Open research questions in Soil and Water Nutrient Dynamics

What the literature leaves open

• Lack of paired environmental matrices: Only fecal samples were analyzed; concurrent water and sediment samples were not collected, preventing quantification of bird-derived phosphorus, ARGs, and pathogens in wetland habitats. Spatially restricted sampling: All samples originated from the Caohai Wetland, limiting generalizability to other plateau wetlands. Limited metagenomic sequencing depth and replication: both the number of biological replicates per bird species and sequencing depth were insufficient to robustly resolve low-abundance ARGs and pathogen communities. Absence of in situ validation: no field microcosm or mesocosm experiments assessed the actual transmission efficiency of ARGs and pathogens from bird feces to resident wetland microbial communities.

  Ecological risk assessment of migratory bird feces in plateau wetland: Phosphorus speciation, ARGs, and pathogens · 2026 · DOI

• There is a lack of understanding of the ecological risks of migratory bird feces in plateau wetlands. The study highlights the need for further research on the interactions between phosphorus speciation, antibiotic resistance genes, and pathogens in migratory bird feces.

  Ecological risk assessment of migratory bird feces in plateau wetland: Phosphorus speciation, ARGs, and pathogens · 2026 · DOI

• The severity of this pollution is governed by the balance between N runoff and aquatic retention, yet how climate change will redistribute this risk across regions remains unclear.

  Climate-driven spatial reorganization of cropland nitrogen pollution hotspots toward arid and semi-arid regions · 2026 · DOI

• However, the microbes, processes, and factors controlling greenhouse gas cycling in these systems have not been described.

  Cattle manure suppresses methane consumption and enhances denitrification-associated nitrous oxide production in farm dams · 2026 · DOI

• Furthermore, mitigation value of fertigation respect to granular fertilization in vegetable systems remains uncertain.

  Comparative Effects of Nitrogen Fertigation and Granular Fertilizer Application on Pepper Yield and Soil GHGs Emissions · 2025 · DOI

• Although the Chinese government is promoting a policy shift to large-scale farming, the benefits of this, when integrated with nitrogen management, remain unclear.

  Unlocking nitrogen management potential via large-scale farming for air quality and substantial co-benefits · 2024 · DOI

• The study is limited by insufficient training data at coarser intervals. The Monticello catchment was not analyzed due to insufficient temporally contiguous segments needed to simulate large data gaps. The approach may not perform well for certain solutes (e.g. NO₃ and K⁺) that require more frequent anchoring observations under stormflow conditions.

  Lowering barriers to probing high-frequency variations in river chemistry through a frugal machine learning-based framework · 2026 · DOI

• High-frequency river chemistry monitoring is limited by logistical and budgetary constraints. The conventional method of grab sampling is limited by cost and logistics.

  Lowering barriers to probing high-frequency variations in river chemistry through a frugal machine learning-based framework · 2026 · DOI

• There is a need to understand the impacts of climatically changing conditions on solute export mechanisms. Prior research has not fully addressed the changes in solute source distribution and hydrological connectivity in response to climate change.

  Exploring controls on solute export mechanisms in anthropogenically impacted catchments in Southern Germany in climatically different periods · 2026 · DOI

• The complexity of the hydrological and water quality monitoring data. The need to quantify the nonlinear relationship between variables. The challenge of identifying the most influential factors on N concentrations.

  Spatial–Temporal Distribution Characteristics of Nitrogen in the Jingjiang Reach of the Yangtze River during 1992–2015 · 2026 · DOI

• The impacts of reservoirs on the migration and transformation of nutrients have not fully been understood. There is a need to investigate the effect of the Three Gorges Reservoir on the migration and transformation of nitrogen in the Jingjiang Reach.

  Spatial–Temporal Distribution Characteristics of Nitrogen in the Jingjiang Reach of the Yangtze River during 1992–2015 · 2026 · DOI

• Excessive use of chemical fertilizers causes high nutrient residue in the soil. Fertilization is conducted with high frequency, often concentrated during the rainy season. Limited research on mitigating nutrient runoff losses from citrus orchards.

  Biochar-based fertilizer can mitigate nitrogen runoff loss from the citrus orchard as comparison with organic fertilizer · 2026 · DOI

• Limited research on mitigating nutrient runoff losses from citrus orchards. The need to investigate the effect of biochar-based fertilizer on nitrogen runoff loss in citrus orchards.

  Biochar-based fertilizer can mitigate nitrogen runoff loss from the citrus orchard as comparison with organic fertilizer · 2026 · DOI

• There is a need to understand the hydrological responses and C-N pools of watersheds under shrub management. Prior studies have not fully addressed the effects of shrub thinning on hydrological and biogeochemical responses. There is a lack of region-specific shrub management strategies, accounting for climatic regime, shrub density, and soil characteristics.

  Hydrological Responses and C-N Pools of Two Watersheds under Shrub Management · 2026 · DOI

• Most studies focus on single pollutants or single environmental media. The evidence required for territorial spatial planning is still insufficient. There is a need for a spatially explicit basis for differentiated watershed management and territorial spatial planning.

  Landscape Controls on Coupled Water–Air Pollution in an Urbanized Watershed: A GeoSHAP Analysis of the Liaohe River Basin, China · 2026 · DOI

• The lack of consideration of legacy phosphorus in watershed management. The need for a better understanding of the role of legacy phosphorus in sustaining harmful algal blooms.

  Legacy brewery phosphorus as a management constraint in the Mashapaug Watershed: unresolved reservoirs and pathways in an urban pond cascade · 2026 · DOI

• The long-term trends of dissolved carbon, nitrogen, and phosphorus ratios in rivers remain unclear. The drivers of global declines in DOC-to-nutrient ratios are unknown.

  Diverging riverine dissolved C:N:P ratios under global environmental change · 2026 · DOI

• Future research should investigate the application of the study's findings to other irrigation networks. The study's results suggest the need for further research on the impacts of acidity on rice productivity.

  Modeling Acidity Dynamics Driven by Tidal–Rainfall Interactions in a Tropical Lowland Irrigation Network · 2026 · DOI

• The research gap is that observational data alone cannot disentangle the mechanisms governing acidity dynamics. Prior work has not investigated the shifts in the controlling mechanisms of acidity under different hydrological conditions.

  Modeling Acidity Dynamics Driven by Tidal–Rainfall Interactions in a Tropical Lowland Irrigation Network · 2026 · DOI

• The study is limited by infrequent water sampling. The performance of GAMPL declined for TP and nitrite/nitrate (NO2/NO3) due to limited observations. Daily boundary inflows supplied to the EFDC model were not always available.

  A Water Quality Modeling Framework to Quantify Seasonal Contributions of Nitrogen and Phosphorus Loads to a Rural–Urban Watershed Given Limited Observations · 2026 · DOI

• Future research should focus on improving the performance of GAMPL for TP and nitrite/nitrate (NO2/NO3). The study suggests increasing winter sampling frequency and implementing operational adjustments to the aerated lagoons of the WWTP.

  A Water Quality Modeling Framework to Quantify Seasonal Contributions of Nitrogen and Phosphorus Loads to a Rural–Urban Watershed Given Limited Observations · 2026 · DOI

• Insufficient understanding of the fine-scale spatial heterogeneity of pollution sources and key driving factors. Lack of a comprehensive analysis framework integrating remote sensing and hydrological analogy.

  Identifying priority control areas and proposing countermeasures for nitrogen and phosphorus pollution in the Jinjiang River Basin: An integrated remote sensing and hydrological analog approach · 2026 · DOI

• The need for integrated nutrient management in semi-arid basins. The lack of comprehensive characterization of nitrate contamination patterns in semi-arid rivers.

  Integrating QUAL2KW nitrate modeling with ambient grey-water dilution pressure and wheat-pathway exposure screening in a semi-arid basin · 2026 · DOI

• The existing studies on polder ecosystems exhibit substantial heterogeneity in characteristics, spatial and hydrological boundaries, monitoring periods, nutrient-accounting approaches, and reported outcome indicators. There is a lack of understanding of the complex and uncertain effects of human intervention on water quality in polders. The study aims to address this gap by conducting a systematic literature review and narrative synthesis.

  Nitrogen–Phosphorus Pollution Dynamics and Export Processes of Anthropogenic Polders in the Middle–Lower Yangtze River: A Regional Review · 2026 · DOI

• Few studies have examined the combined effects of shading and biofilm growth on ammonium (NH 4 + –N) and nitrate (NO 3 − –N) removal in the same experiment.

  Confirming the Primacy of Light Controlling Ammonium Removal in Response to Biofilm Colonization and Shade Using Experimental Streams · 2025 · DOI

Most-cited papers in Soil and Water Nutrient Dynamics

• Managing nitrogen for sustainable development · Nature · 2015 · 2,804 citations
• Enhanced nitrogen deposition over China · Nature · 2013 · 2,406 citations
• The Nitrogen Cascade · BioScience · 2003 · 2,404 citations
• Reactive Nitrogen and The World: 200 Years of Change · AMBIO · 2002 · 1,106 citations
• Human Impact on Erodable Phosphorus and Eutrophication: A Global Perspective · BioScience · 2001 · 782 citations
• Cost-effective mitigation of nitrogen pollution from global croplands · Nature · 2023 · 662 citations
• Riparian Forests as Nutrient Filters in Agricultural Watersheds · BioScience · 1984 · 604 citations
• Reducing Nitrogen Loading to the Gulf of Mexico from the Mississippi River Basin: Strategies to Counter a Persistent Ecological Problem · BioScience · 2001 · 475 citations
• Is Nitrogen Deposition Altering the Nitrogen Status of Northeastern Forests? · BioScience · 2003 · 462 citations
• Ecological Effects of Nitrogen Deposition in the Western United States · BioScience · 2003 · 423 citations

Most recent work

• Best Management Practices for Soil Health and Water Quality: From Practice Catalogs to Decision Intelligence · Agriculture · 2026
• Bioavailable phosphorus across Florida’s diverse soil orders: implications for crop productivity and environmental protection · Frontiers in Environmental Science · 2026
• Sediment-associated processes account for most of the spatial variation in stream ecosystem respiration in the Yakima River basin · bioRxiv · 2026
• Water Regime Effects on Phosphorus Mobility and the Performance of Liquid Phosphorus Fertilizers in Contrasting Soils · Agriculture · 2026
• Plant–arthropod–soil interactions in reservoir water-level fluctuation zones: A novel driver of soil phosphorus cycling · Agriculture, Ecosystems & Environment · 2026
• Reducing agricultural phosphorus pollution by regulating the hydrological processes of small water bodies · Environmental Research Letters · 2026
• Targeted grassland restoration increases potential for reduced nutrient export in the Upper Mississippi River Basin · Environmental Research Letters · 2026
• Contrasting impacts of long-term nitrogen and phosphorus additions on the quantity and quality of soil dissolved organic matter · Soil Ecology Letters · 2026
• Pipelines and Sprinkler Systems: Documenting the Speed–Flexibility Tradeoff in How Jobs Shape Promotion · Academy of Management Journal · 2026
• Regulating grain production-water purification trade-offs through landscape structure in a large-scale basin: insights from the pattern-process-service framework · Applied Geography · 2026

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