Dados do Trabalho

Título

SOIL AMENDMENT OBTAINED AS A BY-PRODUCT OF MAKING INSECT MEAL FOR ANIMAL FEED

Resumo

This work, framed in a Circular Economy project, was carried out in an insect (Tenebrio molitor) rearing plant which elaborates protein meal for animal feed. The insects are fed with residues from craft beer production, obtaining as a by-product a mixture of excrement and unconsumed food (frass). The objective of the work was to study the potential of Tenebrio molitor excreta as soil amendment, determining its nutrient content, and availability for plants. First, the amendment was characterized, analyzing pH, carbon and nutrients’ contents. Then, the reaction of the material with two contrasting soils (a sandy and a clayey soil) was evaluated under controlled conditions, examining the release of nutrients and the activity of microbial biomass (respiration rate). The excreta was dosed based on its N content (N doses: 0, 30, 60 and 90 mg/kg of soil). Three replicates per treatment were prepared and incubated at 25°C with humidity at field capacity for three months. There was an increase in microbial activity in the treatments with amendments compared to the control, with high respiration rates at the beginning of incubation, which decreased rapidly. Regarding the release of nutrients, the addition of excreta produced moderate increases in the availability of P in the sandy soil, but not in the clayey soil, which had a history of high fertilization with P. In both soils the amendment produced a significant increase in the availability of N (content of N-NO3- and N-NH4+). Although there were no major differences between soils, a greater response was observed in the sandy soil, which in turn showed a lower N mineralization rate. At the end of incubation, the increase in mineral N in soils that had received excreta represented on average 41 % of the added N. These results must be confirmed in greenhouse and field experiments, but it can be concluded that Tenebrio molitor excreta is a promising amendment, mainly due to its potential contribution of N to plants.

Palavras-chave

Tenebrio, frass, organic amendment, circular economy, Uruguay

Instituição financiadora

Agencia Nacional de Investigación e Innovación (ANII, Uruguay)