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Phosphorus Mineralization and Transport in the Vicinity of an Anion Sink: Experiment and Modeling
Author(s) -
Kerber Katja,
Zirkler Doreen,
Kaupenjohann Martin,
Peters Andre
Publication year - 2015
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2015.02.0080
Subject(s) - mineralization (soil science) , digestate , chemistry , sink (geography) , rhizosphere , environmental chemistry , incubation , nutrient , phosphate , organic matter , soil water , inorganic ions , ion , nitrogen , soil science , environmental science , anaerobic digestion , geology , biochemistry , paleontology , cartography , organic chemistry , methane , bacteria , geography
Digestates from biogas plants provide valuable crop nutrients, such as P. Plant uptake of anions like PO 4 3− causes an alkalinization of the rhizosphere due to release of HCO 3 − . We investigated the transport of P to an anion sink simulating the anion exchange activity of a plant root in digestate‐amended soils and hypothesized that the HCO 3 − source induces enhanced mineralization of organic P. We expected this effect to strengthen with decreasing distance from the HCO 3 − source. Anion exchange resins (AERs) saturated with HCO 3 − were used in an incubation experiment. Available PO 4 –P was measured in 10 slices of the soil–digestate mixtures (1 mm each) after 2, 8, and 32 d and in the resin and total uncut samples after 2, 4, 8, 16, 32, and 64 d of incubation. Anion exchange resins increased pH by 2 to 3 units. Concentrations of available PO 4 –P in the uncut samples increased within 4 d, which we attribute to enhanced microbial P mineralization activity. Afterward, PO 4 –P concentrations decreased within 4 d, which we attribute to precipitation of calcium phosphate due to further increasing pH. Concentrations of PO 4 –P were lowest near the AER and showed a peak migrating away from the resin with time. A new model linking diffusive transport and mineralization intensity of organic matter as a function of distance from AER could well describe the observed spatial PO 4 –P distribution and accumulation in the resin. However, further studies are needed to account for mechanisms like precipitation in models for P transport.