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DGT technique to assess P mobilization from greenhouse vegetable soils in China: A novel approach
- Kalkhajeh, Yusef Kianpoor, Sørensen, Helle, Huang, Biao, Guan, Dong-Xing, Luo, Jun, Hu, Wenyou, Holm, Peter E., Hansen, Hans Christian Bruun
- The Science of the total environment 2018 v.630 pp. 331-339
- aluminum, eutrophication, greenhouses, leaching, losses from soil, oxalates, phosphorus, risk, soil properties, soil solution, soil types, surface water, topsoil, vegetable growing, vegetables, vegetation, China
- Intensive phosphorus (P) inputs to plastic-covered greenhouse vegetable production (PGVP) in China has led to excessive soil P accumulation increasing the potential for leaching to surface waters. This study examined the mobility and hence the potential risk of P losses through correlations between soil solution P (PSol) and soil extractable P as determined by conventional soil P test methods (STPs) including degree of P saturations (DPSs), and diffusive gradient in thin-films (DGT P) technique. A total of 75 topsoil samples were chosen from five representative Chinese PGVPs covering a wide range of physiochemical soil properties and cultivation history. Total P and Olsen P contents varied from 260 to 4900, and 5 to 740mgkg−1, respectively, while PSol concentrations were between 0.01 and 10.8mgL−1 reflecting the large differences in vegetation history, fertilization schemes, and soil types. Overall, DGT P provided the best correlation with PSol (r2=0.97) demonstrating that DGT P is a versatile measure of P mobility regardless of soil type. Among the DPSs tested, oxalate extractable Al (DPSOx-Al) had the best correlation with PSol (r2=0.87). In the STP versus PSol relationships, STP break-points above which P mobilization increases steeply were 513μgL−1 and 190mgkg−1 for DGT P or Olsen P, respectively, corresponding to PSol concentration of 0.88mgL−1. However, for PSol concentration of 0.1mgL−1 that initiates eutrophication, the corresponding DGT P and Olsen P values were 27μgL−1 and 22mgkg−1, respectively. Over 80% of the investigated soils had DGT P and Olsen P above these values, and thus are at risk of P mobilization threatening receiving waters by eutrophication. This paper demonstrates that the DGT extracted P is a powerful measure for soluble P and hence for assessment of P mobility from a broad range of soil types.