title: Nitrogen balance and groundwater nitrate contamination: comparison among three intensive cropping systems on the North China Plain.
abstract: The annual nitrogen (N) budget and groundwater nitrate-N concentrations were studied in the field in three major intensive cropping systems in Shandong province, north China. In the greenhouse vegetable systems the annual N inputs from fertilizers, manures and irrigation water were 1358, 1881 and 402 kg N ha(-1) on average, representing 2.5, 37.5 and 83.8 times the corresponding values in wheat (Triticum aestivum L.)-maize (Zea mays L.) rotations and 2.1, 10.4 and 68.2 times the values in apple (Malus pumila Mill.) orchards. The N surplus values were 349, 3327 and 746 kg N ha(-1), with residual soil nitrate-N after harvest amounting to 221-275, 1173 and 613 kg N ha(-1) in the top 90 cm of the soil profile and 213-242, 1032 and 976 kg N ha(-1) at 90-180 cm depth in wheat-maize, greenhouse vegetable and orchard systems, respectively. Nitrate leaching was evident in all three cropping systems and the groundwater in shallow wells (<15 m depth) was heavily contaminated in the greenhouse vegetable production area, where total N inputs were much higher than crop requirements and the excessive fertilizer N inputs were only about 40% of total N inputs.
authors.affiliation: Key Laboratory of Plant-Soil Interactions, Ministry of Education, College of Agricultural Resources and Environmental Sciences, China Agricultural University, Beijing.
authors.forename: X T
authors.initials: XT
authors.lastname: Ju
authors.forename: C L
authors.initials: CL
authors.lastname: Kou
authors.forename: F S
authors.initials: FS
authors.lastname: Zhang
authors.forename: P
authors.initials: P
authors.lastname: Christie
mesh_terms: D000383:Agriculture; D002681:China; D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods; D004787:Environmental Pollution / Q000032:analysis*; D005308:Fertilizers; D005506:Food Contamination; D005638:Fruit; D006801:Humans; D008372:Manure; D009566:Nitrates / Q000032:analysis*; D009584:Nitrogen / Q000032:analysis*; D012989:Soil Pollutants / Q000032:analysis; D014197:Trees; D014908:Triticum; D014675:Vegetables; D014874:Water Pollutants, Chemical / Q000032:analysis; D003313:Zea mays
chemical_list: D005308:Fertilizers; D008372:Manure; D009566:Nitrates; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical; D009584:Nitrogen