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Agricultural grass cultivars bred for increased forage yield commonly have extensive root systems. As roots are an important input of organic matter into the soil, it follows that such cultivars could lead to important increases in soil organic carbon (SOC), but this, and the mechanisms involved, are poorly understood with little empirical field evidence. We assessed the effect of two cultivars, Lolium perenne L. cv. "AberMagic" and L. perenne L. × Festuca pratensis Huds. cv. "Prior", in comparison with mixed‐species permanent pasture ("Pasture") in a field experiment on temperate alluvial soil in the southwest UK. Root and SOC stocks, and specific plant‐derived lipids as mechanistic biomarkers for shoot and root inputs of C, were measured on intact 1‐m volumetric soil cores collected on four dates in 2013–2015. Total grass yields were greater for both grass cultivars (40–43 Mg ha−1) than Pasture (39 Mg ha−1), and by 2015 root stocks in the upper 0.1 m were significantly greater by more than 4.7 Mg ha−1. At 0.1–0.3 m depth, SOC stocks (per 0.1‐m depth) were significantly greater under the two grass cultivars (24–50 Mg ha−1) compared to Pasture (18–32 Mg ha−1). In the full 1‐m profile, mean SOC stocks were 137, 133 and 110 Mg ha−1 for AberMagic, Prior and Pasture, respectively, matching root biomass distribution. Odd‐chain n‐alkane concentrations were significantly greater for shoots than roots (274 vs. 64 mg kg−1, respectively), and roots had significantly greater concentrations than shoots of even‐chain hydroxy fatty acids (1829 vs. 305 mg kg−1, respectively) and diacids (317 vs. 93 mg kg−1, respectively). This confirmed lipids as candidate biomarkers for distinguishing shoot and root inputs into the soil, with roots being the dominant source of SOC. Based on the observations of increased forage yield and SOC stock, high‐yielding forage grass cultivars can contribute to future strategies for climate‐smart agriculture in grassland‐dominated temperate regions. Highlights: Selected root traits for increased depth, density and diameter may increase SOC in grassland.The effect of two high‐yielding forage grass cultivars were assessed in a field trial.Fast‐growing, high‐yielding cultivars enhanced root and SOC stocks compared to typical pasture.Lipid biomarkers confirmed that root inputs were the predominant C input to soil. [ABSTRACT FROM AUTHOR]

Perennial ryegrass and perennial ryegrass/white clover permanent dairy pastures are compared with respect to productivity, environmental impact and financial costs in nitrate vulnerable zones (NVZ) in the UK. With appropriate management, and utilisation of recommended perennial ryegrass and white clover cultivars, white clover is likely to stabilise at around 20% of total dry matter production in a mixed pasture. Plant dry matter production and milk production from a perennial ryegrass/white clover pasture are likely to be similar to that from a perennial ryegrass pasture receiving 200 kg N ha−1 annum−1 and around 70% of that obtained with perennial ryegrass supplied with 350–400 kg N ha−1 annum−1. Nitrate, phosphorus and methane losses from the system and decreases in biodiversity relative to a grazed indigenous sward are likely to be similar for a perennial ryegrass/white clover pasture and a perennial ryegrass pasture receiving 200 kg N ha−1 annum−1: nitrate leachate from both systems is likely to comply with European legislation. Greenhouse gas emissions resulting from nitrogen (N) fertiliser production would be avoided with the perennial ryegrass/white clover pasture. Within NVZ stocking rate restrictions, white clover can provide the N required by a pasture at a lower financial cost than that incurred by the application of N fertiliser. [ABSTRACT FROM AUTHOR]

Resistance to the cyclohexanedione (CHD) herbicide sethoxydim was investigated in two UK Lolium multiflorum populations, Yorks A2 and PYL. Resistance screening experiments demonstrated a qualitative difference in the responses of the two populations to sethoxydim, suggesting that the molecular basis of resistance between them was different. After treatment, Yorks A2 plants were either alive (78% of sample tested) or dead (22% tested) but plants of the PYL population showed two further intermediate categories of response. The level of acetyl-CoA carboxylase (ACCase) insensitivity directly correlated with the degree of resistance at the whole plant level, indicating that the molecular basis of resistance is associated with differences in ACCase sensitivity in each population. Direct sequencing of the carboxyl transferase domain of the ACCase gene showed that an Ile-418-Leu substitution in the L. multiflorum chloroplastic ACCase (GenBank accession number ) confers resistance to sethoxydim in Yorks A2. This corresponds to amino acid residue 1781 in the Alopecurus myosuroides full ACCase sequence. This is the first report of this mutation in this L. multiflorum, which has also been reported in four other grass-weeds, including L. rigidum. However, no amino acid substitutions were found to be specifically associated with the resistant phenotypes in the PYL population and the molecular basis of resistance in this population remains to be resolved. [ABSTRACT FROM AUTHOR]

Eight multiparous Holstein–Friesian dairy cows in late lactation were used to investigate the potential of using perennial ryegrass with a high concentration of water-soluble carbohydrate (WSC) to increase the efficiency of milk production. After a pretreatment period on a common pasture, the cows were each given ad libitum access to one of two varieties of zero-grazed grass continuously for 3 weeks. Treatments were: high sugar (HS), an experimental perennial ryegrass variety bred to contain high concentrations of WSC; or control, a standard variety of perennial ryegrass (cv. AberElan) containing typical concentrations of WSC. The two grass varieties were matched in terms of heading date. All animals also received 4 kg day–1 standard dairy concentrate. Grass dry matter (DM) intake was not significantly different between treatments (11·6 vs. 10·7 kg DM day–1 ; s.e.d. 0·95 for HS and control diets respectively), although DM digestibility was higher on the HS diet (0·71 vs. 0·64 g g–1 DM; s.e.d. 0·23; P < 0·01) leading to higher digestible DM intakes for that diet. Milk yield from animals offered the HS diet was higher (15·3 vs. 12·6 kg day–1 ; s.e.d. 0·87; P < 0·05) and, although milk constituent concentrations were unaffected by treatment, milk protein yields were significantly increased on the HS diet. The partitioning of feed N was significantly affected by diet, with more N from the HS diet being used for milk production (0·30 vs. 0·23 g milk N g–1 feed N; s.e.d. 0·012; P < 0·01) and less being excreted in urine (0·25 vs. 0·35; s.e.d. 0·020; P < 0·01). In a separate experiment, using the same grasses harvested earlier in the season, the fractional rate of DM degradation, measured by in situ and gas production techniques, was higher for the HS grass than for the control.... [ABSTRACT FROM AUTHOR]

In official forage grass variety trials in the UK, herbage samples are dried at 100°C or more to facilitate quick drying of the large numbers of samples that are currently needed. When assessing herbage quality, however, 80°C has been recommended as the highest temperature that can be used during drying without serious deterioration. Herbage from six perennial ryegrass varieties, which were known to show a range of variation in in vitro concentration of digestible dry matter (DMD) and water-soluble carbohydrate concentration (WSC) during the vegetative phase of growth, was dried in an oven with forced ventilation at 100°C and at 80°C before analysis. Mean DMD over all varieties was slightly lower [6 g kg-1 dry matter (DM)] and mean WSC over all varieties was considerably lower (24 g kg-1 DM) at 100°C. Varieties differed in mean DMD over both drying temperatures by 37 g kg-1 DM and in mean WSC by 63 g kg-1 DM. There was, however, no significant interaction between variety and drying temperature for either DMD or WSC. Although drying at the higher temperature underestimated both DMD and WSC, it did not significantly alter the ranking of varieties or the range among them. [ABSTRACT FROM AUTHOR]

Reports that for some years ryegrass plants at the Welsh Plant Breeding Station in Great Britain have been killed by a previously unidentified disease. Death of some plants of perennial ryegrass {Lolium perenne L.) were killed; Serious damage was confined to Italian ryegrass (L. multiflorum Lam.) and Italian X perennial ryegrass hybrids; Development of most characteristic symptoms on flowering tillers; Disease's apparent similarity with that reported from Switzerland, France and Germany on Lolium spp. and other forage grasses and recently shown to be caused by Xanthomonas graminis.