• Impact of Soil Type, Biology and Temperature on the Survival of Non-Toxigenic Escherichia Coli O157

      Moynihan, Emma; Richards, Karl G.; Ritz, Karl; Tyrrel, Sean; Brennan, Fiona P.; Teagasc Walsh Fellowship Programme (Royal Irish Academy, 14/06/2013)
      The occurrence of microbial enteropathogens in the environment can represent a serious risk to human health. The fate of enteropathogens introduced into the soil environment is dependent on a wide range of complex interacting environmental factors. While the effect of abiotic factors on enteropathogen survival has been widely examined, the interaction of enteropathogens with the soil microbial community is poorly understood. This study investigated the effect of soil biology and soil type on the survival of a non-toxigenic strain of Escherichia coli O157 under different temperature regimes. Soil microcosms of two soil types, with and without an intact microbial community, were inoculated with the enteropathogen surrogate, and survival was determined over a 64-day period, encompassing a shift from cold to ambient temperatures. In both soil types bacterial numbers decreased in soil with an intact microflora, while in the absence of an intact community E. coli populations increased. This effect was temperature specific, with E. coli populations remaining stable at low temperature, regardless of treatment. Soil type was of importance in survival at both cold and ambient temperatures. This work highlights the signifi cance of the soil microbial community in suppressing enteropathogens in soil, and of investigating die-off in a multi-factorial manner.
    • Nitrogen and Phosphorus Availability From Various Composted Wastes For Use In Irish Agriculture And Horticulture

      Lee, Alan; Teagasc Walsh Fellowship Programme (2016-02)
      Current environmental EU legislation promotes recycling and recovery from organic waste products. Compost has been identified as an alternative to inorganic fertilisers and animal slurries as a nutrient source for crop plants. This study aimed to investigate nitrogen (N) and phosphorus (P) availability from various composted waste through detailed characterisations, complemented by short term lab incubations and long term plant growth experiments. Twenty-five composts were selected and classified by their groups. The composts were characterised by multiple different analytical techniques. Two incubation studies were conducted. One investigating N and P mineralisation potential of the composts and the second on the effects or soil type on P mineralisation. Two large glasshouse based pot experiments were then conducted. A subsequent stability study of two separate methods on mechanical biological treated waste was also investigated for a potential relationship. Characterisation of the composts highlighted the difference between compost feedstocks with the manure waste being distinctly separate from the other groups. The biowaste groups identified as either food waste or brown bin waste. The incubation experiment highlighted that N mineralisation was more predictable than P. From the pot experiment only manure waste mineralised N above 10%. All of the other groups mineralised minute amounts. Prediction of N mineralisation was found to be more accurate from lignin and neutral detergent fibre content over the more traditional C/N ratio. Mineralisation of small amounts of organic N occurred in summer months. There was a distinct lack of a relationship between the P incubation and pot experiment. Plant uptake of P was higher than expected for all treatments. The manure waste composts were higher in cumulative P uptake than inorganic fertiliser. Stability in composts was found not to affect mineralisation or induce immobilisation. The effects of soil type on composts were most pronounced in composts lower in fulvic acid. The composts with higher humic acid were not found to significantly mineralise a higher amount of P. The stability study investigating oxygen uptake rate (OUR) and respiration index (AT4) on the mechanical biological treated waste showed a high correlation between the two methods where AT4 was below 40 mg O2.g DM-1. The findings point to a possible reassessment of compost quality guidelines for composts. The availability of P is far greater and therefore should be considered the primary nutrient available from compost. The stability parameter for manure waste compost may also need assessing as it is unachievable in reasonable composting time frame. The biowaste compost has proven to be high in P. There is also the potential to develop quite specifically produced composts based on their feedstock and composting length for particular agronomic or environmental needs. Compost application is a feasible source of nutrients and organic matter due to escalating fertiliser prices and more stringent regulations surrounding fertilisers and slurries.