Assessment of the Short-Term Fertilizer Potential of Mealworm Frass Using a Pot Experiment

Abstract

The forecasted growth of insect production in the next few years will generate high quantities of frass (insect excreta). Although frass is increasingly considered a potential fertilizer, the dynamics of nutrient supply by frass is still poorly understood. Here, we aimed at gaining insight into the short-term fertilizer value of frass from mealworm (Tenebrio molitor L.) in order to optimize its sustainable use in agroecosystems. Using a short-term pot experiment, we showed that, even though frass has a great potential to be used as a substitute of mineral NPK fertilizer, its N fertilizer potential is mediated by its rate of application. At 10 t ha−1, due to its fast mineralization coupled with improvement in microbial activity (assessed using Biolog EcoPlate), frass was as effective as mineral fertilizer to supply N to plant. By contrast, at 5 t ha−1, the lower frass mineralization induced a reduced N uptake compared to its mineral control. Unlike N, frass was as effective as mineral fertilizer to supply P and K to plants irrespective of its application rate. This was attributed to the presence of P and K in a readily available form in frass. Taken together, our results indicate that mealworm frass supplies very rapidly N, P and K to plants but its effects on N dynamics should be better investigated to warrant its sustainable use as an alternative fertilizer for managing NPK nutrition in cropping systems.

Nutrient quality and maturity status of frass fertilizer from nine edible insects

“…For example, previous studies have reported higher yields and nutritional quality of maize, tomatoes, kales, French beans, cow peas, chilli pepper, shallots and barley grown using H. illucens frass fertilizer and meal worm frass fertilizer compared to conventional fertilizers 27 , 28 , 42 , 52 , 53 . Furthermore, soil amendment with frass fertilizer from H. illucens and T. molitor was found to suppress soil borne pathogens, stimulate soil microbial activity, reduce soil acidity and salinity, improve nitrogen mineralization, and increase availability of nutrients in the soil 29 – 31 , 33 , 53 , thus improving the soil quality for plant growth. It is therefore anticipated that adoption of insect fertilizer would contribute to improving food security by in SSA reversing the worrying trends in soil degradation, nutrient mining and declining crop productivity 1 , 8 , 14 .…”

The Impacts of Black Soldier Fly Frass on Nitrogen Availability, Microbial Activities, C Sequestration, and Plant Growth

“…Previous studies that reported significant effects of mealworm frass on ryegrass (Lolium multiflorum Lam.) and barley (Hordeum vulgare L.) shoot biomass applied frass at a rate equivalent to 250-500 kg N ha −1 , which is much higher than the N required by the plants (Houben et al, 2020(Houben et al, , 2021. A previous study also applied a high rate of frass (1:1 or 2:1 soil-to-frass ratio) and found significant effects on the growth of lettuce (Lactuca sativa var.…”

“…To properly utilize the frass in a sustainable way, their effect on soil health and plant growth should be evaluated. The very limited studies available to date have shown that the application of frass increases yield (Rosmiati et al, 2017;Houben et al, 2020Houben et al, , 2021, activates plant defense responses against abiotic (Poveda, 2021) and biotic stress (Quilliam et al, 2020), and improves soil microbial activities (Gebremikael et al, 2020). On the contrary, few other studies found negative effects of BSF frass and other commercially available frass on soil quality and plant growth, such as phytotoxicity (Alattar et al, 2016;Watson et al, 2021a,b) and excessive nitrite accumulation in soil (Watson et al, 2021a).…”

The Insects as a Workforce for Organic Fertilizers Production – Insect Frass

“…Some pot tests have shown the potential of entomocompost, obtained from substrates of various kinds, to reduce mineral fertilization in several crops, as for instance: With mealworm (Tenebrio molitor L.) frass, in barley [25] and ryegrass [41], and with BSF frass, in basil and Sudan grass [42], chinese cabbage [43], yardlong bean [44], lettuce [45,46], ryegrass [45,47], maize [48] and swiss chard [49].…”

“…In any case, the medium-and long-term promotion and resilience of the fertility of the soils, which should be fostered by insect frass, would be translated, as for the generality of organic fertilizers, by the improvement of the structure of the soils and its capacity to retain water and crop nutrients and as well as by symbiotic interaction with the soil microbial flora and with the plant. Many knowledge within this perspective is still needed, but also a lot have been accumulated, allowing for hopeful evidences, such as: better use efficiency of P and K [57]; improved soil fertility and defense against pathogens [58]; suppression against Pythium ultimum [59]; influence on soil N availability [60]; stimulation of soil microbial activity and diversity [25]; not impairing hygienic properties of soils [47]; improvement of microbial activity [41]; increased dehydrogenase activity [61]; or increased enzyme activity (dehydrogenase and β-glucosidase) [46]. These data augur well, but medium and long-term field trials are indispensable for continued soil fertility management, since organic matter resilience is not its greatest virtue, particularly in tropical and sub-tropical climates.…”