Labile and Non-Labile Fractions of Phosphorus and Its Transformations in Soil under Eucalyptus Plantations, Brazil

Author(s)

Costa, Marlon Gomes ^[1] ; Gama-Rodrigues, Antonio Carlos ^[1] ; de Moraes Goncalves, Jose Leonardo ^[2] ; Gama-Rodrigues, Emanuela Forestieri ^[1] ; da Silva Sales, Marcus Vinicius ^[1] ; Aleixo, Seldon ^[1]

Affiliation

^[1] Univ Estadual Norte Fluminense, UENF, Lab Solos, BR-28013602 Campos Dos Goytacazes - Brazil

^[2] Univ Sao Paulo, ESALQ, Dept Ciencias Florestais, BR-13418900 Piracicaba - Brazil

• Document type: Journal article
• Source: FORESTS; v. 7, n. 1 JAN 2016.
• Web of Science Citations: 15

Abstract

Phosphorus (P) is the main limiting nutritional factor in the cultivation of Eucalyptus in Brazil. Despite this, little is known about the P fractions and dynamics in Eucalyptus soils in tropical regions. The aims of this study were (1) to evaluate the distribution of labile and non-labile fractions of P in soil in 10 sites of Eucalyptus in the state of SAo Paulo, Brazil and (2) to determine the interactions among the P fractions and to identify which fractions act as sinks or sources for the available P fraction. The P fractions were separated using the Hedley sequential extraction method, and the P transformation processes were evaluated via structural equation modeling. The labile P (resin-Pi + Pi and Po in NaHCO3) varied between 6% and 16%, the moderately labile P (Pi + Po in NaOH) varied between 28% and 40%, the occluded P (Pi + Po in Sonicate + NaOH) varied between 6% and 19%, the P associated with Ca (HCl-Pi) varied between 0.4% and 3% and the residual-P varied between 35% and 47%. The hypothetical structural model of soil P cycle was composed of four P pools (latent variables): the organic pool, occluded pool, inorganic pool, and available pool. The structural model was adequate to identify functional pools of P in soil, and to identify transformation processes of P based on the source-sink relationships. The available P pool was highly dependent on inorganic and occluded pools and the organic pool acted predominantly as a sink of P on available and inorganic pools. The results reinforce the high level of recalcitrance of the organic pool and the fact that Eucalyptus plants must access pools of limited-availability P to meet their nutritional demands. (AU)

• FAPESP's process: 10/16623-9 - Ecological intensification of eucalyptus plantations by association of nitrogen fixing leguminous tree species
• Grantee: José Leonardo de Moraes Gonçalves
• Support Opportunities: Research Projects - Thematic Grants