Spatio-Temporal Shifts in Soil Nutrient Dynamics Under Different Fertilizer Sources in a Tomato Cropping System

Fertilizer source shapes soil nutrient dynamics in tomato systems, yet its effects across soil depths and crop season stages remain poorly understood. A two-year field experiment (2024–2025) was conducted on a Crider silt loam soil at Western Kentucky University Agriculture Research & Education Center to evaluate the effects of inorganic fertilizer (IF), organic fertilizer (OF), and an unfertilized control (CK) on soil nutrient concentrations across soil depths and sampling times, using a randomized complete block design with three replications. Soil pH declined under fertilization (IF 6.7, OF 6.6 vs. CK 7.2; p < 0.01). Nitrate-N showed a treatment × depth × sampling time interaction in both years (p ≤ 0.04); IF and OF raised early-season nitrate-N, but concentrations matched CK by harvest. Phosphorus at 0–5 cm was greater under IF and OF than CK in both years (p < 0.001), and surface potassium more than doubled under both fertilizer treatments in 2024. Conversely, IF reduced calcium and magnesium during late-season sampling in 2024, whereas fertilization increased sulfur, iron and zinc, primarily in surface layers. Overall, organic fertilization matched inorganic nutrient dynamics, demonstrating comparable nutrient synchrony and effective soil fertility management in tomato production systems.