ABSTRACT

An experiment to determine the effect of inorganic and organic fertilizers on the yield, fruit quality and soil fertility of Late Valencia (Citrus sinensi (L.) Osbeck) was carried out at the Forest and Horticultural Crops Research Centre, Kade in the semi-deciduous forest agro-ecological zone on a 13year old citrus orchard. The experiment was conducted in a randomized complete block design with four replications. The experiment consisted of six treatments: (I) 9 t/ha Oil palm empty fruit bunches (EFB); (II) 4t/ha poultry manure (PM); (III) inorganic fertilizer (N, P, K and Zn) applied at the rate of 90kg/ha N, 60kg/ha P, 80kg/ha K and 4.80kg/ha Zn (IV) 4.5 t/ha EFB plus 45kg/ha N, 30kg/ha P, 40kg/ha K and 2.40kg/ha Zn; (V) 2t/ha PM plus 45kg/ha N, 30kg/ha P, 40kg/ha K and 2.40kg/ha Zn; (VI) Control. The results indicated that there were significant differences in fruit yield between the treatments. The treatment PM+NPKZn recorded the highest yield of 14.71t/ha with the Control recording the least (6.37t/ha). Fertilizer application did not significantly affect any of the fruit quality parameters studied, nor the level of nutrients (N, P, K, Ca and Mg) in the leaves 253 days after fertilizer application. However, leaf N and K levels were generally higher 253 days after fertilizer application over the initial levels although P levels did not change. Leaf N and P content significantly correlated with fruit quality parameters such as fruit size, juice content, juice volume and TSS indicating the importance of these nutrients in promoting improved fruit quality in citrus. Leaf K level however negatively influenced all the fruit quality parameters (fruit size, juice content, juice volume and TSS) except TA. Leaf Ca content positively correlated with fruit size (r= 0.54), juice volume (r= 0.26), total soluble solutes (r= 0.29) and TSS:TA (r= 0.46) but negatively correlated with TA (r= -0.28). Both juice content and volume were significantly influenced by soil total N and soil available P suggesting the importance of these nutrients in improving citrus juice quality. Soil analysis 253 days after nutrient application showed an increase in some soil chemical properties such as Total N, OC and available P while pH level decreased. The study
suggests the need for farmers to adopt integrated soil fertility management practices to improve the yield and fruit quality of citrus while maintaining soil fertility of