Potassium in silicon-rich biomass wastes: A perspective of slow-release potassium sources

Many plant species that are known as silicon (Si) accumulators can form a so-called phytolith (silicified structure) within their organs. Together with organic matter, potassium (K) has also been found in phytolith structures (phytK). Annually, billions of tons of Si-rich biomass wastes are cycled in agricultural and natural systems worldwide. However, the fate of the phytolith and its phytK have not been fully understood. This study aims to examine the dynamic release of phytK from phytoliths of reed, rice straw, maize and sugarcane leaf samples. Phytoliths obtained from the biomasses by performing heat treatment at 600 degrees C were used for batch kinetic experiments. The phytK was found to have 26.3 +/- 10.6, 98.9 +/- 17.4, 24.9 +/- 14.8 and 58.8 +/- 13.9 mg Kg(-1) for the reed, rice straw, sugarcane and maize leaves, respectively. These phytK amounts comprised at least >45% of the total K budgets in the biomasses and they were observed to be gradually released with time. The retardation of phytK was tightly related to the dissolution rate of phytoliths. The findings highlight that phytoliths carry certain amounts of K, potentially serving as a slow-release K source for soil and crops. Additionally, this short communication suggests a premise for the development of refinery strategies or extending the range of agronomic options for billions of tons of Si-rich biomass wastes worldwide. (c) 2022 Society of Chemical Industry and John Wiley & Sons, Ltd