Trygve S. Aamlid

Timothy is the primary forage grass seed crop in Norway, and thus effective control of dicot weeds and lodging management are critical steps in maximizing timothy seed yield and meeting seed purity standards. Optimal timing of gibberellic acid–inhibiting plant growth regulators (PGRs), such as chlormequat chloride (CCC) and trinexapac-ethyl (TE), often coincides with spring herbicide applications, raising concerns about crop safety and herbicide efficacy when products are tank-mixed. Field experiments were conducted in 2022 and 2023 at two locations in Norway to evaluate the effect of mixing PGRs with commonly used herbicides on timothy lodging, seed yield, and seed quality. Plant growth regulators (1,500 g ai ha⁻ ¹ CCC and 150 g ai ha⁻ ¹ TE) were applied either separately (herbicides at BBCH stage 25; PGRs at BBCH stage 35) or tank-mixed (at BBCH stages 30 to 35) with one of three herbicide combinations: fluroxypyr + florasulam, florasulam + diflufenican, or aminopyralid + 2,4-D + florasulam. Seed yield was affected by PGR treatments (P ≤ 0.05) but not by herbicide treatments. Plant height and lodging were reduced more with TE than with CCC; however, relative yield responses varied with timothy stand age. Tank mixing both products did not reduce seed yield or herbicide efficacy. Crop injury from tank mixtures was minimal and temporary, and no reductions in final seed germination were observed. Tank-mixing CCC and TE PGRs with herbicides maintained optimal seed yield and quality, offering operational flexibility for timothy seed producers.

Seed multiplication of perennial grasses outside their area of adaptation is common practice globally. This also applies to timothy ( Phleum pratense L.), the most important forage grass in Arctic Norway (67°–71° N). Early research suggests little risk for loss of winter hardiness if seed multiplication of Arctic timothy is limited to one or two generations in the south, but recent experiences by North Norwegian farmers suggest otherwise. A study was conducted in which original seed of two northerly adapted timothy varieties ‘Engmo’ (an old landrace originating at 69° N) and ‘Noreng’ (a synthetic variety consisting of 10 clones of ‘Engmo’ and four clones of the South‐Norwegian variety ‘Grindstad’) was multiplied for one, two or three generations at 70° N, 64° N and 58° N. Plants raised from the different generations at each site were subjected to freezing tests to determine LT ₅₀ and ice encasement (IE) tests to determine LD ₅₀ , both tests followed by the weighing of regrowth of surviving plants. On average for generations and compared with the original seed, we found no changes in freezing tolerance or IE tolerance after seed production at 70° N, but significant losses in freezing tolerance of both varieties after seed production at 64° N and in particular at 58° N. The fact that major shifts occurred already in the first generation and were later, at least to some extent, reversible and influenced by the winter before each seed harvest raises the possibility that epigenetic memory of environmental conditions was transferred to the seed progeny in addition to the classical genetic effects.

Timothy ( Phleum pratense L.) is a perennial grass widely grown for livestock feed in temperate regions of the world. It is one of the primary forage grasses grown for seed in Scandinavia due to good cold tolerance and high‐quality feed characteristics. Changes to European Union requirements for use of organic seed in organic forage and livestock production are expected and will soon increase demand for organic timothy seed in the region. An inadequate nitrogen (N) supply is a key yield‐limiting challenge on many arable farms in Norway's main seed‐growing region. In this study, we investigated methods to produce organic timothy seed with limited access to manure, by intercropping seven legume species sown with timothy in the same row or in alternate rows. Timothy seed was harvested for two seed production years in three field experiments in southeastern Norway. Sowing annual legumes with timothy increased seed yield by 10%–25% in first‐year stands. Berseem clover ( Trifolium alexandrinum L.) and subterranean clover ( Trifolium subterraneum L.) sown in the same row with timothy provided the most consistent seed yield increases. Perennial legume intercrops decreased seed yield by 10%–36% in first‐year stands, but black medic ( Medicago lupulina L.) provided 21%–64% seed yield increases in second‐year stands. Seed yield increases in response to legume intercrops were attributable to panicle number and seed number but not seed weight. Timothy seed purity standards can be met if the legume has a seed size and shape that can be removed during seed cleaning.

Timothy (Phleum pratense L.) is a perennial grass widely grown for livestock feed in temperate regions of the world. It is one of the primary forage grasses grown for seed in Scandinavia due to good cold tolerance and high-quality feed characteristics. Changes to European Union requirements for use of organic seed in organic forage and livestock production are expected and will soon increase demand for organic timothy seed in the region. Inadequate nitrogen (N) supply is a key yield-limiting challenge on many arable farms in Norway’s main seed growing region. In this study, we investigated methods to produce organic timothy seed with limited access to manure, by intercropping seven legume species sown with timothy in the same row or in alternate rows. Timothy seed was harvested for two seed production years in three field experiments in southeastern Norway. Sowing annual legumes with timothy increased seed yield by 10 to 25% in first-year stands. Berseem clover (Trifolium alexandrinum L.) and subterranean clover (Trifolium subterraneum L.) sown in the same row with timothy provided the most consistent seed yield increases. Perennial legume intercrops decreased seed yield by 10 to 36% in fist-year stands but black medic (Medicago lupulina L.) provided 21 to 64% seed yield increases in second-year stands. Seed yield increases in response to legume intercrops were attributable to panicle number and seed number but not seed weight. International seed purity standards can be met if the legume has a seed size and shape that can be removed during seed cleaning.

Red fescue (RF, Festuca rubra L.) is one of the most widely used turfgrass species in Europe. The subspecies Chewings fescue (CF) and slender creeping red fescue (SlCRF) are used on putting greens because they tolerate a mowing height of 4–5 mm. Previous research has shown CF to be more winter‐hardy than SlCRF, however, SlCRF has a greener winter color. Our objective was to find the optimal weight ratio of the two subspecies in seed blends for greens in contrasting climatic regions of the Nordic countries. Musica and Cezanne (reference varieties in SCANGREEN variety testing since 2012) were selected as representatives for CF and SlCRF, respectively. Seed blends including CF/SlCRF in weight ratios of 75/25, 50/50, and 25/75 were compared to pure CF and SlCRF at Sydsjælland GC, Denmark, NIBIO Landvik, Norway, NIBIO Apelsvoll, Norway, and Reykjavik GC, Iceland as an add‐on to SCANGREEN variety testing 2015–2018. Results showed the optimal blends to produce higher turfgrass quality and tiller density than monocultures of either subspecies at all sites except Apelsvoll where plots were killed during the first winter. The best‐performing CF/SlCRF blend was 50/50 at Sydsjælland and Landvik and 75/25 at Reykjavik. While this shows seed blends to have advantages compared with the pure subspecies, the study should be repeated with a focus on dollar spot ( Clarireedia spp.), which has become a major turfgrass disease in Southern Scandinavia since these trials were conducted.

As summer droughts become more common and water resources more precious, some golf courses in Scandinavia are turning to lower quality irrigation water to irrigate their courses. We visited seven golf courses on the Baltic coast of Sweden using lower quality irrigation water to interview superintendents and to take soil and water samples for salinity analysis. Four of the seven golf courses experience salinity stress regularly, primarily in a 6–8 week period in July and August. Soil and water samples taken at the seven golf courses in October 2024 generally did not exceed salinity thresholds for cool‐season turfgrasses, but retesting of water and soil will be conducted again in 2025 with at least one of the sampling events conducted during the summer period in which salinity stress symptoms usually occur.

The primary benefits of turfgrass sod include rapid greenery and soil coverage, but its production causes concerns about soil losses at production sites. Soil adheres to the grass root system during harvesting and is removed from the sod farm, which in the long run might lead to soil degradation on the sod farm. In this study, we investigated sod thickness and the removal of organic and mineral matter when harvesting 24 fields representing 12 Norwegian sod farms in 2022 and 2023. On each field, 10 sod strips were randomly chosen, and five sod plugs were collected from each strip. Sod thickness was measured using a sliding gauge. Sod mineral matter (SMM: soil and thatch mineral matter) and sod organic matter (SOM: soil and thatch organic matter) contents were quantified by loss on ignition at 550°C. Management and field properties were also documented. Results showed an average amount of mineral matter in the sod strips of 36 Mg ha ⁻¹ for all fields but with significant variation among fields ( p < 0.001). The average SOM content was 10 Mg ha ⁻¹ . Mean sod thickness was 15.4 mm and had a strong correlation with SOM ( r = 0.8) but only a moderate correlation with SMM ( r = 0.6). Soil water content and surface hardness at harvest affected sod thickness and SMM only slightly. Sod harvesters with twin heads harvested significantly thicker sod strips and removed more mineral matter than harvesters with single cutting heads. Soil texture did not have a significant impact on sod thickness or mineral matter removal.

Ice encasement (IE) is one of the big challenges in winter stress management on golf course putting greens in Northern Scandinavia. The turfgrass is damaged due to lack of oxygen (hypoxia or anoxia) and accumulation of toxic by‐products of anaerobic respiration. Breeding IE‐tolerant turfgrass species and varieties is the best defense against these challenges. A method to simulate ice encasement was tested to screen selected varieties of winter‐hardy bentgrass species and red fescue subspecies. Note that 32 varieties were chosen from the SCANGREEN trial seeded at NIBIO Landvik, Norway, in 2019. Samples were taken in December 2020, 2021, and 2022, vacuum sealed in plastic, and stored in darkness at 0.5°C for up to 77 days to test them for their tolerance to simulated ice encasement (SIE). Samples were incubated at different intervals; plants were potted, and tiller survival was tested after 4 weeks of regrowth. Lethal duration of ice encasement (LD ₅₀ ) that is, the number of days under anoxia that kills 50% of the plant population for each species and variety was calculated. The results showed that the ranking of cool season turfgrass species for tolerance to SIE was velvet bentgrass > Chewings fescue > slender creeping red fescue = colonial bentgrass > creeping bentgrass. This ranking does not fully reflect the ranking found in field tests where velvet bentgrass was superior together with creeping bentgrass. SIE caused a more rapid development of anoxia than IE in the field, and we hypothesize that creeping bentgrass is less tolerant to these conditions compared to the other species tested. To make the SIE method more representative for IE in field, it should be further adapted with incubation at lower temperatures, and with acclimation conditions to be standardized prior to sampling. Within species, the best tolerance to IE was found in velvet bentgrass Nordlys, creeping bentgrass Penncross, Chewings fescue Lykke, and slender creeping red fescue Cezanne.

Winter damage of golf turf in northern environments is a persistent challenge, and reseeding is often necessary to promote recovery and to maintain adequate density and uniformity for play. However, adverse conditions associated with spring seedings can negatively impact reestablishment of creeping bentgrass ( Agrostis stolonifera L.) (CBG) on golf greens, tees, and fairways. The objectives of the research were to examine different strategies to promote rapid reestablishment of CBG in early spring, including cultivar selection, use of a synthetic cover, and application of plant health products. To assess the impacts of CBG cultivars and cover on reestablishment, 12 cultivars and two cover treatments (without or with a permeable synthetic cover) were established at two locations in 2021 (South Deerfield, A, and Saint Paul, MN). The effects of plant health products on CBG establishment were assessed in separate field trials at two locations in 2021 and 2022 (South Deerfield, MA, and Grimstad, Norway). Plant health product treatments were applied on a weekly basis following emergence and included: control (water), chitosan, silica, acibenzolar S‐methyl, glycine betaine, seaweed extracts (alone or together with humic substances), trinexapac‐ethyl, and gibberellic acid. Soil and air temperatures were monitored, and plots were visually assessed for changes in percent green turfgrass cover. The use of a permeable cover increased soil temperatures and decreased the time to achieve 50% turfgrass cover by 7–12 days, depending on location and regardless of cultivar. Compared to effect of covering treatment, most CBG did not significantly vary in spring establishment rates, except for Independence, which exhibited slower establishment. Among the various plant health products tested over 2 years and two locations, we did not identify any specific product that consistently enhanced early spring establishment of CBG.

Turfgrass winter kill due to freeze/thaw cycles and ice encasement (IE) is a problem on putting greens the Nordic countries. Our objectives were (1) to investigate how green coverage with impermeable plastic before IE affects soil temperature, O ₂ and CO ₂ concentrations, winter survival and spring recovery of creeping bentgrass (CRB), red fescue (RF), and annual bluegrass (AB) and (2) to explore how these turfgrasses are affected by snow and ice removal during the entire winter or parts of it. Six treatments were imposed on 5‐month‐old turf of the three species during the winters 2020/2021 and 2021/2022 at NIBIO Apelsvoll, Norway (60°42′ N). With an average soil temperature at 2‐cm depth of −0.9°C and the lowest O ₂ concentrations around 5%, conditions under IE or plastic + IE treatments never became anoxic. On average for six treatments and 2 years, CRB and RF had significantly better winter survival (both 52%) than AB (25%). Turfgrass winter survival, spring color, and spring growth were significantly better (62% survival on average for species) with plastic between the grass and 10‐cm IE than with 10‐cm IE directly on the grass (23% survival). Snow and ice removal throughout the winter or before IE in early January improved turfgrass freezing tolerance in January but did not improve winter survival, green color, or spring growth compared with the control treatment with natural winter conditions. We conclude that putting greens in areas with unstable winters and risk for prolonged IE ought to be protected by impermeable plastic. Ventilation under the plastic may be necessary on old greens with more organic matter than in this experiment. On frozen uncovered greens, it is better to avoid prolonged IE by snow removal before rain or warm spell in December/early January than by mechanical ice removal in March.