The availability of soil P
The ratios of C-to-N (C/N) was negatively correlated with all CGP-41251 P content parameters (p < 0.05) with the exception of MBP. As one of the important humification parameters, the humification degree increased with decreasing C/N ( Wei et al., 2014a), which may also be combined with increasing levels of TP, IP and AP (Olsen P, WSP and CAP). Significant positive correlations were found between DON and all phosphorus indexes except the proportions of MBP and MAP&NAP ( Table 2). Here, the proportion of MBP had significant correlations with some of the physicochemical and biological parameters during composting. The proportion of MBP in TP was positively correlated with moisture content (MC) (r = 0.431, p < 0.05), C/N (r = 0.402, p < 0.05), organic matter (OM) (r = 0.483, p < 0.01) and NH4–N (r = 0.436, p < 0.05), but it was negatively correlated with germination index (GI) (r = −0.460, p < 0.05). The parameters for dissolved organic carbon (DOC), dissolved organic nitrogen (DON) and the preceding WSP significantly correlated with MBP content ( Fig. 4 and Table 2), suggesting that the movement of dissolved organic matter (DOM) appears to be related to microbial activities.