Implementing plantain (Plantago lanceolata) to mitigate the impact of grazing ruminants on nitrogen losses to the environment: A review

Urine patches from grazing ruminants contain high concentrations of nitrogen (N) and are the main source of N leaching from grazed pastoral farming systems. While there have been various options identified to substantially reduce N leaching, in general these practices increase the cost of production or reduce production per hectare. In New Zealand, multi-species pastures were evaluated as a cheaper option that would potentially retain productivity. Early research showed these pastures had lower urinary N excretion from grazing animals and increased plant N uptake, compared with standard New Zealand perennial ryegrass/white clover (PR-WC) pastures. Further research highlighted the beneficial attributes of the pasture herb narrow-leaved plantain (Plantago lanceolata; PL), specifically: reduced urine N concentration, reduced urine N excretion, and reduced rate of soil nitrification. Significant reductions (14%-89%) in N leaching were found from cow urine applied to lysimeters with pastures including PL, compared with PR-WC pasture. Paddock-scale measurements confirmed the effects of PL, with 20%-60% lower N leaching when PL comprised 30%-40% of the dry matter (DM) of PL-PR-WC grazed pastures. There were no negative effects on milk production and composition when feeding PL to dairy cows, but small positive effects on fatty acid profiles. However, weed and pest management, palatability and persistence remain challenging in pastures containing PL on commercial farms. Management options need to be clarified to ensure successful establishment and maintenance of PL. Additionally, the cultivar differences in secondary compounds and their impact on nitrification rate and N leaching need to be better understood.