Drought Resistance and Recovery of Kentucky Bluegrass (Poa pratensis L.) Cultivars under Different Nitrogen Fertilisation Rates

Kentucky bluegrass (Poa pratensis L.) is one of the most popular cool-season turfgrass species. However, little is known about the effects of N supply on its resistance to drought stress. The objective of this study was to assess the effects of acute drought followed by a recovery period on four Kentucky bluegrass cultivars (‘Barduke’, ‘Brooklawn’, ‘NuBlue Plus’ and ‘Marauder’) and one tall fescue (‘Rhambler SRP’) under two different nitrogen fertilisation rates (100 or 200 kg N ha−1 yr−1). The study was conducted over two years in a rain-out structure to control water input in spring and summer. The cultivars were subjected to a drought stress phase (absence of irrigation) followed by a recovery phase (weekly irrigation with an intake of 80% of ET). The green cover percentage, visual quality, NDVI, and soil moisture were measured weekly. We found that Kentucky bluegrass maintains sufficient turf quality for 2 weeks without irrigation. During the first year of the experiment, slight differences were observed among the Kentucky bluegrass cultivars, with ‘Marauder’ showing a 15% of green turf cover less than ‘Brooklawn’ after 6 weeks of acute drought, while in the second year, ‘NuBlue Plus’ displayed higher green turf cover and NDVI than the other cultivars. Nitrogen treatment had limited influence on the performances of the cultivars, ‘Marauder’ being the only one benefitting from the higher rate of applications.