Effects of freeze-thaw cycles on phosphorus adsorption and desorption in the black soil of northeastern China

Abstract

Frequent freeze-thaw cycles (FTCs) can profoundly affect the chemical properties of soils. We conducted laboratory experiments to explore the effects of freeze-thaw treatments on phosphorus (P) adsorption (Pads) and desorption (Pdes) and to determine the capacity of P retention (Pret) via Pads and Pdes in the fertile black soil of northeastern China. The effects of 0, 1, 3, 6, and 10 FTCs on soil P adsorption and desorption were determined. Each cycle consisted of freezing for 12 h at -10 °C and thawing for 12 h at +7 °C, mimicking a diurnal pattern, at initial soil-moisture contents of 20%, 30%, 40%, and 50% and at amounts of added P of 10, 20, 40, 60, and 80 mg P L-1. Pads increased significantly with increasing amounts of added P. The freeze-thaws of black soils significantly decreased Pads and buffering capacities, which would promote the release of adsorbed P and increase the risk of reducing soil P. High moisture content also affected the behavior of soil P adsorption by reducing adsorbed P as the number of FTCs increased. The P-isotherm data for all soils at equilibrium-P concentrations fit the Langmuir equation well (R2 = 0.93 or higher). Pads had exponential and linear relationships with Pdes capacity and Pret capacity, respectively. © 2014 © 2014 Taylor & Francis.