Long-term biochar addition significantly decreases rice rhizosphere available phosphorus and its release risk to the environment
Hao Chen , Jiahui Yuan , Guanglei Chen , Xu Zhao , Shenqiang Wang , Dengjun Wang , Lei Wang , Yujun Wang , Yu Wang
Biochar ›› 2022, Vol. 4 ›› Issue (1)
Phosphorus (P) availability, diffusion, and resupply processes can be altered by biochar addition in flooded rice rhizosphere, which controls the risk of P release to the environment. However, there are few in-situ investigations of these rhizospheric processes and effects. To explore the effects of biochar addition on soil P availability, high-resolution dialysis (HR-Peeper), diffusive gradients in thin films (DGT), and zymography techniques were used to provide direct evidence in the rice rhizosphere at the sub-millimeter scale. Long-term (9-years) field and greenhouse pot experiments demonstrated that biochar addition notably decreased the soluble/labile P and Fe concentrations in rice rhizosphere (vs. no biochar addition; CK) based on the results of Peeper, DGT, and two-dimensional imaging of labile P fluxes. DGT-induced fluxes in the soil/sediment (DIFS) model and sediment P release risk index (SPRRI) further indicated that biochar addition decreased the diffusion and resupply capacity of P from soil solid to the solution, thereby decreasing P release risk to the environment. These processes were dominated by Fe redox cycling and the hydrolysis of Al (hydro)oxides that greatly increased the unavailable P (Ca-P and residual-P). Additionally, greenhouse pot experiments (without additional biochar) showed that the previous long-term biochar addition significantly increased soil phosphatase activity, due to an adaptive-enhancing response to P decrease in the rhizosphere zone. The in-situ study on the biogeochemical reactions of P in the rice rhizosphere may provide a new and direct perspective to better evaluate the biochar addition and potential benefits to agricultural soils.
| • | Long-term (9-years) biochar amendment field and greenhouse pot experiments were conducted. |
| • | DGT/DIFS/SPRRI were used to in-situ assess P availability, resupply, and release risk to the environment. |
| • | Long-term biochar addition significantly decreased rice rhizosphere available P and its release risk to the environment. |
| • | Fe/Al-P and unavailable P dominated the mobility and resupply of P. |
The National Key Research and Development Program of China(2021YFD1700802)
The Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No. XDA28090300)
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