Phosphorus availability under annual cropping, alley cropping, and multistrata agroforestry systems |
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Authors: | L. T. Szott G. Melendez |
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Affiliation: | (1) Soil Science Department, North Carolina State University, P.O. Box 7619, Raleigh, North Carolina 27695-7619, USA;(2) Centro de Investigaciones Agronomicas, Universidad de Costa Rica, San Pedro Montes de Oca, Costa Rica |
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Abstract: | The hypothesis that agroforestry systems conserve P in forms that are more crop-available than those found in annual cropping systems was tested on two tropical sites: an Ultisol in Yurimagas, Peru, and a volcanically derived Inceptisol in Turrialba, Costa Rica. In both sites, the Hedley P fractions were compared in annual cropping, alley cropping, multistrata agroforestry and old forest systems. On the Ultisol, the effect of P fertilization on the soil P fractions was also examined. Under non-fertilized conditions, the multistrata and forest systems maintained more and a greater proportion of P in plant-available resin form than the annual or alley cropping systems. Greater resin P was associated with greater amounts and percentages of P in bicarbonate fractions and less P in residual fractions. The latter may be caused by greater and more temporally constant organic matter additions, less mineralization of labile soil organic matter fractions due to lower soil temperatures, and the long-term mobilization of residual P due to P immobilization in the biomass of the multistrata or forest systems. With P fertilization, resin P was related to inorganic P fractions. However, resin P increased even more when inorganic P fertilizers were combined with organic residue additions. This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | Costa Rica Hedley P fractions humid tropics inceptisol Peru ultisol |
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