Leaching of Phosphorus and Cadmium in Soils Amended with Different Bone Chars

Abstract

The benefits of bone char (BC) application may include both the mobilization of P for plant nutrition and immobilization of contaminant Cd in the soil. However, previous studies were conducted under equilibrium conditions that do not adequately reflect field conditions. Therefore, the objective was to study the effect of BC, surface-modified BC (BC plus ) and sulfur-enriched activated char (AC S ) application at different particle sizes on P-and Cd-mobilization under non-equilibrium conditions in a combined incubation-leaching experiment. Two soils each with the treatments (i) BC, (ii) BC plus , (iii) BC þ AC S , (iv) control (0 mg P kg À1 soil), and (v) AC S were leached five times during 70 days incubation. Over the complete incubation P-contents in leachates were significantly increased by BC and BC plus of 0.5-1 mm size. P-release from BCs was larger under non-equilibrium condition in this experiment compared with a previous continuous incubation experiment. AC s application reduced the P-release from BC of all particle sizes. The lowest leachate Cd-concentrations were found in soils amended with the smallest BC particles. Addition of BC plus and AC S significantly increased Cd leaching and the highest amounts of Cd were leached at the smallest particle size. In conclusion, the 0.5-1 mm size class of BCs performed best and should be introduced in practical agriculture using standard machinery.

Bone char effects on soil: sequential fractionations and XANES spectroscopy

“…This is consistent with the study of according to which the BC application (< 90 µm BC thoroughly mixed in soil) significantly increased the insoluble P proportion (H 2 SO 4 -P). Additionally, our study confirmed previous findings concerning the effect of particle sizes on the P release from BCs (Morshedizad and Leinweber, 2017) and consequently the P status of treated soils (Ma and Matsunaka, 2013). Sequentially extracted P contents increased with the decreasing size of BC particles whereby BC plus treatments appeared more dependent on particle size than BC treatments.…”

“…These results imply that considerable changes in P speciation were more attributed to pH reductions, and accordingly leaching losses of solubilized P forms compared with P enrichment by BC plus dissolution. This is supported by results from a previous publication in which two particle sizes of BC plus gave a significant rise in the leached P concentration after 1, 5, 13, 34 and 70 days of incubation along with reductions in soil pH (Morshedizad and Leinweber, 2017). This is in line with Sato et al (2005) who found that increasing soil pH in a naturally acidic soil (pH = 4.32) was an effective approach to minimize P leaching, while pH decrease resulted in the transformation of stable to soluble and more leachable P species.…”

“…The results indicated that the P uptake, ryegrass yield and apparent nutrient recovery efficiency (ANR) of BC plus treatments exceeded those of the BC and control treatments and increased to values comparable with triple superphosphate (TSP) fertilizer (Zimmer, D. and Panten, K., personal communication). The addition of BC and BC plus did not significantly change the bulk soil pH, although local acidification around BC plus particles (pH 4.9; Morshedizad and Leinweber, 2017) can probably lower soil pH in small-scale areas compared to BC treatments (pH about 8).…”

“…All compiled data in this study are published in figures and tables. Detailed primary data, including the acquired XANES spectra, are saved and published in the BonaRes Data Centre and available at: https://doi.org/10.20387/BonaRes-PDY6-HHGS (Morshedizad and Leinweber, 2017).…”

“…The P concentrations in collected leachates were measured using inductively coupled plasma-optical emission spectrometry (ICP-OES). The outcomes of the leaching experiment were described in Morshedizad and Leinweber (2017). After the incubationleaching experiment, the treated soil samples were carefully removed from the glass columns and air-dried, and the BC-BC plus particles were manually separated from the soils very gently.…”