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Phosphorus pool responses under different P inorganic fertilizers for a eucalyptus plantation in a loamy Oxisol

Foltran, Estela Covre, Rocha, José Henrique Tertulino, Bazani, José Henrique, Gonçalves, José Leonardo de Moraes, Rodrigues, Marcos, Pavinato, Paulo, Valduga, Giancarlo Ribas, Erro, Javier, Garcia-Mina, Jose M.
Forest ecology and management 2019 v.435 pp. 170-179
Eucalyptus, Oxisols, bioavailability, citrates, forest stands, fractionation, oxalates, phosphorus, phosphorus fertilizers, plant nutrition, rock phosphate, superphosphate
Phosphate fertilizers play an important role in plant nutrition. Different P fertilizer sources such as high-solubility (simple superphosphate, SSP), low-solubility (rock phosphate, RP) and complex superphosphate (CSP) are available for plant supplementation. The objective of this study was to investigate the short- and long-term redistribution of soil P after application of different P sources at establishment of an Eucalyptus forest stand. We carried out two experiments to identify the short- and long- term changes in a Brazilian Oxisol. To property identify the P pools in different times, Hadleýs fractionation methodology was applied to a long-term studies and citrate and oxalate to short-term. From zero to 180 days, the soluble P fractions were not altered in the non-fertilized treatment. Under SSP, a slight increase in this P fraction was found until 30 days, followed by a decrease in later evaluations. During the same period, a slight reduction in Pi extracted by citrate and oxalate was found under the control and a large reduction (approximately 50%) under the SSP treatment. Intermediate behavior was observed under the CSP and RP treatments, whereas there was an increase in P-citrate and P-oxalate until 30 days followed by a reduction afterwards. These results suggest that this pool comprises a potential bioavailability of P to plants. Different fertilizer sources did not increase the most recalcitrant P pool. However, different sources increased the organic P pool, mainly organic moderately labile P at long-term evaluations. Organic labile pools showed a fertilizer-specific response where CSP and RP increased respectively by 43% and 41% during the first year, and decreased to 39% in CSP treatment and 50% in RP treatment during the third year. 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 residual P in order to maintain their nutritional demands.