## 3 Results and Discussion
### Bio-Mixture Effect on N-Compounds, Macro-Nutrients and Micro-Nutrients Content of the Soil  
A rise in total nitrogen of bio-mixture-soil at 0-20 cm layer samples was observed in 1% biomix (8%) and 3% biomix (14%), indicating that bio-mixture contributes to the increase of total nitrogen concentration of soil, while there was not much differentiation in the total N of soil at 20-40 cm layer samples. Noteworthy is the increase (13-14%) of the nitrate-nitrogen in biomix 3% at both bio-mixture-soil at 0-20 cm and soil at 20-40 cm layer samples, whilst the ammonium nitrogen concentration increased in biomix 1% and in biomix 2% at both 0-20 cm and 20-40 cm layer samples (Figure 6). It is also worth commenting on the fact that the concentration of phosphorus increases significantly in proportion to the percentage of bio-mixture, in relation to its concentration in the control soil, both at the surface horizon (0-20 cm) where bio-mixture was applied and in the soil samples at a depth of 20-40 cm (Figure 7). In particular, the phosphorus increased rates observed were 16%, 47% and 55% for 1% biomix, 2% biomix and 3% biomix, respectively, regarding bio-mixture-soil at 0-20 cm layer samples. Furthermore, increase rates of phosphorus in the soil at 20-40 cm layer samples were 11%, 21% and 23% for 1% biomix, 2% biomix and 3% biomix, respectively. Regarding potassium, a higher increase was recorded at the upper layer of the soil (0-20 cm). As far as the potassium concentration of bio-mixture-soil at 0-20 cm layer samples, an increase of 8% took place in biomix 1%, 18% in biomix 2% and 36% in biomix 3% compared to the control soil concentration (Figure 7). The suchlike trend was observed at 20-40 cm layer samples, with the corresponding increase being up to 5%, 13% and 26% for biomix 1%, biomix 2% and biomix 3%, respectively (Figure 7). Compared to other soil treatments with OMW as an amendment [34; 35], there was not a large increase in potassium content compared to the control, but nevertheless, this increase is considered quite significant. In this case, sodium content was not affected by the application of the bio-mixture and remained constant in control soil and in all three bio-mixtures, as there were no changes in its concentration (Figure 7). Figure 6: Average Ntotal (g kg\({}^{-1}\)), NO\({}_{3}\)-N (mg kg\({}^{-1}\)) and NH\({}_{4}\)-N (mg kg\({}^{-1}\)) concentrations and their standard deviations (SD) of samples of the four treatments at 0–20 cm and 20–40 cm depth. Each value is the mean of three replicates. Different letters above each column within the same parameter evaluated, indicate significant differences among treatments. There was also an upward trend in magnesium content in both bio-mixture-soil and soil samples, reaching growth rates of 14% and 11%, respectively, for biomix 2% and 13% for biomix 3% (Figure 7). As observed in other works concerning the addition of OMW as a soil amendment, as far as the soil magnesium contents were concerned, no significant differences were noted [36]. It is well known that one of the main soil parameters that controls the micronutrient distribution and availability in soils is organic matter because it supplies chelating agents, which increase their solubility [37]. According to our results, a gradual increase of iron concentration was observed as the percentage of the bio-mixture increased. More specifically, iron concentration of samples from the 0-20 cm depth increased from 36.4 mg kg\({}^{-1}\) to 37.5, 39.9 and 43.5 mg kg\({}^{-1}\) for 1% biomix, 2% biomix and 3% biomix, with values corresponding to 3%, 10% and 20% rates, respectively. It is noteworthy that iron content increased significantly even in the soil at a depth of 20-40 cm (Figure 8). Concerning zinc concentration, a rise of 6%, 19% and 50% took place for 1% biomix, 2% biomix and 3% biomix at 0-20 cm layer samples, respectively.