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Articles by K.P. McDonnell
Total Records ( 5 ) for K.P. McDonnell
  E.M. Curley , M.G. O`Flynn and K.P. McDonnell
  The objective of this study was to examine Phosphorus (P) loss from agricultural land under a range of conditions, to investigate the effects of applying various rates of cattle slurry on the P loss to drainage water under newly established Miscanthusxgiganteus grass. The P concentration in drainage water was assessed for two years 2008 and 2009. The role of P from agricultural sources in the pollution (non-point source) of surface waters has been an environmental issue for decades because of the recognized contribution of P to the eutrophication (increase in the concentration of nutrients) of surface waters. Research to-date has concentrated mainly on the P losses by surface erosion and runoff, due to the relative immobility of P in soils. Consequently, P leaching and losses via subsurface runoff have rarely been considered important pathways for the movement of agricultural P to surface waters. However, there are situations where, environmentally significant exports of P in agricultural drainage has occurred (e.g., high organic matter soils or soils with high soil P concentrations). In this study, the crop received either no fertilizer (0-unfertilized control) or an annual application of 6, 12 or 18 kg P ha-1. Soil water solution samples were collected fortnightly from porous ceramic cup samplers. The P levels in these soil water samples were determined and monitored. Soil water phosphorus concentrations were found in the range of 4.3-6.5 in 2008 and in 2009 levels of, 8.8, 8.2, 8.1 and 9.4 mg L-1 were recorded for 0, 6, 12 and 18 kg P ha-1, respectively. However, there was no significant difference between treatments. Nutrient losses have a number of environmental consequences. N and P losses in particular can negatively affect the quality of soils, groundwater, surface water and the atmosphere; thus, contributing to eutrophication, toxic algal blooms and a general deterioration of water quality.
  E.M. Curley , M.G. O`Flynn and K.P. McDonnell
  Ceramic cup samplers are widely used in agriculture to obtain samples of soil pore water for nitrate analysis. This method has become well developed over the past 30 years; however, it is not fully clear what preparation and installation procedure gives the most reliable results or what factor could limit the validity of their use. This study describes the design and use of these samplers including modifications made during large-scale experimental work, on heavy soils in the East of Ireland. Ceramic cup samplers must be installed carefully to avoid preferential flow through the disturbed soil around them and to maximize contact between cup and soil. Furthermore, if samplers are not prepared adequately prior to installation, the cup material may release contaminants into the collected samples resulting in prejudice study results. Newly installed ceramic cups were used at University College Dublin (UCD), Ireland, in 2008 to determine the degree of nitrate leaching from various crops post-fertilization with organic manures. The ceramic cups were cleaned using a dilute acid and repeatedly rinsed with deionized water. During the installation process sodium bentonite and silica flour were used to minimize preferential flow and ensure good hydraulic contact between the sampler and the soil.
  E.M. Curley , M.G. O`Flynn and K.P. McDonnell
  Gaining knowledge of solute concentration and movement is one of the many keys to understanding the response of agricultural ecosystems to would-be pollutants. Monitoring the leaching of pollutants throughout the unsaturated zone is an important means of identifying the potential for groundwater contamination. Water solute monitoring and data collection, at present, can be obtained using either, in situ solute collection or via geophysical measurement. As data collated from the latter often requires support from knowledge gathered using in situ solute collection, this review evaluates the most common method for in situ solute extraction- the ceramic cup method. Ceramic cups are widely used for the extraction of soil pore water for monitoring of solute transport and concentration. This method offers the potential to simultaneously sample soil water at different depths in the soil profile to record the sequence of solute progress. The installation of the ceramic cup sampler into the soil profile is relatively easy when compared to other sampling techniques and causes only negligible disturbance of the soil, coupled with cost-effectiveness and the knowledge obtained makes them the most universally used technique for extracting soil water. However, the use of this system is not without problems. The spatial variability of the properties under investigation is often underestimated requiring clarification by replication. The matter of inherent bias in preferentially monitoring nutrient composition and flow of soil water in profile macropores is acknowledged and the associated possible alteration of the water sample. This study reviews the suitability of the ceramic cup as an experimental aid for the retrieval of soil solution samples for analysis and the issues associated with its use.
  E. Walsh and K.P. McDonnell
  The recorded rate at which water infiltrates into a soil is influenced by the physical condition of the soil, current and previous uses of the soil and the method and equipment used to record the infiltration rate. Soil’s natural variability and the potential inaccuracy associated with particular methods can overestimate infiltration rate. To determine the most suitable apparatus for repeated use at a small-scale, a number of trials were conducted to investigate the influence of the method and moisture regime on the recorded infiltration rate. Trials were conducted on a medium clay-loam soil which has cropping history of maize-winter wheat-grass-grass-grass. It was observed that there was no significant difference in recorded infiltration rates which could be attributed to the practice of pre-saturating the soil prior to measuring infiltration rate. Furthermore, there was no significant difference between the rates recorded using a single ring infiltrometer and a double ring infiltrometer, indicating that these methods are equally suitable for infiltration rate determination when working at this scale which facilitates multiple replications in the same location or within a short timeframe.
  E.M. Curley , M.G. O`Flynn and K.P. McDonnell
  The objective of this study was to determine whether there was an increase in nitrate concentrations in soil water samples as a result of fertilizer nitrogen (N), in the form of cattle slurry, being applied at various rates to an establishing crop of Miscanthus; this trial was conducted during 2008/09. The crop received either no fertilizer (0-unfertilized control) or an annual application of 60, 120 or 180 kg N ha-1. Soil water solution samples were collected fortnightly from porous ceramic cup samplers. Nitrate (NO3¯) levels in these soil water samples were determined and monitored. In 2008, the soil water nitrate concentrations were high on all treatments, 14, 16 and 20 mg l-1, respectively for 0, 60 and 120 kg N ha-1. However, there was no significant difference between treatments. Soil water nitrate concentrations were again high (12-21 mg l-1) in 2009, particularly at the 180 kg N ha-1 levels which showed significantly higher levels of nitrate leaching when compared to all other treatments. A high level of nitrate is seen as a threat to both public health and natural waters. Of these threats the latter is the more immediate, but the health issue has attracted more public concern, as the presence of nitrate in drinking water has been linked to a number of medical conditions such as blue baby syndrome (methaemoglobinaemia) in infants. The results indicate that leaching losses were closer to those recorded under arable land than extensively managed grassland; slurry application on an establishing Miscanthus crop does not appear to contribute adversely to levels of nitrate in groundwater when compared to other more extensive cropping systems.
 
 
 
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