Degree of phosphorus saturation of an Oxisol amended with biosolids in a long-term field experiment
2014
Alleoni, Luís Reynaldo Ferracciú | Fernandes, Antônio Rodrigues | de Campos, Murilo
When applied to agricultural soils, phosphate fertilizers and the mineral or organic compounds present in solid and/or liquid waste may raise phosphorus (P) content and increase soil P saturation. The degree of phosphorus saturation (DPS) is a good indicator of potential P loss from agricultural soils. The purpose of this study was to calculate the DPS of samples from an Oxisol amended for 5 years with biosolids and mineral fertilizer. DPS was calculated based on P, iron, and aluminum extracted by ammonium oxalate and oxalic acid (DPSₒₓ) or by Mehlich-1 solution (DPSM₁). Treatments included NPK mineral fertilization (175 kg ha⁻¹of P), B1 = 19.02 t ha⁻¹of biosolids (350 kg ha⁻¹of P), B2 = 38.17 t ha⁻¹of biosolids (703 kg ha⁻¹of P), B3 = 76.26 t ha–¹of biosolids (1,405 kg ha⁻¹of P), and a control (no P added). Water-extractable P (WEP) was also measured. Critical levels of DPSₒₓand DPSM₁(21 and 24 %, respectively) were only achieved in the topsoil (0–0.1 m) at the highest biosolid dose. Concentration of WEP was positively correlated to DPSₒₓand DPSM₁. The DPSM₁method may be an alternative to DPSₒₓfor assessing the environmental risk of P loss from soil into surface runoff.
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