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This study examines the effectiveness of a model called LINGRA-N-Plus to simulate the interaction of climate, soil and management on the green leaf and total dry matter yields of ryegrass in England and Wales. The LINGRA-N-Plus model includes modifications of the LINGRA-N model such as temperature- and moisture-dependent soil nitrogen mineralization and differential partitioning to leaves and stems with thermal time from the last harvest. The resulting model was calibrated against the green leaf and total grass yields from a harvest interval x nitrogen application experiment described by Wilman et al. (1976). When the LINGRA-N-Plus model was validated against total grass yields from nitrogen experiments at ten sites described by Morrison et al. (1980), its modelling efficiency improved greatly compared to the original LINGRA-N. High predicted yields, at zero nitrogen application, were related to soils with a high initial nitrogen content. The lowest predicted yields occurred at sites with low rainfall and shallow rooting depth; mitigating the effect of drought at such sites increased yields by up to 4 t ha−1. The results highlight the usefulness of grass models, such as LINGRA-N-Plus, to explore the combined effects of climate, soil, and management, like nitrogen application, and harvest intervals on grass productivity. [ABSTRACT FROM AUTHOR]

In a field experiment carried out over 3 years, the nitrate content of herbage from perennial ryegrass (Lolium perenne) swards increased exponentially with nitrogen application rate, but herbage nitrate content appeared to reach potentially dangerous concentrations only when nitrogen application rates were greater than those needed to stimulate dry-matter production. Thus, on average over all the harvests, maximum yield could be obtained with annual application rates of 400 kg N ha–1 (six applications of 67 kg N ha–1) for perennial ryegrass and 300 kg N ha–1 (six applications of 50 kg N ha–1) for perennial ryegrass/white clover (Trifolium repens) swards, whereas the mean nitrate concentrations were 3340 and 2929 mg NO3 kg–1 dry matter (DM) respectively. Nitrate content, however, varied considerably from harvest to harvest, reaching maxima of 9345 mg NO3 kg–1 DM at 400 kg N ha–1 for perennial ryegrass and 6255 mg NO3 kg–1 DM at 300 kg N ha–1 for perennial ryegrass/white clover. The nitrate content of herbage from perennial ryegrass/white clover swards was always greater than that of perennial ryegrass swards receiving the same rate of nitrogen application, even though in the herbage from the mixed sward the nitrate content of white clover was usually less than half that of the perennial ryegrass component. The physical environment did not have a clearly interpretable effect on nitrate content, although herbage harvested in May had a much lower nitrate content than that harvested at any other time of the season. It was not possible to find a single multiple regression equation relating herbage nitrate content to nitrogen application and to other environmental variables that explained more than 60% of the variance in herbage nitrate, but it is suggested that, by reducing the later-season nitrogen applications from 67 to 50 and finally to 33 kg N ha–1 for perennial ryegrass and from 50 to 33 kg N ha–1 for perennial ryegrass/white clover, it would be possible to achieve over 90% of the maximum yield while reducing average nitrate content to <40% of that at maximum yield, with no samples containing more than 2300 mg NO3 kg –1 DM. [ABSTRACT FROM AUTHOR]

The effect of spreading mown perennial ryegrass (Lolium perenne) herbage over the total ground area on water loss during field-wilting was compared with leaving herbage in swaths (three swaths put together into one, occupying 0·18 of ground area) in three experiments. Spread crops were not tedded during wilting but were rowed up immediately before harvest. In all experiments, conventional silage-making equipment was used on a field scale. Feeding value was assessed with lactating dairy cows and growing heifers (Experiment 1) and sheep (Experiment 3). The periods of field wilting were 48 h (Experiment 1), 24 h (Experiment 2) and both 24 h and 48 h (Experiment 3). Spreading the crop was associated with larger increases in loss of water in all three experiments compared with leaving grass in swaths. Losses of dry matter (DM) during wilting were similar in Experiment 2 but were higher for the swathed crop wilted for 48 h than for 24 h in Experiment 3. Spreading resulted in restricted fermentations associated with higher crop DM contents at ensiling. In Experiment 1 the concentrations of DM, ash and water-soluble carbohydrate in silage were higher (P < 0·001) for spreading the crop and the concentrations of crude protein and neutral-detergent fibre were lower (P < 0·05) than for swathed material. In Experiment 3, spreading was associated with higher concentrations of water-soluble carbohydrates and ethanol and lower concentrations of fermentation acids, ammonia-N and neutralizing value in silage. Voluntary DM intake of silage by dairy cows and heifers was higher for spread than for swathed material (P < 0·05), but in Experiment 3 (sheep) there were no significant differences between treatments in voluntary intake of DM. The increased intake by dairy cows of silage from spread herbage was reflected in increased concentrations of milk fat (P < 0·01) and protein (P < 0·05) but not in milk yield (P > 0·05). It is concluded that spreading herbage during field wilting prior to ensiling accelerates water loss and has the potential to improve the feeding value of the ensiled product. [ABSTRACT FROM AUTHOR]

In experiments in 1979 and 1980 in eastern England, the spread of eriophyid mites and ryegrass mosaic virus (RMV) from transplanted old sward through plots of newly sewn Italian ryegrass greatly exceeded spread by windborne mites from outside the plots. During the summer and autumn of each year, mites and RMV spread at least one metre through the ryegrass (6/7 rows) from the old sward. Applying aldicarb (10 kg/ha equivalent) to the seedbed before sowing the Italian ryegrass prevented colonisation by mites and greatly decreased spread of RMV from old sward. lt is concluded that old diseased swards should be completely killed before reseeding and that RMV is likely to spread quickly to plants slot-seeded into old pastures. The use of acaricides might prevent this spread but would be costly. [ABSTRACT FROM AUTHOR]

Dazomet, applied to the soil in September 1972, increased the dry matter yield in 1973 of perennial ryegrass (Lolium perenne L.) cv. Gremie sown that spring in Hertfordshire. The greatest increase (60 per cent) was where least nitrogen had been applied and was not apparently the result of differences in pathogen or pest incidence. Sprays of the fungicides benodanil and benomyl, and drenches of captafol, did not affect yield in 1973 or 1974, although benodanil controlled crown rust (Puccinia coronata Corda) in August and September 1973. Sprays of the acaricide endosulfan and the aphicide menazon had no detectable effects in 1973. In 1974, endosulfan sprays, either alone or " with menazon, controlled Abacarus hystrix (Nal.), the mite vector of ryegrass mosaic virus (RMV), decreased RMV incidence from 54 to 26 per cent and increased dry matter yield by six per cent. Mildew (Erysiphe graminis DC.) was observed in 1973 and leaf spot (Drechslera spp.) was common in 1973 and 1974, but infection by both diseases was only slight. The incidence of barley yellow dwarf virus was slight and not apparently affected by the treatments. Root discoloration was common but not affected by dazomet or captafol. Fusarium culmorum (W. G. Smith) Sacc. was commonly isolated from very discoloured roots and one isolate, which was weakly pathogenic to ryegrass, killed wheat seedlings. After cutting, patches of grass in plots given 150 kg nitrogen/ha/cut showed poor regrowth, but this could not be associated with pathogens. Mildew and RMV were most common on plots given most nitrogen (150 kg N/ha/cut). RMV and its vectors were apparently more detrimental during the experiment than were other pathogens. [ABSTRACT FROM AUTHOR]

This article cites a study that described lolium (L.) mottle virus (LMV). A previously unrecorded virus with isometric particles 27 nanometer diameter had been isolated from L. perenne and Cynosurus (C.) cristatus from Eire and from C. cristatus from Yorkshire, England. Then this was named LMV. The virus could be inoculated into cultivars of wheat, oats, barley and rye, and Lagurus ovatus. It was symptomless in L. multiflorum and Phleum pratense. Some properties of LMV were reported. The virus, though readily sap transmissible, was not transmitted by two Oulema species or by three species of aphids.

Forage plants underpin the livestock industry. Selective breeding, including polyploidization, where genome size is increased by whole genome duplication, changes the productivity and stress tolerance of new varieties. We conducted a growth chamber experiment to investigate the likely responses of Lolium perenne L. to drought, testing four diploid and four tetraploid varieties. We simulated projected spring and summer temperatures for the South-West of England in 2080, applying three projected rainfall scenarios, which varied in drought severity. Drought caused a reduction in productivity, but there was substantial variation between varieties (up to 82%), with the optimal variety changing depending on drought severity. Across three harvests, productivity declined by 43% and 27% (dry biomass) for the severe and likely drought scenarios, respectively. In the final harvest, tetraploids exhibited a greater biomass under severe drought, whereas diploids had a greater biomass under the current rainfall and likely drought scenarios. Longer stomata were observed in tetraploids; however, stomatal conductance was not significantly different between ploidy levels. Trait selection will be important for future drought adaptation. Local climate projections will need to be consulted when selecting L. perenne varieties to tolerate the spatially variable reductions in future rainfall. [ABSTRACT FROM AUTHOR]