Objective  Effect of adding soft rocks to aeolian sandy soil in varied ratios on the vertical distributions of carbon (C), nitrogen (N), and texture of the soil was studied for improving fertility of the wasteland.

  Method  At Fuping, Shaanxi, soft rocks were blended to the local sandy soil in different ratios, i.e., 0:1 (CK), 1:5 (C1), 1:2 (C2), and 1:1 (C3) by volume to determine the C/N ratio and texture of soil in different depths.

  Result  The organic C and total N contents decreased with depth upon the additions. The average C content ranged from 1.45 g·kg^-1 to 2.70 g·kg^-1, and it was significantly higher in the 0-10 cm layer than 20-30 cm layer (P < 0.05). The mixing ratio had a significant effect on C, as the soft rocks increased (i.e., C3) so was C content in the top layer. The total N ranged 0.28-1.31 g·kg^-1, and that in the 0-10 cm layer significantly higher than in the deeper soils. In the top layer, C3 rendered significantly more N than other treatments. The average C/N ranged 1.72-5.92 with the lowest in the 0-10 cm layer and a decline upon increased addition of soft rocks. The varied mixing ratios did not affect the nitrate N and ammonium N contents, which ranged 33.56-197.00 mg·kg^-1 and 5.51-70.02 mg·kg^-1, respectively, with the top layer being the highest. Sand content in the soil gradually increased with depth, while silt and clay particles decreased. Along with the addition of soft rocks the soil texture changed from sand to loamy sand, and to sandy loam. There was a significant inversed correlation between C/N and nitrate N and ammonium N, and a correlation with the particle size distribution in soil. The correlations were most significant in the 10-20 cm soil layer.

  Conclusion  The blending ratio of soft rocks and sand at 1:1 seemed to promote the C and N accumulation in the 0-10 cm layer of soil. It also enhanced the microbial degradation in the soil.