Organic fertilizers often contribute to nitrate (NO3−) leaching and impair drinking water quality, because the mineralization of applied organic nitrogen (N) is often asynchronous with crop N uptake. Crop yield, crop N uptake, seepage water and NO3− leaching were investigated in a lysimeter facility (Zurich, Switzerland) under temperate climate conditions during two consecutive four-year organically managed crop rotations. The study compared untreated cattle slurry, anaerobically digested slurry, liquid digestate from a non-agricultural biogas plant and a zero-N fertilization control. The ammonium N (NH4-N) fraction of the organic fertilizers was labeled with 15N tracer to investigate the fate of NH4-N in the plant-soil–water system. Organic fertilization significantly increased crop yields and N uptake, with no differences among organic fertilizers, despite the higher NH4-N proportion of the digestates. Mean annual NO3− leaching was low (12–18 kg N ha−1) and was not increased by organic fertilization, indicating that N inputs were balanced by crop N uptake. Digestates did not differ from untreated cattle slurry in NO3− leaching. Higher modeled ammonia (NH3) emissions of digestates suggest that N losses may occur primarily via NH3 volatilization rather than NO3− leaching. The 15N recovery showed 1
Ammonia (NH3) emissions from intensive cropping systems remain a critical environmental challenge. While previous studies have largely captured NH3 fluxes within individual seasons, an integrated, year-round perspective is essential to unravel the complex mechanisms governing canopy-atmosphere exchange. Addressing this gap, this study integrated micrometeorological measurements, laser-based NH3 profiling, and physiological assays to quantify leaf NH3 compensation points at successive representative growth stages across a complete wheat–maize rotation cycle in the North China Plain. During the 2015/2016 observation cycle, the system was a net NH3 source (40.7 ± 5.5 kg N ha−1 yr−1). Outside fertilization periods, the wheat field remained a net NH3 source (26.3 and 27.2 kg N ha−1 in the 2015/2016 and 2018/2019 wheat seasons, respectively). During non-fertilization periods, net exchange was negative in the 2015 and 2018 maize seasons (− 28.6 and − 16.2 kg N ha−1, respectively), indicating net uptake; when fertilization periods were included, the 2015 maize-season field budget remained positive (29.5 kg N ha−1). Interannual comparisons showed lower atmospheric NH3 concentrations but higher net emissions in 2018/2019 (49.2 ± 7.5 kg N ha−1 yr−1), coinciding with weaker maize deposition. This source-sink divergence is mechanistically driven by crop-specific leaf NH3 compensation points. Measurements across successive growth stages showed that fertilization significantly modulated crop-specific leaf NH3 compensation points. High nitrogen input (N400) substantially elevated wheat compensation points (peaking at 243 nmol mol−1), driving emissions, whereas maize maintained low compensation points (< 30.5 nmol mol−1), facilitating uptake. Sparse wheat canopies further favored emission, while dense maize enhanced deposition. A structural equation model confirmed the compensation point as the dominant direct driver (path coefficient = 0.27), with ambient NH3 exerting a strong negative effect (− 0.82), explaining 75
This Special Issue on “Soil Health and Fertilizer Strategies: Bridging Research and Practice” presents current research and review papers from the International Fertilizer Development Center (IFDC) and its collaborative partners, focusing on the roles of fertilizers and soil fertility management in sustaining soil health. While commemorating IFDC’s 50th anniversary, this collection emphasizes translational research—the development, refinement, and delivery of technologies and innovations to key stakeholders, including the fertilizer industry and smallholder farmers. IFDC’s mission has evolved over time, but improving nutrient-use efficiency and enhancing fertilizer accessibility and affordability remain central priorities. The featured papers reaffirm IFDC’s commitment to soil health and fertility through judicious fertilizer and amendment use.
Poultry litter is an affordable, widely available nutrient source in the Southeastern USA, but National Organic Program’s “90–120-Day Rule” complicates nutrient-crop synchronizationn, making application of raw manures to cover crops a suitable and compliant alternative. In this study, four rates of poultry litter (0, 1.8, 3.6, and 7.2 Mt ha−1) were applied to white oat (Avena satvia L. ‘Rushmore’) cover crop in October 2022/2023 on certified organic land. Treatments were evaluated for impacts on cover crop biomass and quality (nitrogen, carbohydrates, cellulose, lignin, and carbon); soil chemical properties (inorganic nitrogen, pH, electrical conductivity), and subsequent kale crop (Brassica oleracea ‘Winterbor’). Significant differences were determined between years for cover crop biomass but not treatment with 1920 kg ha−1 for Year 1 and 4308 kg ha−1 for Year 2, respectively. Cover crop quality differed significantly due to a mid-season freeze in Year 1 but not in Year 2. Soil inorganic nitrogen and kale biomass were unchanged in Year 1 but increased in Year 2 at the highest application. Kale yield was unimpacted in Year 1, but in Year 2, was significantly greater in all poultry litter applications compared to the control. Due to differences in the field study between years, a 21-day incubation was conducted to determine the effect of freezing and poultry litter applications on nitrogen cover crop/soil dynamics. Oats with poultry litter application and freeze treatments had significantly less inorganic N recovery compared to unfrozen oats with poultry litter application recovering, 1.7
Optimizing nitrogen (N) efficiency in European silage maize cultivation requires better quantification of N savings beyond existing regulations and identifying further opportunities to enhance efficiency. This study focuses on understanding how site and management factors influence net N mineralization. A comprehensive dataset from silage maize field trials across five Central European countries was analyzed using a multistage framework to develop a linear regression equation for estimating net N mineralization during the growing season based on key parameters known before the growing season. The final regression model, with a Radj2 of 0.38, identified ten significant variables affecting net N mineralization. Evaluation of German and French fertilization frameworks, using representative regional use cases, indicated that national guidelines may underestimate or insufficiently capture net N mineralization. Major factors influencing soil net N mineralization included management practices impacting biomass quantity and the carbon-to-N ratio of plant residues, with N fertilization showing a negative effect on net N mineralization. Weather conditions and soil clay contributed to the observed variability to a lesser extent. For silage maize following grain cereals, a predominant cropping sequence within the investigated regions, the highest net N mineralization was achieved by combining straw removal with a frost-killed non-legume cover crop, suggesting potential for reduced N fertilization without yield loss.
Long-term compost addition often increases soil organic carbon (SOC) and improves soil structure, yet its effect on nitrous oxide (N2O) emissions remains uncertain. This study investigated N2O emissions from a 13-year compost amendment experiment with 11 Mg compost ha−1 year−1 on a sandy loam in Belgium. Emissions from a treatment with (Com) and without (NCom) compost addition were monitored over an entire year using static chambers. In year 13 since the start of the experiment, annual N2O emissions were slightly higher under Com than under NCom (5.361 vs. 4.835 kg N2O-N ha−1), but this difference was not statistically significant. Variation in soil mineral nitrogen content (Nmin) and water filled pore space (WFPS) through time strongly shaped the temporal emission pattern. During the potato growing season under a ridge-furrow system, emissions were monitored separately for each of these field positions. Cumulative emissions from both positions did not differ significantly, likely because higher Nmin in the ridge was counterbalanced by lower WFPS, while the opposite was observed in the furrow position, showing lower Nmin and higher WFPS. Potato yield was not significantly affected by compost application. These findings suggest that long-term compost addition does not substantially increase annual N2O emissions, and that although ridges and furrows show different Nmin and WFPS, these shifts may not translate into significant differences in cumulative N2O emissions.
Crop diversification, particularly through integration of nutrient-enriching legume-based systems, is essential for improving soil micronutrient availability through their transformations in soil. The present study, conducted at Punjab Agricultural University, Ludhiana, evaluated the effects of crop diversification on distribution and transformation of operationally defined micronutrient fractions in soil and their relationship with DTPA-extractable micronutrients. There were noticeable variations in all micronutrient fractions studied, emphasizing the significance of crop selection on micronutrient dynamics. Among the cropping systems evaluated, the soybean-wheat system enhanced the soil organic carbon and labile micronutrient pools, including water soluble + exchangeable (WS + EX)-Zn, Mn and Cu (9.0, 0.99 and 0.05 mg kg−1, respectively), specifically adsorbed (SpAd)-Mn (4.37 mg kg−1) and organically bound (OM)-Cu, Mn and Zn (0.78, 7.87 and 37.9 mg kg−1, respectively). The residual (unavailable pool) fraction accounted for the largest pool ( 70
Frass produced from biowaste treatment with black soldier fly (BSF) larvae is a promising fertilizer, but its short bioconversion time can lead to phytotoxicity. A recently proposed method called ‘frass recirculation’ was found to improve frass quality by reintroducing fresh frass into subsequent rearing cycles. This study evaluated the effects of frass produced through different levels of recirculation on soil nitrogen (N) dynamics and plant performance. Five frass types were tested: fresh frass and frass recirculated once, twice, three, or four times. In the first experiment, the fertilizers were applied to the soil, and N mineralization was monitored over 84 days. The same treatments were then used to cultivated pak choi, where plant growth and photosynthetic activity were assessed. Frass recirculated four times had a higher intrinsic concentration of N-NH4+ and produced significantly higher soil mineral N after 84 days compared to fresh frass. This increased N availability allowed for lower application rates while still providing sufficient nutrients for supporting plant growth. Pak choi fertilized with highly recirculated frass achieved biomass comparable to that of plants supplied mineral fertilizer. In addition, nutrient concentrations and accumulation in plant tissues were similar between the highly recirculated frass and mineral fertilizer treatments. Notably, frass-fertilized plants exhibited higher chlorophyll content and greater CO2 assimilation rates, indicating an enhanced photosynthetic performance. Overall, frass recirculation enhanced N mineralization and improved the fertilization efficiency of BSF frass. These results demonstrate that recirculated frass have fertiliser potential comparable to that of mineral fertilizers, highlighting its potential as a sustainable organic alternative for greenhouse crop production.
Empirical field-scale evidence for site-specific management of bio-based fertilizer (BBF) application is largely missing. Hence, implementing BBFs in this manner on commercial maize farms in this study delivers rare applied insight into agronomic, economic, and environmental performance under real farming conditions. Recent EU Soil Monitoring Law (2025) and the RENURE approval in EU (2025) formalize soil-health restoration and circular nitrogen (N) use as defined regulatory priorities, situating precision variable-rate (VR) bio-based fertilizer (VR-BBF) application within an emerging compliance-oriented nutrient management framework. Three commercial fields (2.7–6 ha) in East Flanders received uniform-rate RENURE ammonium sulphate as a bio-based alternative (UR-BBF) and variable-rate bio-based fertilization. In two fields, these treatments were benchmarked against uniform-rate synthetic fertilizer (UR-S) to reflect standard practice. All VR treatments were informed by on-line soil sensing, crop sensing, and farmers field-knowledge. Comparing VR treatments against UR-BBF and UR-S, the results demonstrated that VR efficacy is site-specific. In Aalter (6 ha) and Beervelde (3 ha), VR-BBF application outperformed uniform practices, delivering fresh matter (FM) yield gains of 2.72–4.06 t ha−1 and increasing gross margins by 356–465 EUR ha−1. Conversely, the Lemberge field (2.5 ha) exhibited FM yield and profit losses, attributed to a non-N limiting constraint. These findings indicate that while VR-BBF application can be a promising pathway for integrating circular nutrient production outputs via precision agriculture to ensure better nutrient allocation, nevertheless, its practical success depends on strategies that are strictly linked to local soil properties and capable of addressing non-N limiting constraints to prevent economic and environmental trade-offs.
Nutrient management plan (NMP) tools aim to enhance crop production while minimising environmental harm from over-fertilisation by aligning applications with crop demands and with soil and atmospheric conditions. The characteristics of 14 widely used NMP tools from nine countries (Austria, Bulgaria, China, Czech Republic, Hungary, Italy, New Zealand, Spain, and United Kingdom) were compared. All tools employed a mass balance approach at the field and seasonal scales. To evaluate the tools, matrices of the presence/absence of 24 desirable characteristics, 22 nutrient cycle processes and sources, and 38 required input data were compiled. To compare the NMPs, cumulative scores were calculated for each category evaluated. Additionally, two theoretical case studies compared fertiliser recommendations for winter wheat in arable and livestock farming systems. Cluster analysis classified the 14 tools into six clusters, reflecting distinct levels of complexity, usability, adaptability, and interoperability. The number of input data required was strongly and positively correlated with the number of nitrogen (N) processes and sources considered, confirming that input demand reflects tool sophistication. More comprehensive tools tended to recommend lower N application rates in the livestock system, suggesting that simpler tools overestimated N requirements by omitting key processes. However, practical usability characteristics did not determine different recommendations. While N recommendations were broadly aligned with national guidelines, P and K recommendations showed considerably higher variability reflecting the lack of harmonised guidelines for these macronutrients.
In organic farming, different bioproducts such as plant extracts and compost (obtained from recycling organic waste/residues) can promote the mineral fortification of vegetables. This study evaluated the agronomic performance and nutritional effects of an on-farm compost and a liquid extract derived from basil residues on organic tomato crop over two cropping cycles (2022–2023), within a fennel – tomato crop sequence, in Mediterranean environment. The tested treatments were on-farm compost applied alone (OC) or with basil extract spraying to crops (OCex), compared to a commercial organic vegetal fertilizer (ORG-V), an unfertilized control (NF), and NF with the extract (NFex). In 2022, treatments of OCex showed fruit weights higher by 36
Vegetables are a vital component of the human diet, contributing substantially to nutritional security and overall health through their supply of vitamins, minerals, dietary fiber, and bioactive phytochemicals such as flavonoids and polyphenols. However, the continuous and excessive use of chemical fertilizers to maximize yields has disrupted soil structure, fertility, and microbial ecology, potentially impairing nutrient bioavailability, nutraceutical synthesis, and vegetable quality. The objective of this study was to evaluate the effects of different nutrient sources, with particular emphasis on organic amendments supplemented with plant growth-promoting microorganisms (PGPMs), on soil physicochemical and biological properties and their subsequent influence on vegetable nutritional, sensory, and nutraceutical quality. Results demonstrated that replacing chemical fertilizers with organic nutrient sources supplemented with a microbial consortium significantly enhanced soil health indicators, including soil organic carbon (+ 110
Cascade cropping is a type of closed-loop soilless system where effluent from a primary crop is used to irrigate a more salt-tolerant secondary crop, and the growing medium can be reused in subsequent cultivation cycles. This approach has emerged as a promising strategy to optimize nutrient use efficiency and mitigate leaching-related environmental pollution. This study assesses the effectiveness of cascade cropping in enhancing environmental sustainability compared to conventional soil and soilless cultivation. The case study is rocket salad cultivation, with glasswort as a secondary crop in the cascade system. A cradle-to-farm-gate life cycle assessment was performed according to the ISO 14040/44 standards to study nine midpoint impact categories recommended by the European Commission’s Product Environmental Footprint Category Rules. The results show that the cascade system significantly outperformed conventional cultivation across most environmental impact indicators, particularly when incorporating locally produced compost into the growing medium. The following impact reductions were achieved compared to the soil and soilless systems respectively: 38
Warm-season cover crops can reduce nitrogen (N) leaching, build soil organic matter (SOM), and provide N to subsequent cash crops, but the extent of these functions in northern climates remains unknown. We evaluated these ecosystem functional responses to cover crop quantity and quality in contrasting northern US soil types. Cover crop single species (buckwheat, sunn hemp) and bicultures (chickling vetch/sudex and cowpea/sudex) were established for two seasons at two organic, tilled vegetable production sites: a loamy sand (11 g SOM kg−1) and a silt loam (23 g SOM kg−1) at the 0–15 cm depth. Cover crop treatments were grown for two growing season lengths and compared to bare fallows. Soil samples were collected before and after cover crop termination for analysis of extractable organic and mineral N (EON, MinN), potentially mineralizable N (PMN), permanganate oxidizable C (POX-C), extractable organic C (EOC), and fluorescein diacetate hydrolysis (FDA). Cover crops decreased MinN compared to bare fallows by up to threefold at the low OM site (4.2 vs. 1 mg kg−1 soil), and 11-fold at the higher OM site (36 vs. 3 mg kg−1 soil), while PMN and EON showed the opposite trend but only in some site-years and treatments. Effects on FDA and soil C were inconsistent. Relationships among soil variables, cover crop biomass, and C:N were analyzed with Pearson and partial correlations controlling for cover crop variables. Significant ( Δ R > 0.25) changes in correlations between MinN and PMN/EON/EOC were seen at the lower OM site, indicating cover crop biomass was the primary driver of correlations. Lack of significant correlation changes in the higher OM site indicate buffering effects from SOM. Warm-season cover crops can contribute to MinN retention in northern climates but do not appear to impact labile C.
The traditional calibration approach for process-based models, such as DayCent, consists of the iterative adjustment of model parameters and comparison of the simulated total N2O flux to measured observations. However, the contributions of individual production pathways, namely nitrification and denitrification, are uncertain. Here, N2O emissions from the soil of sugar beet plots with control (Null) and mineral (NPK) fertilizer treatments were measured by a static chamber technique. The isotopic composition of emitted N2O was analyzed to identify the N2O production pathways. The latter showed that denitrification was the predominant source of N2O emissions at this site. The model’s default settings strongly overestimated the contributions of nitrification. This incorrect allocation of N2O emissions to nitrification could partly be explained by the model’s tendency to underestimate the soil water content during the growing season. DayCent model parameters were also manually adjusted to better represent the observation derived contributions of nitrification and denitrification. Although, this “expert-informed approach”, showed a slightly lower performance concerning the cumulative N2O flux (Null: RMSE = 0.37 kg N ha−1 yr−1, NPK: RMSE = 0.50 kg N ha−1 yr−1) than the traditional calibration (Null: RMSE = 0.15 kg N ha−1 yr−1, NPK: RMSE = 0.10 kg N ha−1 yr−1), it may be considered as more representative because it better reflected the higher contribution from denitrification shown by the isotope data. This study demonstrates that the inclusion of observational methods, such as isotope measurements, can provide important insight into model function and improve pathway-specific estimation of N2O emissions in DayCent.
Nitrous oxide fluxes from urine patches (F(N2O)urine) of grazing livestock are variable over time due to fluctuations in driving parameters, such as soil temperature, water-filled pore space (WFPS), and availability of the source substrates ammonium and nitrate. Therefore, the frequency and timing of flux measurements after urine application are important when determining cumulative F(N2O)urine. In this study, F(N2O)urine was measured in eight experiments at high temporal frequency using an automatic chamber system in a pasture located in Switzerland. A driver analysis using random forest identified the time since urine application as most important predictor for F(N2O)urine. The exponential decay in F(N2O)urine after urine addition was in parallel to decreasing soil ammonium but anticorrelated to nitrate concentration, suggesting that nitrification and nitrifier denitrification are major source processes. Since nitrate showed elevated concentrations up to 122 days after application, bacterial denitrification is most likely responsible for late F(N2O)urine peaks following an increase of WFPS. The isotopic composition of the emitted N2O indicates that nitrification dominates the N2O production immediately after urine application, while bacterial denitrification and nitrifier denitrification become more important with increasing time since urine application. The observed high-frequency emission time series were also used to simulate typical low-frequent manual chamber sampling schedules. They led to considerable deviations (up to ± 30
Detecting the spatial heterogeneity of soil carbon and its key driving factors is critical for soil management. However, this remains poorly understood in saline–alkali arable soils at a large scale. In this study, geostatistical analysis combined with statistical analysis was employed to investigate the key drivers of the spatial heterogeneity of soil total carbon (TC), soil organic carbon (SOC), soil inorganic carbon (SIC), and SOC forms in the 0–20 cm and 20–40 cm soil layers in saline–alkaline soils of Da’an city (496 km2), Northeast China. (1) TC, SIC, SOC, soil dissolved organic carbon (DOC), soil mineral-associated organic carbon (MAOC), and soil particulate organic carbon (POC) exhibited distinct spatial aggregation patterns across the study area (P < 0.05). SIC constituted a large proportion of TC (53.7–58.0
Nitrogen (N) fertilizer is essential for rice production, and its formulation critically influences nitrogen use efficiency (NUE) and environmental impacts. This is particularly relevant for the rice–crayfish co-culture system (RC), a system prone to nutrient surplus and water quality concerns due to multiple nutrient inputs and prolonged flooding. A comprehensive understanding of how different N fertilizers affect NUE, N balance, soil microbial communities, and field water quality in RC is currently lacking. Therefore, this study aimed to evaluate these effects and assess the overall sustainability of RC under different N management practices. Three long-term field trials were conducted to evaluate suitable nitrogen (N) types. Four treatments were included in the trials: no N (CK), conventional fertilizer (CF), controlled-release fertilizer (CRF), and organic–inorganic fertilizer (OF). We measured soil inorganic N, rice agronomic traits, N balance, microbial biomass/diversity (via Illumina sequencing), and field water N concentrations. CRF significantly enhanced soil N availability (NH₄⁺–N by 36.5–166.9
