Phosphorus sorption, desorption and resorption by soils of the Brazilian Cerrado supporting eucalypt

✍ Scribed by Nairam F. Barros; Filho; N.B. Comerford; Nairam F. Barros

• Publisher: Elsevier Science
• Year: 2005
• Tongue: English
• Weight: 224 KB
• Volume: 28
• Category: Article
• ISSN: 0961-9534
• DOI: 10.1016/j.biombioe.2004.08.005

✦ Synopsis

Oxisols of the Brazilian Cerrado are highly weathered phosphorus deficient soils, on which eucalypt is increasingly being grown as a source of carbon and energy for steel manufacturing. Phosphorus (P) fertilization is a necessary practice to assure adequate eucalypt production; therefore, an understanding of cycling by inorganic soil P should lead to efficient P management and more accurate modeling of P bioavailability. Since sorption and desorption reactions control inorganic P bioavailability, the purpose of this study was to contrast P sorption, desorption and subsequent resorption for a range of Cerrado soils. Its specific objectives were to determine (i) if desorption and resorption show the same hysteresis shown by sorption and desorption, (ii) if K d values of resorption and desorption for Cerrado soils are dependent on the soil's clay content and (iii) if resorption and desorption K d values are a function of the amount of labile P on the soil surface. Three levels of P were sorbed onto four Cerrado soils with clay contents between 13% and 81%. Phosphorus desorption was measured using anion-exchange membranes. Sorption was a function of soil clay content, and a pedotransfer function for the soil partition coefficient was calculated with an r 2 =0.99. Desorption and resorption were dependent on both the clay content of the soil (r 2 =0.59-0.99) and the amount of sorbed labile P. Pedotransfer functions for each of these processes depend on accurate measurement of the inorganic P that responds to disequilibria exchange. Desorption and resorption were not hysteretic; yet desorption was hysteretic with the original sorption isotherm. This suggests the question: how useful are commonly produced sorption isotherms?