ALBERT

Description: Nitrogen availability is often a limiting factor for optimum crop growth on agricultural soils amended with papermill biosolids (PB). The objective of our study was to evaluate the effect on corn (Zea mays L.) and soybean (Glycine max L.) production of adding supplementary nitrogen fertilizer to soils amended with increasing rates of PB. Papermill biosolids were applied annually on four agricultural soils in southern Ontario, Canada. Treatments included three rates of PB (50, 100, and 150 Mg ha-1), combined with four levels of nitrogen fertilizer [crop recommended [CR], [CR] + 0.5 kg N Mg-1 PB, [CR] + 1.0 kg N Mg-1 PB, and [CR] + 1.5 kg N Mg-1 PB]. In addition, non-amended plots were also established receiving either (a) zero PB and zero nitrogen fertilizer or (b) zero PB and [CR] nitrogen fertilizer only. All the plots received the same treatment combinations, i.e., PB × N, each year for the duration of the study. In corn, [CR] nitrogen fertilizer was insufficient to satisfy plant growth and PB decomposition requirements. Supplementary nitrogen fertilizer at a rate of 1.0 kg N Mg-1 PB was generally required to maintain or increase corn grain production relative to the control plots receiving the [CR] nitrogen fertilizer only. Corn grain yield increases ranged from 1000 to 6000 kg ha-1 relative to the control at some of the research sites. The optimum rate of supplementary nitrogen fertilizer varied by soil texture (location) and year. In contrast, production of soybean did not require high supplementary nitrogen fertilizer, or in some cases any, in order to maintain or increase yields at most locations. Our study shows that nitrogen fertility management had a greater impact on yields in production systems planted to corn than soybeans while receiving annual PB amendments. No residual effects on corn yield or corn grain protein content were observed after PB amendments were stopped.Key words: Papermill biosolids, carbon:nitrogen ratio, corn, soybean, nitrogen fertilizer

Description: Gillis, J. D., Price, G. W. and Stratton, G. W. 2014. Detection and degradation of organic contaminants in an agricultural soil amended with alkaline-treated biosolids. Can. J. Soil Sci. 94: 595–604. The agricultural use of wastewater biosolids is a common practice in many countries, but concerns exist regarding the presence of organic wastewater contaminants that remain in the land-applied biosolids. The objective of this study was to determine if contaminants present in biosolids are detectable in soil following land application. A suite of organic contaminants were monitored by gas chromatograph with mass spectrometer in agricultural soil samples from a site amended with increasing rates of alkaline-treated biosolids. Triclosan, a common antimicrobial agent, was detected at levels greater than the reporting limit in an environment-controlled incubation study and validated through in situ field samples from soils receiving the same alkaline-treated biosolid. A rapid decrease in triclosan concentration was observed during the first few weeks of the incubation study, with concentrations decreasing from 92±26 to 20±2 ng g−1 (average 78% decrease) after 4 mo. The field results indicate that triclosan in fall-applied may persist overwinter. However, a rapid decrease in triclosan concentration during the spring and summer months led to levels lower than predicted following the spring application, and levels below our reporting limit (up to 85% decrease) by the end of the study. Removal is posited to be through aerobic microbial degradation.