Effects of nitrogen, calcium and cation exchange capacity on gum yield in Acacia senegal under plantation and savanna woodland conditions in northern Guinea savanna, Nigeria

Abstract

Several reports have indicated fertilizer application is not required for increased gum yield in Acacia senegal. This study investigated the relationships between soil properties and gum yield under plantation and savanna woodland conditions. Multi-stage sampling was used to demarcate a 900 ha plantation into 20 blocks of 45 ha, and a 300 ha savanna woodland into 10 blocks of 30 ha. Twenty sub-plots per site were randomly selected for yield assessment by tapping for gum collection, weighing, and recording yield figures in grams. Twelve soil pits were established for soil analysis. Data were analyzed using log-log correlation, and linear regressions. Plantation results showed nitrogen (r = 0.72) and Cation Exchange Capacity (r = 0.67) were positively correlated with yield, and calcium and yield were negatively correlated (r = -0.73). The plantation results indicated the coefficient of determination (R2) and standard error (SE) were respectively 0.99 and 0.005 for nitrogen,0.79 and 0.024 for calcium, and 0.53 and 0.036 for CEC. Ninety-nine percent, 79%, and 53% of the variation in yield were explained by nitrogen, calcium and CEC, respectively. Under savanna woodland conditions, only nitrogen was positively correlated with yield (r = 0.65), and R2 and SE were respectively 0.70 and 0.014, with 70% of the variation in yield explained by nitrogen. Regression equations were subsequently developed to predict gum yield. Gum yield was correlated with soil chemical properties, and could be predicted based on nitrogen, calcium, and CEC values.