Impact of cattle on soil physical properties and nutrient concentrations in overland flow from pasture in Ireland

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Abstract

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 nutrient losses from grassland that can specifically be attributed to the presence of grazing animals were found mainly in the particulate nitrogen, the organic phosphorus and in the potassium exports. Overall, the presence of cattle had a longer lasting effect on the soil hydrological parameters measured than on the nutrient concentrations in overland flow.

Introduction

Grassland managed with the aim of supporting intensive animal husbandry can, under some circumstances, become a source of nutrients in water bodies (Kurz et al., 2005a, Sharpley and Syers, 1979). Stock can impact on stream water quality directly by entering and excreting into the streams (Sharpley and Syers, 1979), and by trampling and eroding the stream banks (Line et al., 2000). Grazing animals can alter the hydrology and the drainage pathways at a site by compacting the topsoil, which is indicated by increased bulk density (BD) and decreased macroporosity (MP) (Singleton et al., 2000). This can result in a decrease of the infiltration capacity of the soil (Pietola et al., 2005) and, consequently, in an increased occurrence of overland flow (Heathwaite et al., 1990), which is considered to be an important nutrient loss pathway (Kurz et al., 2005b). Grazing animals can also change the characteristics of grassland as a nutrient source. They may alter the type and amount of nutrients that can be mobilised and lost to water by effecting a spatial and chemical re-distribution of nutrients and, sometimes, by causing enough soil physical damage to reduce grass growth (Drewry and Paton, 2000).

The effects of grazing animals on nutrient losses to water are reported to range from not measurable (Owens et al., 1989) to considerable (Heathwaite and Johnes, 1996). This variation is probably due to the great number of variables involved in the nutrient loss process, and to the considerable effect the relative timing of management and weather factors can have on nutrient movement.

The aims of this project were (1) to measure the impact of rotationally grazing cattle on bulk density, macroporosity and resistance to penetration; (2) to investigate whether rotationally grazing cattle influence the nutrient concentrations in overland flow produced at pasture sites; (3) to assess the likely impact of rotationally grazing cattle on nutrient concentrations in overland flow.

Section snippets

Overview of study sites and measurements taken

Four fields of pasture were used as study sites for the soil physical investigations. Two of the sites (JC1 and JC2) were located at Johnstown Castle, Wexford, Ireland (302404/11fc UTM) and two (G1 and G2) at Grange, Co. Meath, Ireland (297959/254978 UTM). At each of the four field sites two treatments were applied to small (1.5 m × 15 m) delineated plots. Treatment 1 (UnAc) gave cattle unrestricted access to the five plots assigned to that treatment. Treatment 2 (NoTrEx) allowed cattle to eat the

Soil nutrient concentrations

The analyses of variance of the soil nutrient concentration data are summarised in Table 3. At the end of the experiments, the potassium concentrations were significantly higher in plots of the UnAc treatment than in plots of the NoTrEx treatment at all study sites. There was no statistically significant effect of treatment on soil P levels at site JC1 and the two sites at Grange. At site JC2, soil P levels were significantly higher in the UnAc than the NoTrEx treatment.

Resistance to penetration and soil moisture

The repeated measures

Soil hydrology

Bulk density and MP are known to represent an important influence on the infiltration characteristics of soils (Free et al., 1940), and they have been found to be the most useful indicators of topsoil compaction caused by cattle treading (Drewry et al., 2000). Soil moisture and BD are the main parameters influencing RP at sites of equal soil type (Vaz and Hopmans, 2001).

The treatment effects of about 30–50% on RP show that either BD or SM or both differed greatly between UnAc and NoTrEx areas

Conclusions

At the sites examined in this study, the presence of cattle led to physical changes in the topsoil. Bulk density and RP were increased and MP decreased in areas to which cattle had access. These changes favoured the occurrence of overland flow and altered the natural drainage characteristics of soil. They persisted over the winter period when the animals were housed. Soil physical recovery did, however, occur when cattle were excluded from areas over the growing season.

The effect of cattle on

Acknowledgements

This report has been prepared as part of the Environmental Research Technological Development and Innovation Programme 2000–2006. The programme is financed by the Irish Government under the National Development Plan 2000–2006.

References (41)

  • B. Coulter

    Nutrient and Trace Element Advice for Grassland, Tillage, Vegetable and Fruit Crops

    (2004)
  • N. Culleton et al.

    The Evaluation of Environmental, Agronomic and Economic Implications of High and Low Input Dairy Systems. End of Project Report 4020

    (1999)
  • J.A. Daniel et al.

    Long-term grazing density impacts on soil compaction

    Trans. ASAE

    (2003)
  • J. Diamond et al.

    Infiltration rate assessment of some major soils

    Ir. Geogr.

    (2003)
  • J.J. Drewry et al.

    Effects of cattle treading and natural amelioration on soil physical properties and pasture under dairy farming in Southland, New Zealand

    N. Z. J. Agric. Res.

    (2000)
  • J.J. Drewry et al.

    A survey of soil physical properties on sheep and dairy farms in southern New Zealand

    N. Z. J. Agric. Res.

    (2000)
  • FAO-UNESCO

    Soil Map of the World

    (1974)
  • G.R. Free et al.

    Relative Infiltration and Related Physical Characteristics of Certain Soils. Technical Bulletin No. 729

    (1940)
  • A.L. Heathwaite et al.

    Contribution of nitrogen species and phosphorus fractions to stream water quality in agricultural catchments

    Hydrol. Process.

    (1996)
  • A.L. Heathwaite et al.

    The effect of land use on nitrogen, phosphorus and suspended sediment delivery to streams in a small catchment in southwest England

  • Cited by (0)

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