Daire Ó hUallacháin

Storm Event Suspended Sediment-Discharge Hysteresis and Controls in Agricultural Watersheds: Implications for Watershed Scale Sediment Management

Within agricultural watersheds suspended sediment-discharge hysteresis during storm events is commonly used to indicate dominant sediment sources and pathways. However, availability of high-resolution data, qualitative metrics, longevity of records, and simultaneous multiwatershed analyses has limited the efficacy of hysteresis as a sediment management tool. This two year study utilizes a quantitative hysteresis index from high-resolution suspended sediment and discharge data to assess fluctuations in sediment source location, delivery mechanisms and export efficiency in three intensively farmed watersheds during events over time. Flow-weighted event sediment export was further considered using multivariate techniques to delineate rainfall, stream hydrology, and antecedent moisture controls on sediment origins. Watersheds with low permeability (moderately- or poorly drained soils) with good surface hydrological connectivity, therefore, had contrasting hysteresis due to source location (hillslope versus channel bank). The well-drained watershed with reduced connectivity exported less sediment but, when watershed connectivity was established, the largest event sediment load of all watersheds occurred. Event sediment export was elevated in arable watersheds when low groundcover was coupled with high connectivity, whereas in the grassland watershed, export was attributed to wetter weather only. Hysteresis analysis successfully indicated contrasting seasonality, connectivity and source availability and is a useful tool to identify watershed specific sediment management practices.

Barley (Hordeum vulgare)-induced growth inhibition of algae: a review.

Many field and laboratory studies have attempted to explain the inhibitory effect of rotting barley on algae. Early field studies lacked controls and replication and results depended on visual observations. Such studies offer information on barley bale field construction and application rates. In the laboratory, discrepancies in the barley variety used, algal species tested, barley liquor preparation and phenol extraction methodologies existed. Inconsistencies have led to different growth responses for the same species of algae tested, i.e. with some studies finding an inhibitory response and other studies reporting an accelerated growth response of algae. Two successful forms of investigation have been identified: (a) using commercially available compounds, i.e. with known shikimate-pathway-producing phenols and acids, which can then be combined with algal assays of different algal species and (b) using commercially available algal species from which batch cultures are grown, which are then added to barley liquor of different ages. Algal growth may then be investigated using in vivo fluorescence and the filtrate can be analysed via HPLC/MS. The identification of allelochemicals, which range from phenolics to quinones within the Poaceae family of which barley is a member, has received a lot of attention in recent years.

Site-specific P absorbency of ochre from acid mine-drainage near an abandoned Cu-S mine in the Avoca–Avonmore catchment, Ireland

Abstract Acid mine-drainage from an abandoned Cu-S mine adit, located in the Avoca-Avonmore catchment in the southeast of Ireland, results in low-value ochre deposition. Ochre found on-site had similar physical (particle size 97.7% <2 mm and dry bulk density 0.8 g cm3), but dissimilar maximum P-retention characteristics (16-21 g P kg-1) to coal-mining ochre found in the UK. Stereomicroscopy identified oolites and diatoms in the ochre that were indicative of acidic environments. X-ray diffraction showed Fe mineralogy consisting of goethite, jarosite and minor amounts of ferrihydrite. Investigations by inductively coupled plasma-mass spectrometry and bulk energy-dispersive spectroscopy showed potentially toxic concentrations of Fe, Zn, Pb, As and Cu. Rapid mobilization of metals occurred during P-adsorption tests, which makes Avoca ochre unsuitable for use in a surface-water environmental technology.

A review of evidence on the environmental impact of Ireland’s Rural Environment Protection Scheme (REPS)

Received 19 October 2009. Accepted 28 February 2011. Published 29 March 2012. Since its inception in 1994, there has been strong demand for evidence of the environmental effectiveness of the Rural Environment Protection Scheme (REPS), which has paid farmers in the Republic of Ireland over €3 billion up to 2010. A variety of research projects have been undertaken that investigate the environmental effects of REPS through an examination of either specific environmental measures or specific geographical areas. A review of available publications has confirmed the absence of a comprehensive, national-scale study of the environmental impacts of REPS. For this reason, there is insufficient evidence with which to judge the environmental effectiveness of the national-scale implementation of the whole scheme. For some specific meas ures, however, sufficient evidence is available to inform an objective assessment in some cases, and to help learn how to improve environmental effectiveness in most cases. The majority of the REPS payments are now dedicated to biodiversity objectives. Thus, biodiversity measures and options should be a priority for any national-scale environmental assessment of the scheme. Such a study would help identify the environmental benefits of REPS, the specific elements of REPS that are performing adequately, and those elements that are in need of improvement. Given the considerable overlap between REPS measures and options and those included in the 2010 Agri Environment Options Scheme (AEOS), the assessment of REPS measures could also be used to inform the likely environmental performance of the AEOS.

Agricultural Dairy Wastewaters

In Ireland, farming is an important national industry that involves approximately 270,000 people, 6.191 million cattle, 4.257 million sheep, 1.678 million pigs and 10.7 million poultry (CSO, 2006). Agriculture utilizes 64% of Ireland’s land area (Fingleton and Cushion, 1999), of which 91% is devoted to grass, silage and hay, and rough grazing (DAFF, 2003). Grassbased rearing of cattle and sheep dominates the industry (EPA, 2004). Livestock production is associated with external inputs of nutrients. Phosphorus (P) surpluses accumulate in the soil (Culleton et al., 2000) and contribute to P loss to surface and groundwater (Tunney, 1990; Regan et al., 2010). Elevated soil P status has been identified as one of the dominant P pressures in Ireland (Tunney et al., 2000). Schulte et al. (2010) showed that it may take many years for elevated soil P concentrations to be reduced to agronomically and environmentally optimum levels. The extent of these delays was predominantly related to the relative annual P-balance (P balance relative to total P reserves). While the onset of reductions in excessive soil P levels may be observed within five years, this reduction is a slow process and may take years to decades to be completed. Agricultural wastes and in particular dairy slurry and dirty water are discussed in this chapter. However, while the term ‘waste’ is commonly used for these materials, it is an unfortunate label, as it suggests that the materials have no further use and are merely a nuisance by-product of farming systems that must be managed. However, given the high nutrient contents of these materials, it is far more appropriate for them to be considered as organic fertilizers, and as such being a valuable commodity for the farmer. With higher and more volatile chemical fertilizer prices in recent years, the fertilizer replacement value in economic terms of these materials is increasing. Therefore, the management of agricultural ‘wastes’ in a manner that maximises the nutrient recovery and fertilizer value to crops should be a priority within any management plan for these materials. Nutrient contents and various research areas regarding management, remediation and control of such nutrients to prevent losses to the environment are discussed. The Surface Water Directive, 75/440/EEC (EEC, 1975), the Groundwater Directive, 80/68/EEC (EEC, 1980), the Drinking Water Directive, 98/83/EC (EC, 1998), the Nitrates Directive, 91/676/EEC (EEC, 1991(a)) and the Urban Wastewater Directive, 91/271/EEC (EEC, 1991(b)), combined with recent proceedings taken against the Irish State by the EU Commission alleging non-implementation of some aspects of the directives, has focused

Field margins: a comparison of establishment methods and effects on hymenopteran parasitoid communities

Field margins within intensively managed ecosystems are often seen as a last refuge for biodiversity, and are typically targeted with measures within many agri‐environment schemes. Grassland accounts for 81 million ha of land within the EU; however, the ecology of field margins associated with permanent grassland has not been well studied. This study investigated the effects of experimental field margin measures on hymenopteran parasitoid communities over a 5‐year period. Hymenopteran parasitoids were chosen because they occupy high trophic levels, feed on a diverse range of plant and invertebrate hosts, and are considered good indicators of arthropod diversity. Establishment methods included: fencing, natural regeneration, and reseeding with a wildflower mixture, at three margin widths. Field margin establishment method had a significant effect on abundance of parasitoids. Establishment method did not have a significant effect on parasitoid genera diversity, but did affect parasitoid community composition. Margin width had no significant impact on parasitoid communities. Grazing had a significant negative effect on parasitoid genus richness and community structure. This suggests that structural diversity of vegetation plays an important role in parasitoid community structure. Plant species richness did not significantly affect parasitoid abundance or genera richness. Noxious species within plots resulted in a significantly greater abundance and diversity of parasitoids and of idiobionts in particular. Where plant species richness is limited, simple measures such as fencing of narrow field margins may be as effective at increasing parasitoid taxon richness and abundance (indicators of arthropod richness and abundance) as expensive measures such as reseeding and wider margin widths.

Multiple-stressor effects of sediment, phosphorus and nitrogen on stream macroinvertebrate communities

Multiple stressors affect stream ecosystems worldwide and their interactions are of particular concern, with gaps existing in understanding stressor impacts on stream communities. Addressing these knowledge gaps will aid in targeting and designing of appropriate mitigation measures. In this study, the agricultural stressors fine sediment (ambient, low, medium, high), phosphorus (ambient, enriched) and nitrogen (ambient, enriched) were manipulated simultaneously in 64 streamside mesocosms to determine their individual and combined effects on the macroinvertebrate community (benthos and drift). Stressor levels were chosen to reflect those typically observed in European agricultural streams. A 21-day colonisation period was followed by a 14-day manipulative period. Results indicate that added sediment had the most pervasive effects, significantly reducing total macroinvertebrate abundance, total EPT abundance and abundances of three common EPT taxa. The greatest effect was at high sediment cover (90%), with decreasing negative impacts at medium (50%) and low (30%) covers. Added sediment also led to higher drift propensities for nine of the twelve drift variables. The effects of nitrogen and phosphorus were relatively weak compared to sediment. Several complex and unpredictable 2-way or 3-way interactions among stressors were observed. While sediment addition generally reduced total abundance at high levels, this decrease was amplified by P enrichment at low sediment, whereas the opposite effect occurred at medium sediment and little effect at high sediment. These results have direct implications for water management as they highlight the importance of managing sediment inputs while also considering the complex interactions which can occur between sediment and nutrient stressors.

Soils and Water Quality

Ireland has a diverse physical landscape of upland and lowland inland waters represented by 13,200 km of river and 12,000 lakes framed by an estimated 3171 km of coastline providing a range of freshwater ecosystem services. The quality and quantity of water flowing through Ireland’s inland and coastal waters are determined by the complex interaction of anthropogenic activities with soil and climate. It is the mosaic of soils that characterise the catchment draining a waterbody that regulates the flow of water through a catchment and the movement of nutrients and contaminants. In this chapter, we describe the role of soil as the matrix through which, water and contaminants can be transported and retained within the Irish landscape, and the impacts on water quality in Ireland. Here we reference current water quality policies relating to diffuse of pollution from soils and describe processes and functions identified in Irish soils that influence nutrient and sediment transport to affect water quality in Ireland.

The Environmental Impact of Cattle Access to Watercourses: A Review

The degradation of freshwater resources and loss of freshwater biodiversity by anthropogenic activities, including agriculture, are of major global concern. Together with diffuse pollutants, point sources, such as where cattle have direct access to riparian margins and watercourses, can potentially present significant environmental challenges. These can include impacts on stream morphology, increased sedimentation, nutrient additions, microbial contamination, and impacts on aquatic biota. Mitigation measures aimed at reducing these frequently include reducing the amount of time cattle spend in riparian margins and watercourses. This is often accomplished through the provision of an alternative water supply and grazing management, or even cattle exclusion measures. Although a number of studies refer to potential negative impacts, there has been little attempt to review previous research on this topic. The key aim of this paper is to collate and review these disparate studies, as well as those relating to the effectiveness of mitigation measures. Although it is difficult to draw generalizations from studies due to the inherent variability between and within catchments, evidence pertaining to impacts in relation to sedimentation, pathogens, and riparian margin vegetation were strong. Conclusions in relation to impacts on stream morphology and nutrient parameters were less clear, whereas studies on responses of macroinvertebrate communities were particularly variable, with differences due to cattle access difficult to separate from catchment scale effects. A greater understanding of the impact of cattle access on watercourses under varying conditions will help inform policymakers on the cost effectiveness of existing management criteria and will help in revising existing measures.

A comparison of grassland vegetation from three agri-environment conservation measures

Abstract Semi-natural grassland habitats have declined significantly throughout Europe. To halt the decline, grassland conservation measures have been included in most European agri-environment schemes. This is the first study to compare the botanical composition of grassland habitats managed under the Irish Agri-Environment Options Scheme (AEOS). Sixty fields on drystock pastoral farms in receipt of agri-environment payments for grassland conservation were surveyed, with 20 fields being enrolled in each of the following AEOS options: Traditional Hay Meadow (THM), Species-Rich Grassland (SRG) and Natura 2000 species-rich grassland (Natura). The vegetation quality of sites enrolled in the Natura measure was higher than the quality of those enrolled in the THM and SRG measures. Natura sites had the greatest species richness, with a mean >40 species per site, which included approximately 17 species indicative of high botanical quality. Traditional Hay Meadows sites had the lowest species richness (mean: 29 species per site) and were dominated by species associated with improved grassland. Some THM sites had good levels of botanical richness and were similar in composition to Natura sites, with some Natura sites having lower vegetation quality, more similar to that of THM sites. Species-Rich Grassland had botanical richness that was intermediate between THM and Natura sites. A thorough assessment of the effectiveness of these measures was confounded by a lack of quantitative objectives for the target community composition to be attained. We discuss limitations and potential opportunities regarding the design, targeting, implementation and cost-effectiveness of these agri-environment measures.