Response of Perennial Ryegrass/Kentucky Bluegrass Mixture to Mulching Mower Under Different Nitrogen Fertilisation Levels

Mowing is a fundamental turfgrass management practice where grass clippings are either removed or returned to the canopy. The process of clipping return is referred to as mulching, which can create several advantages for low-maintenance/sustainable turfgrass systems. The objective of this research was to evaluate the effect of mulching on a perennial ryegrass (Lolium perenne L.) and Kentucky bluegrass (Poa pratensis L.) turfgrass mixture under four different nitrogen fertility rates (0, 80, 120, and 200 kg N ha⁻¹ year⁻¹). Turfgrass quality and colour, as well as NDVI and percent green turfgrass cover, were evaluated bi-weekly. Turfgrass canopy height was measured before and after mowing in order to determine clipping dry matter (DM) production and clipping nitrogen (N) content. Mulching had a positive effect on turfgrass visual quality and colour, NDVI, and percent green turfgrass cover. The impact of mulching was more noticeable during reduced growth periods (summer and winter). The largest differences occurred in July 2023, when turfgrass visual quality for mulching and non-mulching was 7 and 4.5, respectively. In January 2023, turfgrass colour, NDVI, and percent turfgrass cover was 7.1 and 6.1, 0.8 and 0.72, and 60% and 50% for mulching and non-mulching, respectively. The N content observed within turfgrass clippings from mulched plots was enhanced by the increase of N fertilisation rates. The difference between mulched and non-mulched plots receiving 200 kg N ha⁻¹ year⁻¹ was 2.5 kg N m⁻², while the difference between non-fertilised mulched and non-mulched plots was 2.2 kg N m⁻². Mulching helps maintain turfgrass quality year-round, especially in winter, with greater benefits under low nitrogen input. It supports reduced fertilisation without affecting performance.