Experimental study on the changes of nutrient salt and trace element contents in soils of vegetable greenhouse for different cultivation years

The experiment was conducted in calcareous cinnamon soil under vegetable greenhouses for one year, 3, 6, 9 years of utilization. The results showed that the contents of nutrient, total salt, trace elements and heavy metals were significantly higher than that of plot under conventional cultivated dryland. The ratios of annual increase were as follows: organic matter