3.3 SOC decomposition and NCB
N and P additions differently affected SOC mineralization and NCB (Figure 3). Specifically, with glucose amendment SOC mineralization increased by 33% under P addition while decreased by 9%, and 7% under N, and NP addition, respectively (Figure 3a). SOC mineralization was significantly correlated with soil C:P, N:P, and microbial C:N, C:P and N:P (Table 2). When vanillin was amended, SOC mineralization was increased by 7% and 8% under P and NP addition but decreased by 11% under N addition (Figure 3a). SOC mineralization was significantly correlated with soil and microbial C:N, C:P, N:P (Table 2).
The NCB were positive for all nutrient treatments regardless of glucose or vanillin was amended (Figure 3b). Compared with control, the NCB with glucose amendment were increased by 7% and 6% under N and NP additions, respectively, while decreased by 40% under P addition. The NCB with vanillin amendment was increased by 17% under N addition but decreased by 36% and 42% under P and NP addition, respectively (Figure 3b).