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Mode of Transport of Surface‐Applied Phosphorus‐33 through a Clay and Sandy Soil
Author(s) -
Djodjic Faruk,
Bergström Lars,
Ulén Barbro,
Shirmohammadi Adel
Publication year - 1999
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1999.00472425002800040031x
Subject(s) - soil water , lysimeter , macropore , leaching (pedology) , lessivage , water flow , phosphorus , soil science , environmental science , leachate , leaching model , environmental chemistry , chemistry , hydrology (agriculture) , geology , soil fertility , geotechnical engineering , mesoporous material , biochemistry , organic chemistry , catalysis
Phosphorus (P) is the limiting nutrient for primary production in most freshwater ecosystems. The magnitude of P leaching from agricultural soils is therefore critical. Preferential flow has been proposed as a major cause for high P losses in structured clay soils. Undisturbed soil of two texturally different soils, that is, a day soil in which preferential flow was expected to be the main mode of water transport and a sandy soil where piston flow is the dominant process, were used in this study. Use of labeled P made it possible to determine the origin of leached P. An equivalent of 100 kg P ha −1 , labeled with 33 P, was added to the soil surface of each lysimeter. Water equivalents to 100 mm were added on five occasions with 7 d between each watering event. Ponded flow conditions were established during periods when water was added, to trigger preferential Bow behavior. Phosphorus leaching loads from day columns were much higher than P loads from sand columns. The average P leaching load for the five day columns was 4.0 kg ha −1 , compared to only 56 g ha −1 for the three sand columns. The main part of leached P was in dissolved (PO 4 ‐P) form. The recently added P prevailed in leachate from the clay soil indicating rapid transport of added P from the soil surface through the profile via macropores.