The effect of flooding and reducing conditions on phosphorus dynamics in Manitoba soils

Abstract

Anaerobic conditions resulting from flooding often lead to enhanced release of phosphorus (P) to overlying water. This study examined the effect of flooding and anaerobic conditions on soil P dynamics. A field ponding study using Scanterbury heavy clay soil (unamended, inorganic fertilizer- or manure-amended), and a laboratory incubation study using 12 soils (unamended or manure-amended) from Manitoba showed that P release to flood water under reduced conditions varied substantially. In the field ponding study, flooding and development of anaerobic conditions did not enhance P release into surface flood or soil pore water. In the incubation study, the response to flooding and anaerobic conditions ranged from a small decrease to a 15-fold increase in dissolved reactive P concentration (DRP) in flood water. Partial least squares analysis indicated that measures of degree of P saturation in soils can effectively predict DRP concentration changes in surface flood water under anaerobic conditions.