Nutrients and pollutants in agricultural soils in the peri-urban region of Beijing: Status and recommendations

Large-scale animal production plants and specialized cash crop production systems have developed in China in recent decades. In the Beijing region this has led to livestock densities of nearly 11 livestock units (LU) per hectare, resulting in over-fertilization of soils and pollution of the aquatic and atmospheric environments. A soil screening investigation including five main cropping systems was carried out in the Shunyi and Huairou Districts of Beijing from 2009 to 2011. Soils (calcaric Eutric Cambisols) were sampled on 26 farmers' field plots to a depth of 200 cm and analysed for soil organic carbon (SOC), hot water-soluble carbon (C-hws), total and plant-available macronutrients, pH (H2O) and CaCO3. Fertilization practice was obtained via farmers' interviews. The status of major potential pollutants in animal husbandry (veterinary antibiotics and growth-promoting heavy metals and arsenic) reaching the field plots via manure application was investigated. Most of the investigated soils were over-supplied with nutrients. High amounts of farmyard manure (FYM) averaging 45 +/- 69 t DM ha(-1) y(-1) were applied to most of the observed field plots in 2008, with mean total pure nutrient amounts of 967 +/- 1297 kg nitrogen (N), 379 +/- 535 kg phosphorus (P) and 751 +/- 889 kg potassium (K) ha(-1) y(-1) (n = 19). Additional nutrient applications with mineral fertilizers amounted to 276 +/- 122 kg N, 37 +/- 62 kg P and 21 +/- 26 kg K ha(-1) y(-1) (n = 16). Comparing current (2009) soil nutrient contents in 0-20 cm with data from the Second Chinese National Soil Survey of 1981, significant increases in SOC (from 0.71% to 0.95%), total N (from 0.08% to 0.13%) and available P (from 7.3 mg kg(-1) to 60 mg kg(-1)) were observed. Sulfonamide antibiotics were found in topsoils and subsoils, whereas tetracyclines and fluoroquinolones mainly remained in the topsoil. The "natural background value" for Cu and Zn, based on the Chinese environmental quality standard was exceeded in topsoil samples on four and three sites, respectively. Crop-specific fertilizer recommendations were derived and options for different manure processing and transport technologies are discussed. An evaluation of the risks associated with veterinary antibiotics, heavy metals and arsenic is given. (C) 2015 Elsevier B.V. All rights reserved.