OFS and Beta Hatch conduct a frass fertility demonstration on leeks and onions

Applying frass on bed top using a drop spreader

Andrew Corbin, Director of Research, OFS 

Insect production for alternative sources of protein has exploded in recent years. With that, so has their frass (insect manure). Our friends at Beta Hatch , the largest mealworm farm in North America, produces mealworm protein and frass using byproducts from local agricultural production. They even humidify their grow rooms using waste heat from a nearby data center, furthering the sustainability of their operation. The mealworms are used for feed, but what do they do with all that frass? Turns out, mealworm frass is a great alternative fertilizer for soil and plants! In a controlled greenhouse experiment Houben et al., (2020) found that mealworm frass “…has a great potential to be used as a partial or a complete substitute of mineral NPK fertilizer.” In fact, they determined that frass was equally effective in supplying Nitrogen, Phosphorus and Potassium, with Carbon and Nitrogen mineralizing (made plant available) nearly 60% in 90 days. Other important findings in the study indicated that the water-soluble concentrations of Phosphorus were up to five times lower when frass was present – that’s more P for the soil and less P loss to the watershed! Perhaps the most notable finding of the study was that the addition of frass can increase microbial activity and diversity in the soil, improving soil quality, and when used in combination with mineral fertilizer, microbial activity and diversity was even greater compared to mineral fertilizer alone. 

While the findings of this study are very exciting to organic growers, a controlled environment greenhouse study is different than on the farm – and every farm has different soil type, soil structure, temperature, moisture and so many variables. We at the Organic Farm School are partnering with Beta Hatch to conduct a side-by-side demonstration comparing our business-as-usual organic fertilizer to substituting frass and combinations of the two on leeks and two varieties of storage onions. "We're very excited to work with the Organic Farm School on this frass fertility demonstration. OFS's leadership in ecological, economic, and social regeneration is well aligned with Beta Hatch's mission, and we're looking forward to continuing this collaboration toward a more resilient food system." said Matthew Harband, Business Development Specialist with Beta Hatch. Because OFS is a working farm, we don’t necessarily have the luxury of conducting a controlled, randomized and replicated experiment subject to statistical scrutiny. We are, however, dedicating 10 full 100-foot beds to one of three treatments and will be able to observe differences (if any) in crop growth, time to harvest and total above ground plant biomass. We also plan on doing a cost analysis to see how we can potentially save money and time on our fertility inputs. If we don’t notice any differences in the final product going to market – that’s a good thing! What that tells us is frass (produced locally in Cashmere, WA) may be substituted for the more expensive organic fertilizer and we still improve our soil microbial activity, diversity, and overall soil quality! 

Houben, D. et al. Potential use of mealworm frass as a fertilizer: Impact on crop growth and soil properties. Nature Scientific Reports 10:4659 (2020) 

https://www.nature.com/articles/s41598-020-61765-x.pdf