AbstractPlots of an established perennial ryegrass sward (cv. Talbot) fertilized with 100 or 300 kg N ha−1 were harvested with one of three plot mowers; an Agria with 38‐mm finger spacing and an Allen Mayfield with 38‐mm finger spacing or 78‐mm finger spacing. The choice of mower was arranged factorially with four post‐harvest treatments: no post treatment; a second (cleaning) cut using the same mower and cutting in the same direction as the first (sampling) cut; a cleaning cut using the same mower, but in the opposite direction to the sampling cut; and a cleaning cut using a rotary mower. Sward productivity as organic matter (OM) was measured over four harvests at 6‐ to 7‐week intervals. The Agria mower resulted in 12·3 and 15‐9% more OM yield than the Allen Mayfield fitted either with knife‐bars at a similar spacing, or with wider‐spaced fingers, respectively. Yield of OM in the subsequent cut was reduced when a cleaning cut was taken; particularly when it was taken in the opposite direction to the sampling cut or when using a rotary mower.