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2,4‐D Residues in Aggregates of Tropical Soils as a Function of Water Content
Author(s) -
Rocha Wadson S. D.,
Regitano Jussara B.,
Alleoni Luís R. F.
Publication year - 2006
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2005.0385
Subject(s) - mineralization (soil science) , soil water , humus , water content , chemistry , environmental chemistry , organic matter , moisture , soil science , environmental science , geology , geotechnical engineering , organic chemistry
The effects of soil moisture on reactions between pesticides and soil aggregates are little understood, particularly in soils from the humid tropics. Thus, the influence of soil water content on retention and mineralization of the herbicide 2,4‐D [(2,4‐dichlorophenoxy)acetic acid], as well as its distribution on the aggregate fractions (diameter >150, 53 to 150, 20 to 53, 2 to 20, and <2 μm) were evaluated. Soil samples from a Xanthic Dystrudox, a Xanthic Acrudox, and two Rhodic Acrudoxes were collected and moisture was adjusted to 25, 50, and 75% maximum water holding capacity. 14 C 2,4‐D was then applied and the flasks incubated in a semi‐dark, climatized room at 22 ± 2°C, for 42 d. 2,4‐D mineralization was determined weekly. After three extractions with a 0.01 mol L −1 CaCl 2 solution, soil aggregates were sonicated using water as a dispersing agent. 2,4‐D retention increased with soil moisture. Higher soil moisture favored 2,4‐D retention in aggregates < 20 μm, ratifying the hypothesis of 2,4‐D diffusion to less accessible soil sites. 2,4‐D mineralization was also enhanced with soil moisture. For the Acrudoxes, in which the clay fraction was less dispersed in water, 2,4‐D retention was higher in larger aggregates (>53 μm), having higher total organic C (OC) content and higher degree of humification of its organic matter (OM).