Objective  Soil fertility has an extremely important influence on the yield and quality of medicinal plants in semi-arid areas, and soil fertility will gradually decline with the increase of planting years of Traditional Chinese medicine. This paper took the traditional Chinese medicine planting area in Longxi County as the research area to explore the influence of long-term planting of traditional Chinese medicine on spatial variation of soil nutrients.

  Method  Based on the statistics, geo-statistics and GIS, the spatial distribution pattern of tillage soil nutrients and comprehensive fertility was studied.

  Result  ① Here soil electrical conductivity and pH were 108.63 ms cm⁻¹ and 8.50. Average contents of organic matter, total nitrogen (TN), total phosphorus (TP) and total potassium (TK) in the study region were 7.54 g kg⁻¹, 0.73 g kg⁻¹, 0.73 g kg⁻¹ and 17.96 g kg⁻¹, respectively. Meanwhile, the variable coefficient illustrated soil pH was the weak variation but organic matter, TN, TP, TK and electrical conductivity were moderate variation. ② Soil organic matter was high at the southwest and low at the northeast. TN content of soil presented the patch distribution, which was characterized by high at the south and lower at the east. Interestingly, soil TP content of this region ranged from 0.60 - 0.80 g kg⁻¹, and TP showed a climax at the southwest in the study region. Soil TK was higher at the center of the county than that in other directions. Soil electrical conductivity also presented the patch distribution. ③ The spatial distribution of soil fertility in the Longxi County illustrated a trend of high at the west and low at the northeast, and soil fertility of the center was higher than that in the north and the south. Furthermore, according to the comprehensive scores of Nemerow Comprehensive Index ( IFI₁), Principal Component Analysis (IFI₂ ) and Fuzzy Comprehensive Assessment (IFI₃ ), soil fertility of the Longxi County was distinguished as five levels. Across three methods, we found that land area in the soil fertility lowing to the III level accounted for 74.97%, 43.28%, and 67.57% of the total area in the study region.

  Conclusion  Long-term and unscientific planting of Chinese medicine decreased the total soil fertility. Lower soil fertility of the Longxi County can be improved by adding organic fertilizer and the mixed fertilizer of N:P:K in a scientific ratio, crop rotation and unplanted and so on.