The influence of soil potassium status on the productivity of docks (Rumex obtusifolius L.) in intensively managed temperate grassland

Abstract

Docks are a widespread problem in grassland, necessitating novel management solutions as pesticides become increasingly regulated. The objective was to investigate the role of soil test Potassium (K) concentrations (Morgan's solution; Na acetate + acetic acid, pH 4.8; STK) on competitiveness of docks in grassland. The experimental site (52°21 N, 7°18 W) was reseeded with perennial ryegrass in October 2009. A plot experiment was laid down in a randomised complete block design with seven rates of fertiliser K (0, 50, 100, 150, 200, 250 and 300 kg ha−1) and eight replicates. Dock numbers were measured over 6 years (2010–2015) and herbage production over 5 years (2012–2016). There was poor alignment between fertiliser K and STK in the early years of the study, however this alignment improved over time. While fertiliser K had no effect on dock numbers, there were positive correlations between STK early in the study and dock numbers m−2 throughout the study. Dock numbers m−2 were relatively static between 2010 and 2012 and increased substantially between 2013 and 2015. Between 2013 and 2016 there were strong inverse relationships (r > −.765; p < .001) between dock and grass herbage production. Towards the end of the study the lower annual fertiliser K inputs (0 and 50 kg ha−1) resulted in lower (p < .01) dock root and herbage production with an associated increase (p < .05) in grass herbage production. It is evident there is a threshold STK for permanent grassland infested with docks at which grass is more competitive for plant‐available soil K than the docks to the detriment of the dock component of the sward.

Key management practices to reduce the risk of the occurrence of Rumex obtusifolius in productive grasslands

“…The medians of soil P content (Table 2) were in line with values under medium to high LUI in permanent grasslands of CH (Frossard et al, 2004), and such values have been shown to be non‐limiting for about 90% maximum production for many grassland species in contrasting soil types and climates (Gourley et al, 2019; Jouany et al, 2021; McCaskill et al, 2019). Thus, the higher risk of occurrence of R. obtusifolius at increased soil P and K contents reflects that the species can take an advantage from high availability of these nutrients (O'Donovan et al, 2023). In a study based on a 30‐year national survey in the UK to assess changes in abundance of weed species in grasslands (Maskell et al, 2020), abundance of R. obtusifolius was positively related to indicators of soil fertility, specifically Ellenberg nutrient scores.…”

Topics from the 2023 EGF Symposium: The future role of ley‐farming in cropping systems, and other recent grassland events

“…Another Grass and Forage Science theme relates to plant-soil relationships (e.g., Gao et al, 2021;Kajzrová et al, 2022;Mayel et al, 2021;O'Donovan et al, 2023;Poeplau, 2021;Schimpf et al, 2023;Xue et al, 2023;Yates et al, 2021). Effects of grassland use on soil properties and root-associated microbiota, and effects of soil structure on grass and forage performance are illustrated by work of Augusto et al (2024), Franzluebbers (2024, Lavi et al (2024), Oyharçabal et al (2024) and Vaughn et al (2024) in this issue.…”