## 4 Results
### Nitrogen Uptake by Ryegrass Fertilised with Kitchen Waste-Based Fertilizers  
Figure 2 indicates the amount of N taken up by ryegrass in each month. The highest contents of N after month 1 ranging from 30 to 45 g/kg were noticed for DKW 1 EM ST  
Figure 1: Ryegrass biomass yields response to kitchen waste-based fertilizers after 4 subsequent harvests, compared to the commercial organic fertilizer (CMG) for harvests after 30, 60, 90, and 120 days. Standard errors included, insignificant if not visible. treatment. All treatments except DKW ST followed the linear increase in N in plants with more N input to the soil for this month. Subsequent growths provided less N in plant cells (7-21 g/kg after month 2, 8-14 g/kg after month 3 and 7-13 g/kg after month 4). Most of the N was absorbed during the first 2 months of the growth, whereas months 3 and 4 showed more or less stable N content in plants with increasing N application rate. Higher N contents in plants for kitchen waste treatments (10-13 g/kg) were noticed after month 4 in comparison to kitchen waste digestate (DKW ST-dig) and cow manure (CMG) which ranged from 7 to 10 g/kg, which again proves that these materials in undigested form could work as slow-N-release fertilizers even after sterilization or EM addition. However, in order to see the full picture, the N use per ha has to be calculated and compared, as seen in Figure 3.  
N use per ha is displayed in Figure 3, where N content from Figure 2 was multiplied by ryegrass dry matter yields from Figure 1. Again, most N was used during the first 2 months with CMG and DKW ST-dig having the best absolute agronomic effectiveness, expressed by the slopes of the linear trend lines (if the regression was possible) visible on the plots for each material. After month 1, both CMG and DKW ST-dig were a few times better than other materials in utilizing N from the soil, as they provided up to 25 (DKW ST-dig) and up to 35 (CMG) kg N/ha, whereas other treatments only provided  
Figure 2: Nitrogen uptake by ryegrass fertilized with kitchen waste-based fertilizers after 4 subsequent harvests, compared to the commercial organic fertilizer (CMG) for harvests after 30, 60, 90, and 120 days. Standard errors included, insignificant if not visible. Please note different scale on y axis after 30 days. 4-17 kg N/ha. After month 3, agronomic effectiveness of reference cow manure dropped from 6.7% (month 1) to 2.9%, whereas all other treatments showed similar effects ranging from 3.57% for DKW 1 EM ST to 4.38% for DKW ST-dig. Although N use values after month 4 were only up to 8.5 kg N/ha, this month showed the domination of treated kitchen waste in the following order: DKW 2 EM, DKW ST, KW 1 EM, and DKW 1 EM ST with in contrary DKW ST-dig and CMG expressing the weaker effectiveness (1.55 and 1.02%, respectively). The differences between 2 EM addition (DKW 2 EM), sterilization without EM addition (DKW ST), and EM addition coupled with sterilization (DKW 1 EM ST) were small as their effectiveness ranged from 1.84% to 2.20%. However, the slow-N-release fertilizer character of these materials and fast exploitation of N bank from digested kitchen waste and cow manure is again backed up here by Figure 3.  
Here in Figure 4, the final N use is taken into account after summing up ryegrass yields with their N contents after months 1, 2, 3, and 4. This final picture evidences that in absolute terms CMG has the highest agronomic effectiveness (20.3%), followed by DKW ST-dig (17.9%), DKW 2 EM (13.8%), and DKW 1 EM ST (12.2%), and the weakest one for DKW ST and KW 1 EM (9.9%). Anaerobic digestion allows the bioenergy in the form of methane to be extracted and provides more NH\({}_{3}\)-N into the digestate; however, both 2 EM addition without sterilization has still a very high effect on N use. Sterilization which  
Figure 3: Nitrogen use from 1 ha of ryegrass fertilized with kitchen waste-based fertilizers after 4 subsequent harvests, compared to the commercial organic fertilizer (CMG) for harvests after 30, 60, 90, and 120 days.