Minogue D. 1,2, Murphy P.N.C. 1, French P. 1, Bolger T. 2 1 Teagasc, Moorepark Research Centre, Fermoy, Co. Cork, Ireland. 2 School of Biology and Environmental Science, University College Dublin, Dublin, Ireland. A Lysimeter Experiment to Assess Environmental Impacts of Soiled Water Application to Grassland Soils Aims: Assess environmental risk of nutrient leaching and N 2 O emission from land-spreading of soiled water Assess effect of soil type (free-draining v. poorly drained) Assess effect of application timing (season) Lysimeter Design and Treatments Ireland: 90 % of agricultural land is grassland. Irish dairy farming is pasture-based. Soiled water is produced from washing-down milking parlours and holding areas. Contains nutrients that are potentially available to grass, but also pose a potential threat to environmental quality if not managed correctly. Typically land-spread. Currently no guidance for nutrient management. Provides both nutrient and hydrologic loading- potentially increase nitrate leaching. Very little known of environmental risks of land-spreading. EU Nitrates Directive requires study of nitrate leaching under intensive dairy production on vulnerable soil types. Research project established to investigate soiled water production on dairy farms, environmental risks of land-spreading and management options. This poster details a lysimeter experiment to investigate environmental impacts of land- spreading on contrasting soils. 1. Application to grassland. Management Options 2. Treatment with a wood-chip filter followed by re-use of water and land application of wood chips. Initial Results N, P, K in drainage N, P, K in grass, microbial biomass N 2 O gas Lysimeter Construction and Installation Conclusions 70 cm 30 cm Poorly-drained Gleysol Clay loam with clay lenses Well-drained Acid Brown Earth Sandy loam High vulnerability for N leaching SeasonCT1T2T3 Jan-AprCANSWCAN May-AugCAN SWCAN Sep-DecCAN SW Total N (kg N/ha) 198 BackgroundContrasting Soils Karstified Limestone 5 m Glacial till Free-draining sandy loam soil Gas sampling chamber Water-filled rim for air seal Intact soil core Petrolatum seal to prevent side-flow Leachate collection vessel Coarse sand Two soil types 4 treatments 4 replicates 32 lysimeters Sampling: Weekly leachate volumes Bulk samples (3-4 weeks) N fractions, P, K, Ca, Mg, Na, K Br tracer Gas sampling- N2O emissions Soil sampling- microbial biomass C and N Grass- yield and N, P, K uptake Treatments: Control and soiled water applied over three different 4-month periods (seasons) Soiled water applied at max legal rate: 50,000 l/ha every six weeks Soiled water N accounted for in agronomic nutrient management strategy Excavating lysimeters Petrolatum seal Coarse sand base End cap, nozzle and tubing Lysimeters installed Trenches back- filled Gas sampling chamber Gas sampling Completed installation during gas sampling Leachate collection vessels Precipitation Sandy Loam Drainage Clay Loam Drainage Total Drainage from two Soil Types 32 intact soil-core lysimeters installed Soiled water application has commenced Nutrient leaching and N 2 O emissions will be monitored for 1 year to assess environmental risks of land-spreading soiled water at the maximum legal rate The effect of application timing will be assessed The effect of soil type (free-draining v. poorly drained) will be assessed 0.5 m Low vulnerability for N leaching Poorly drained clay loam soil SW = soiled water, CAN – Calcium Ammonium Nitrate fertiliser