Pre-vegetated green roof sedum mats: Mineral nutrient status and apparent fertiliser recovery during production

• Published in: Scientia horticulturae 2024-10, Vol.336, p.113428, Article 113428
• Main Authors: Oskarsson, Camilla, Pettersson, Lina, Larsson Jönsson, Helene, Caspersen, Siri
• Format: Article
• Language: English
• Subjects: Apparent nutrient recovery efficiency; biomass; green roofs; nitrogen; nitrogen fertilizers; phosphorus; Plant sap analysis; polyethylene; potassium; Pre-grown green roof mats; sap; seasonal variation; Sedum album; urbanization; winter; Winter coverage
• ISSN: 0304-4238; 1879-1018
• DOI: 10.1016/j.scienta.2024.113428

•Nutrient status during Sedum mat pre-cultivation was followed at three sites.•Shoot mineral concentrations in Sedum album varied over time and between sites.•Correlation between tissue and plant sap concentrations was found for NO3− and K+.•Winter coverage with shade net improved apparent recovery efficiency of P and K. Increased urbanisation and requests for more sustainable urban environments create a strong demand for sedum mats used for green roof establishment. However, little information is available on mineral nutrient status and nutrient requirements in pre-vegetated sedum mat production. In this study we present tissue mineral nutrient concentrations in Sedum album L. as affected by production site, sampling date and pre-winter treatment at a commercial pre-vegetated green roof mat producer. In 2018, seasonal variation in shoot nutrient concentrations were examined at three sites (Elnaryd, Lagan, Tutaryd). In 2019, pre-winter application of phosphorus (P) and potassium (K) combined with winter coverage with polyethylene shade net (PKS) was compared with pre-winter PK fertilisation alone (PK) at the Elnaryd site. Plant sap analyses were performed at several sampling occasions both years. We observed a large variation in nutrient concentrations between sites, years and sampling occasions, which is consistent with earlier findings of large variation in nutrient concentrations for Crassulaceae spp. The nitrogen (N), P and K shoot concentration ranges were 0.85–3.7 %, 0.18–0.44 % and 1.1–2.7 %, respectively. In 2019, biomass was significantly higher for PKS than for PK. The apparent nutrient recovery efficiency of P and K were doubled at PKS in comparison with PK, increasing from 11 to 20 % for P and from 20 to 40 % for K. Even if the effects of winter coverage could not be separated from extra N fertiliser added to PKS, our results indicate that shade net coverage during winter could be a strategy in the production of green roof mats, promoting early deliveries. Plant sap concentrations of NO3− and K+ were correlated with N and K concentrations in the dry shoot tissue, suggesting that plant sap analysis with hand-held instruments could be used by pre-vegetated mat producers to develop a more requirement-oriented fertilisation strategy.