Abstract:
Soil fertility degradation presents a critical challenge to sustainable agriculture in Sri Lanka's
central highlands, particularly in selected areas of the Kotmale Highlands, where intensive
farming practices and unregulated agrochemical inputs have significantly altered soil nutrient
dynamics. This study employs an integrated approach combining multi-parameter soil analysis
with advanced geospatial techniques to characterize and map soil fertility variations across
diverse agro-ecological zones. Soil samples were systematically collected from representative
zones using GPS-guided stratified random sampling method and laboratory analyses were
conducted to assess key fertility indicators: pH, organic matter content, available phosphorus
(P), exchangeable potassium (K), cation exchange capacity (CEC), and electrical conductivity
(EC). Results reveal widespread soil acidity problems, with pH values predominantly below
5.5, significantly constraining nutrient availability and microbial activity. Organic matter levels
were critically depleted (<2%) in approximately 70% of sampled locations, indicating
compromised soil biological health and reduced resilience to environmental stressors.
Phosphorus deficiency emerged as a ubiquitous concern across all sampling zones, while
potassium concentrations exhibited marked spatial heterogeneity, ranging from severe
deficiency to excessive levels that risk creating antagonistic nutrient interactions. Interpolated
fertility maps generated through GIS analysis identified distinct spatial patterns and critical
hotspots requiring urgent intervention, enabling the development of site-specific management
strategies. The study demonstrates the efficacy of integrating laboratory soil analyses with
geospatial modelling to create comprehensive soil fertility assessments that can guide precision
agriculture approaches and sustainable soil management policies in highland agro-ecosystems.
