Tuesday, April 21, 2009: 2:10 p.m.
Agave Ballroom (Hilton Tucson El Conquistador Golf & Tennis Resort )
Recent field studies have shown that both the application method and application rate influence the likelihood of liquid manure breakthrough to tile drains. Although a substantial amount of observational evidence exists to support the intuitive concept that higher application rates and pressures promote rapid liquid manure breakthrough to tiles, there is a scarcity of information regarding how physical processes govern the movement of manure constituents through macroporous soils in tile drained fields. Here we employ a dual permeability, flow and transport model to simulate liquid swine manure application experiments conducted in Sebringville , Ontario between 2000 and 2002. During the Sebringville experiments, ammonium and phosphate were detected in tile effluent soon after application. Using nutrient breakthrough data from the field experiment as a benchmark, the model was employed to predict how ammonium and phosphate are transported and ultimately distributed between tile drains, groundwater and the unsaturated zone within a 48 hour period following application. Simulations were conducted for broadcast and injection application techniques with manure loading rates of 18.7, 37.4, 56.1 and 74.8 m3ha-1. Domain geometry and application boundary conditions in the model were designed to reflect the uniqueness of the two application methods.
Model results show that broadcast application of liquid manure increases the shallow lateral distribution of both ammonium and phosphate, while injection application increases the vertical distribution. With injection application, higher application rates induce rapid transport of ammonium and to a lesser degree phosphate to the tile drain. Within all simulation scenarios, the transport distance of phosphate was less than that of ammonium since phosphate was subject to linear sorption while ammonium was considered to be conservative over the 48 hours following application. When the anisotropic nature of the macropore network is considered, the tile drain capture zone is limited to a narrow region immediately overlying the tile.
Model results show that broadcast application of liquid manure increases the shallow lateral distribution of both ammonium and phosphate, while injection application increases the vertical distribution. With injection application, higher application rates induce rapid transport of ammonium and to a lesser degree phosphate to the tile drain. Within all simulation scenarios, the transport distance of phosphate was less than that of ammonium since phosphate was subject to linear sorption while ammonium was considered to be conservative over the 48 hours following application. When the anisotropic nature of the macropore network is considered, the tile drain capture zone is limited to a narrow region immediately overlying the tile.