IMPACT OF TAMARINDUS INDICA L. ON SOIL FERTILITY IN SMALLHOLDER AGROFORESTRY SYSTEMS OF GUMEL, JIGAWA STATE, NIGERIA

Abstract

This study evaluates the impact of Tamarindus indica L. on soil fertility in smallholder agroforestry 
systems of Gumel, Jigawa State, Nigeria, where semi-arid conditions and sandy soils challenge 
agricultural productivity. Through systematic sampling across 20 mature trees in five farmlands, we 
analyzed spatial gradients of soil properties at varying distances from tree trunks (2m, 4m, and 10m 
controls). Results demonstrated significant soil quality improvements under canopies, with organic matter 
content doubling (3.2% vs 1.5% control), moisture retention increasing by 14% (14.2% vs 12.1%), and 
cation exchange capacity enhancing by 52% (1.2 vs 0.79 meq). Bulk density decreased by 9% (1.25 vs 1.38 
g/cm³), while total nitrogen was 31% higher (0.17% vs 0.13%). Although ANOVA revealed no significant 
differences in pH and phosphorus availability (p>0.05), effect sizes (η²=0.18-0.25) confirmed practical 
benefits for farmers. The findings validate the island of fertility concept while identifying alkaline soil 
conditions (pH 6.7-7.0) and residue burning practices as limiting factors for phosphorus availability and 
organic matter accumulation. This research provides empirical evidence for T. indica conservation in 
agroforestry systems, recommending farmer-led regeneration programs and policy incentives to enhance 
soil fertility and climate resilience in line with Sustainable Development Goals 2 (Zero Hunger) and 15 
(Life on Land). The study bridges critical knowledge gaps regarding tree-soil interactions in Nigeria's 
Sahelian zone, offering science-based strategies for sustainable land management in semi-arid 
agroecosystems.