Major concerns for the use of velvet bentgrass ( vb) in Scandinavia are whether current cultivars have sufficient winter hardiness and whether it is possible to control the rapid formation of thatch in this species. To meet these challenges, our project is divided into 4 subprojects:
1) In controlled environments at umb (2006-07, 2007-08, 2008-09) and at Rutgers University and University of Massachusetts, usa (2009), we compared the freezing tolerance of vb cultivars with creeping bentgrass ( vb) ‘Penn a-4’ and evaluated effects of cold acclimation on freezing survival and metabolic changes in crowns. vb and cb were equally tolerant to freezing temperatures. Cold acclimation resulted in carbohydrate changes and enhanced the freezing tolerance of vb and cb. In vb, 20 proteins were responsive to cold acclimation and their functional distribution was: metabolism (6), energy (5), disease/defence (2), secondary metabolism (1), and unknown (6).
2) Field trials combining two fertiliser levels, two topdressing levels and four methods for mechanical/biological thatch control were started in 2007 on usga greens at Apelsvoll and Landvik, se Norway. An annual n input of 1.50 kg/100 m2 proved reasonable during the grow-in year, but during 2008 and 2009 this level led to excessive mat/thatch accumulation (Photo 1) and resulted in a soft playing surface. High topdressing rates turned out to be an effective method of thatch control. Our preliminary observations suggest that Scandinavian velvet bentgrass greens must receive 12-15 mm of sand per year, at least in areas with ample rainfall and a long growing season. 3) A lysimeter trial comparing two root zones (straight sand (ss) and Green Mix (ss+20% v/v garden compost) (gm)) and two irrigation regimes (light and frequent (lf) vs. deep and infrequent (di)) was established in 2007 at Landvik. di irrigation resulted in higher infiltration rates in both root zones and less thatch/mat and roots above 4 cm on gm root zones. Root development deeper than 4 cm was highly affected by growth medium: ss > gm (Photo 2). 4) Practical evaluation / large-scale demonstration trials with vb are being carried out on nine Nordic golf courses (1 in Denmark, 2 in Finland, 2 in Sweden and 4 in Norway). The head-greenkeepers have formed the ‘ vb reference group’, which meets regularly. The experimental field work is now finished. The project goes into its final year in 2010, which involves publication of four scientific papers and a PhD thesis by t. Espevig.
Photo 1. Effect of n input and topdressing levels on thatch/mat thickness (left to right) 0,75 kg N/100 m2 and 7 mm sand per yr; 0,75 kg n/100 m2 and 14 mm sand per yr; 1,50 kg N/100 m2 and 7 mm sand per yr; 1,50 kg n/100 m2 and 14 mm sand per yr. Photo taken in October 2009. Photo 2. Root development as affected by irrigation regime and growth medium: (left to right) gm+di, ss+di, gm+lf, ss+lf (ss=straight sand; gm=Green Mix; lf=light and frequent irrigation; di=deep and infrequent irrigation). Photo taken in October 2009 by Tatsiana Espevig.
