Effect of zinc fertilization on growth and yield of cocoyam (Colocasia spp) in Anambra East Local Government Area

Abstract

Two field experiments were conducted for two seasons (2007 and 2008) at the research farm of the National Root Crops Research Institute, Igbariam Sub-Station. The aim of the research was to assess the effect of zinc fertilizer (ZnO) on growth and yield of cocoyam. The experiment was a randomized complete block design (RCBD) replicated three times. Zinc fertilizer was applied at 5 levels 0, 3, 6, 9 and 12 kg ha^-1. The result showed that zinc fertilizer had no significant (P<0.05) effect on plant height, number of croms, cormels and tuber yield. Zinc rates at 12 kg ha^-1 and 6 kg ha^-1 gave the highest plant height of 76.1 cm and 103.2 cm in 2007 and 2008 cropping season respectively. Number of corms produced slightly increased with increasing rate of zinc up to 3 kg ha^-1 and 9 kg ha^-1 in 2007 and 2008 respectively. The failure of zinc fertilizer to influence cormel production may be related to the risk of phosphorus-induced zinc deficiency, which occurs when zinc is applied in combination with phosphorus fertilizer. However, in 2007 zinc rate at 12 kg ha^-1 gave the highest tuber yield of 11.6 t ha^-1 compared with tuber yield of 8.4 t ha^-1 obtained at the same rate in the corresponding year. Hence, the lack of significance observed on plant height, number of corms, number of cormels and tuber yield of cocoyam in the study area may be attributed to the inherent characteristics of zinc oxide applied which is very slow in releasing nutrient to the test crop because its specific gravity surface decreased when it is applied to the soil.