The continuous application of biochar in field: effects on P fraction, P sorption and release

It is unclear how biochar can affect P availability in soil, especially in field under continuous application. In this study, a field experiment was conducted to study the effect of 2-years application of biochar on P availability, P fractionation, P sorption and release in a clay soil. The biochar in this study was produced from rice straw through pyrolysis at 700 degrees C. As compared with no fertilizer treatment (CK) and chemical fertilizer treatment (CF), the biochar application with chemical fertilizer treatment (BCF) significantly increased total P and available P content in soil. And BCF treatment significantly increased resin P, NaHCO3-extracted P, Fe/Al-Po and HCl-extracted P but decreased Fe/Al-Pi and residual P as compared with CF treatment. Surprisingly, BCF treatment showed higher sorption capacity and release capacity of soil P than that of CF treatment. These results imply that continuous application of biochar for 2-years in field may adsorbed P through physical sorption rather than chemical reaction and then improve P availability in soil. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The application of biochar in conjunction with chemical fertilizer significantly increased total and available phosphorus content in soil, as well as enhanced sorption and release capacity of phosphorus. Surprisingly, the biochar treatment showed higher sorption and release capacity compared to the chemical fertilizer treatment, implying physical sorption may be the main mechanism for improving phosphorus availability in soil after continuous 2-years application in the field.