Phosphorus Adsorption and Desorption Potential of Stream Sediments and Field Soils in Agricultural Watersheds
- Sandra C. Agudeloa,
- Nathan O. Nelson *a,
- Philip L. Barnesb,
- Timothy D. Keanec and
- Gary M. Pierzynskia
- a Dep. of Agronomy, Kansas State Univ., 2004 Throckmorton Hall, Manhattan, KS, 66506
b Dep. of Biological and Agricultural Engineering, Kansas State Univ., 047 Seaton Hall, Manhattan, KS, 66506
c Dep. of Landscape Architecture, Kansas State Univ., 216 Seaton Hall, Manhattan, KS, 66506. Contribution no. 10-284-J from the Kansas Agricultural Experiment Station, Manhattan, KS
Phosphorus release from stream sediments into water could increase P loads leaving agricultural watersheds and contribute to lag-time between implementation of best management practices and improvement in water quality. Improved understanding of P release from stream sediments can assist in setting water quality goals and designing stream monitoring programs. The objective of this study was to estimate the relative potential of sediments and soils to release P to stream water in two agricultural watersheds. Stream sediments were collected from banks, pools, riffles, and depositional features. Soils were sampled from wheat, row crop, pasture, and manure-amended fields. Sediments and soils were analyzed for equilibrium P concentration at zero net P sorption (EPC0), maximum P adsorption capacity (Pmax), anion exchange extractable P (Plab), and degree of P saturation. Dissolved reactive P (DRP) of stream water was monitored. Stream sediment EPC0 was similar to or less than EPC0 from field soils; however, Plab of stream sediments was three times less than field soils. Sediments were sandy and had low Pmax due to low oxalate-extractable Fe and Al, which could be explained by stream geomorphology. Manure-amended fields had the highest EPC0 and Plab due to continued inputs of manure-based P; however, conventionally fertilized fields also represented an important P source due to their vast extent. Stream water DRP was similar to EPC0 of stream sediments during base flow and similar to EPC0 of field soils during storm flow. These results indicate that sediments in these streams are a relatively minor P source.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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