Journal of Korean Society of Agricultural Engineers ISSN:1738-3692(Print) 2093-7709(Online) 한국농공학회논문집

The purpose of this study is to investigate characteristics of total phosphorus (TP) and phosphate phosphorous (PO₄-P) concentrations in ponded water and redox potential (Eh) in paddy soil during the growing season. The TP and PO₄-P concentrations showed twice peak values after basal dressing and tillering fertilization. The ratio of PO₄-P to TP showed low values (0.07～0.18), indicating that most of phosphorus is particlulate. The PO₄-P concentrations significantly decreased with dissolved oxygen (DO) concentrations. The Eh showed high values (179～636 mV) under non-ponded aerobic condition, but low values (74～112 mV) under ponded anaerobic condition The TP and PO₄-P concentrations in ponded water increased shortly after tillering fertilization even if phosphorus was not applied. This may be due to the release of dissolved phosphorus from the bottom sediment and its associated algal and water flea blooms under anaerobic condition. Therefore, proper water management should be needed shortly after tillering fertilization.