Object  Soil health issues caused by long-term continuous cropping in vegetable greenhouses in northwest arid regions could not be ignored. This study aimed to clarify the evolution patterns of soil quality at different depths with planting years, which is of great significance for the comprehensive evaluation of the field effects of greenhouse planting.

Method Traditional solar vegetable greenhouses in Qingyuan town, Wuwei, Gansu Province, which have been continuously planted for 5 years (Y1), 9 years (Y2), and 13 years (Y3), as well as maize fields (CK) were selected as the research objects. The spatio-temporal changes of soil physical, chemical, and biological characteristics of soil layers at 0 ~ 20, 20 ~ 40, 40 ~ 60, 60 ~ 80, and 80 ~ 100 cm depths were analyzed. The soil health index was quantified by fuzzy comprehensive evaluation method.

Result Compared with CK, the water retention of greenhouse soil was enhanced, the contents of total nitrogen, available phosphorus, available potassium, and organic matter in the soil within the range of 0 ~ 40 cm were significantly increased. The residual amount of ammonium nitrogen in the soil within the range of 0 ~ 100 cm also increased significantly. The soil bulk density and electrical conductivity of Y2 were the highest, while the pH was the lowest. The soil nutrient contents within the range of 0 ~ 100 cm were the highest in Y2, but the soil enzyme activity decreased significantly. The comprehensive evaluation results showed that the soil health maintained well in the soil range of 0 ~ 100 cm after 9 years of planting, but the soil health index decreased significantly in the soil within the range of 0 ~ 80 cm or 0 ~ 60 cm compared with that of 5 years.

Conclusion Soil properties of vegetable greenhouse continuous cropping are better than those of field soil in short term due to the change of irrigation and fertilization management, but there are potential risks of salinization and acidification. About 10-year continuous cropping is the critical point for the transformation of soil properties. The adverse effects of physical and chemical indices can be alleviated by deep tillage measures, but the improvement of soil biological indices was limited.