Characteristics of Nitrate Accumulation and Its Effects on Groundwater under Typical Cropping Systems in North China Plain

In order to solve the problem of nutrient waste and environmental pollution with traditional fertilization and irrigation to typical farm in north China,this article took plastic greenhouse vegetable and wheat-maize rotation soil samples and corresponding groundwater samples in Dingzhou,analyzed the NO3--N accumulation of different farm utilization,different plastic greenhouse vegetable cultivation age and different plant type and groundwater by the extent of NO3--N pollution.The results showed that,NO3--N accumulation of plastic greenhouse vegetable is significantly higher than wheat-maize rotation in 0-400 cm soil profile,NO3--N accumulation of plastic greenhouse vegetable of 0-100 cm,100-200 cm,200-300 cm and 300-400 cm were:815.0,93.6,394.9,313.4 kg/hm2,respectively 12.3,3.8,4.6 and 5.1 times than which in wheat-maize rotation.NO3--N accumulation of plastic greenhouse vegetable increased with the cultivation ages,especially in 0-60 cm.NO3--N accumulation of old plastic greenhouse vegetable(12 years) in 0-100 cm and 100-200 cm were 815.0,293.6 kg/hm2and 216.2,11.4 kg/hm2 higher than young plastic greenhouse vegetable(8 years).NO3--N accumulation of cucumber plastic greenhouse was higher than tomato,and there were significantly many NO3--N accumulation peaks in deep soil profile.The content of NO3--N in greenhouse irrigation water,wheat-maize rotation irrigation water and hand press wells were 9.6,7.4,10.5 mg/L,and there were 38%,16% and 46% samples exceeding the maximum permissible limit for drinking water (10 mg/L).Come to a conclusion that the superficial layer underground water of investigative zone was polluted by NO3--N.