Evaluation of sand‐alumina‐P media for studies of P nutrition¹

Authorized for publication as Paper No. 125 in the Department of Horticulture Series and as Paper No. 7948 in the Journal Series of the Pennsylvania Agricultural Experiment Station. Supported by USDA Specific Cooperative Agreement 58–32U4–5‐98.

Abstract

Sand cultures in which P is supplied by a solid‐phase buffer offer several advantages in studies of P nutrition. Phosphorus concentrations may be maintained at realistically low levels, P supply can be localized in the medium, and roots can readily be removed from sand. However, information on pH, P adsorption and P desorption is needed to use solid‐phase buffers effectively to simulate P supply in soil. Experiments were conducted to characterize the effects of acid washing treatments and P concentration on P adsorption by alumina, and subsequent desorption of P from alumina‐P. Increasing the concentration of H in acid washing treatments decreased the equilibrium desorption P concentration and solution pH for any given adsorption P concentration. Increasing P concentration of adsorption solution led to increasing P concentration and pH of desorption solutions. Further experiments were conducted to determine the effect of percentage alumina‐P in sand‐alumina‐P mixtures on P concentration in the solution phase and on P accumulation by maize (Zea mays L.) seedlings. Solution phase P concentration was unaffected by percentage alumina P, but seedling growth and P accumulation increased in a linear manner with increasing percentage alumina‐P. Phosphorus supply in a sand‐alumina‐P mixture was compared to that in a soil‐sand mixture. Sand‐alumina‐P had higher Bray #1 P concentration than soil‐sand, but lower P concentration in an equilibrium solution. When P was added to sand‐alumina‐P or soil‐sand mixtures, P concentrations decreased more rapidly and there was less net increase in P in sand‐alumina‐P than in soil‐sand. Results confirm the utility of sand‐alumina‐P mixtures as a solid medium for studies of P nutrition, and provide the basis for establishing predetermined P concentration and pH in the medium.

Notes

Authorized for publication as Paper No. 125 in the Department of Horticulture Series and as Paper No. 7948 in the Journal Series of the Pennsylvania Agricultural Experiment Station. Supported by USDA Specific Cooperative Agreement 58–32U4–5‐98.