Fischer P, Pöthig R, Gücker B, Venohr M
Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Justus von Liebig Straße 7, Berlin 12489, Germany E-mail:
Department of Geosciences, Federal University of São João del-Rei, Campus Tancredo Neves, R. Visconde do Rio Preto s/n, São João del-Rei, MG, Brazil.
Water Sci Technol. 2016;74(3):691-7. doi: 10.2166/wst.2016.169.
The degree of phosphorus saturation (DPS) of agricultural soils is studied worldwide for risk assessment of phosphorus (P) losses. In previous studies, DPS could be reliably estimated from water-soluble P (WSP) for European and Brazilian soils. In the present study, we correlated measured WSP and Mehlich-1 P (M1P) from soils of Minas Gerais (MG) and Pernambuco (PE) (R(2) = 0.94, n = 59) to create a DPS map from monitoring data. The resulting DPS map showed high spatial variability and low values of DPS (54 ± 22%, mean and standard deviation; n = 1,827). Measured soil DPS values amounted to 63 ± 14% and resulted in relatively low dissolved P concentrations measured in a surface runoff study in MG. However, fertilizer grains on the soil surface led to high WSP values (>30 mg/kg) indicating high risks of dissolved P losses. We suppose that small Oxisol particles with Fe and Al hydroxides sorbed most of the dissolved fertilizer P in runoff so that P was mainly exported in particulate form. In soils with lower contents of P sorption and binding partners, e.g. Entisols in PE, this effect may be less dominant. Consequently, superficial fertilizer effects have to be considered in addition to DPS in risk assessment of P losses from agricultural areas in Brazil.
为评估磷（P）流失风险，全球都在研究农业土壤的磷饱和度（DPS）。在以往研究中，对于欧洲和巴西的土壤，可根据水溶性磷（WSP）可靠地估算DPS。在本研究中，我们将米纳斯吉拉斯州（MG）和伯南布哥州（PE）土壤中测得的WSP和Mehlich-1磷（M1P）进行关联（R² = 0.94，n = 59），以根据监测数据创建DPS地图。所得的DPS地图显示出高空间变异性和较低的DPS值（54 ± 22%，均值和标准差；n = 1,827）。测得的土壤DPS值为63 ± 14%，在MG进行的一项地表径流研究中测得的溶解磷浓度相对较低。然而，土壤表面的肥料颗粒导致WSP值较高（>30 mg/kg），表明溶解磷流失风险较高。我们推测，带有铁和铝氢氧化物的小氧化土颗粒吸附了径流中大部分溶解的肥料磷，因此磷主要以颗粒形式输出。在磷吸附和结合伙伴含量较低的土壤中，例如PE的新成土，这种影响可能不那么显著。因此，在评估巴西农业区磷流失风险时，除了DPS外，还必须考虑表层肥料的影响。
