# Farmed Insect Frass as a Future Organic Fertilizer
## 3 Results and Discussion
### Chemical Changes in Acid Peat
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Fertilizer**} & \multicolumn{6}{c}{**Nitrogen Rates (mg dm\({}^{-3}\))**} & \multirow{2}{*}{**Mean**} \\ \cline{2-2} \cline{4-7}  & **0** & **50** & **100** & **200** & **400** \\ \hline \multicolumn{7}{c}{N-NH\({}_{4}\)} \\ \hline Frass & _1.92 b_ & _2.09 b_ & _2.16 b_ & _2.81 b_ & _13.30 a_ & 4.47 \\ Urea & 2.41 d & 5.42 d & 15.50 c & 47.40 b & 142.69 a & 42.60 \\ Significant & ns & ns & *** & *** & *** & *** \\ Mean & 2.16 D & 3.75 D & 8.84 C & 25.10 B & 77.70 A & \\ \hline \multicolumn{7}{c}{N-NO\({}_{3}\)} \\ \hline Frass & _1.59 d_ & _2.60 d_ & _22.30 c_ & _88.00 b_ & _156.00 a_ & 54.00 \\ Urea & 1.83 e & 37.90 d & 68.00 c & 105,00 b & 127.00 a & 67.8 \\ Significant & ns & *** & *** & *** & *** \\ Mean & 1.71 E & 20.30 D & 45.10 C & 96.50 B & 141.00 A & \\ \hline \multicolumn{7}{c}{Mineral N} \\ \hline Frass & _3.51 d_ & _4.69 d_ & _24.50 c_ & _90.80 b_ & _169.00 a_ & 58.50 \\ Urea & 4.24 e & 43.30 d & 83.50 c & 152.00 b & 269.00 a & 110.00 \\ Significant & ns & *** & *** & *** & *** \\ Mean & 3.88 E & 24.00 D & 54.00 C & 121.00 B & 219.00 A & \\ \hline \hline \end{tabular} Significant differences between nitrogen rates in frass and urea groups: *** significant at \(p\) < 0.001; *** significant at \(p\) < 0.0001; ns—total significant. Capital letters A, B..., E indicate significant differences between nitrogen rates. Lowercase letters a, b,..., e indicate significant differences between nitrogen rates only within the frass group (italics) and only within the urea group (without italics).  
\end{table} 
Table 3: Average mineral nitrogen content of acid peat, supplied with different fertilizers and nitrogen rates. respectively [43]. This incubation experiment met the above requirements when acid peat was fertilized with frass at the two highest rates (200 and 400 mg N dm\({}^{-3}\)). However, when urea was applied at these rates, the maximum permissible level of N-NH4 exceeded 1.6- and 4.7-fold, respectively, for ornamental trees and shrubs with high nutrient requirements. In contrast to the NO3- ion, the NH4+ ion can be toxic to plants even at low concentrations, although the nitrate form is more available in an acidic environment. Figure 1: Changes in the content of N-NH4 (**a**), N-NO3 (**b**), and mineral nitrogen (**c**) in acid peat incubated with frass and urea. Differences are presented on a logarithmic scale. High nutrient availability under optimized nutrient management may promote crop growth [44]. In order to improve its fertilizing potential and increase its yield-forming effects, acid peat can be enriched and deacidified with the use of Ca fertilizers, NPK, zeolite, calcined clay, and diatomaceous earth [31; 34; 35; 36]. However, the demand for acid horticultural substrates has been growing steadily for several reasons. The popularity and production of relatively new fruit species, such as aronia and northern highbush blueberry, have increased in recent years. Coniferous trees and shrubs, heaths and heathers, azaleas, and rhododendrons are widely planted in expanding urban areas [45; 46]. They have relatively low soil requirements, play an important ecological role, resist adverse environmental conditions, and are prized for their esthetic appeal. In the cultivation of most ornamental trees and shrubs with low nutrient requirements grown in nursery containers and pots, the recommended pH in H\({}_{2}\)O is 4.2-6.5 [47; 48]. Before the experiment, acid peat was characterized by highly acidic pH (pH in H\({}_{2}\)O = 5.0), and frass was characterized by acidic pH (pH in H\({}_{2}\)O = 5.6; Table 2). Irrespective of the applied fertilizer, N rates higher than 100 mg dm\({}^{-3}\) significantly decreased the pH of peat relative to the control treatment and the lowest N rate (Table 4). Frass had a more acidifying effect on peat than urea, and a significant decrease in pH was noted at F50 and F400. Mealworm frass and urea did not change the pH of peat when applied at moderate rates of 100 and 200 mg N dm\({}^{-3}\).