Evaluation of Soil Fertility Status Based on CEC and Variation across Disturbed and Intact Tropical Coastal Forests Sites in Tanzania

Abstract

Aims: Although an understanding of different levels of soil calcium, magnesium, potassium, sodium, cation exchange capacity, and percentage base saturation, is important in the management of forest ecosystems; however, there is limited documentation on the status of these elements in forest subjected to crop-agriculture and livestock grazing disturbances in the tropical coastal forests. This study aimed to evaluate soil fertility based on exchangeable bases’ status and variation across closed forest (control), agriculture and livestock disturbed sites in the coastal zone of Tanzania to add knowledge on the management of tropical coastal forests. Methodology: Systematic sampling and stratification approaches were used to get representative samples of forested blocks and disturbed sites. Forty-seven (50 m x 50 m) sampling plots on each of the forest sites were established in the study area from which 141 soil samples were drawn. Ammonium acetate solution was used to extract exchangeable calcium, potassium, magnesium, and sodium from which cation exchange capacity and base saturation were calculated.  Results: The mean, correlation and t-values were used to compare nutrients across land uses. The mean values were 3.75, 3.11 and 0.63 for Ca2+; 0.80, 5.87 and 6.67 for Mg2+; 0.03, 0.55, and 0.52 for K+; 0.01, 0.31 and 0.31 for Na+; 2.61, 13.74 and 16.36 (cmol(+)/kg) for cation exchange capacity and 10.29, 5.86 and 4.42 (V%) for base saturation in three areas: closed forest, agriculture and livestock disturbed sites. Conclusions: The variations show that crop-agriculture and livestock grazing disturb soil chemical properties in tropical coastal forests. Therefore, it is essential to protect closed forest sites while putting more efforts to restore the disturbed sites for sustainable forest management along the coastal areas.