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CV 2018

Biography

Education:  Dr. Scient in soil science at Agricultural University of Norway in 1995.

Areas of expertise:

-Sources for phosphorus runoff from agricultural fields

-Recycling of phosphorus in organic waste

-Plant-available phosphorus in organic waste products

-Soil analyses

-Plant nutrition

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Abstract

In agricultural areas dominated by subsurface drainage, leaching of phosphorus (P) from soils is a concern for downstream water quality. Still, the role of chemical processes in subsoils and organic soils in influencing dissolved P leaching needs to be clarified for better predicting the P leaching. In ten mineral and organic soils, we examined a wide range of chemical characteristics including various P pools and sorption–desorption properties at different soil depths and related those characteristics to leaching of dissolved P at the drain depth in an indoor lysimeter experiment. Results showed significant correlations between different P pools (R2-adj = 0.61 to 0.98, p < 0.001) and between sorption capacity measurements (R2-adj = 0.60 to 0.95, p < 0.001). Some organic soils followed the same patterns in P sorption capacity and P lability as sandy soils but some did not, suggesting organic soils differ among themselves possibly due to differences in origin and/or management. Flow-weighted mean concentrations of dissolved reactive P and dissolved organic P depended on both the labile P pools (labile inorganic and organic P pools, respectively) in the topsoil and P sorption and desorption characteristics in the subsoils. Mass-weighted whole-profile degree of P saturation based on the ammonium lactate extraction method (DPS-AL) was an excellent indicator of flow-weighted mean concentration of total dissolved P (FWMC-TDP) (R2-adj = 0.93, p < 0.001). Two profiles, one with organic soils overlaying on sand and the other with sandy soils in all layers, had the greatest FWMC-TDP among all profiles (316 and 230 µg/L versus 33–84 µg/L) due to the same reason, i.e., large labile P pools in the topsoils, low P sorption capacity in the subsoils, and high whole-profile DPS-AL. All results point to the need to include subsoil characteristics for assessing the risks of dissolved P leaching from both mineral and organic soils. Also, the study suggests the need to investigate further the roles of the origin and management of organic matter and organic P in influencing P lability and dissolved organic P (DOP) leaching, as well as the bioavailability of DOP in recipient waters.