Crop performance on soils receiving annual papermill biosolid amendments with and without supplementary nitrogen

Abstract

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