You can use a vinegar and water solution or a muriatic acid and water solution to remove fertilizer stains from concrete. Muriatic acid may etch concrete, however, so it should only be used if the vinegar and water solution does not work. You will need water, vinegar or muriatic acid and a scrubbing brush or sponge. The minerals in fertilizer stains are not water-soluble and thus cannot be simply removed with water and scrubbing; they need to be treated with an acid solution.Continue Reading
Use a clear white vinegar, and dilute it 50:50 with water.
Apply the vinegar and water solution to the stains several times.
Scrub the stain between each application of the solution, and see if the fertilizer stains are being removed. Rinse the area, and wash the fertilizer stain away.
Muriatic acid is much stronger than vinegar and should be diluted with water 40 to 1 rather than half and half. Use the same process with the muriatic acid as with the vinegar solution: apply, scrub lightly and rinse. Repeat as necessary to fully remove the fertilizer stains.