PERTANIKA JOURNAL OF TROPICAL AGRICULTURAL SCIENCE

The growing demand for sustainable agriculture and effective organic waste management has increased interest in the use of black soldier fly larvae (BSFL) frass. It has a high content of nitrogen, phosphorus, potassium, organic carbon, and beneficial microbial communities. However, the frass application methods and rate are not clearly stated. Thus, this review objective is to determine the frass application methods and rate. This review synthesises data from 16 studies conducted across various soil types, climates, and cropping systems to evaluate the agronomic, ecological, and microbiological effects of BSFL frass application. Direct soil incorporation is most common and effective for the soil and plant benefit. Frass improves plant and soil health. Low-to-moderate frass application rates (2-25 t/ha) enhance plant growth, nutrient uptake, and yield, particularly in nutrient-poor soils. However, higher application rates can cause phytotoxic effects, salinity stress, and microbial imbalance. This emphasises the importance of identifying crop- and context-specific optimum doses. Despite promising outcomes, significant research gaps remain, such as long-term field validation, interactions with diverse soil microbiomes, the fate of potentially harmful elements like heavy metals, and standardised processing and quality control of frass.