the fruits. By the second year, poorly managed orchard gave fruits that had the highest acidity, potassium, sugar and total soluble solids, whereas fairly managed orchard produced fruits that had the highest sodium, pH and vitamin C. Biplot analyses of the effect of manure treatment on juice quality revealed distinct trend across the three years of evaluation. After the first year of fertilizer application, plants that received 10 t/ha poultry manure and those that received 300 kg/ha NPK 15:15:15 + 5 t/ha poultry manure produced fruits that had the highest quality traits of sugar, potassium, moisture and sodium. After the second year of fertilizer application, the best fruit quality was obtained from plants that received 300 kg/ha NPK 15:15:15 + 5 t/ha poultry manure. The residual effect of fertilizer application on juice quality by the third year of the study revealed that better juice quality was obtained from plants that received 600 kg NPK/ha + 20 t/ha ricehull mulch.
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TABLE OF CONTENTS
TITLE PAGE –          –          –          –          –          –          –          –          –          i
PUBLICATION FROM THE WORK         –          –          –          –          –          ii
CERTIFICATION    –          –          –          –          –          –          –          –          iii
DEDICATION          –          –          –          –          –          –          –          –          iv
ACKNOWLEDGEMENT    –          –          –          –          –          –          –          v
TABLE OF CONTENTS      –          –          –          –          –          –          –          vi
LIST OF TABLES    –          –          –          –          –          –          –          –          vii
LIST OF FIGURES – –          –          –          –          –          –          –          –          x
ABSTRACT              –          –          –          –          –          –          –          –          xi
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INTRODUCTION    –          –          –          –          –          –          –          –          1
LITERATURE  REVIEW   –          –          –          –          –          –          –          3
MATERIALS AND METHODS     –          –          –          –          –          –          44
RESULTS      –          –          –          –          –          –          –          –          –          52
DISCUSSION           –          –          –          –          –          –          –          –          –          115
SUMMARY AND CONCLUSION –          –          –          –          –          –          124
REFERENCES   –       –       –       –       –       –       –       –       –       125
CHAPTER ONE
INTRODUCTION
Citrus species (Citrus sinensis) probably originated in North Eastern India, Burma and the surrounding areas from where the species crossed into China, the North East and to the Mediterranean region. From the Mediterranean, it was carried to other parts of the world. The subtropics and warm temperate regions of the world are the largest producers of citrus especially the sweet orange cultivars. Tropical areas are also producing sizeable quantities of other citrus cultivars (Davies et al., 1994).
Citrus is grown in several parts of the world, where minimum temperatures stay above – 4oC (Spiegel-Roy and Goldschmidt, 1996). The worldwide production of citrus, about 102 million metric tonnes per year, is much greater than that of other tropical and subtropical fruits, including banana, mango, apple, pear and peach. The majority of the world best quality fruits is produced in the subtropical region. Brazil and the United States account for up to 45% of the total world orange production; whereas the United States accounts for up to 40% of grapefruit production in the world (FAO, 2004). Around 80% of this total fruit production is processed into orange juice by more than 10 concentrated and frozen juice processing plants located in the state of Sao Paulo, which encompassed Brazil’s major citrus production region.
Citrus ranks among the foremost fruit trees cultivated in Nigeria along side mango, and it is industrially used mainly for the manufacture of soft drinks (Opeke, 2005). In Nigeria citrus production is more concentrated in the guinea and Sudan Savanna zones (Olaniyan, 2004), with Benue State giving the highest annual production of the commodity (Avav and Uza, 2002). Unfortunately, there have been little or no studies involving crucial aspects of the production in this important area.
Although citrus production extends over a wide range of soils, sandy to clay loam soils are best suited for the production of high quality fruits. Adequate soil drainage is an important factor for good tree growth. Citrus is planted on raised beds in high rainfall areas with fine textured soils, where drainage would not be a problem. Soil pHÂ is an important factor that influences nutrient availability and other soil chemical and biological processes. Soil pHÂ range of 5.5-7.5 can support adequate growth of citrus trees, depending on the rootstock used.
To underscore the importance of maintaining flourishing citrus industry, there is a need to establish sustainable production management system that would support optimal production of fruits with minimal negative impacts on the environment. The philosophy takes into account best management practices (BMPs) of agricultural resources to improve the efficiency of fertilizer inputs by minimizing the losses (Havlin et al., 1999). Therefore, BMPs for soil nutrients imply timing and placement of fertilizer, combined with optimal scheduling of irrigation.
There has been a steady rise in citrus production globally due mainly to increase in hectarage, consumer preference for more healthy or convenient food and rising incomes (UNCTAD, 2010). Although about 140 countries are known to be involved in citrus production year 2007 estimate indicates that the top 10 citrus producing countries are Brazil, China, United States, Mexico, India, Spain, Iran, Italy, Nigeria and Turkey (UNCTAD, 2010).
Citrus production in West Africa is on a small scale and unorganized (Opeke, 2005), the ranking of Nigeria on the 9th position among the world top 10 producers of the commodity signifies that the situation might be changing. This is in consideration of the fact that previous statistics did not feature Nigeria or any of the West African countries (FAO, 1991). In any case, most of the citrus fruits produced in the country are consumed locally (Opeke, 2005) and does not seem to feature in the international trade (UNCTAD, 2010). Another factor that could constitute considerable waste to citrus fruits is postharvest management (Samson, 1980; Davies and Albrigo, 1994). This is especially true of developing nations like Nigeria, where the necessary equipment do not seem to be in place and awareness is generally low.
Citrus fruits are rich sources of vitamin C, the deficiency of which results in scurvy (Davies and Albrigo, 1994). One glass of orange or mandarin juice is said to contain enough vitamin C to supply the daily requirement (Samson, 1980). Citrus fruits are consumed fresh, as juice or concentrate. The pulp and molasses are valuable as livestock feed particularly cattle, while the peel is a rich source of pectins and essential oils (Samson, 1980).
Due to the strategic position of Benue State in citrus production in Nigeria, this study surveyed the constraints and production status of citrus in Benue State; some agronomic and postharvest management strategies for the crop were evaluated.
The specific objectives of the study were:
- To survey and document the agronomic practices, cultivars grown, disease and pest prevalence and the postharvest management practices of citrus in Benue State;
- To evaluate the effects of previous farm management and five manure rates on the yield of citrus; and
- Determine the effects of previous farm management and the five manure rates on the quality of juice produced thereof.
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