the other treatments during the experiment period, whereas that in
CK remained relative stable (about 10 g?kg21).
The dynamics of TN content in the five treatments followed
similar patterns with SOC during 1998–2009 (Fig.4B). In the first
few years, TN content tended to increase rapidly in the OM
treatment (from 1.01 to 1.76 g?kg21), followed by NPK treatment
(from 1.02 to 1.33 g?kg21). Thereafter, both of them declined and
then maintained a certain level. Meanwhile, the soil TN contents
in SR, GM and CK treatments were relatively steady, at
approximately 1.05 g?kg21.