Mealworm frass affects the chemical properties and nutrient dynamics in two lupin varieties under contrasting soils

Insect-derived frass has recently gained attention for its role in improving soil fertility and plant nutrition. In this research, two lupin varieties, namely Nelly and Tennis, were cultivated in a 187-day pot experiment using two soils differing in pH and initial fertility status (Soil A, alkaline; Soil B, acidic). Mealworm frass from Tenebrio molitor was applied at two rates, 0.5% (FR-1) and 1% (FR-2), to evaluate its effects on soil chemical properties and nutrient dynamics in both soil and plants. The experiment also included an unamended negative control (NC) and a conventional fertilizer-added positive control (PC). Soil organic carbon (OC) increased by approximately 0.4-0.5% at FR-2, indicating the potential of frass to enhance soil carbon and contribute to soil fertility. Soil nitrate-nitrogen (NO₃-N) increased after frass application, with temporal peaks that may be associated with nitrification, while leaf nitrogen (N) concentrations also increased during the growing period, potentially reflecting enhanced N assimilation. Overall, mealworm frass showed potential as a soil organic fertilizer for improving soil nutrient availability and enhancing the nutrient status of lupins. Further field studies are needed to confirm these results under real agricultural conditions.