IMPACT OF STRUVITE (ORGANIC), NPK, AND UREA (INORGANIC) FERTILIZERS ON PHYSICOCHEMICAL PROPERTIES OF SOIL SAMPLES

This study assessed the effects of struvite, NPK, and urea fertilizers on selected soil physicochemical properties. A randomized complete block design (RCBD) was employed with four treatments: struvite, NPK (20:10:10), urea, and an unfertilized control, each replicated four times. Struvite was synthesized from human urine using standard procedures. All fertilizers were analysed for nitrogen (N), phosphorus (P), and potassium (K) content prior to application. Soil parameters evaluated included pH, organic and inorganic matter, carbon content, trace elements (K, Zn, Fe, Mn, Cu, and B), and soluble salts (NO₃⁻, PO43⁻, SO₄²⁻, and Cl⁻). Measurements were taken before planting and three weeks after cultivating Cucurbita maxima in soils treated at a rate of 0.004 g/cm². Comparative analysis showed that urea contained the highest nitrogen concentration, while struvite had significantly greater phosphorus (15.00±0.06%) and potassium (3.70±0.07%) levels. Although soil pH increased with all fertilizer applications, the changes were not statistically significant. Organic carbon improved across treatments, with struvite producing the greatest increases in both organic and inorganic carbon. Struvite-treated soils also showed the highest levels of K, Zn, and Fe across both sampling periods, along with notable reductions in Mn and Cu. Nitrate depletion was greatest in NPK-treated soils, whereas struvite showed the least reduction (61.64±5.17ug/g). Urea-treated soils exhibited the highest PO43- levels (3.70±0.36ug/g). A marked rise in SO₄²⁻ was observed in the struvite group (546.11±41.92ug/g), while chloride increased in all treatments, especially with urea (1.69±0.39ug/g). Overall, large-scale production and agricultural application of struvite as a slow-release fertilizer should be promoted to enhance crop productivity and support environmental sustainability through waste reutilization.