Phosphorus Behavior in Flooded‐Drained Soils. I. Effects on Phosphorus Sorption

Abstract

Abstract This study examines the effects of flooding periods (FP), organicmatter (OM) addition, and temperature changes during soil flooding on P sorption in 10 flooded‐drained (FD) California soils. The soils were flooded for 0 to 90 d, drained, air dried, and used for P‐sorption studies at six (0.3–2.0 m M ) initial P concentrations ( P i ). Four soils, showing a wide variation in P‐sorption capacity, were evaluated for the effects of OM and temperature treatments. Using P‐sorption isotherms, a relationship between P sorption and FP was developed for a given final P concentration ( P f ) for each soil. Flooding soil without added OM increased P sorption by 10 to 70% in half of the 10 soils. Organic‐matter treatment and elevated temperature during flooding further increased P sorption and shortened the FP at which P sorption reached maxima. The soils in which P sorption did not increase without OM treatment were low in either OM or reducible Fe. The largest increase in P sorption as a result of OM and temperature treatments was found in a soil that had low OM but a high level of reducible Fe. These findings suggest that OM and temperature are important factors determining the impact of FD conditions on P sorption.