AbstractThe concentration of mineral elements in herbage from permanent swards of mixed species composition (predominantlyAgrostisspp.,Holcus lanatus, Festuca rubra, Lolium perenne, Poaspp., etc.) was compared with that from sown perennial ryegrass (Lolium perenne) at two fertilizer rates (0 and 300kg N ha−1year−1, both with P and K) and withL. perennel Trifolium repens(at 0 N with P and K). The investigation was conducted over four years at sixteen contrasting sites in England and Wales. Herbage samples for mineral analysis were taken at first and fourth harvests (May and August) each year from plots under 4‐weekly cutting. There was a wide degree of variation between sites, particularly for concentrations of Ca, Mg, Na and all trace elements analysed. Herbage fromL. perennereseeds had significantly higher concentrations of Ca, Mg, Na, Co and S, but K, Mo, Zn, Cu and P were generally lower than in the permanent swards.L. perennel T. repensswards had the highest concentration of major cations, but trace element levels were generally intermediate between those for 0 N permanent andL. perenneswards. Fertilizer N reduced concentrations of Ca, Mn, Mo and S, and increased Mg, Na and Zn, with no consistent effects on K, Co and Cu. Herbage at harvest 4, compared with harvest 1, had higher Ca, Mg, Na, Mn, Zn and S. Permanent andL. perenneswards responded similarly to fertilizer N and between harvest dates. Results are discussed in relation to previous reports of botanical and fertilizer effects on mineral concentrations, and the mineral requirements of livestock. Changes in mineral concentration resulting from reseeding permanent swards are considered unlikely to increase mineral‐related livestock disorders, and in many cases could be beneficial, though problems might arise on sites where some elements, e.g. Cu and Mg,