Statistical Analysis of Optimum Phosphorous Fertilizer Requirement for Improved Yield Performance of Cowpea in Nigeria

Abstract

This paper investigates optimum required amount of Phosphorous fertilizer  and optimal duration of maturity for cowpea. The study was conducted on a cowpea variety using randomized complete block design (RCBD) replicated three times. Appropriate Analysis of variance technique for the design type was used in collecting datasets on growth variables of the plant, using fixed effects, in an experiment conducted by the teaching and research farm of University of Ilorin, Ilorin, Nigeria in year 2010. Five quantitative and equally spaced levels of 0Kg/Ha, 30Kg/Ha, 60Kg/Ha, 90Kg/Ha and 120Kg/Ha respectively, of the fertilizer type were considered in the experiment. Measurements were taken on a number of variables namely, plant height (cm), number of branches, number of leaves, number of flowers  and number of pods of cowpea. The datasets were inspected for homogeneity of variances using Bartlett’s and Fligner-Killeen’s tests respectively in the language R. The tests revealed that ANOVA assumption of homoscedasticity was not violated in the datasets except for cowpea height. Logarithmic transformation was performed on the dataset for cowpea height to correct for violation of homoscedasticity assumption. Shapiro-Wilk’s test of normality was conducted on the residuals of the ANOVA models for the various response variables. The results of the test revealed that ANOVA assumption of normally distributed residuals was not violated in the datasets. We also investigated presence of potential outliers in the datasets using standardized residuals. The results were adequately supported by residuals plot and normal quantile plot respectively. It was observed that minimum and maximum standardized residuals lie within  as expected. Phosphorous fertilizer level of 60Kg/Ha was found to be the most economically efficient and optimum for growing cowpea with the corresponding optimum yield from the 8th through the 11th week after planting.

Keywords: RCBD, Phosphorous, fixed Effects, Shapiro-Wilk’s test, Fligner-Killeen’s test, Bartlett’s test, ANOVA, and R