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The benefit of using access materials for soil stress reduction depends on the material's properties and vehicle mean ground pressure
No full textConstruction activities can induce soil compaction due the use of heavy vehicles and repeated vehicle passes. Driving on access material reduces the risk of compaction, but data on soil stress reduction are lacking. This study investigated the effect of three access materials (0.5 m thick sand track, 0.3 m thick timber mattresses, and 0.1 m thick composite mats) on soil stress, relative to driving on unprotected soil. Mean normal stress was measured at 0.2 and 0.4 m soil depths for tracked and tyred construction vehicles (bulldozer, excavator, dump truck, and tractor-trailer). We used finite element modelling to investigate the effect of material's thickness and stiffness on soil stress reduction. Measurements revealed that driving on access material reduced soil stress by 21-77 % and 0-60 % at 0.2 and 0.4 m depths, respectively. Stress reduction increased with increasing mean ground pressure and was larger for tyred than for tracked vehicles. The tested access materials reached a comparable effect, but simulations indicated that additional stress reduction could be achieved by increasing the stiffness or thickness of the material. Thus, more rigid or thicker material achieve greater soil stress reductions. These characteristics should be balanced against costs, transport, and ease of handling of the material
Agronomic and environmental performance of animal manure-derived ammonium salts vs synthetic mineral fertilisers: 4-year field trial evidence
No full textThe European Union (EU) increasing focus on sustainable practices, especially in agriculture, highlights the critical importance of addressing concerns related to the geographical polarity of nutrients and the limited availability of natural reserves. This growing awareness is fueling the adoption of eco-friendly bio-based fertilisers (BBFs) over their mineral counterparts. This study addresses this knowledge gap by subjecting two BBFs, ammonium sulphate (AS) and ammonium nitrate (AN), to a comprehensive 4-year field trial involving crop rotation with maize, spinach, and potatoes at incremental application rates of 40 %, 70 % and 100 % crop total nitrogen (N) demand. The study also evaluates the environmental impacts of these BBFs by comparing gaseous emissions and nitrate leaching risks against their mineral counterparts. Despite challenges arising from the variability in weather conditions during the 4 years of the trial, the selected BBFs demonstrated comparable performance to synthetic ammonium nitrate. The comparative yield range ratio (YieldBBF: Yieldmineral fertiliser) ranged from 0.86 to 1.09 for AS and from 0.49 to 1.02 for AN throughout the 4-year field trial duration at 100 % N rate. Moreover, laboratory-based experiments showed significantly lower gaseous emissions for AS (10.39 CO₂- eq) and AN (2.81 CO₂-eq) than for their mineral counterpart (15.25 CO₂-eq), likely reflecting slower mineralisation, reduced N₂O emission peaks, and soil pH dynamics relative to the calcium ammonium nitrate reference. Additionally, residual nitrate during winter period from field in the soil remained similar in the case of BBFs and mineral counterparts at all dosages for all 4 years. This indicates that crop uptake and seasonal variability outweighed differences in fertiliser source. These findings emphasize the potential of BBFs to perform at par with mineral fertilisers while offering environmental benefits, making them well suited as a future alternative in circular agriculture
Nitrogen fertilization does not affect non-symbiotic N2 fixation in northern forest soils despite its negative impacts on diazotroph communities
No full textTree productivity in northern regions is limited by low soil nitrogen (N) availability, and biological N2 fixation is a crucial N input to these forests. To enhance forest productivity, N fertilization has been proposed as a strategy although it may negatively affect N2 fixation and the abundance of diazotrophic microorganisms. In contrast to N2 fixation by the cyanobacteria-moss associations, there is limited understanding of non-symbiotic N2 fixation in northern forest soils and the free-living diazotrophs involved. To assess the impact of N fertilization on non-symbiotic N2 fixation and the diazotrophic community in soil, we sampled 15 forest sites along a latitudinal gradient in Sweden that are part of a fertilization experiment. Fertilization started between 41 and 55 years ago, using ammonium nitrate at 100-150 kg N ha-1 every 5th year for the first 25 years and thereafter every 7th year. We measured non-symbiotic N2 fixation in the soil organic layer in laboratory incubations and analyzed the diazotrophic community. Both the abundance and diversity of diazotrophs decreased in response to N fertilization. However, this decline did not translate into significant changes in non-symbiotic N2 fixation rates (22.4 +/- 4.2 and 22.5 +/- 5.7 ng N g-1 dry weight soil h-1 in the control and N treatments, respectively). Yet, N2 fixation per area increased by 24 % in fertilized plots because of the increase in the organic layer stock caused by higher primary production. Additionally, we observed an influence of fertilization and mean annual temperature on diazotroph community composition across the gradient. Our findings indicate that N fertilization in northern forests strongly affects diazotrophs, the organic layer stock, and N2 fixation. Although N fertilization positively affected the N2 fixation rate per area in this experiment, its negative effect on diazotroph diversity might reduce N2 fixation in the long run
Long-term carbon sequestration and heatwave resilience in an old hemiboreal upland coniferous forest
No full textBoreal forests play an important role in the global carbon cycle due to their extensive area and ability to sequester a considerable amount of atmospheric carbon dioxide (CO2). They are generally stable ecosystems that function as carbon sinks. However, their sink capacity is vulnerable to the impact of extreme weather conditions. In this study, we aim to investigate the multi-year and seasonal carbon dynamics of an old upland coniferous forest in the hemiboreal zone, identify the main environmental drivers influencing annual NEP, and explore the potential legacy effects of the 2018 heatwave. Over an eight-year period (2016-2023), the forest shifted from a carbon sink (mean net ecosystem productivity (NEP) of 238 f 52 g C m-2 year-1) to a carbon-neutral state in 2020 (NEP = -2 f 5 g C m-2 year-1) and back to a net carbon sink (NEP = 136 f 50 g C m-2 year-1). The average NEP over the eight-year period was 170 f 42 g C m-2 year-1. Our research showed no significant yearto-year changes in GEP during the study period, while the changes in Reco were substantial. Our results confirm that air temperature has the greatest influence on annual NEP. The warmest autumn over the past 19 years, recorded in 2020, and an atypical June together resulted in a noticeable increase in ecosystem respiration, which shifted annual NEP towards negative net values, while no significant impact on GEP was found. Additionally, our study found that the old upland hemiboreal forest showed no legacy effect in the years following the 2018 heatwave, demonstrating its resilience to extreme temperature events. Our results underscore the importance of continuous monitoring carbon dynamics variability to determine the ecosystem's resilience to seasonal temperature fluctuations and to inform management strategies for forests preservation
Closed-loop air recirculation architecture for alkaline urine dehydration and water recovery using regenerable superabsorbent polymers
No full textWe evaluated a novel closed-loop evaporative system designed to concentrate alkalised human urine while simultaneously recovering water using regenerable superabsorbent polymers (SAPs). This architecture recirculates air and physically isolates urine from atmospheric CO₂, thereby maintaining high alkalinity and preventing enzymatic urea hydrolysis. The system was operated at ∼30 °C using sodium polyacrylate, potassium polyacrylate, or a 1:1 (w/w) blend of both SAPs across eight absorption–desorption cycles. All treatments exhibited high initial water uptake (>1.4 kg m−2 day−1) and gravimetric absorption (>0.8 g g−1), with performance declining due to polymer fatigue after repeated use. FT-IR spectra revealed the depolymerisation of the acrylate backbone leading to the formation of acrylic acid residues, confirming chemical deterioration during the thermal regeneration of the SAPs. Notably, the closed-loop design eliminated the need for supersaturating urine with Ca(OH)₂, which is required in open evaporative systems to buffer against CO₂-induced acidification. Colorimetric and targeted metabolomic analyses confirmed complete nitrogen retention and > 99 % recovery of the 30 most abundant endogenous organic solutes in urine, including urea, creatinine, and hippuric acid. These results demonstrate that low-temperature evaporation can preserve the full biochemical complexity of urine, producing a dry, sanitised fertiliser as well as water with extremely low organic content
Under-sown ryegrass cover crops mitigate increased nitrogen leaching risks in a warming climate: Evidence from a 34-year field study in south-west Sweden
No full textThe effects of repeatedly cultivating under-sown cover crops (CC) on nitrogen (N) leaching were investigated in a long-term field experiment in SW Sweden (1989-2023). Treatments with and without CC and with and without N fertilization were compared (CC_90N, 90N, CC_0N, and 0N). The impact of temperature, precipitation and the large-scale North Atlantic Oscillation index (NAOi) was also explored. N leaching was measured in separately tile-drained field plots in which also the yield of the main crop, biomass and N content of the cover crop, and soil nitrate were determined. The mean annual N concentration in drainage and the annual N leaching were significantly smaller in CC_90N than in 90N in 18 out of 34 years. A trend analysis showed that N concentrations in drainage increased significantly after 2010 in both treatments without CCs but not in those with CCs. The reduction in N leaching by growing CCs averaged 48 % (CC_90N) over the period and did not decrease over time. NAOi correlated with temperature and precipitation and showed a positive trend after 2010. NAOi was positively correlated with N leaching in 90N but not in CC_90N. Furthermore, NAOi was positively correlated with N content in CC biomass. Our results suggest that on-going climate change in Scandinavia and periods of high NAOi result in higher N mineralization and higher N leaching. The study also shows that under these circumstances, growing an under-sown ryegrass cover crop is an effective measure for environmental protection since its N uptake compensates for higher N mineralization
How accurate are food waste tracking systems? Insights from healthcare and hotel kitchens
No full textFood waste tracking systems (FWTS) have become increasingly common as monitoring tools in the food service sector. Yet, staff-reported FWTS data are subject to uncertainties from enumerator bias, and their accuracy has rarely been investigated or empirically tested. This study provides insights into the reliability of FWTS data from three healthcare kitchens and one hotel kitchen. Using a staggered experimental design, staff-reported data (≥ 21 days) were compared with scientific control data (6 days) collected with the same FWTS under constant conditions. Staff-reported FWTS data underestimated food waste quantities by up to 80 %, with an average underreporting of approx. 29.4 % across mealtimes (breakfast, lunch, dinner) in the healthcare kitchens and approx. 30.7 % during breakfast buffet in the hotel kitchen. Our results also show that staff-reported FWTS quantities can shift the true mean values toward a biased underestimation without widening the confidence interval, making comparisons appear precise but inaccurate
Effects of whole-tree harvesting on nutrient accumulation in the subsequent forest stand: An examination of 6 Swedish long-term experiments
No full textWhole-tree harvesting (WTH) is associated with increased nutrient losses compared to stem-only harvesting (SOH), potentially depleting the soil nutrient stocks and causing reduced growth and lower nutrient accumulation in biomass of the subsequent stand. This reduction in nutrient uptake, when expressed as a reduced net base cation uptake, can act as an "uptake brake", that may lead to lower biological soil acidification. We used six Swedish long-term field experiments with randomized block design on WTH vs SOH performed in final fellings or thinnings to examine the long-term effects on nutrient status. The nutrient stocks in soil and biomass were examined 25 - 37 years after final felling, and 13-20 years after thinning. Following final felling, the total aboveground biomass, as well as stocks of N, P, and base cations (BC) in biomass, were significantly larger in SOH than WTH, but no such treatment differences were revealed after thinning. The differences in growth, not element concentrations, were in general the most important factor affecting rates of element accumulation in biomass. The "total stocks" of BC (salt exchangeable fraction in the soils plus aboveground biomass) were significantly larger following SOH than WTH after both final felling and thinning. The same pattern was found for the soil C stocks while only final felling exhibited significantly larger soil N stocks in SOH compared with WTH. These results support the hypotheses that WTH in final felling results in reduced tree growth in the subsequent forest stand, leading to lower nutrient uptake and thereby lower acidification pressure of the new stand compared to SOH
Intensive land use enhances soil ammonia-oxidising archaea at a continental scale
No full textArchaea are an important group of soil organisms that play key roles in carbon and nitrogen cycling, particularly in nitrification (ammonia oxidation) and methanogenesis. However, there are knowledge gaps regarding their importance in ecosystem processes relative to other microbial groups and how they may be impacted by land-use and environmental changes. Here, by carrying out a continental-scale sample collection and utilising archaeaspecific primers for metabarcoding and shotgun metagenomics, we aimed to decipher the structure and function of archaeal communities across various land-use types in Europe. Metagenomic data reveal that land-use intensification increases the relative abundance of archaea, whereas bacteria and eukaryotes show no increase. Alongside this, ammonia oxidising archaea (AOA) increase as a proportion of the total metabarcoding reads, from 1 % of archaea in coniferous woodland to >90 % in croplands. Functional gene profiles reveal that land-use intensification shifts archaeal communities from adaptive metabolic pathways in forests to specialised, ammonia-oxidising microbes in fertiliser-enriched cropland soils. Our data suggest that land-use intensification may shift archaeal communities toward greater dependence on external nitrogen inputs, with potential consequences for soil fertility and greenhouse gas emissions
Agro-environmental profile of potato cultivation under water and nitrogen managements - A case study in Denmark
No full textPotato field management in Europe is already optimized for high production and tuber quality; however, numerous environmental challenges remain if the industry is to achieve "green economy" targets, such as less resources utilized, and less nitrate leached to the environment. Strategic co-scheduling irrigation and nitrogen (N) fertilization might increase resource use efficiency while minimizing reactive losses such as nitrate leaching. This study aimed to quantify the combined effect of irrigation and N fertilization on potato production, growth, and resource use efficiencies. A field experiment was conducted from 2017 to 2019 on a coarse sandy soil in Denmark, with a drought event occurring in 2018. Full (Ifull, maximized), deficit (Idef, 70-80 % of Ifull) and low irrigation treatments (Ilow, minimized amount to keep crop survival), each under full (Nfull, maximized) and variable (Nvar, variable amount according to the crops' needs) N fertilization were applied. The analyses results show that Ilow limited potato growth under a drought-heat event; otherwise, potato growth was comparable between Ifull and Idef treatments, with 31-32 % higher irrigation efficiency (IE) under Idef than under Ifull. Nitrate leaching was variable and not significantly different among the treatments, being in general 9-13 % lower under Idef in absolute terms than under Ifull. Unexpectedly, outcomes from Nvar were statistically lower compared to those from Nfull. Radiation use efficiencies (RUEs) from Ilow and Nvar were significantly lower than from Ifull and Idef (14-19 %), and from Nfull (9-11 %). N use efficiencies (NUE) were comparable between N fertilization treatments but significantly different among different irrigation treatments. Overall, this study confirms that Idef is the best irrigation strategy. Future efforts should focus on developing improved approaches for detecting inseason crop N status and further quantifying N requirements, as well as promoting the co-scheduled management of irrigation and N fertilization. Remote sensing approaches have great potential to assist with this