Macronutrient Enrichment Patterns In Biosolid-Amended Soils: Evidence From PCA And Correlation Analysis In Tumkur District, Surrounded By Bangalore

Abstract

Application of Sewage sludge in agriculture has gained significance role as a sustainable strategy for nutrient recovery from urban waste streams while enhancing the soil fertility. The study assess the spatial variations of macronutrients of nitrogen (N), phosphorus (P₂O₅), and potassium (K₂O) in sludge-amended agricultural soils of selected taluks of Tumkur district. Surface soil samples (0–15 cm depth) were collected from sludge applied taluks and analyzed as per standard soil-testing protocols. The nutrient data were evaluated using violin plots, one-way ANOVA, principal component analysis (PCA), and correlation heatmaps. The mean value of N ranged from 361.7 to 470.3 kg ha⁻¹, P₂O₅ from 104.9 to 150.9 kg ha⁻¹, and K₂O from 321.5 to 609.5 kg ha⁻¹. Gubbi taluk consistently showed the highest nutrient enrichment followed by Tumkur, and Kunigal taluk displayed the lowest values of organic carbon concentrations. The results of ANOVA test confirmed statistically significant differences for N, P₂O₅, and K₂O (p < 0.05). Strong positive correlations were observed between organic carbon and N (r = 0.88), P₂O₅ (r = 0.81), and K₂O (r = 0.79). PCA was indicated a dominant nutrient enrichment gradient explaining 73.1% of total variance, strongly associated with organic carbon and macronutrients. Overall, the findings highlight the agronomic benefit of sewage sludge recycling and the importance of site‐specific nutrient management to minimize environmental risks of long-term nutrient accumulation.