Denitrifying woodchip bioreactors (WBR), which aim to reduce nitrate (NO₃⁻) pollution from agricultural drainage water, are less efficient when cold temperatures slow down the microbial transformation processes. Conducting bioaugmentation could potentially increase the NO₃⁻ removal efficiency during these specific periods. First, it is necessary to investigate denitrifying microbial populations in these facilities and understand their temperature responses. We hypothesized that seasonal changes and subsequent adaptations of microbial populations would allow for enrichment of cold-adapted denitrifying bacterial populations with potential use for bioaugmentation. Woodchip material was sampled from an operating WBR during spring, fall, and winter and used for enrichments of denitrifiers that were characterized by studies of metagenomics and temperature dependence of NO₃⁻ depletion. The successful enrichment of psychrotolerant denitrifiers was supported by the differences in temperature response, with the apparent domination of the phylum Proteobacteria and the genus Pseudomonas. The enrichments were found to have different microbiomes’ composition and they mainly differed with native woodchip microbiomes by a lower abundance of the genus Flavobacterium. Overall, the performance and composition of the enriched denitrifying population from the WBR microbiome indicated a potential for efficient NO₃⁻ removal at cold temperatures that could be stimulated by the addition of selected cold-adapted denitrifying bacteria.

Nitrogen (N) and phosphorus (P) losses to surface and coastal waters are still critically high across Europe and globally. Measures to mitigate and reduce these losses are being implemented both at the cultivated land surface and at the edge-of-fields. Woodchip bioreactors represent a new alternative in Denmark for treating agricultural drainage water, and the present study—based on two years of data from five Danish field-based bioreactors—determined N removal rates varying from 1.49 to 5.37 g N m⁻³ d⁻¹ and a mean across all bioreactors and years of 2.90 g N m⁻³ d⁻¹. The loss of phosphorus was relatively high the first year after bioreactor establishment with rates varying from 298.4 to 890.8 mg P m⁻³ d⁻¹, but in the second year, the rates ranged from 12.2 to 77.2 mg P m⁻³ d⁻¹. The investments and the costs of the bioreactors were larger than expected based on Danish standard investments. The cost efficiency analysis found the key issues to be the need for larger investments in the bioreactor itself combined with higher advisory costs. For the four woodchip bioreactors considered in the cost efficiency analysis, the N removal cost was around DKK 350 per kg N ($50 per kg N), which is ca. 50% higher than the standard costs defined by the Danish authorities. Based on the estimated costs of the four bioreactor facilities included in this analysis, a bioreactor is one of the most expensive nitrogen reduction measures compared to other mitigation tools.

FAO AquaCrop model ver. 6.1 was calibrated and validated by means of an independent data sets during the harvesting seasons of 2016/2017 and 2017/2018, at El Noubaria site in western north of Egypt. To assess the impact of the increase in temperature and CO2 concentration on potato biomass and tuber yield simulations, experiments were carried out with four downscaled and bias-corrected of General Circulation Models (GCMs) data sets based on the fifth phase of the Coupled Model Intercomparison Project (CMIP5) scenarios under demonstrative Concentration Trails (RCPs) 4.5 and 8.5, selected for 2021–2040 and 2041–2060. The study showed that the model could satisfactorily simulate potato canopy cover, biomass, harvest and soil water content under various irrigation treatments. The biomass and yield decreased for all GCMs in both future series 2030s and 2050s. Biomass reduction varied between 5.60 and 9.95%, while the reduction of the simulated yield varied between 3.53 and 7.96% for 2030. The lowest values of biomass and yield were achieved by HadGEM2-ES under RCP 8.5 with 27.213 and 20.409 Mg∙ha–1, respectively corresponding to –9.95 and –7.96% reduction. The lowest reductions were 5.60 and 3.53% for biomass and yield, respectively, obtained with MIROC5 under RCP 8.5 for 2030. Reductions in biomass and yield in 2050 were higher than in 2030. The results are showing that higher temperatures shortened the growing period based on calculated growing degree days (GDD). Therefore, it is very important to study changing sowing dates to alleviate the impact of climate change by using field trials, simulation and deep learning models.