# Farmed Insect Frass as a Future Organic Fertilizer
## 3 Results and Discussion  
### Chemical Changes in Acid Peat  
Both mealworm frass and urea (46% N), applied at increasing N rates, significantly differentiated the chemical properties of incubated acid peat (Table 3). Irrespective of the applied fertilizer, the concentrations of ammonium nitrogen (N-NH4) and nitrate nitrogen (N-NO3) in peat increased significantly and steadily with increasing N rates. Compared with the control treatment, the highest increase (more than six-fold) in the content of mineral N (N-NH4 + N-NO3) was found after the application of 50 mg N dm\({}^{-3}\), which resulted from a high concentration of N-NO3. Each of the higher N rates nearly doubled the mineral N content of the substrate relative to the previous rate. In the first days of incubation, the rate of N ammonification was high in peat fertilized with urea (Figure 1a) and much slower in peat fertilized with frass. The rate of nitrification was high already in the first week of incubation, irrespective of the applied fertilizer (Figure 1b). In the first seven weeks of incubation, the mineral N content of peat fertilized with frass steadily increased and nearly doubled (from 28 to 54 mg dm\({}^{-3}\), Figure 1c). A rapid increase (2.2-fold, to approximately 120 mg dm\({}^{-3}\)) in mineral N content was also noted in the last two weeks of incubation. Only in the last week of incubation was the content of N-NO\({}_{3}\) (Figure 1b) and mineral N (Figure 1c) in peat fertilized with frass similar to or higher than in peat fertilized with urea. Peat incubated with urea was characterized by a smaller variation in the content of mineral N than peat incubated with frass (Figure 1c), despite the fact that the content of plant-available N, in particular ammonium N (Figure 1a), was much higher after the application of the N fertilizer. In peat fertilized with urea, the mineral N content was high (110 mg dm\({}^{-3}\) of the substrate) in the first week of incubation and remained stable until week 9 (Figure 1c). Similar mineralization and nitrification rates were described by [PERSON] et al. [21; 26], who demonstrated that N mineralization was positively correlated with microbial activity and that nitrification was the dominant process [21]. A considerable decrease in ammonium N content in the first week of soil incubation with frass was also observed by [PERSON] and [PERSON] [24], who attributed this loss to ammonia volatilization and N immobilization by soil-dwelling microorganisms. In this study, the concentration of mineral N did not decrease in acid peat incubated with frass. Such a decrease was noted in week 7 of incubation in deacidified peat enriched with frass in our previous study [37]. According to [PERSON] [42], a drastic decrease in plant-available nitrate N around day 50 of incubation results from excessive growth of cellulolytic bacteria that suppress the development of nitrifying bacteria. The average content of N-NH\({}_{4}\) and N-NO\({}_{3}\) in peat incubated with frass was 9.5- and 1.3-fold lower, respectively, than that in peat incubated with urea (Table 3). In peat incubated with urea, the content of mineral N increased significantly compared with peat incubated with frass. In treatments supplied with frass, the N-NH\({}_{4}\) content increased significantly only in response to F400, compared with lower rates. The N-NO\({}_{3}\) content increased significantly in response to F100 and higher rates. Urea applied at increasing N rates contributed to a significant and gradual increase in the content of N-NH\({}_{4}\), N-NO\({}_{3}\), and mineral N in peat. In the cultivation of ornamental trees and shrubs with low, moderate, and high nutrient requirements, the optimal content of N-NH\({}_{4}\) and N-NO\({}_{3}\) is <20 and 90-110 mg N dm\({}^{-3}\), <25 and 120-140 mg N dm\({}^{-3}\), and <30 and 150-170 mg N dm\({}^{-3}\)