GST on potassic mineral and chemical fertilisers set at a concessional rate under the cited notification, affecting Schedule I classification. GST applies a concessional 5% rate to mineral or chemical potassic fertilisers under Schedule I, excluding goods clearly not intended for use as fertilisers; the rate and effective date are specified by the integrated tax rate notification issued on 17-09-2025 and operative from 22-09-2025.