Phosphorus Sorption by Biochars and Soil-Biochar Mixtures.

Phosphorus Sorption by Biochars and Soil-Biochar Mixtures

ABSTRACT 

A better understanding of the sorption characteristics of biochars which can influence the partitioning behavior of plant essential nutrients such as P (phosphorus) in soil has been limited. P can be either limited in soil or become an environmental concern at higher concentrations in soil solution. Knowledge of P retention and release mechanisms when applying carbon-rich amendments such as biochar to soil is needed. The objectives of this study were to quantify the P sorption and lability potential of corn stover (Zea mays L.), Ponderosa pine (Pinus ponderosa Lawson and C. Lawson) wood residue, and switchgrass (Panicum virgatum L.) biochars, and the impact of biochar application to soils with different chemical characteristics on P sorption and lability. Sorption of P by biochars and soil-biochar mixtures was studied by fitting the equilibrium and sorbed concentrations of P using Freundlich and Langmuir isotherms. Biochar produced from Ponderosa pine wood wood residue had very different chemical characteristics than corn stover and switchgrass. Corn stover biochar had the highest P sorption  followed by switchgrass biochar and Ponderosa pine wood residue biochar. Ponderosa wood residue biochar had relatively higher labile P followed by switchgrass biochar  and corn stover biochar. The incorporation of biochars to acidic Grummit soil at 40 g kg^-1 increased the equilibrium P concentration (reduce the sorption) and the lability of sorbed P. In calcareous Lenghei soil, the sorption of P was significantly increased by especially alkaline biochars (corn stover and switchgrass biochars) as was the lability of sorbed P.

Keywords: biochar, P sorption, Labile P, feedstock, corn stover (Zea mays L.) biochar, Ponderosa pine (Pinus ponderosa Lawson and C. Lawson) wood residue biochar, switchgrass (Panicum virgatum L.) biochar, Ustorthents, and Eutrudepts