Effects of Manure Application and Plowing on Transport of Colloids and Phosphorus to Tile Drains

Abstract

Preferential flow and particle-facilitated transport may be largely responsible for observed leaching patterns of strongly sorbing contaminants such as phosphorus. A series of field experiments was performed to investigate the effects of slurry application and plowing on the subsurface transport of colloids and P. Two 25-m 2 plots at a structured sandy loam site were irrigated on six occasions during 1 yr. Effluent sampled in tile drains below the plots was analyzed for turbidity and fractions of dissolved (,0.24 mm) and particulate inorganic and organic P. The observed flow conditions indicated macropore flow. The particle concentration in the effluent was initially high, peaking before flow peak, and later gradually decreased with flow rate. The colloid leaching pattern was attributed to an initial depletion of high colloid concentrations in the pore water and an eventual diffusion-limited release of colloids from immobile intra-aggregate water to mobile water. Seasonal variability and management practices caused significant variations in the leaching of P forms. After slurry application dissolved P dominated P loss to the drains. At the events in autumn and winter, particle-facilitated transport of P came to dominate over dissolved P transport, reaching a maximum of 80% of P loss. Results suggested that plowing increases the risk of particle-facilitated and dissolved P leaching in rainstorms shortly after the inversion of the soil. We observed an almost fourfold increase in the leaching of P per volume of leachate when comparing irrigation experiments before and after plowing. Amounts of P associated with particulate matter in drain water were constant within events, but varying between storms. For Danish structured clay soils, P density in leached particles was found to range between a maximum of 6 mg P g 21 for soils having recently been fertilized and an approximate minimum of 3 mg P g 21 for soils not recently fertilized.

Effect of direct incorporation of poultry litter on phosphorus leaching from coastal plain soils

“…Particulate P was strongly tied to total P concentration in leachate (r 2 > 0.94), accounting for at least 58% to 64% of total P. The largest concentrations of particulate P were associated with the first rainfall simulation followed by the first irrigation event (figure 4a). Findings clearly implicated particulate P as a primary fraction of leached P, consistent with studies elsewhere that have evaluated leaching of P from manured soils (Toor et al 2005;Schelde et al 2006;Kleinman et al 2009). In those studies, however, liquid manures were evaluated.…”

Flow and transport experiments for a streambank seep originating from a preferential flow pathway

“…Of course, phosphorus in these floodplain systems may be more associated with colloid-sized soil particles, which could still be subject to piping through the PFP (Schelde et al, 2006;Fuchs et al, 2009;Heeren, 2011), rather than being dissolved, and therefore the calculated K d may be conceptually inappropriate. Future work is needed to investigate this question.…”

Application of manure to no-till soils: phosphorus losses by sub-surface and surface pathways

“…Findings of sediment-bound P transport in subsurface flow have been reported elsewhere (e.g., Sharpley and Syers 1979;Dils and Heathwaite 1999). In studies of well-structured soils amended with liquid cattle manure, Schelde et al (2006) observed that up to 80% of P in tile drain effluent was associated with sediment, while Toor et al (2004) observed that over 70% of leachate P from soil columns amended with dairy slurry was in sediment-bound form. Clearly, such substantial contributions of sediment-bound P confirm the importance of bypass flow via macropores as a dominant transport mechanism of P transport in such soils.…”