# Popular Biochar as an Alternative Substrate for Curly Endive Cultivated in a Soilless System
## 4 Discussion  
In this study, we assessed the potential employ of diverse peat/biochar-based mixtures as growing substrates for curly endive grown in a protected environment. Results on pH confirmed those by [PERSON] et al. [15] who evidenced lower pH values in a peat-based substrate compared to the peat/biochar mixtures or biochar-based growing substrates. Our findings are also similar to those by [PERSON] et al. [24], who evidenced lower pH levels in a peat based growing medium than in green waste biochar and in their combination. Our outcomes on pH values are, furthermore, in accord with those reported by [PERSON] et al. [11], who by inquiring the influence of biochar combinations with pine-bark based growing media on growth and development of horticultural crops, found that 100% biochar addition increased the substrate pH. In the present study, the pH detected in those growing media, which included up to 70% of biochar were in the 6.1-8.2 range. This range is convenient for curly endive [25]. Results on pH revealed that pH values increased with the increase of the pyrolysis temperature. This is in accord with the results of [PERSON] et al. [26] who, studying the influence of pyrolysis temperature and feedstock type on agricultural properties and stability of biochars, found that, overall, pH increased with the increase of the pyrolysis temperature (ranging from 350 to 650 \({}^{\circ}\)C). Results concerning EC demonstrated that both increased the biochar percentage in the growing substrate and pyrolysis temperature increase EC values. Similarly [PERSON] et al. [15] found that substrate EC increased with the increase of biochar content (from 12 to 36 mS m\({}^{-1}\) for 100% peat and 100% biochar, respectively) when biochar substituted peat in the growing medium used for _Euphoria \(\times\) lomi_. Moreover our findings on EC are in accord with those obtained by [PERSON] et al. [27], [PERSON] et al. [28] and [PERSON] and [PERSON] [29], who found increased EC with the pyrolysis temperature increase. Higher EC values feature higher soluble salt availability, which in turn, presumably, accounted for the higher plant performance evidenced in this study. Nevertheless, our study is in contrast with the report of [PERSON] et al. [26], who found that increasing pyrolysis temperature did not increase EC. In this regard, we could hypothesize that this different result is due to a different type of raw materials used for biochar production. Our outcomes are partially conform to those by [PERSON] et al. [15] who found higher values of N in the medium with 100% peat and affirmed that the N content had no significant variation  
Figure 2: Plot of scores (trial) produced by PC1 and PC2 of the principal component analysis (PCA) analysis. among the growing media amended with (from BC20 to BC100). In the present study, P concentrations dropped as biochar percentage increased. However, pyrolysis temperature did not influence substrate P content. Our outcomes are in line with those experienced by [PERSON] et al. [30], who testing green waste compost and biochar soil amendments in order to reduce lead and copper mobility and uptake to ryegrass, report that P availability was lower in a soil amended with biochar than in green waste compost-amended soil. Furthermore, results are in accord with those of [PERSON] and [PERSON] [31] who, inquiring how biochar type might affect macronutrient retention and release from soilless media, evidenced that increasing levels of biochar will result in a substantial increase of K in the substrate and should be considered for fertility programs although being a modest source of P for ornamental plant production. Our outcomes on P content are, also, in accord with those by [PERSON] et al. [26] who evidenced equal P concentration with the increase pyrolysis temperature for sawdust and rice husk biochars. Results on K content confirmed that, both increased biochar percentage in the growing substrate and pyrolysis temperature increase K concentrations.