Affiliations: Institute of Soil Science, Chinese Academy of
Sciences, Nanjing 210008, China | Research Centre for Eco-Environmental Sciences,
Chinese Academy of Sciences, Beijing 100085, China | Soil and Land System, School of Earth and
Environmental Sciences, The University of Adelaide, SA 5005, Australia
Abstract: Low-molecular-weight (LMW) organic acids widely exist in soils,
particularly in the rhizosphere. A series of batch experiments were carried out
to investigate the phosphorus release from rock phosphate and iron phosphate by
Iow-molecular-weight organic acids. Results showed that citric acid had the
highest capacity to solubilize P from both rock and iron phosphate.
P solubilization from rock phosphate and iron phosphate resulted in net proton
consumption. P release from rock phosphate was positively correlated with the
pK_a values. P release from iron phosphate was positively
correlated with Fe-organic acid stability constants except for aromatic acids,
but was not correlated with PK_a. Increase in the
concentrations of organic acids enhanced P solubilization from both rock and
iron phosphate almost linearrly. Addition of phenolic compounds further
increased the P release from iron phosphate. Initial solution pH had much more
substantial effect on P release from rock phosphate than from iron
phosphate.
Keywords: organic acid, phosphate release, rhizosphere, rock phosphate, iron phosphate
