Potassium mineral fertilizers from upgraded waste streams : as effective as traditional mineral fertilizer?

Sammanfattning

Recirculating potassium from waste could limit our dependence on finite potash extraction. This study tested a potassium sulphate (SOP) made by EasyMining, in a pilot-scale process turning ashes into valuable fertilizer. The study tested SOP originating from the ash of incinerated poultry litter and straw, plus two other EasyMining products (glaserite and untreated ash), against a commercial SOP. This was done in a seven-week greenhouse pot trial with perennial ryegrass. Eleven treatments (including a control and several K rates) were applied with four replicates. Pots used coarse sand blended with peat and a full non potassium (K) nutrient solution to isolate K effects. Measured parameters were dry matter yield, plant K concentration and uptake, cadmium (Cd), zinc (Zn) and copper (Cu) uptake. Mineral Fertilizer Equivalent (MFE) was calculated by comparing K uptake and DM yield between treatments. Overall biomass did not differ significantly between treatments. No significant differences in K uptake could be determined between control, commercial SOP and the tested fertilizers in the lower K rates which were given to the tested fertilizers. MFE estimates were inconsistent and unreliable, particularly those based on uptake. The experiment failed to create a clear potassium limitation: controls and K fertilized pots showed similar growth, likely because the substrate released more K than anticipated. This undermined the ability to draw firm agronomic conclusions about fertilizer equivalence. Cadmium uptake was higher in ash-treated pots versus glaserite at the medium rate, indicating that EasyMining's processing can reduce Cd content. Zn and Cu uptakes showed no treatment effects. The study offers indications that EasyMining's process can lower heavy metal risks. A repeat study using a lower K growing medium, refined dosing and pre trial soil K testing, and ideally multiple harvests is recommended to get more accurate information about the agronomic performance of recycled potassium fertilizers.