Comparative efficacy of insect-based fertilizers: physicochemical properties and their implications for the growth of Brassica rapa subsp. chinensis

Insect frass offers a sustainable alternative to chemical fertilisers for optimal crop growth. This study evaluated the efficacy of frass from three edible insects, namely Hermetia illucens (black soldier fly), Teleogryllus commodus (black field cricket), and Tenebrio molitor (mealworm), on the growth of Brassica rapa subsp. chinensis, using a feed substrate, broiler small intestine meal (BSIM). A control group of chemical fertilisers was included for comparison in a controlled environment. The physicochemical qualities exhibited substantial variation among the types of frass, reflecting changes in their nutritional composition and fertilisation quality, while chemical fertiliser showed distinct physicochemical properties compared to the frass. Despite the high nutrient profile of T. commodus, H. illucens frass produced the greatest plant growth outcomes. Plants treated with H. illucens frass recorded the highest values for leaf count (10.8 ± 1.3), leaf length (78.12 ± 2.80 mm), leaf width (43.01 ± 1.31 mm), plant height (153.12 ± 4.24 mm), and stem diameter (13.53 ± 0.43 mm). Furthermore, H. illucens promoted the greatest root width (28.55 ± 2.39 mm) and longest root length (48.06 ± 1.00 mm). These results point to the potential of H. illucens as a useful biofertilizer for promoting the growth of Brassica rapa subsp. chinensis.