NPK accumulation in greenhouse soil and its effect on groundwater

In allusion to the problems of fertilizer waste and environmental pollution brought about by traditional fertilization and irrigation, greenhouse and farmland soil samples along with corresponding groundwater samples in Dingzhou City, Hebei Province were collected. Then accumulated NPK in greenhouse soil profile and its effects on the groundwater were analyzed for different cultivation ages. The results show that accumulated available nutrients in the 0~200 cm and 0~400 cm greenhouse soil profiles are higher than in farmland soils. In soil of greenhouse within 10 years, nitrate (377.2 mg·kg^-1), available P (448.8 mg·kg^-1), available K (1 405.6 mg·kg^-1) and water-soluble P (30.6 mg·kg^-1) are respectively 4.7, 4.6, 1.4 and 11.5 times of the cropland soils. For greenhouse older than 10 years, the respective variables are 6.4, 16.3, 2.7 and 12.0 times. The proportion of available soil nutrient in deep soil profiles increases with cultivation age. NO₃^--N pollution in drinking water at the depth of 20 m is serious with common and serious overproof rates of 39.3% and 7.1% respectively. NO₃^--N content in irrigation water for farmland and greenhouse at the depth of 40 m is 7.4 mg·L^-1 and 9.6 mg·L^-1 with respective common overproof rates of 25.0% and 37.5%, and zero serious overproof rate.