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Applied and Environmental Soil Science
Volume 2015 (2015), Article ID 720167, 8 pages
http://dx.doi.org/10.1155/2015/720167
Research Article

Effectiveness of Extractants for Bioavailable Phosphorus in Tropical Soils Amended with Sewage Sludge

1Department of Soil Science, University of São Paulo (ESALQ/USP), P.O. Box 9, 13418-900 Piracicaba, SP, Brazil
2Department of Technology, São Paulo State University, 14884-900 Jaboticabal, SP, Brazil
3São Paulo State Agribusiness Technology Agency, 13400-970 Piracicaba, SP, Brazil
4Department of Soil Science, ESALQ/USP, Brazil

Received 15 August 2014; Revised 17 October 2014; Accepted 22 October 2014

Academic Editor: Rodrigo Studart Corrêa

Copyright © 2015 Roberta Corrêa Nogueirol et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Urban wastes such as sewage sludge can be an economically viable alternative source for providing macro- and micronutrients to plants in tropical conditions. Sewage sludge is normally rich in phosphorus (P), which is present in soils mainly in organic forms, so that it is very important to establish methods for estimating its availability to plants. This study aimed to test three extractants that simulate P-uptake by maize (Zea mays) cropped in plots after 13 consecutive years of fertilization with sewage sludge, in a cycle of fertilized sugarcane (Saccharum L.) amended with sewage sludge and organic compost. Soil samples were collected at depths of 0–10, 10–20, and 20–40 cm in March 2010 from the two experimental areas. Soil P was extracted via ion exchange resin, Mehlich-I, and 0.025 M H2SO4 and determined via colorimetry. Maize and sugarcane diagnostic leaves were collected in the experiments, subjected to nitric-perchloric digestion, and the leaf-P content was determined via colorimetry. No significant correlations were found between phosphorus extracted from soils and phosphorus concentrations in diagnostic leaves. Resin extracted larger amounts of P in the short-term experiment, while acidic extractants yielded larger amounts in the long-term experiment.