Frass from Tenebrio molitor as alternative to NPK-mineral fertilization: Results from a germination test and pot experiment on sunflower
Alessandro Foscari, Luisa Dalla Costa, Francesca Tulli, Costanza Uboni, Guido Fellet
Abstract
The use of alternative fertilizers instead of conventional mineral fertilizers, such as the insect excreta (frass) is a new sustainable agronomic practice. Rearing insects for mass consumption has a small ecological footprint, but produces high quantities of frass. The aim of this work was to verify the potentials of frass from Tenebrio molitor L. as fertilizer. Two experiments were performed: firstly a germination test to observe the effects of frass on sunflower, tomato, lettuce and cress at four levels of frass added to a potting mix, and; secondly, a pot experiment to compare frass as organic fertilizer against NPK-mineral fertilization on sunflower. We provided 120 kg ha −1 N, 43 kg ha −1 P and 47 kg ha −1 K via the application of frass or NPK mineral fertilizer or the combination of the two. From the germination test, all species show a reduction in the germination rate. Considering the seedlings biomass, sunflower performs better than the other species especially at the lowest frass dose. In the pot experiment, sunflower plants from soil amended with frass or NPK mineral fertilizer had a similar biomass, demonstrating that frass from T. molitor can be used as organic fertilizer being capable of meeting the crop requirements. • Tenebrio molitor frass affects germination of cress, lettuce, tomato and sunflower and the of effect is species dependant. • Soil amended with T. molitor frass stimulated the growth of sunflower in the same extent as mineral NPK fertilization. • NPK accumulation in plants from T. molitor frass amended substrate was not lower than plants from NPK fertilizer substrate. • T. molitor frass application shortened the vegetative growth phases. • Application of T. molitor frass can sustain sunflower growth throughout its entire life cycle.