Influence of Phosphorus and Zinc Application on Leaf Area Ratio (LAR) of Cowpea (<i>Vigna unguiculata</i> (L.) Walp) Varieties in the Scrub Savanna of Nigeria

Abstract

Currently there is increasing attention to evaluate the possible Relative Growth Rate (RGR) of plant species, and to evaluate whether the disparities are principally caused by structural or by physiological characters. Leaf area ratio (LAR) of plant is defined as leaf area per unit total plant biomass and net assimilation rate. Phosphorus (P) and Zinc (Zn) are the most important factors affecting LAR of cowpea (Vigna unguiculata L. Walp). Two field trials were conducted at the Faculty of Agriculture and Agricultural Engineering Research Farm of Abubakar Tafawa Balewa University, Bauchi, North Eastern, Nigeria, between 2006 and 2007. The experiments consisted of fifty-four (54) treatments consisting of six varieties by three SSP levels by three Zinc levels. The objective of this study was to examine whether there are disparities in the LAR of cowpea varieties at different P and Zn levels or none? Bauchi is located at 10⁰ 22’, N latitude and 90⁰ 47’ E longitude at about 109.45m above sea level. Results indicated that year, varieties, P and Zn were found to have significant (P<0.05) effect on LAR. Kanannado recorded the highest LAR than other five varieties. The differences in LAR observed in the varieties may be attributed to the differences in phenotypes and climatic factors such as rainfall, sunshine and availability of nutrients. The increase in LAR indicated an encouraging influence on crop growth rate, dry matter and yield. Application of SSP at 50kgha^-1 to Kanannado and IT89KD-288 was observed to be more valuable for enhancement of LAR and hence recommended for growers in the study area.