Yield and Storage Characteristics of White Yam (Dioscorea rotundata Poir) as Influenced by Fertilizer Application and Time of Harvesting in Forest Zone of Ghana

A field trial was conducted at the CSIR-Crops Research Institute (CRI) experimental fields to evaluate the effects of organic and inorganic fertilizers, and time of harvesting on the yield and quality of white yam (Dioscorea rotundata). The experiment was a 4x3 factorial arranged in a Randomised Complete Block Design (RCBD) with three replications. The treatments consisted of four fertilizer rates [(i) No fertilizer (ii) 4t poultry manure (PM) per hectare (iii) 300 kg NPK 15:15:15/ha (iv) 2 t poultry manure + 150 kg NPK 15:15:15/ha and three harvesting times [(i) milking at 20 weeks after planting (WAP) (ii) milking at 24 WAP and (iii) harvesting at 32 WAP]. The combined application of organic and inorganic fertilizer gave significantly higher (P=.05) total yield of yam than their sole applications. All treated plots had higher (P=.05) yields than the control. The combination of PM+NPK gave higher number of tubers of 2.12 per stand. Tuber length of 37.9 cm was significantly higher (P=.05) in PM treatment than 29.23 cm for the PM+NPK amended treatment. The study also revealed significant tuber weight loss of 23.8%, 19.0% and 16.7% for PM, PM+NPK and the control respectively, over a three month storage period. Tuber weight was 36% and 41% higher at 32 WAP than at 24 and 20 WAP, respectively. Higher rotting rates were recorded under PM+NPK amended treatments compared to the other amended treatments and the control.