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

Forests

Marlon Gomes Costa²  Antonio Carlos Gama-Rodrigues²  José Leonardo de Moraes Gon๺lves¹  Emanuela Forestieri Gama-Rodrigues²  Marcus Vinicius da Silva Sales²  Seldon Aleixo² 

[1] USP, Departamento de Ciências Florestais , Universidade de São Paulo, ESALQ, Piracicaba CEP 13418-900, Brazil;UENF, Laboratório de Solos, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes CEP 28013-602, Brazil;

关键词: tropical forest soils;    organic P pool;    inorganic P pool;    occluded P pool;    structural equation modeling;   

DOI  :  10.3390/f7010015

来源: mdpi

【 摘 要 】

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 São 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.

【 授权许可】

CC BY   
© 2016 by the authors; licensee MDPI, Basel, Switzerland.