Exploring the use of Dicranopteris pedata ash as a rare earth fertilizer to Ipomoea aquatica Forsskal

This study examines a new method to dispose the biomass of a rare earth elements (REE) hyperaccumulator, Dicranopteris pedata, as a REE containing additive of a basal fertilizer for agricultural application. The D. pedata laminas were calcinated to fabricate ashes. The total REE content was 2.65 % for AshDp500, and 4.12 % for AshDp815, respectively. However, as for the heavy metals, Cd or Pb, a higher content could be found in AshDp500 than in AshDp815. The elemental contents of D. pedata ashes are qualified for fertilizer application. Pot experiments were then conducted to investigate the effects of AshDp815 on both the yield and quality of Ipomoea aquatica Forsskal grown in a yellow brown earth, or in a red soil. The application of the ashes increased the I. aquatica height, biomass, vitamin C, soluble protein, and soluble sugar contents, but decreased the I. aquatica nitrate and free amino acids contents. Furthermore, none of the microelements of I. aquatica leaf exceeded the Chinese national standard. The observations indicate the favorable effect of using D. pedata ash on the growth of I. aquatica which is most likely the result from the fertilizer effects of both macroelements and REE present in the ash.