Characterizing Phosphorus Loss in Surface Runoff: Impact of Source, Application Method and Wetting-Drying Cycles

Abstract

Previous studies have shown greater risk of Phosphorus (P) loss from commercial fertilizer (CF) than manure especially when they are surface applied. The P losses from soils of varying texture amended with either CF or manure at rates comparable to agronomic recommendation for CF was studied. Manure represented a greater and steady source of dissolved P to runoff. In addition, surface-placed P presented the greatest risk of P losses to runoff, while a subsurface band was a much better option of placing P except where efficient P source burial was restricted. The importance of post-application soil moisture condition prior to runoff on P losses was also examined. Exposing the soils to wetting and drying cycles increased the potential for dissolved P losses compared to when the soils were always wet. Selection of on-farm P management strategies should target appropriate P sources, rate, placement and timing while considering the soil’s properties.