Phytoavailability of Al and Zn in household ash-amended soils

Fuel combustion in households leads to the generation of ashes, and the effect of such wastes on plant growth and Al and Zn uptake is poorly understood. Therefore, in this study, two soils (A-1: sandy loam and B-1: sandy soils) were amended with two ashes (10 %) after coal-wood co-combustion in households (ASH1; ASH2). The control and ash-amended control soils were subjected to a pot experiment where Raphanus sativus and Spinacia oleracea were cultivated. The mobilization of Al and Zn in soils was assessed in the leaching experiment with Pseudomonas fluorescens. The study reveals that ashes do not significantly affect the biomass of Raphanus sativus. In turn, both ashes increase the biomass of Spinacia oleracea regardless of the soil used (up to 3049 mg DW in biomass of leaves in the ash-amended soil compared to the control soil where the biomass is 1180 mg DW). The highest Al translocation factor (TF) is noted for Raphanus sativus in the ash-amended soil (0.84; with ASH1), whereas for Zn, for Spinacia oleracea (3.03) also in soil amended with ASH1. The Al and Zn mobilization with Pseudomonas fluorescens is higher in soils from all treatments compared to the sterile growth medium as the control. Furthermore, bacteria can mobilize Al in the short term in ash-amended soil from the river valley (up to 1.18 % in the ash-amended soil) indicating that even the long-term mobilization of Al and Zn by the bacteria is possible. Therefore, household ashes are not recommended for soil amelioration and fertilization.