Root growth and NPK status of cassava as influenced by oil palm bunch ash

Experiments were carried out at Omoku and Umudike in southeast Nigeria to study effect of oil palm bunch ash (OBA) on number, length, diameter of roots, dry root yield and leaf N, P and K content of bitter and sweet cassava (Manihot  esculentaGrantz). The 0.00, 1.25, 2.50, 3.75, 5.00 t/ha OBA and 600 kg/ha NPKF [15:15:15) fertilizer were applied on soil to cassava and root growth parameters were determined at 3, 6, 9, and 12 months after planting (MAP). Root dry weight and leaf N, P and K were determined at 12 MAP. OBA treatments and NPKF increased root length, root diameter, number of roots, root weight and leaf N, P and K concentrations significantly (P = 0.05). The 2.50, 3.75, 5.00 t/ha OBA and NPKF gave similar values of root diameter. The 2.50 t/ha OBA gave the highest mean root yield and tuber yield of sweet cassava. The 2.50 and 3.75 t/ha OBA increased tuber yield than NPKF by 83%. Application of 2.50 t/ha OBA is recommended.   Key words: Cassava, oil palm bunch, fertilizer, yield.