Physicochemical Properties and Quality Evaluation of Soil Profiles in Different Soil Types in Yanji

Objective The characteristics of cultivated land soil in Yanji were clarified, and a soil quality evaluation system suitable for the local area was constructed to provide a reliable basis for precise management and scientific fertilization of regional cultivated land.

Method Three typical soils, paddy soil, dark brown earth and meadow soil, were selected to determine 11 physical and chemical indices of their natural occurrence layers (Ap, Ah, B, C). Based on principal component analysis combined with Norm value, the full data set (TDS) was screened to construct the minimum data set (MDS), and the soil quality index (SQI) was calculated accordingly.

Result The bulk density of the three soil types increased with depth, and the surface bulk density of paddy soil was the lowest. Nutrients such as organic matter, total nitrogen and total phosphorus generally showed the characteristics of ‘surface accumulation’, among which nitrate nitrogen was enriched in meadow soil, and available potassium and available phosphorus were prominent in dark brown soil. The electrical conductivity decreased with depth, and the electrical conductivity of paddy soil was significantly higher than that of dark brown soil. Four indices of total nitrogen, nitrate nitrogen, available potassium and conductivity were included in MDS. Linear regression analysis showed that there was a significant positive correlation between SQI-MDS and SQI-TDS (R² = 0.8637, P < 0.001), indicating that MDS could effectively replace TDS for soil quality evaluation in the study area. Based on the MDS evaluation results, the SQI of the plough layer was meadow soil (0.620) > paddy soil (0.526) > dark brown soil (0.517), and the overall SQI of the profile was dark brown soil (0.426) > meadow soil (0.420) > paddy soil (0.378).

Conclusion There are obvious differences in soil physical and chemical properties of three typical cultivated land in Yanji. The MDS constructed by total nitrogen, nitrate nitrogen, available potassium and electrical conductivity can effectively evaluate regional soil quality. The soil quality of cultivated land in the study area is generally at a ‘medium’ level.