• The impact of grazing cattle on soil physical properties and nutrient concentrations in overland flow from pasture, Part B

      Kurz, Isabelle; O’Reilly, Conor; Tunney, Hubert; Bourke, David; Environmental Protection Agency (Teagasc, 01/06/2007)
      The loss of nutrients from agricultural land to water bodies is a serious concern in many countries. To gain information on the contribution of grazing animals to diffuse nutrient losses from pasture areas to water, this study looked at the impact of cattle on nutrient concentrations in overland flow and on soil hydrology (bulk density, macroporosity and resistance to penetration). Rainfall simulations to produce overland flow were conducted and soil physical measurements were taken on experimental plots assigned to one of two treatments: 1) cattle had unrestricted access to the plot; 2) cattle could graze the plot but they could neither walk on the plot area nor deposit excrements on it. Areas to which the cattle had free access were characterised by 57%-83% lower macroporosity, by 8%-17% higher bulk density and by 27%-50% higher resistance to penetration than areas from which the cattle were excluded. The nutrients in overland flow from grassland that were affected by the presence of grazing animals were mainly the particulate nitrogen, the organic phosphorus and the potassium concentrations. Overall, the presence of cattle had a longer lasting effect on the soil hydrological parameters measured than on the nutrient concentrations in overland flow.
    • The impact of the grazing animal on phosphorus, nitrogen, potassium and suspended solids loss from grazed pastures, Part A

      Tunney, Hubert; Kurz, Isabelle; Bourke, David; O'Reilly, Colin; Jeffrey, D.W.; Dowding, P.; Foy, B.; Kilpatrick, D.J.; Haygarth, P. (Teagasc, 01/06/2007)
      In Ireland 90% of the 4.2 million ha of farmland is grassland. Phosphorus deficiency limited grassland production in Ireland and this was corrected by chemical fertiliser use in the 1960s and 1970s. The increased inputs of fertilisers led to increased intensification of grassland with a doubling of grass yield and of grazing animal numbers, from about 3 million to over 6 million livestock units. There is little information on relative contribution of increased chemical fertiliser use compared to increased grazing animal numbers on phosphorus loss to water. The main objective of this study was to obtain information on nutrient loss, particularly phosphorus, in overland flow from cut and grazed grassland plots, with a range of soil test phosphorus levels over three years and implications.