Compared to the soil in cereal cropland

the physical

chemical and biological properties of the soil in the protected field

such as organic matter

total N

available nutrient(N

P and K)

exchangeable Ca and Mg

(acidity) and alkalinity

salinity accumulation and bio-activity

have obviously changed with the prolongation of cropping duration.This has decreased soil quality

impacted crop growth and potentially threatened human health.In order to sustain the vegetable production with high yield

high quality and high efficiency

it is of great theoretical and practical significance to study soil fertility and its affecting factors in the protected field cropping system.