Black Soldier Fly Frass as a Sustainable Organic Fertilizer: Enhancing productivity of Leafy Vegetables and Soil Health in Benin

Carline Christelle Joanne SANTOS^1,2*Elie Ayitondji DANNON^3,4Honorine Hortence BOUGNA TCHOUMI³Serge MBOKOU FOUKMENIOK³Sètondji Alban Paterne ETCHIHA AFOHA⁵Djana MIGNOUNA⁶Titilayo Falade⁷Olapeju PHORBEE⁷Daniel Chèpo CHOUGOUROU²Paul TEMATIO⁸Sali ATANGA NDINDENG^9*Rousseau DJOUAKA^6*

• ¹International Institute of Tropical Agriculture (Benin), Cotonou, Benin
• ²Universite d'Abomey-Calavi Ecole Polytechnique d'Abomey-Calavi, Cotonou, Benin
• ³International Institute for Tropical Agriculture Benin, Cotonou, Benin
• ⁴Universite Nationale des Sciences Technologies Ingenierie et Mathematiques Ecole Normale Superieure de Natitingou, Natitingou, Benin
• ⁵Universite d'Abomey-Calavi Faculte des Sciences et Techniques, Cotonou, Benin
• ⁶International Institute of Tropical Agriculture Ghana, Tamale, Ghana
• ⁷International Institute of Tropical Agriculture, Ibadan, Nigeria
• ⁸Universite de Dschang, Dschang, Cameroon
• ⁹Africa Rice Center, Abidjan, Côte d'Ivoire

Soil nutrients depletion directly threatens sustainability of food systems by reducing agricultural productivity, degrading ecosystem services, thus increasing the need for external inputs. Frass, a nutrient-rich byproduct of insect farming, is increasingly recognized for its potential in sustainable agriculture. In the current study, we explored the effects of composted Black Soldier Fly (BSF) frass on the growth and yield of Solanum macrocarpon (African eggplant) and Lactuca sativa (Lettuce), as well as its effect on soil nutrient composition, compared to poultry manure and inorganic fertilizers (NPK and urea). Two field experiments were conducted separately for lettuce and the African eggplants, each involving six treatments and four replicates per crop species. The treatments consisted of sole BSF frass at different doses, poultry manure only, NPK + urea, and a combination of BSF frass and urea. The results showed that, BSF frass at 20t/ha and 15t/ha significantly performed better than the other fertilizers in promoting plant growth and increasing yield in lettuce (3.53 Kg/3m2 and 5.12 Kg/3m2 in season 1 and 2, respectively) and of the African eggplant (5.04 Kg/m2). However, there were no significant differences between treatments in soil fertility, except pH as indicated by variations in nitrogen, phosphorus, potassium content, and Electrical Conductivity after crop harvesting. These findings suggest that BSF frass is a viable alternative to both inorganic and organic fertilizers, offering a sustainable solution for improving crop productivity and soil health.