Fe/Al (hydr)oxides engineered biochar for reducing phosphorus leaching from a fertile calcareous soil

Excessive input of phosphate fertilizer into agricultural soils has caused critical environmental concerns due to high phosphorus (P) accumulation in farmland and P leaching into subsurface drainage. In this study, an Fe/Al (hydr)oxides modified biochar (FA-BC) was fabricated from corn straw via a wet-precipitation method and utilized to reduce P leaching from a fertile calcareous soil. Spectroscopic techniques demonstrated that the FA-BC exhibited a higher oxidation resistance than the raw BC due to oxide impregnation on the BC surface. The maximum Langmuir P adsorption capacities (393 and 528 mg kg(-1)) of the BC (4%, w/w) and FA-BC (4%, w/w) treated soils demonstrated a more efficient P adsorption capacity of the FA-BC. Application of the 2% (w/w) FA-BC also significantly reduced the leaching of total P (81.3%) from the soil column, while maintained an appropriate level of bioavailable P in the soil for sustaining plant growth. The chemical sequestration test and in-situ P k-edge XANES analyses of the FA-BC incubated soils revealed that the labile CaeP fractions were transformed into stabilized Fe/AleP complexes. The increased soil pH, a higher degree of soil P saturation, and intensive interaction between P and Fe/Al (hydr)oxides also contributed to the superior ability of the FA-BC amended soils towards P retention. This study provided field-relevant implications for the design and application of engineered biochar for green and sustainable improvement of agricultural soils. (c) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study developed an Fe/Al (hydr)oxides modified biochar (FA-BC) to reduce P leaching in calcareous soils, demonstrating its higher efficiency in P adsorption compared to raw biochar. The application of FA-BC significantly decreased total P leaching, while maintaining adequate levels of bioavailable P in the soil. Chemical sequestration tests and analyses further showed the transformation of labile Ca-P fractions into stabilized Fe/Al-P complexes, highlighting the superior P retention ability of FA-BC amended soils.