Spatial Variability of Soil Texture, Organic Matter and Microbial Activity Under Faidherbia Albida System on a Tropical Soil in Zambia.

Faidherbia albida, a deciduous and indigenous tree species, is native to much of Africa, the Arabian Peninsula, and western Asia. It is used in agroforestry systems to stabilize and improve soil fertility. Faidherbia albida sheds off its leaves during the wet season and resumes leaf growth during the dry season. Spatial variability of soil properties under Faidherbia albida has received little attention. The study was therefore conducted to evaluate the degree of spatial variability of selected soil properties inside and outside Faidherbia albida tree canopies. Specific objectives were (i) to characterize the variability of selected soil properties (soil texture, soil organic matter, and microbial activity) under Faidherbia albida trees; and (ii) to evaluate the spatial structure and variability of selected soil properties using the spherical model and kriging techniques. Soil samples were collected from 0-0.20 m soil depth using a regular 2 m x 2 m grid system in an area of 24 m x 24 m with a row of Faidherbia trees in the center. Data were analyzed using descriptive analysis and geostatistics for describing statistical differences and spatial distribution using the spherical model. Results reviewed both positive and negative correlations among the soil properties, especially the relationship between particle size fractions, soil organic carbon, and microbial activity. Faidherbia tree influenced the spatial pattern of silt fraction, soil organic carbon and soil microbial activity, while sand fraction and clay fraction were not significantly affected. Characterizing the spatial influence on soil variables provide important implications for water and nutrient management in agricultural production systems with Faidherbia tree species.