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Nutrient export from agricultural land to surface waters is a significant environmental concern within the Great Lakes Basin (GLB). A field-based watershed-scale study was completed to investigate spatial and temporal variations of phosphorus and nitrate to assess nutrient transport pathways and groundwater-surface water interactions in an agriculturally dominated clay plain system. This was conducted in the 127 km2 Upper Parkhill Watershed, near Lake Huron in southwestern Ontario, Canada. Data collection occurred from June 2018 to May 2019 via continuous sensor deployment and discrete sampling of stream water, groundwater, hyporheic zone, and tile drainage water. Samples were analyzed for various nutrient species (total, total dissolved, soluble reactive, and particulate phosphorus, and nitrate-N) to examine the hydrological dynamics of principal transport pathways of agriculturally-derived nutrients. Total phosphorus and nitrate concentrations in stream water ranged from 0.007 to 0.324 mg/L and 0.32 to 13.13 mg NO 3 −-N/L, respectively. Tile drainage water total phosphorous concentrations varied from 0.006 to 0.066 mg/L. Groundwater total dissolved phosphorus concentrations ranged from <0.003 to 0.085 mg/L. Transport of phosphorus through tile drainage was observed to be greater than through groundwater over the study period. No distinct relationship was observed between nutrient concentrations in the hyporheic zone and the vertical hydraulic gradient within this zone in the studied stream reach. Preliminary correlations were discerned between water quality observations and recognized land management practices. Given the elevated stream nutrient concentrations, these results are consequential for the continual improvement of strategies and programs devised to conserve water resources within the GLB. [ABSTRACT FROM AUTHOR]

Currently, there are no published data available to describe the influence of herbicide residues on establishment and function of fall-seeded cover crops. Field experiments were conducted in 2012/2013 and 2013/2014 in Ontario, Canada, to characterize the effects of soil residues of selected herbicides on establishment and function of oat ( Avena sativa L.), hairy vetch ( Vicia villosa L.), oilseed radish ( Raphanus sativus L.) and cereal rye ( Secale cereale L.). These cover crops were planted three months after application of imazethapyr at 100 and 200 g ha −1 , s-metolachlor/atrazine plus mesotrione at 2880 + 140 and 5760 + 280 g ha −1 , and saflufenacil/dimethenamid-p at 735 and 1470 g ha −1 . Imazethapyr residues caused up to 65 and 30% visible injury to oilseed radish at 1 and 4 WAE, respectively. Plant light attenuation, shoot dry weight and shoot nitrate-nitrogen uptake from imazethapyr residues three months after application were reduced up to 77, 34 and 43%, respectively in oilseed radish compared to non-treated control. Oat, hairy vetch and cereal rye were not negatively impacted by any of the herbicide residues tested. Preliminary evidence suggests that oat, hairy vetch and cereal rye may be safely seeded three months after saflufenacil/dimethenamid-p, s-metolachlor/atrazine plus mesotrione, and imazethapyr applied PRE at the currently registered rates. It is recommended however, that oilseed radish not be seeded three months after imazethapyr application. [ABSTRACT FROM AUTHOR]

Abstract: Composting is an environmentally sound method for the disposal of on-farm livestock mortalities that generates material suitable for use as fertilizer; however, this method is not generally permitted for disposal of transgenic livestock mortalities during the research and development phase. This study has explored the application of the polymerase chain reaction (PCR) as a method for assessing the persistence of transgene and mitochondrial DNA markers during the composting of euthanized transgenic pig. There was at least a 107 fold reduction of genetic material to a level that not either transgene or mitochondrion markers were detectable. At the end of the composting period, only bone fragments that were completely demineralised and chalky were detected. Chemically the compost was similar to that from pig litter and poultry mortalities, except the copper content was lower. Based on these data, composting appears to be an appropriate method for the disposal of transgenic animals. [Copyright &y& Elsevier]