Effects of acidic phosphorus-rich biochar from halophyte species on P availability and fractions in alkaline soils

Abstract

Conditioning alkaline soil with acidic phosphorus-rich biochar might contribute to achieving sustainable phosphorus (P) use and residue management. In this study, acidic phosphorus-rich biochar was prepared from halophyte species biochar (HBC) by the modification of H3PO4 (P-HBC) and H4P2O7 (PA-HBC). The P combination method and fractions in biochars were characterized, and the effects of biochars on P fractions in different types of alkaline soil were examined with incubation experiments. The results showed that the pH values of P-HBC (3.31) and PA-HBC (2.17) decreased significantly, and the total P content increased to 4.66 g·kg− 1 and 5.24 g·kg− 1, respectively. The spectral analysis confirmed the doping of P and acid groups in biochar. The addition of modified biochars in alkaline soils will makes the soil tend to be neutral. Sequential extraction of soil P confirmed that biochars application facilitated the transformation of stable P into active fractions, with greater effects from modified biochars than HBC. Activation mechanism of biochar to soil P fractions varies from soil types. Overall, acidic phosphorus-rich biochars can be employed to improve alkaline soil properties and increase P activity.