Spatial variability and sampling optimization of soil organic carbon and total nitrogen for Minesoils of the Loess Plateau using geostatistics

• Geostatistics was used to analyze the variability of SOC and TN in minesoils.
• Interpolation using kriging displayed a high heterogeneity of TN and SOC.
• Mining activities have large effect on the variability of SOC and TN of minesoils.
• The number of soil monitoring points was determined based on cross-validation.

Drastically disturbed minesoils can result in a significant loss of soil organic carbon (SOC) and total nitrogen (TN). To assess the effect of mining activities on minesoils and to track the changes in reclaimed soil quality, the variability of SOC and TN concentrations in the Shanxi Pingshuo Antaibao opencast coal-mine inner dump after dumping and before reclamation was analyzed using geostatistics, and a number of soil monitoring points were evaluated after land reclamation. Soil samples were collected from depths of 0–20 cm, 20–40 cm, 40–60 cm and 60–80 cm at 78 sampling sites in the study area over an area of 0.44 km2. The coefficient of variation (CV) for TN was the least at <15% for depths of 0–40 cm and 60–80 cm. For TN at a depth of 40–60 cm and the SOC at all depths, the CV was moderate at 15–35%. Interpolation using kriging displayed a high heterogeneity of TN and SOC, and the spatial structure of the original landform was partially or completely destroyed. Revegetation was an important measure for increasing the accretion of C and N compared to an unmined site. The kriging-interpolated maps were a very valuable tool in monitoring soil properties after land reclamation at the field scale, and RMSE can be used to determine the number of sampling point for soil properties.