Gudni Thorvaldsson

The effects of growth temperature on digestibility and fibre concentration of seven temperate grass species

Abstract The effects of growth temperature on digestibility and fibre concentration of seven grass species: Kentucky bluegrass (Poa pratensis L), timothy (Phleum pratense L), meadow foxtail (Alopecurus pratensis L), perennial ryegrass (Lolium perenne L), red fescue (Festuca rubra L), tufted hair-grass (Deschampsia caespitosa L (PB)) and meadow fescue (Festuca pratensis Huds) were investigated in growth chamber and greenhouse experiments. Seedlings from each grass species were established in a greenhouse and then transferred at five weeks of age to three growth chambers with day/night temperatures of 9/5, 13/9 and 17/13°C, respectively. Three pots of each species from each temperature treatment, and from the greenhouse control, were harvested weekly for three weeks. The rate of decline of in vitro true digestibility (IVTD) and in vitro cell wall digestibility (IVCWD) increased with increasing temperature for all species. Each degree of increase in temperature decreased the IVTD by an average of 0.22 g kg−1 dry matter (DM) day−1 between 9 and 13°C, and by 0.35 g kg−1 DM day−1 between 13 and 17°C. On average, the neutral detergent fibre (NDF) increased at a rate of 0.78 g kg−1 DM day−1 for each degree increase in temperature between 9 and 17°C. The effects of temperature were less for perennial ryegrass and meadow fescue than for the other species. Perennial ryegrass was consistently ranked as highest in digestibility, followed by meadow fescue; tufted hair-grass had the lowest digestibility. The rate of decline in digestibility was slower for perennial ryegrass and meadow fescue than for the other species.

Botanical Composition of Icelandic Grass Fields

Abstract The botanical composition of grass fields in Iceland was investigated during the years 1990-1993. The investigation included 1294 grass fields on 191 farms. More than 50 species were recorded. The most common species were Poa pratensis, Festuca rubra, Phleum pratense, Deschampsia caespitosa and Agrostis sp. Other common species were Poa annua, Alopecurus pratensis, Alopecurus geniculatus, Stellaria media, Ranunculus acris, Taraxacum spp., Cerastium fontamum and Rumex acetosa. The most important factors affecting the proportion of the species were region and age of the sward. Other important factors were soil type, soil moisture, winter kill, spring grazing, height above sea level, and distance from the sea.

Growth response of seven perennial grass species to three temperature regimes applied at two growth stages

The effect of temperature on the growth rate of shoots and roots for seven grass species was investigated in a growth chamber experiment. The following species were tested: Alopecurus pratensis L, Deschampsia caespitosa L (PB), Festuca pratensis Huds, Festuca rubra L, Lolium perenne L, Poa pratensis L and Phleum pratense L. Plants were grown in pots in a greenhouse, then placed in three growth chambers (9/5, 13/9 and 17/13 day/night °C) when the seedlings were two weeks old (5–8 cm high) or five weeks old (14–37 cm high). The young seedlings responded immediately to different temperatures and grew more slowly in the colder growth chambers. Shoot growth of the older plants was similar at all temperatures. Percentage of root was significantly affected by temperature at both growth stages. The results of this experiment indicate that growth of temperate grasses in early growth stages is more dependent on temperature than at later stages.

Turfgrass species and varieties for Integrated Pest Management of Scandinavian putting greens

Abstract EU requirements for Integrated Pest Management (IPM), perhaps even pesticide-free management, have implications for choice of turfgrass species and varieties for golf courses. This paper reports results from variety testing for putting greens in the southern Nordic zone comprising Denmark and coastal areas in south Sweden and south Norway, and the northern zone comprising Finland, Iceland and remaining regions of Sweden and Norway. Forty-one varieties of seven species/subspecies were compared from 2007 to 2010 at Apelsvoll (Norway, 61° 42′ N, 250 m asl) and Korpa (Iceland, 64° 09′ N, 30 m asl) (northern zone), and at Landvik, (Norway, 58° 11′ N, 12 m asl) (southern zone). Once established, the trials were mowed at 3 mm for Agrostis and 5 mm for Festuca, Poa and Lolium. Mean fertilizer rates were 1.7 kg N 100 m−2 yr−1 to A. stolonifera and 1.0 kg N 100 m−2 yr−1 to other species. No pesticides were used. On average for varieties within species, F. rubra, especially ssp. commutata, had significantly less winter damage (biotic and abiotic) than L. perenne and Agrostis sp. F. rubra also had significantly less in-season diseases (mainly Microdochium patch) than A. capillaris and A. canina in the southern zone and in comparison with all Agrostis sp. in the northern zone. On average for varieties, the ranking based on overall visual merit was F. rubra ssp. commutata>F. rubra ssp. litoralis>A. canina>A. stolonifera>A. capillaris>P. trivialis>L. perenne in the northern zone, and A. canina>A. stolonifera>F. rubra ssp. commutata>F. rubra ssp. litoralis>A. capillaris>L. perenne>P. trivialis in the southern zone. For pesticide-free management of putting greens, we recommend pure seed blends or F. rubra in both zones. Seed blends of A. stolonifera or A. canina, and seed mixtures of F. rubra and A. capillaris are compatible with IPM including limited fungicide use. Ranking lists of varieties are presented.

The Effect of Temperature on Growth, Development and Nitrogen in Shoots and Roots in Timothy (Phleum pratense L.), Tested in Growth Chambers

Abstract The effect of temperature on growth, development and crude protein content of timothy (Phleum pratense L.) was investigated. Plants were grown in pots outdoors and placed in four growth chambers at different mean temperatures (8, 12, 16 and 20°C) and at three different phenological stages in order to study the interaction between temperature, development and growth. They were then harvested at weekly intervals for up to six weeks. Pots left outdoors were harvested at the same time. The dry matter yield of shoots and roots, number of tillers per plant, plant height and crude protein content in shoots and roots were recorded.