Phosphorus speciation and distribution in a variable‐charge Oxisol under no‐till amended with lime and/or phosphogypsum for 18 years

Abstract

AbstractLong‐term management with lime and/or phosphogypsum (PG) can change phosphorus (P) forms across the soil profile. In this study, we used synchrotron‐based spectroscopy and sequential chemical fractionation to investigate P chemical species after long‐term (18 years) application of amendments in a subtropical Oxisol. The availability of nutrients increased with the combined use of lime and PG and a stratification of attributes was identified due to long‐term broadcast applications. X‐ray absorption near edge structure (XANES) spectra profiles revealed the predominance of P bounded to haematite (Hm) (48% on average) and also P bound to kaolinite (32% on average) species. Low proportions (16%) of calcium‐phosphates in the uppermost soil layer (0–5 cm) were found in the treatment that received high calcium (Ca) inputs by lime and PG broadcast. Few correlations were identified between the proportions of P species obtained by XANES and P fractions operationally defined by sequential chemical fractionation (SF). Our results suggest that P‐species bound to kaolinite can store stable P forms, which correlated (p < 0.05) with the residual P fractions obtained by SF, highlighting the importance of kaolinite as a legacy P store in Oxisols.Highlights Lime and phosphogypsum broadcast under no‐till improve soil fertility and P availability. Labile and moderately labile P fractions were the only ones influenced by lime and/or phosphogypsum. Proportions among P bounded to Fe‐ and Al‐(hydr)oxides with different structural may be affected by long‐term Al‐suppressors. P‐species bounded to kaolinite may store stable P forms in Oxisols.