Phosphorus Releasing Potentials of Amino Acids and Low Molecular Weight Organic Acids from Highly Calcareous Soils

Aims: The present study was conducted to investigate the potentials of amino acids and low molecular weight organic acids, two major components of plant root exudates on phosphorus release from highly calcareous soils.

Study Design: Factorial experiment based on completely randomized design was used.

Place and Duration of Study: Department of Soil Science and Agricultural Chemistry, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India between 21st and 22nd of December 2020.

Methodology: An incubation experiment was conducted with two amino acids (glycine and lysine) and four low molecular weight organic acids (citric acid, malic acid, oxalic acid and acetic acid) at seven different concentrations (0, 20, 40, 60, 80 & 100 mM) for assessing their potentials of phosphorus release from highly calcareous soils (>15% free CaCO3). The soils were incubated for a time interval of 5, 10, 20, 30, 60, 120, 240, 960 & 1440 minutes. Available Phosphorus status in the soils treated with both acids were analyzed after the expiry of each incubation time.

Results: Organic acids had higher impact on phosphorus release than amino acids. Kinetic data obtained from the experiment were adequately described by Simple elovich (r2 ≥ 0.90, P < .001) and Power function (r2 ≥ 0.80, P < .001) models for both acids. Glycine among amino acids and citric acid among low molecular weight organic acids were highly effective in releasing phosphorus from highly calcareous soils.

Conclusion: The experiment concludes that, incubating the highly calcareous soils with 100 mM citric acid for 1440 minutes increased the kinetics of phosphorus release. The Simple elovich model was the best fitted model to explain the phosphorus release from calcareous soils as influenced by amino acids and low molecular weight organic acids.