3.2.2 SOM, TN, AN and C/N
In MSSL of L. chinensis , N addition also increased the contents of SOM, TN and AN, and reduced the ratio of carbon to nitrogen (C/N). With N addition rate increasing, the content of SOM increased in a straight line, and it reached a significant level when N addition rate was 60 kg ha-1 compared with that of the control treatment (P <0.05). When N addition rates were 150-210 kg ha-1, the contents of SOM increased 2.16-2.53 times compared with that of the control treatment (Fig.5A). Similarly, soil TN and AN contents were also improved significantly with N addition rates increasing (P <0.05). Soil TN content was the highest when N addition rate reached 150 kg ha-1, and increased by 269.3% compared with that of the treatment without N addition (Fig.5B). Soil AN content was the highest when N addition rate reached 180 kg ha-1, and increased by 255.1% compared with that of the treatment without N addition (Fig.5C). Nitrogen addition significantly decreased the soil C/N (P < 0.05). The C/N ratio of the N addition treatments with 90-210 kg ha-1 was stable at about 15 (14.6-16.1), and those were lower by 38.3% - 44.3% than that of the control treatment without N addition (Fig.5D).