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Three experiments investigating factors influencing the abundance of Rumex spp. (docks) in silage and grazed grassland swards are presented. In Experiment 1, Rumex obtusifolius plants were sown with perennial ryegrass and white clover in pots in March and harvested at either 5‐ or 10‐week intervals between June and October. The 10‐week harvest interval increased root dry‐matter production of R. obtusifolius compared with the 5‐week interval; herbage (above‐ground material) production was not significantly affected. In Experiment 2, R. obtusifolius and Rumex crispus population densities in grassland swards were correlated with soil P, K and Mg concentrations, and soil pH. In general, silage swards contained higher population densities than grazed swards. There were significant positive correlations between soil K concentrations and abundance of Rumex spp. in grazed swards and in silage swards. In Experiment 3, R. obtusifolius was sown with perennial ryegrass in pots in March. Treatments consisted of nine rates of K fertilization ranging between the equivalent of 0 and 600 kg K ha−1 year−1. Herbage was harvested at regular intervals (4–6 weeks except during the winter) until May of the following year. In general, perennial ryegrass dry‐matter yields were not greatly affected by soil K, whereas limited soil K supply tended to reduce dry‐matter production of R. obtusifolius. It is possible that maintenance of moderate soil K concentrations may play a role in limiting abundance of Rumex spp. in grassland.

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Phosphorus is essential for plant and animal health. The aim was to determine the impacts of P fertilizer on changes in Morgan's soil test P (STP) and liveweight gain (LWG) of mature beef animals over the last 10 yrs (1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008) of a 40 yr P experiment on temperate permanent grassland in northwestern Europe. There were three original treatments: 0 (P0), 15 (P15) and 30 (P30) kg ⁄ ha ⁄ yr P for 40 yrs , and three new treatments on the same area that started in 1999: P0 for 30 yrs then 30 kg P ⁄ ha ⁄ yr for 10 yrs (P0-30), P15 then 5 kg P ⁄ ha ⁄ yr (P15-5) and P30 then zero P (P30-0). Six plots (0.18 0.27 ha) per treatment were rotationally grazed by beef animals from April to October. The STP levels on the three original treatments were stable over the last 10 yrs and averaged 2.4 (P0), 5.8 (P15) and 16.0 (P30) mg ⁄ L soil. The STP decreased from 18.0 to 8.5 mg ⁄ L in the P30-0 treatment, from 6.5 to 5.0 mg ⁄ L in the P15-5 treatment and increased from 2.4 to 4.8 mg ⁄ L in the P0-30 treatment. Liveweight gains were lowest on P0 but similar on the other treatments (mean of 651 compared to 988 kg ⁄ ha ⁄ yr). It is concluded that of the order of 4-6 mg ⁄ L STP and a fertilizer input of 810 kg ⁄ ha ⁄ yr P was adequate for beef production on a grazing system under the conditions of this experiment.