Agronomic Performance of Sweet Potato (Ipomoea batatas (L.) Lam) Fertilized with Poultry Manure Enriched with Oil Palm Refuse Bunch Ash in a Low Fertile Soil

Abstract

A field experiment was conducted to investigate the efficiency of poultry manure enriched with oil palm refuse bunch ash (OPRBA) on the growth and yield of sweet potato in a low fertile soil. The experiment was laid out in a randomized complete block design with three replications. The treatments involved five rates (0, 2, 4, 6 and 8 t ha-1) of oil palm refuse bunch ash (OPRBA) in the first year of the experiment. In the second year, the treatments were 0, 4, 6, 8 and 10 t ha-1 of OPRBA. All plots were treated with a basal application of 15 t ha-1 of poultry manure. Data were collected on vine length (cm), number of branches, number of nodes, number of leaves, leaf area index (LAI) and total dry weight (g m-2) at 8 weeks after planting. Data on yield components were collected on tuber length (cm), tuber girth (cm), number of tubers, tuber size (kg), tuber weight (kg) and tuber yield (t ha-1). The results showed that vine length, number of branches, number of nodes, number of leaves and leaf area index and total dry weight increased significantly (p < 0.05) while increasing the rate of OPRBA. The highest tuber yield (50.22 t ha-1) was recorded for plants treated with 6 t ha-1 of OPRBA in 2016. In 2017, plants treated with 6, 8 and 10 t ha-1 OPRBA had the highest tuber yield (29.10, 30.00 and 32.00 t ha-1, respectively). Tuber yield correlated significantly (p < 0.05) and positively with total dry weight (r = 0.748), LAI (r = 0.938), number of branches (r = 0.679), number of leaves (r = 0.879), number of nodes (r = 0.440), number of tubers (r = 0.561), tuber girth (r = 0.751), tuber length (r = 0.864), tuber size (r = 0.952) and vine length (r = 0.940). It is therefore suggested that poultry manure at the rate of 15 t ha-1 should be enriched with OPRBA at the rate of 6 t ha-1 for optimum production of sweet potato.