Vertical Distribution of Phosphorus in Agricultural Drainage Ditch Soils

Pedological processes such as gleization and organic matter accumulation may affect the vertical distribution of P within agricultural drainage ditch soils. The objective of this study was to assess the vertical distribution of P as a function of horizonation in ditch soils at the University of Maryland Eastern Shore Research Farm in Princess Anne, Maryland. Twenty‐one profiles were sampled from 10 agricultural ditches ranging in length from 225 to 550 m. Horizon samples were analyzed for total P; water‐extractable P; Mehlich‐3 P; acid ammonium oxalate‐extractable P, Fe, and Al (Pox, Feox, Alox); pH; and organic C (n = 126). Total P ranged from 27 to 4882 mg kg−1, Pox from 4 to 4631 mg kg−1, Mehlich‐3 P from 2 to 401 mg kg−1, and water‐extractable P from 0 to 17 mg kg−1 Soil‐forming processes that result in differences between horizons had a strong relationship with various P fractions and P sorption capacity. Fibric organic horizons at the ditch soil surface had the greatest mean Pox, Feox, and Alox concentrations of any horizon class. Gleyed A horizons had a mean Feox concentrations 2.6 times lower than dark A horizons and were significantly lower in total P and Pox Variation in P due to organic matter accumulation and gleization provide critical insight into short‐ and long‐term dynamics of P in ditch soils and should be accounted for when applying ditch management practices.