Effect of Stake Length and NPK Fiertilizer on White Yam (Dioscorea rotundata) Minisett in Umudike, South-East, Nigeria

Staking and soil fertility are critical factors that affect yam production in the humid forest zone of South-East, Nigeria; where high rainfalls and cloud cover are prevalent. Field experiments were conducted at Umudike, South-East, Nigeria in the 2016 and 2017 cropping seasons, to study the effects of stake length and NPK fertilizer on the minisett of white yam cultivar Yandu. The experiment was laid out as a 4× 5 factorial in a randomized complete block design (RCBD) with three replicates. Treatments consist of four levels of stake length (0, 1, 2 and 3m) and five levels of NPK (15:15:15) fertilizer (0, 200, 400, 600 and 800kg/ha). Stake of 2 and 3m lengths had significantly longer vine lengths at 3 and 4 months after planting  (MAP) and leaf area index at 3MAP than no staking. Averaged across the two cropping seasons, staking did not affect tuber yield, but the 2 or 3m stakes in 2016 had significant higher tuber yields than the yields obtained in 2017 regardless of stake length. NPK fertilizer application did not significantly influence vine length, leaf area index, and tuber yield, but the application of fertilizer at 200kg/ha increased the number of tubers per plant in 2017. The non-significant effects of staking and NPK fertilizer on tuber yield were ascribed to high rainfall that caused flooding and leaching of nutrients