ABSTRACT

A field study was conducted at the University of Uyo Teaching and Research Farm for two cropping seasons (2005 and 2006) to evaluate the influence of poultry manure (PM) and NPK fertilizer rates on selected soil properties, nutrient uptake, growth and yield of Colocasia esculenta (cob) and Xanthosoma sagittifolium (Xantho) at various stages of growth. Experimental Design was 3x4 factorial fitted into Randomized complete Block Design (RCBD) with three replications. Factor A, poultry manure (PM) was applied at 3 levels; 0, 5 and lOt/ha, and factor B, NPK fertilizer was applied at 4 levels; 0, 200, 400 and 600kg/ha. Selected soil properties were sampled at 5 and 11 months after planting (MAP). The uptake of N, P and K by Colocasia and Xanthosoma were determined. Xanthosoma and Co/ocasia growth and yield parameters were also determined. At 5 MAP, application of lOt/ha PM and 400kg/ha NPK fertilizer together increased soil pH and total N by 6.14 and 0.08% representing 43 nd 166.67% increase over control. The combination of lOt/ha PM x 600 kg/ha NPK fertilizer increased available P and exchangeable K by 186mg/kg and 0.35 cmol/kg representing 12.73 and 600% increase respectively over control. Without NPK fertilizer (0kg/ha) application of lOt/ha PM increased base saturation status by 81.32 percent representing 68.47% increase over other rates of application. At 11 MAP, application of lOt/ha PM x 200kg/ha NPK fertilizer reduced soil bulk density up to 1.54 Mg/rn3representing 21.85% reduction over control. Application of l0tiha PM+600kg/ha NPK fertilizer together increased soil available P, Ca and CEC by 620mg/kg, 4.64 cmol/kg and 7.27 cmol/kg representing 111.60, 75.76 and 70.66% increase respectively when compared with control. The combination of 5tlha PM x 0kg/ha NPK fertilizer improved Xanthosoma N uptake by 3.02 percent representing 174.5% increase over control. The combination of lOt/ha PM x 600kg/ha NPK fertilizer increased Xanthosoma P uptake by 0.47 percent representing 147.37% increase over control. When lOt/ha PM x 600kg/ha NPK fertilizer were applied together the uptake of K by Colocasia and Xanthosoma increased by 2.61 and 2.67percent representing 100 and100.75% increase over control. Application of lOt/ha PM x 600kg/ha NPK fertilizer remained the best combination rates for increasing Colocasia and (Agboola and Fagbenro, 1985; Onofiok 1993). Opara-Nadi et al., (1987) reported less losses of N. K and Ca in organic manure treated soils than in inorganic fertilizer treated soils, while loss of Mg was higher, for organic manured soils than in soils which received mineral fertilizer treatment. Arable soils of Southeast Nigeria are mostly sandy, acidic Ultisols with low organic matter and nutrient status (Obi and Asiegbu, 1980). Similar conditions are dominant in the rainforest zones of the humid tropics. The use of chemical fertilizers alone to sustain high crop yield has not been quite successful due to enhancement of soil acidity, nutrient leaching and degradation of soil physical and organic matter status. Peasant farmers took to the use of organic sources of plant nutrients such as wood ash, animal manure and composts due to constraints encountered in mineral fertilizer use (Ogbalu 1999). Cocoyam (Colocasia and Xanthosoma) demands and consumption in Akwa lbom State are high but its cultivation is hampered by low inherent soil fertility and other management problems. Although much research works have been carried out on organic manure and mineral fertilizer using various test crops in Nigeria, research information on the use of cocoyam as test crop in south eastern Nigeria is very scanty. This study was conducted to investigate the influence of poultry manure (PM) and NPK fertilizer rates on selected soil properties, nutrient uptake, and yield of two cocoyam cultivars in an acid sand of South-eastern Nigeria. This was done to find out ways of exploiting the potentials of cocoyam production in an Ultisol of Uyo. The objectives of the study were;