Spatial variation of soil phosphorus within a drainage ditch network.
Agricultural drainage ditches serve as P transport pathways from fields to surface waters. Little is known about the spatial variation of P at the soil-water interface within ditch networks. We quantified the spatial variation of surficial (0-5 cm) soil P within vegetated agricultural ditches on a farm in Princess Anne, MD with an approximately 30-yr history of poultry litter application. Ditch soils from 10 ditches were sampled at 10-m intervals and analyzed for acid ammonium oxalate-extractable P, Fe, Al (P(ox), Fe(ox), Al(ox)), and pH. These variables were spatially autocorrelated. Oxalate-P (min = 135 mg kg(-1), max = 6919 mg kg(-1), mean = 700 mg kg(-1)) exhibited a high standard deviation across the study area (overall 580 mg kg(-1)) and within individual ditches (maximum 1383 mg kg(-1)). Several ditches contained distinct areas of high P(ox), which were associated with either point- or nonpoint-P sources. Phosphorus was correlated with Al(ox) or Fe(ox) within specific ditches. Across all ditches, Al(ox) (r = 0.80; p < 0.001) was better correlated with P(ox) than was Fe(ox) (r = 0.44; p < 0.001). The high level of spatial variation of soil P observed in this ditch network suggests that spatially distributed sampling may be necessary to target best management practices and to model P transport and fate in ditch networks.
Vaughan
Robert E
RE
Department of Environmental Science and Technology, University of Maryland, College Park, MD 20742, USA.
Needelman
Brian A
BA
Kleinman
Peter J A
PJ
Allen
Arthur L
AL
D000383:Agriculture; D000535:Aluminum / Q000032:analysis*; D005843:Geography; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000032:analysis*; D008396:Maryland; D010070:Oxalates; D010758:Phosphorus / Q000032:analysis*; D012987:Soil / Q000032:analysis*
D010070:Oxalates; D012987:Soil; D010758:Phosphorus; D000535:Aluminum; D007501:Iron