Heat-map reporting the correlations (Pearson’s r) of the growth on water extracts of six target organisms: Two plants (Brassica, Lepidium), four fungi (Rhizoctonia, Aspergillus, Fusarium, Trichoderma) and survival of a nematode (Meloidogyne), to the chemical parameters of olive mill waste (OMW) and its biochars pyrolyzed at 300 °C, 500 °C, 800 °C, or 1000 °C.

Asterisks indicate statistically significant correlation values, negative or positive. Labels in the x-axis indicate the parameters measured (carbon and nitrogen contents, pH, C/N and H/C ratios, EC), and the numbers refer to the ¹³C NMR spectral ranges (in ppm) for reference regions of the different C types: alkyl C (0–45 ppm), methoxyl and N-alkyl C (46–60 ppm), O-alkyl C (61–90 ppm), di-O-alkyl C (91–110 ppm), H- and C-substituted aromatic C (111–140 ppm), O-substituted aromatic C (141–160 ppm), carboxylic C (161–190 ppm).