Biochar Chemistry in a Weathered Tropical Soil: Kinetics of Phosphorus Sorption

Marina Moura Morales,Nicholas Brian Comerford,Daniel Carneiro De Abreu,Iraê Amaral Guerrini,Maurel Behling

doi:10.3390/agriculture11040295

Abstract

The phosphorus (P) chemistry of biochar (BC)-amended soils is poorly understood. This statement is based on the lack of published research attempting a comprehensive characterization of biochar’s influence on P sorption. Therefore, this study addressed the kinetic limitations of these processes. This was accomplished using a fast pyrolysis biochar made from a mix of waste materials applied to a highly weathered Latossolo Vermelho distrofico (Oxisol) from São Paulo, Brazil. Standard method (batch method) was used. The sorption kinetic studies indicated that P sorption in both cases, soil (S) and soil-biochar (SBC), had a relatively fast initial reaction between 0 to 5 min. This may have happened because adding biochar to the soil decreased P sorption capacity compared to the mineral soil alone. Presumably, this is a result of: (i) Inorganic phosphorus desorbed from biochar was resorbed onto the mineral soil; (ii) charcoal particles physically covered P sorption locations on soil; or (iii) the pH increased when BC was added SBC and the soil surface became more negatively charged, thus increasing anion repulsion and decreasing P sorption.

Highlights

More than 3 billion people live in the tropics, which was larger than the world’s population in 1950 [1]
The fast pyrolysis BC was developed from a sequence of three distinct BCs produced by sawdust of mixed woods and leaves of elephant grass (Pennisetum purpureum Schumach) and sugar cane (Saccharum officinarum)
The kinetics of sorption in the presence of BC showed that the soil solution P concentrations remained higher, which made P more bioavailable for a longer period of time

Summary

Introduction

More than 3 billion people live in the tropics, which was larger than the world’s population in 1950 [1]. They rely on the soil to provide food, fiber, and bioenergy. Of the 134 million hectares in humid, tropical South America that are potentially arable, 73 million are located in Brazil [1]. The majority of these acres suffers from some level of phosphorus (P) deficiency due to low native soil P content and high P fixation capacity [2]. The weathered nature of tropical soils promotes P fixation by Fe and Al oxides which, when chemisorbed to the soil, are not released by simple equilibrium desorption [3]

Methods

Results

Conclusion