Effects of thermal heat units on the phenology and yield of kenaf in the sorghum/kenaf/okra intercrop in the forest-savanna transition zone of Nigeria

Abstract

This study investigated the effects of thermal heat units on the phenology and yield of kenaf in the sorghum/kenaf/okra intercrop at the Teaching and Research Farm of the Department of Water Resources Management and Agricultural Meteorology, Federal University of Agriculture, Abeokuta, Nigeria during the 2011 and 2012 planting seasons. One kenaf (Cuba 108) and okra (NHAe 47-4) cultivars and two sorghum cultivars (Janare and Farin-Dawa) were intercropped to form 11 treatments. The treatments were randomised in a complete block design, with three replicates. Daily agrometeorological data were collected from the agrometeorological station of the Department of Water Resources Management and Agricultural Meteorology, Federal University of Agriculture, Abeokuta, Nigeria, to determine the growing degree days (GDD). Helio thermal units (HTU), photothermal units (PTU), relative temperature disparity (RTD), and heat unit efficiency (HUE) using empirical formulae. The results of the study showed that the accumulated GDDs, PTU, HTU, and RTD required to attain different growth stages of kenaf with sorghum and okra in the sole, two-, and three-tier stands were significantly affected. The HUE values of kenaf in the sole stand were significantly higher than those in their mixtures. HUE correlated positively and significantly with the yield of kenaf bast fibre (0.986**) and seed (0.801**), indicating that the temperature was efficiently utilised by the crops in sole and mixtures. Hence, it may be concluded that kenaf can be incorporated with sorghum and okra to give a new crop combination.