3.6 Soil fractions
The POC and MAOC contents decreased with depth and were significantly affected by N application (Fig. 8a–b). NT increased the POC and MAOC contents by 12.1% and 10.1% compared with CT in the 0–10 cm layer, respectively. The POC and MAOC contents increased with increasing N application rates and the rate of increase under NT was higher than under CT in the 0–10 cm layer. However, tillage and N treatment had no influence on MAOC in the 10–25 cm layer.