Maintain Forage Yields in Long- and Short-Term Grasslands in Norway

Various reasons have been invoked explaining the low renovation activity in Norwegian grassland farming: swards are often located in marginal areas, ploughing and reseeding gives low or no yield in the renovation year, and it may be unprofitable to establish a new sward. The establishment of new leys can also prove difficult in seasons with unfavourable weather conditions. Thus, farmers prefer long-term or permanent swards as opposed to ploughed and reseeded swards. The hypotheses of this study is that under equal management conditions, permanent and temporary swards (leys) that are reseeded frequently are equally productive. We present results from an experimental field trial at Særheim (58o47’N 5o41\u27E), SW Norway, which was established 1968. The experiment includes grass plots maintained without ploughing for more than 50 years, and frequently (every 3 to 6 years) ploughed treatments. Three different fertiliser strategies are included: mineral fertiliser (210 N kg ha-1) and cattle slurry in combination with mineral fertiliser (210 kg and 340 N kg ha-1). In 2016, the frequently ploughed treatments and half of the 25-years-old sward was renewed by ploughing and reseeding with grass-clover seed mixtures. The second half of the 25-years-old sward was sod-seeded using perennial ryegrass (Lollium perenne) only in 2017 and grass-clover mixtures in 2019. Herbage yields and forage quality was determined after each of the three annual cuts. In the first year after reseeding, 2017, the leys had significantly higher forage yield than the 50- and 25-year-old permanent grasslands regardless fertilisation strategy. This difference between leys and long-term grasslands was evened out in the second production year. In 2019, the permanent grassland yielded significantly more than in the leys except in the plots, which received 210 kg N ha-1 in combined form. There was no difference in herbage yield between swards that had been renovated by sod-seeding or by ploughing and reseeding

Kvalitet av biff fra beite

Diekalvproduksjon på utmarksbeite kan gi like stor tilvekst og slaktevekt som tilsvarende produksjon på innmarksbeite. Begge beitetypene gav meget god kjøttkvalitet med kun små forskjeller i kvalitet mellom kjøtt produsert på inn- og utmark. Prosjektet er gjennomført av Nortura og Bioforsk med besetninger av forskjellige storferaser fra Lillehammer, Gausdal, Øyer og Ås

Simulating impacts of climate and management on timothy growth in Northern countries

201

Specialization and optimization of constraint programs with dynamic scheduling

In this report we discuss some of the issues involved in the specialization and optimization of constraint logic programs with dynamic scheduling. Dynamic scheduling, as any other form of concurrency, increases the expressive power of constraint logic programs, but also introduces run-time overhead. The objective of the specialization and optimization is to reduce as much as possible such overhead automatically, while preserving the semantics of the original programs. This is done by program transformation based on global analysis. We present implementation techniques for this purpose and report on experimental results obtained from an implementation of the techniques in the context of the CIAO compiler

Process-based modelling of the nutritive value of forages: a review

201

Plant diversity greatly enhances weed suppression in intensively managed grasslands

Weed suppression was investigated in a field experiment across 31 international sites. The study included 15 plant communities at each site, based on two grasses and two legumes, each sown in monoculture and 11 four-species mixtures varying in the relative proportions of the four species. At each site, one grass and one legume species was selected as fast establishing and the other two species were selected for persistence. Average weed biomass in mixtures over the whole experiment was 52% less (95% confidence interval, 30 to 75%) than in the most suppressive monoculture (transgressive suppression). Transgressive suppression of weed biomass persisted over each year for each mixture. Weed biomass was consistently low and relatively similar across all mixtures and years. Average sown species biomass was greater in all mixtures than in any monoculture. The suppressive effect of sown forage species on weeds in mixtures was achieved without any herbicide use. At each site, weed biomass for almost every mixture was lower than the average across the four monocultures. The average proportion of weed biomass in mixtures was less than in the most suppressive monoculture in two thirds of sites. Mixtures outyielded monocultures, and mixture yield comprised far lower weed biomass