Agricultural Nitrogen Research Articles

Examining Relationships Between Groundwater Nitrate Concentrations in Drinking Water and Landscape Characteristics to Understand Health Risks.

Nitrate ingested from drinking water has been linked to adverse health outcomes (e.g., cancer, birth defects) at levels as low as ∼2 mg/L NO3‐N, far below the regulatory limits of 10 mg/L. In many areas, groundwater is a common drinking water source and may contain elevated nitrate, but limited data on the patterns and concentrations are available. Using an extensive regulatory data set of over 100,000 nitrate drinking water well samples, we developed new maps of groundwater nitrate concentrations from 76,724 wells in Michigan's Lower Peninsula, USA for the 2006–2015 period. Kriging, a geostatistical method, was used to interpolate concentrations and quantify probability of exceeding relevant thresholds (>0.4 [common detection limit], >2 mg/L NO3‐N). We summarized this probability in small watersheds (∼80 km2) to identify correlated variables using the machine learning method classification and regression trees (CARTs). We found 79% of wells had concentrations below the detection limit in this analysis (<0.4 mg/L NO3‐N). In the shallow aquifer (focus of study), 13% of wells exceeded 2 mg/L NO3‐N and 2% exceeded the EPA maximum contaminant level of 10 mg/L. CART explained 40%–45% of variation in each model and identified three categories of critical correlated variables: source (high agricultural nitrogen inputs), vulnerable soil conditions (low soil organic carbon and high hydraulic conductivity), and transport mechanisms (high aquifer recharge). These findings add to the body of literature seeking to identify communities at risk of elevated nitrate and study associated adverse health outcomes.

Engineered plant control of associative nitrogen fixation

Engineering N2-fixing symbioses between cereals and diazotrophic bacteria represents a promising strategy to sustainably deliver biologically fixed nitrogen (N) in agriculture. We previously developed novel transkingdom signaling between plants and bacteria, through plant production of the bacterial signal rhizopine, allowing control of bacterial gene expression in association with the plant. Here, we have developed both a homozygous rhizopine producing (RhiP) barley line and a hybrid rhizopine uptake system that conveys upon our model bacterium Azorhizobium caulinodans ORS571 (Ac) 103-fold improved sensitivity for rhizopine perception. Using this improved genetic circuitry, we established tight rhizopine-dependent transcriptional control of the nitrogenase master regulator nifA and the N metabolism σ-factor rpoN, which drove nitrogenase expression and activity in vitro and in situ by bacteria colonizing RhiP barley roots. Although in situ nitrogenase activity was suboptimally effective relative to the wild-type strain, activation was specific to RhiP barley and was not observed on the roots of wild-type plants. This work represents a key milestone toward the development of a synthetic plant-controlled symbiosis in which the bacteria fix N2 only when in contact with the desired host plant and are prevented from interaction with nontarget plant species.

Characteristics of carbon emission and approaches of carbon mitigation and sequestration for carbon neutrality in China&amp;rsquo;s crop production

<p id="C3">Crop production not only ensures national food security, but also is the main source of agricultural carbon emissions and an important pool of carbon sequestration. To clarify the characteristics of carbon emissions from crop production and discuss the approaches to reach the peak and neutrality in major agricultural areas can provide important scientific basis to the decision making of green and high-quality agricultural development and “dual-carbon” goal. Based on the national statistical data, this study compared and analyzed the characteristics of carbon emissions in crop planting regions in China, and presented the recommendations for carbon sequestration and greenhouse gas emission mitigation. The carbon emissions of crop production accounted for 45.5% of the national agricultural total carbon emissions in 2018, and the emissions of farmland methane (CH₄), nitrous oxide (N₂O), and carbon dioxide (CO₂) of diesel consumption accounted for 22.9%, 14.7%, and 7.9% of the total carbon emissions of agricultural production, respectively. In terms of the regional emissions, both the total carbon emission of crop production and the carbon emission per sowing area are higher in South than North China, with the highest emissions in East and central China and the greatest potential for emission mitigation. In the carbon emission from crop production, CH₄ emission from rice fields accounts for the main part (50.3%) and is the focus of emission reduction. The annual carbon emission of crop production in China peaked in 2015, and then dropped down. It was mainly attributed to the decrease trend of rice sown area, agricultural nitrogen application rate, and diesel oil consumption. If the existing agricultural imports are not significantly affected, the carbon emissions in crop production have basically reached the peak. However, it is very difficult to achieve carbon neutrality in crop production if only by soil carbon sequestration of farmland, and it is necessary to consider both farmland emission reduction and carbon sequestration. On the premise of high and stable grain yield, the carbon neutrality of modern crop production should prioritize CH₄ and N₂O reduction, and fully exploit the integrated carbon sequestration potential of farmland ecosystems, such as straw utilization, combination of the use and protection of farmland, and construction of farmland forest network.

Metabolic Diversity and Aero-Tolerance in Anammox Bacteria from Geochemically Distinct Aquifers.

ABSTRACTAnaerobic ammonium oxidation (anammox) is important for converting bioavailable nitrogen into dinitrogen gas, particularly in carbon-poor environments. However, the diversity and prevalence of anammox bacteria in the terrestrial subsurface—a typically oligotrophic environment—are little understood. To determine the distribution and activity of anammox bacteria across a range of aquifer lithologies and physicochemistries, we analyzed 16S rRNA genes and quantified hydrazine synthase genes and transcripts sampled from 59 groundwater wells and metagenomes and metatranscriptomes from an oxic-to-dysoxic subset. Data indicate that anammox and anammox-associated bacteria (class “Candidatus Brocadiae”) are prevalent in the aquifers studied, and that anammox community composition is strongly differentiated by dissolved oxygen (DO), but not ammonia/nitrite. While “Candidatus Brocadiae” diversity decreased with increasing DO, “Candidatus Brocadiae” 16S rRNA genes and hydrazine synthase (hzsB) genes and transcripts were detected across a wide range of bulk groundwater DO concentrations (0 to 10 mg/L). Anammox genes and transcripts correlated significantly with those involved in aerobic ammonia oxidation (amoA), potentially representing a major source of nitrite for anammox. Eight “Candidatus Brocadiae” genomes (63 to 95% complete), representing 2 uncharacterized families and 6 novel species, were reconstructed. Six genomes have genes characteristic of anammox, all for chemolithoautotrophy. Anammox and aerotolerance genes of up to four “Candidatus Brocadiae” genomes were transcriptionally active under oxic and dysoxic conditions, although activity was highest in dysoxic groundwater. The coexpression of nrfAH nitrite reductase genes by “Candidatus Brocadiae” suggests active regeneration of ammonia for anammox. Our findings indicate that anammox bacteria contribute to loss of fixed N across diverse anoxic-to-oxic aquifer conditions, which is likely supported by nitrite from aerobic ammonia oxidation.IMPORTANCE Anammox is increasingly shown to play a major role in the aquatic nitrogen cycle and can outcompete heterotrophic denitrification in environments low in organic carbon. Given that aquifers are characteristically oligotrophic, anammox may represent a major route for the removal of fixed nitrogen in these environments, including agricultural nitrogen, a common groundwater contaminant. Our research confirms that anammox bacteria and the anammox process are prevalent in aquifers and occur across diverse lithologies (e.g., sandy gravel, sand-silt, and volcanic) and groundwater physicochemistries (e.g., various oxygen, carbon, nitrate, and ammonium concentrations). Results reveal niche differentiation among anammox bacteria largely driven by groundwater oxygen contents and provide evidence that anammox is supported by proximity to oxic niches and handoffs from aerobic ammonia oxidizers. We further show that this process, while anaerobic, is active in groundwater characterized as oxic, likely due to the availability of anoxic niches.

Evaluation of interactive and prescribed agricultural ammonia emissions for simulating atmospheric composition in CAM-chem

Abstract. Ammonia (NH3) plays a central role in the chemistry of inorganic secondary aerosols in the atmosphere. The largest emission sector for NH3 is agriculture, where NH3 is volatilized from livestock wastes and fertilized soils. Although the NH3 volatilization from soils is driven by the soil temperature and moisture, many atmospheric chemistry models prescribe the emission using yearly emission inventories and climatological seasonal variations. Here we evaluate an alternative approach where the NH3 emissions from agriculture are simulated interactively using the process model FANv2 (Flow of Agricultural Nitrogen, version 2) coupled to the Community Atmospheric Model with Chemistry (CAM-chem). We run a set of 6-year global simulations using the NH3 emission from FANv2 and three global emission inventories (EDGAR, CEDS and HTAP) and evaluate the model performance using a global set of multi-component (atmospheric NH3 and NH4+, and NH4+ wet deposition) in situ observations. Over East Asia, Europe and North America, the simulations with different emissions perform similarly when compared with the observed geographical patterns. The seasonal distributions of NH3 emissions differ between the inventories, and the comparison to observations suggests that both FANv2 and the inventories would benefit from more realistic timing of fertilizer applications. The largest differences between the simulations occur over data-scarce regions. In Africa, the emissions simulated by FANv2 are 200 %–300 % higher than in the inventories, and the available in situ observations from western and central Africa, as well as NH3 retrievals from the Infrared Atmospheric Sounding Interferometer (IASI) instrument, are consistent with the higher NH3 emissions as simulated by FANv2. Overall, in simulating ammonia and ammonium concentrations over regions with detailed regional emission inventories, the inventories based on these details (HTAP, CEDS) capture the atmospheric concentrations and their seasonal variability the best. However these inventories cannot capture the impact of meteorological variability on the emissions, nor can these inventories couple the emissions to the biogeochemical cycles and their changes with climate drivers. Finally, we show with sensitivity experiments that the simulated time-averaged nitrate concentration in air is sensitive to the temporal resolution of the NH3 emissions. Over the CASTNET monitoring network covering the US, resolving the NH3 emissions hourly instead monthly reduced the positive model bias from approximately 80 % to 60 % of the observed yearly mean nitrate concentration. This suggests that some of the commonly reported overestimation of aerosol nitrate over the US may be related to unresolved temporal variability in the NH3 emissions.

A novel seasonal-spatial integrated model for improving the economic-environmental performance of crop production

Excess agricultural nitrogen, mainly from manure and chemical fertilizers, is a primary source of nutrient pollution and presents serious environmental threats to natural ecosystems and human health. Improvements in nitrogen-use efficiency in crop production are critical for addressing the triple challenge of food insecurity, environmental degradation, and climate change. Approaches such as sustainable intensification that stress technological innovations have received the most attention. But science-based cropland use planning, a promising complementary approach, has so far been largely overlooked. Here we develop a spatially integrated economic-ecological modeling method to assess this previously unexplored potential for improving the economic-environmental performance of crop production by examining the seasonal and spatial implications of cropland and fertilizer use in Bangladesh. In doing so, we aim to make the modeling method accessible to researchers and practitioners interested in achieving the dual goal of food production and environmental sustainability for countries that are characterized by seasonal and spatial variations in crop mix and cropping practices.-The modeling method combines economic and ecological models to explore trade-offs between food security and environmental sustainability.-The modeling method considers both spatial and seasonal dimensions when measuring trade-offs.-The modeling method is highly suitable for adaptation to study topics concerning food security-ecosystem service trade-offs or to inform the design of related models.

Progress on improving agricultural nitrogen use efficiency: UK-China virtual joint centers on nitrogen agronomy

Progress on improving agricultural nitrogen use efficiency: UK-China virtual joint centers on nitrogen agronomy

Assessment of Reactive Nitrogen Flows in Bangladesh’s Agriculture Sector

To assess the status of and trends in agricultural nitrogen (N) flows and their wider consequences for Bangladesh, in this study, we analyzed data from national and international bodies. The increased rates of N fertilizer applied for increased food production leaves behind a huge amount of unutilized reactive N (Nr). N fertilizer use is the largest in the crop sector, an important sector, where current annual consumption is 1190 Gg. The present combined annual Nr production from crop, fishery, and livestock sectors is ~600 Gg, while emissions of nitrous oxide (N2O), a potent greenhouse gas, are ~200 Gg. Poor N management results in Nr leaking into the environment, which has increased approximately 16-fold since 1961. One potential consequence is the disruption of ecosystem functioning. The balanced tradeoff between food production and reducing Nr input needs to be achieved. One solution to reducing Nr may be a holistic approach that optimizes N application rates and incorporates waste of one subsector as an input to another applying the principle of the circular economy.

Spatiotemporal characteristics of agricultural nitrogen and phosphorus emissions to water and its source identification: A case in Bamen Bay，China

The spatiotemporal characteristics and sources identification of agricultural nitrogen (N) and phosphorus (P) emissions to the gulf are rarely reported in tropical regions of China, mainly due to the lack of local reliable data and quantitative tools for spatiotemporal changes. In this study, we constructed a high-resolution NUFER (NUtrient Flow in food chains, Environment and Resources use) model based on geology, meteorology, land use data, statistical data, and field investigation to quantify the spatiotemporal characteristics and sources of N and P emissions. Bamen Bay (BMB), a bay with a mangrove national wetland Park in the Hainan Island, China, was chosen as a case study. The results showed that agricultural N emission to water in 2018 increased fivefold compared to 1990. Leaching was the main method of agricultural N emission and was mainly distributed in farms in the west and north. The contribution of N emission from crop system to water increased 20.3% in 28 years. Poultry and fruits have contributed the most to N output, and the trend is continuing. P emission to water increased sevenfold compared 1990. The contribution of P emission from animal system to water increased from 86.8% in 1990 to 90.1% in 2018 due to low removal rate of livestock manure. P emission was mainly via direct discharge of manure, mainly distributed in livestock breeding sites near the bay. Poultry has consistently contributed the most to P output in 28 years, accounting for 49.1% in 2018. Fertilizers and fodder were the largest sources of N and P. The average N and P loss rates of BMB were 5.32 t km2 yr−1 and 0.26 t km2 yr−1. The future agricultural transformation is essential, and it is necessary to reduce the application of N fertilizer and increase the removal rate of livestock manure. These results can provide reference for other typical agricultural pollution bays in exploring the spatiotemporal characteristics of N and P emissions to water and the identification of agricultural sources.

Responses of surface ozone to future agricultural ammonia emissions and subsequent nitrogen deposition through terrestrial ecosystem changes

Abstract. With the rising food demands from the future world population, more intense agricultural activities are expected to cause substantial perturbations to the global nitrogen cycle, aggravating surface air pollution and imposing stress on terrestrial ecosystems. Much less studied, however, is how the terrestrial ecosystem changes induced by agricultural nitrogen deposition may modify biosphere–atmosphere exchange and further exert secondary feedback effects on global air quality. Here we examined the responses of surface ozone air quality to terrestrial ecosystem changes caused by year 2000 to year 2050 changes in agricultural ammonia emissions and the subsequent nitrogen deposition by asynchronously coupling between the land and atmosphere components within the Community Earth System Model framework. We found that global gross primary production is enhanced by 2.1 Pg C yr−1, following a 20 % (20 Tg N yr−1) increase in global nitrogen deposition by the end of the year 2050 in response to rising agricultural ammonia emissions. Leaf area index was simulated to be higher by up to 0.3–0.4 m2 m−2 over most tropical grasslands and croplands and 0.1–0.2 m2 m−2 across boreal and temperate forests at midlatitudes. Around 0.1–0.4 m increases in canopy height were found in boreal and temperate forests, and there were ∼0.1 m increases in tropical grasslands and croplands. We found that these vegetation changes could lead to surface ozone changes by ∼0.5 ppbv (part per billion by volume) when prescribed meteorology was used (i.e., large-scale meteorological responses to terrestrial changes were not allowed), while surface ozone could typically be modified by 2–3 ppbv when meteorology was dynamically simulated in response to vegetation changes. Rising soil NOx emissions, from 7.9 to 8.7 Tg N yr−1, could enhance surface ozone by 2–3 ppbv with both prescribed and dynamic meteorology. We, thus, conclude that, following enhanced nitrogen deposition, the modification of the meteorological environment induced by vegetation changes and soil biogeochemical changes are the more important pathways that can modulate future ozone pollution, representing a novel linkage between agricultural activities and ozone air quality.

Nutrient-extended input–output (NutrIO) method for the food nitrogen footprint

Agro-food systems require nutrient input from several sources to provide food products and food-related services. Many of the nutrients are lost to the environment during supply chains, potentially threatening human and ecosystem health. Countries therefore need to reduce their nutrient/nitrogen footprints. These footprints are importantly affected by links between sectors. However, existing assessments omit the links between sectors, especially between the agriculture, manufacturing, and energy sectors. We propose a novel approach called the nutrient-extended input–output (NutrIO) method to determine the nutrient footprint as a sum of direct and indirect inputs throughout the supply chains from different sources of nutrients. The NutrIO method is based on a nutrient-based material flow analysis linked to economic transactions. Applying this method, we estimated the nitrogen footprint of Japan in 2011 at 21.8 kg-N capita−1yr−1: 9.7 kg-N capita−1 yr−1 sourced from new nitrogen for agriculture and fisheries, 7.0 kg-N capita−1 yr−1 from recycled nitrogen as organic fertilizers, and 5.1 kg-N capita−1 yr−1 from industrial nitrogen for chemical industries other than fertilizers. A further annexed 55.4 kg-N capita−1 yr−1 of unintended nitrogen input was sourced from fossil fuels for energy production. The nitrogen intensity of the wheat and barley cultivation sector, at 1.50 kg-N per thousand Japanese yen (JPY) production, was much higher than that of the 0.12 kg-N per thousand JPY production for the rice cultivation sector. Industrial nitrogen accounted for 2%–7% of the nitrogen footprint of each major food-related sector. The NutrIO nitrogen footprint sourced from new nitrogen for agriculture and fisheries, at 8.6 kg-N capita−1 yr−1 for domestic final products, is comparable to the food nitrogen footprint calculated by other methods, at 8.5–10.5 kg-N capita−1 yr−1. The NutrIO method provides quantitative insights for all stakeholders of food consumption and production to improve the nutrient use efficiencies of agro-food supply chains.

Quantifying N leaching losses as a function of N balance: A path to sustainable food supply chains

Growing public concern over agricultural nitrogen (N) pollution is now reflected in consumers’ food choices and shareholders’ resolutions, causing rapid changes in global food supply chains. Nitrate (NO3) leaching represents the primary N source for groundwater contamination and freshwater ecosystem degradation. However, simplified science-based indicators are still lacking to facilitate improved N management practices at the farm-level. We conducted a global analysis of published field studies to evaluate N balance (N inputs minus N outputs) as a robust predictor for NO3 losses. Using 82 studies (1110 observations) for rainfed cereal crops in temperate regions, we 1) quantified the response of NO3 losses to changes in N balance for major rainfed cereal crops while accounting for environmental and management variables; and 2) assessed the feasibility of improving water quality through lower N balance under different scenarios using the case study of maize (Zea mays L.) data from the US Corn Belt. Observations were grouped in studies from the US and non-US regions. Results show that NO3 losses increased exponentially as N balance increases for both the US and non-US regions, though they were 60% higher in the US at a given N balance. Scenario analysis revealed that reducing the N rate from the agronomic optimum to the lower point within the economic optimum N rate range decreased NO3 losses by 13% without impacting economic returns. The case study for maize showed that improvements in N use efficiency that increase grain yield at a given fertilizer rate can substantially reduce N balance and mitigate NO3 losses. This study provides an evidence-based foundation for food supply chain companies to mitigate global NO3 pollution, specifically by using the generalized relationships presented here to track progress in NO3 leaching mitigation. To further resolve uncertainties and improve region-specific estimates for NO3 losses, we propose a tiered monitoring and assessment framework similar to the IPCC (Intergovernmental Panel on Climate Change) methodology for N2O emissions, widely implemented in science and used for policy.

Sulphur coated urea improves morphological and yield characteristics of transplanted rice (Oryza sativa L.) through enhanced nitrogen uptake

Imbalanced and non-judicious use of nitrogen in agriculture is one of the major factors responsible for ecological disturbance and threat to biodiversity. Among cultivated crops, nitrogen losses in rice are the highest that resulted in low nitrogen use efficiency. Urea coating with sulphur can deaccelerate nitrogen release and contribute to higher availability for plants. An experiment was conducted during two consecutive years 2016 and 2017 for the assessment of sulphur coating on urea in transplanted rice under varied nitrogen levels. There were two levels of urea source, U1 = granular urea (UG) and U2 = sulphur coated urea (USC) and three levels of nitrogen rate were kept as, N1 = 100% of the recommended nitrogen (160 kg ha−1), N2 = 75% of the recommended nitrogen (120 kg ha−1) and N3 = 50% of the recommended nitrogen (80 kg ha−1). Results indicated that in both years highest kernel yield was recorded in USC as compared to UG. Almost all morphological traits were influenced by nitrogen levels and urea sources. Chlorophyll a and b were also significantly higher in USC at 90 and 120 DAT (days after transplanting). Nitrogen contents in leaf and panicle were also increased when nitrogen was applied in form of USC. Leaf nitrogen contents were almost same at 90 and 120 DAT while panicle nitrogen contents increased significantly at 120 DAT under USC. It is concluded that urea coating with sulphur is more efficient than application of granular urea. To obtain higher yield in puddled rice, it is recommended that nitrogen must be applied at the rate of 160 kg ha−1 through coating of sulphur.

Geochemical Characteristics and Driving Factors of NO3-Type Groundwater in the Rapidly Urbanizing Pearl River Delta

In response to rapid economic development, nitrate pollution of groundwater is becoming a serious issue in many parts of China. Urbanization and industrialization are the main drivers of NO3-type groundwater expansion. Focusing on the Pearl River Delta, the occurrence and driving factors of shallow nitrate groundwater are discussed. Overall, groundwater nitrate concentrations are generally high in this region. Of 1538 groundwater samples, 5.7% had nitrate concentrations higher than the groundwater quality standard(88.6 mg·L-1) and 18.5% were classified as NO3-type waters, which are mainly distributed in the hilly and piedmont areas. Guangzhou, Dongguan, Foshan, Zhuhai and other areas show high total dissolved solid(TDS)-concentration NO3-type waters, which are affected by urbanization and industrialization. In comparison, low-TDS NO3-type waters are distributed in the hilly and valley areas. In the Xijiang and Dongjiang plains, the TDS concentrations on groundwater increased significantly due to inputs of industrial wastewater and saline seawater. The NO3- concentration in the groundwater in this area exceeded the class III water standard but did not change the hydrochemical type classification. However, industrialization has led to the frequent appearance of SO4-type water in this area. The NO3-type water occurs in acidic or weakly acidic environments, typically characterized by low TDS and total hardness concentrations, and high Cl-, SO42-, and K+ concentrations. The formation of NO3-type water is mainly affected by domestic sewage, industrial wastewater, agricultural nitrogen fertilizer, septic tank outflows, and landfill leachate leakage. Generally, the pollution loads of high-TDS NO3-type waters are higher than low-TDS NO3-type waters. The delineation of NO3-type waters, especially the low-TDS type, is helpful for identifying groundwaters posing greater risks for human activities, and those with low nitrate concentrations but potential pollution risk, which is of great significance in the prevention and control of groundwater pollution.

Distribution of mineral nitrogen in long-term conservation agriculture under semi-arid condition

Depthwise and temporal distribution of soil nitrogen release was carried out in pigeon pea [Cajunus cajan (L.) Millsp.] under conservation agriculture (CA) experiment (since 2010) during kharif 2019-20. The treatment includes conventional tillage (CT) and zero tillage (ZT), which includes: permanent narrow bed (PNB); PNB with residues of previous crop (PNB+R); permanent broad bed (PBB), PBB with residues (PBB+R), flat bed (FB) and FB with residues (FB+R). Soil samples were collected at different stages; pre-flowering, flowering, pod filling and harvest of pigeon pea from two depths (0-15 and 15-30 cm). Adopting CA practices increased NH4-N, NO3-N and mineral N over without CA plots irrespective of crop growth stages and depth of soil. As soil depth increases, NH4-N, NO3-N and mineral-N decreased and the reduction was more under CT and ZT without residues retained plots. The maximum NH4-N was observed at the flowering stage followed by pod filling &gt; pre-flowering &gt; harvest stage in 15 cm soil depth. The average NO3-N decreased from pre-flowering (34.3 mg/kg) to flowering (28.7 mg/kg) and increased at the pod filling stage (33.7 mg/kg). Among all treatments, PBB+R recorded significantly higher NH4-N, NO3-N, and mineral-N. In nutshell, adopting CA practices (PBB+R) may be a viable option for enhancing N availability, especially in semi-arid and arid conditions where N is always a limiting factor for crop growth and yield.

German pig farmers’ perceived agency under different nitrogen policies

Agricultural nitrogen (N) emissions represent the most substantial N source in Germany. Even though multiple policies have been introduced at the EU and German national level to reduce agriculturally sourced reactive Nitrogen (N), Germany is exceeding the target of the government’s national sustainability strategy to limit N surpluses. To form a better view of the current N policy challenges, this paper seeks to identify what constrains family-managed pig farmers in Germany from adopting N-reduced farming practices. Our study applies a practice-based approach and reconstructs farmers’ practice and individual perception of the possible capability to change practices (perceived agency) through problem-centred interviews. The study identifies different ideal types of farmers based on their reported farming practices and perceived agency: The first type feeling overburdened and weary of the current requirements, the second type acting based on routine and incremental improvement efforts, and the third type adapting early and inventing. However, regarding the perceived agency to adopt N-reduced farming practices our results show that all three farmer types report only low to little agency. Based on the findings, the study identifies type-specific and type-spanning constraining factors. To resolve farmers’ perceived contradictions and inconsistencies which result in the unwillingness to accept further N reduction measures, we argue that policies need to address these factors. To enhance long-term paths for sustainable N-reduced farming practices, this study concludes that N policies need to shift towards outcome-oriented policies to create a collective and holistic understanding of the desired outcome while considering their embeddedness into regional and individual contexts.

Incapability of biochar to mitigate biogas slurry induced N2O emissions: Field investigations after 7 years of biochar application in a poplar plantation

Nitrous oxide (N2O) is a potent atmospheric greenhouse gas that is largely emitted from soils due to the enhanced use of reactive nitrogen in agriculture and plantations. In this study, we evaluated the N2O mitigation ability of biochar after 7 years of application in a poplar plantation. The field experiment was based on combinations of three biochar (0, 80, and 120 t ha−1) and four biogas slurry (0, 125, 250, and 375 m3 ha−1) rates following a factorial design. N2O flux rates were measured for seven consecutive months using in situ static chambers. Soil physicochemical characteristics, potential nitrification rate (PNR), denitrification (DEA), and N2O reduction were recorded once each in September 2019 and January 2020 via lab incubations. In addition, qPCR assays were used to assess the abundance of key nitrifying and denitrifying functional genes. Biochar application after 7 years had no significant effects on N2O flux rates, PNR, and DEA rates. However, a triggering effect of biogas slurry on soil N2O emission was observed, although there was no correlation between biogas slurry rates and N2O emission rates. Factorial ANOVA showed a significant effect of biogas slurry and its interaction with biochar on the relative abundance of bacterial denitrifying and nitrifying functional genes. Additionally, significant correlations of N2O emission rates with PNR rates and NO3− concentration indicated that nitrification was the dominant pathway of N2O emission. Thus, a single biochar application did not mitigate N2O emission rates induced by biogas slurry on a long-term scale.

Spatial and Temporal Assessment of Nitrate-N under Rice-Wheat System in Riparian Wetlands of Punjab, North-Western India

The nitrate (NO3−) leaching assessment from extensive fertilizer nitrogen (N) applications to croplands is crucial to optimize fertilizer-N recommendations that do not threaten the quality of drinking groundwater. SWAP (Soil Water Atmosphere Plant), a water balance model, was linked with ANIMO (Agricultural NItrogen MOdel), a nitrate leaching model and the Geographical Information System (GIS) to assess the spatial and temporal leaching of NO3−-N from fields under rice-wheat cropping system in the riparian wetlands in the Punjab in north-western India. The results revealed that NO3−-N concentration in the groundwater exceeded the 10 mg NO3−-N L−1 limit set by the World Health Organization (WHO) for drinking water only during December–January. The verification of these results using measured values indicated that the SWAP-ANIMO model satisfactorily predicted NO3−-N concentrations in the leachate in the vadose zone. A low value of the mean absolute error (0.5–1.4) and a root mean square error (0.6–1.5) was observed between the measured and the predicted NO3−-N concentration across the soil profile during the validation at five sampling sites. The NO3−-N predictions revealed that in the long-term, the ongoing fertilizer-N management practices in the riparian wetlands will not significantly change the average NO3−-N concentration in the groundwater. The modeling approach was satisfactory for an efficient quantitative assessment of NO3−-N pollution in groundwater while accounting for the spatial and temporal variability.

Preparation and Properties of Urea Slow-Release Fertilizer Hydrogel by Sodium Alginate-Gelatin Biopolymer

Urea is high solubility nitrogen fertilizer. There is major nitrogen pollution in ecosystem. Slow-release nitrogen fertilizer the way to decrease nitrogen form agriculture. Slow-release nitrogen fertilizer the way to decrease nitrogen in agriculture. Slow-release formulations of nitrogen fertilizer were developed based on alginate-gelatin by using calcium chloride as the cross-linker in the egg-box model as hydrogels. Water-retaining ratio, loading behavior, and the release kinetics were examined. The release kinetic rates were investigated by Zero-order kinetic, First-order kinetic, Higuchi, Korsmeyer-Peppas, Weibull, and Hixson-Crowell models. The results showed that the S1G0.5 sample (alginate 1 g and gelatin 0.5 g) was the optimum condition for application as urea slow-release fertilizers because it was a minimal release kinetic rate for 12 hrs. These results indicate that the alginate-gelatin hydrogel can be a slow-release nutrient to plant an environmentally friendly fertilizer.

A Research Road Map for Responsible Use of Agricultural Nitrogen

Nitrogen (N) is an essential but generally limiting nutrient for biological systems. Development of the Haber-Bosch industrial process for ammonia synthesis helped to relieve N limitation of agricultural production, fueling the Green Revolution and reducing hunger. However, the massive use of industrial N fertilizer has doubled the N moving through the global N cycle with dramatic environmental consequences that threaten planetary health. Thus, there is an urgent need to reduce losses of reactive N from agriculture, while ensuring sufficient N inputs for food security. Here we review current knowledge related to N use efficiency (NUE) in agriculture and identify research opportunities in the areas of agronomy, plant breeding, biological N fixation (BNF), soil N cycling, and modeling to achieve responsible, sustainable use of N in agriculture. Amongst these opportunities, improved agricultural practices that synchronize crop N demand with soil N availability are low-hanging fruit. Crop breeding that targets root and shoot physiological processes will likely increase N uptake and utilization of soil N, while breeding for BNF effectiveness in legumes will enhance overall system NUE. Likewise, engineering of novel N-fixing symbioses in non-legumes could reduce the need for chemical fertilizers in agroecosystems but is a much longer-term goal. The use of simulation modeling to conceptualize the complex, interwoven processes that affect agroecosystem NUE, along with multi-objective optimization, will also accelerate NUE gains.