Understanding the fate of fertilizer nitrogen (N) in cropping systems is critical to improving agricultural sustainability and minimizing environmental losses. However, efforts to trace fertilizer N are often complicated by manure application in dairy cropping systems. We used a stable isotope tracing approach to investigate how different manure products influence the fate of synthetic fertilizer N in a Midwestern maize silage system by tracking 15N-labled ammonium sulfate into crop biomass, soil organic matter fractions (particulate (POM) and mineral associated (MAOM)), and gaseous loss as nitrous oxide (N2O). Treatments included unprocessed liquid manure (LM), solid manure derived through chemical (CS) or physical (PS) separation, and a no-manure control (NM), combined with fertilizer rates of 90, 180, and 270 kg N ha−1. Cumulative N2O emissions increased significantly with both manure application and higher fertilizer rates, with PS having lower emissions than LM following fertilizer application. Fertilizer contributed similar proportions to cumulative N2O emissions regardless of manure treatment. Total fertilizer N uptake by crops did not differ among manure treatments, but crops took up more fertilizer N at higher fertilizer application rates. Notably, application of CS and PS enhanced fertilizer N retention in the 0–15 cm soil MAOM pool compared to LM and NM. These findings highlight that although manure type does not significantly affect fertilizer N uptake by crops or fertilizer-derived N2O emissions, solid manures (i.e., CS and PS) can significantly increase fertilizer N retention in soils, offering potential benefits for long-term soil fertility and reduced N losses.

In cropland soils, the majority of organic nitrogen (N) is stored in the mineral associated organic matter (MAOM) fraction of soil organic matter (SOM). Because strong bonds with mineral surfaces are thought to limit microbial access to MAOM, particulate organic matter (POM) is often assumed to drive N mineralization and nutrient cycling, despite being a smaller and more N-poor pool. Emerging evidence suggests that N in MAOM can be mobilized into mineralization pathways, challenging this assumption. Yet, when and how MAOM contributes to N mineralization remains unclear, particularly how SOM quantity, composition, and stoichiometry influence its contribution. To examine these dynamics, we reconstructed soils from physically isolated POM and MAOM fractions, systematically varying SOM composition. The MAOM was isolated from a soil previously amended with 15N fertilizer, which retained a distinct isotopic signature relative to the POM fraction. Leveraging this difference in isotopic composition, we applied a two-pool isotopic mixing model, with POM and MAOM as the endmembers, to quantify the contribution of both fractions to mineral N production. Across treatments, we observed strong effects of SOM content, POM C:N ratio, and POM:MAOM ratio on mineral N production. In the treatment most representative of agricultural soil conditions, ~ 75% of mineralized N originated from the MAOM. Higher POM C:N ratios increased the proportional contribution of MAOM to mineralized N, consistent with hypotheses around microbial N mining. While POM mineralized more rapidly on a per-unit basis, MAOM consistently contributed more total N to the mineralized pool. These findings demonstrate that MAOM can be a dominant source of mineralized N across a range of SOM conditions, even in the presence of high-quality POM. As MAOM represents the largest pool of organic N in cropland soils, understanding the factors governing its turnover is essential for improving nutrient management.

Land-use changes caused by urbanization profoundly impact biodiversity and ecosystem functioning. The impact of land-use changes on soil invertebrate communities has garnered attention, but few studies focused on how the intensity of land-use change associated with urbanization affects soil invertebrates. In this study, we investigated variations in Collembola taxonomic and isotopic diversity in four land-use types (natural forests, urban forests, urban parks and green median strips) in a subtropical city, representing a gradient of increasing land-use intensity. Collembola richness and biomass did not follow the studied land-use intensity gradient, rather, they were high in urban parks but low in urban forests. Similarly, isotopic diversity, as an indicator of niche diversity of Collembola communities, did not correlate with land-use intensity, with isotopic richness peaking in natural forests and urban parks, while isotopic uniqueness being highest in urban forests. Litter properties explained major variations in both taxonomic and isotopic diversity of Collembola, with their impacts largely outweighing those of land-use intensity and soil properties. Particularly, litter complexity, as indicated by litter species richness and the amount of decomposed litter, was the major factor promoting Collembola richness, biomass and isotopic diversity, while litter nutrients and moisture content played a subordinate role. Overall, our study demonstrates that well-managed urban greenspaces can act as restoration hubs for soil invertebrate communities. To foster soil animal communities and associated ecological functions in city systems, management approaches promoting litter complexity by increasing native plant diversity and litter accumulation should be adopted.

Evaluation of tidal marsh restoration success is typically based on the recovery of habitat size and target species. However, food-web structure may provide valuable insight into ecosystem functionin...

We used stable isotope analysis to investigate the association between foraging choices and reproductive success in roof-nesting herring gulls. Surprisingly, δ13C values indicated predominantly terre...

Isotopic study of antlers is proving to be a source of annualized data on caribou diet and migration, but uncertainty remains in the magnitude and drivers of isotopic changes across individual antler....

We show intact skin tissue of a fossilised fish (Diplomystus dentatus) from the Fossil Basin Lagerstätte (USA) that was preserved via phosphate permineralisation in an oxygen-enriched microenvironmen...

The urea to ammonium concentration ratio is a good predictor of the relative importance of urea and ammonium to nitrite and N2O production in the ocean. In addition, the urea to ammonium ratio may be....

This study explored how nitrogen (N) addition affects a mature beech forest after 4 years of fertilization, comparing soil and above-canopy fertilization to mimic increased atmospheric nitrogen. Whil....

Rationale The Japanese sea lion (Zalophus japonicus), once abundant in Japan, Korea, and Russia, went extinct by the mid-20th century due to hunting and environmental change. This study examines the.....

Rationale The isotopic composition of foods is useful for verifying origin and provides baseline information for interpreting isotopic data from human tissues in dietary and forensic research. Despi...

Rationale The stable carbon isotopic composition (δ13C) of individual lipids is of great value in studying carbon cycling. Among those, microbial lipids in sediments impacted by high methane turnove.....

Accurate source tracking of dissolved organic matter (DOM) in anthropogenically disturbed watersheds is crucial for pollution control. This study took…

Bioconversion is a sustainable method to recycle nutrient-rich aquaculture waste. This study explored waste bioconversion in the context of species co…

The response of fluvial nitrate (NO3–) export to climate warming remains poorly constrained in high-elevation basins. Here, we integrate multi-decadal NO3– flux records with multi-year measurements of...

The Neotropical catfish family Trichomycteridae contains parasitic fishes that include scale and mucus feeders (subfamily Stegophilinae) and blood feeders (i.e., ‘candirus’, subfamily Vandelliinae). ...

Isotopic analysis as a method of assessing diet or geographical origin is now ubiquitous in archaeology, to the point where seemingly no project is co…

Scientific Reports - Trophic dynamics and metabolic pathways in host parasite interactions revealed by nitrogen isotope analysis of amino acids in multiple tissues

Use of nitrogen and oxygen isotopic signatures of nitrate to investigate atmospheric nitrogen fixation by volcanic lightning Evidence for atmospheric nitrate enrichment in volcanic deposits relat...

Substantial quantities of nitrogen (N) and phosphorus (P) released by human activities, enter terrestrial ecosystems, thereby affecting the carbon cyc…

Frequent wildfires worldwide have severely disturbed soil organic carbon (SOC) pools, yet their effects on organic carbon turnover are still under deb…

Arbuscular mycorrhizal (AM) fungi are an important part of the soil microbial community. While their effects on soil properties and nutrient cycles ar…

Abstract. The sulfur cycle is very important in lake sediments, despite the much lower sulfate concentrations in freshwater than seawater. To date, little is known about the formation and preservation...

Topsoil nitrogen stocks declined over a ten-year field warming experiment in a permafrost ecosystem due to enhanced plant nitrogen uptake, nitrogen leaching and gaseous losses, suggesting that permafrost soil nitrogen stocks are vulnerable to warming.