Table 1.
The average mass proportion and soil C saturation value (Csat) of silt and clay fractions for topsoils (0–20 cm) under the seven treatments at the three long-term experimental sites.
| Treatments | Gongzhuling | Qiyang | Urumqi | |
|---|---|---|---|---|
| Mass proportion | CT | 0.89a (0.01) | 0.89a (0.00) | 0.70d (0.01) |
| N | 0.90a (0.01) | 0.88a (0.04) | 0.74c (0.03) | |
| NP | 0.89a (0.02) | 0.87a (0.01) | 0.74c (0.00) | |
| NPK | 0.88a (0.02) | 0.89a (0.01) | 0.81a (0.01) | |
| NPKS | 0.90a (0.01) | 0.88a (0.01) | 0.59e (0.02) | |
| NPKM | 0.89a (0.00) | 0.86a (0.01) | 0.76bc (0.00) | |
| hNPKM | 0.88a (0.04) | 0.87a (0.01) | 0.78ab (0.01) | |
| Average | 0.89a (0.01) | 0.88a (0.02) | 0.73b (0.07) | |
| Average C saturation value (g kg−1) | 33.5a (0.30) | 28.4c (0.52) | 30.1b (1.46) |
Different lowercase letters indicate that values are significantly different among treatments within a site or that average values are significantly different among study sites at P < 0.05. Data in parentheses are the standard error (n = 3 at the Qiyang site and n = 4 at the Gongzhuling and Urumqi sites for each treatment). CT, non-fertilized control; N, mineral nitrogen; NP, mineral N and phosphorus; NPK, mineral N, phosphorus, and potassium combination; NPKS, NPK plus crop straw return; NPKM, NPK plus livestock manure; hNPKM, higher rates of mineral fertilizer and manure input.