N-fertilizer Application Research Articles

Diversity of ammonia sources in Tianjin: nitrogen isotope analyses and simulations of aerosol ammonium

Environmental context Atmospheric particulate NH4+, primarily produced from the reaction of NH3 and acids, is an important component of PM2.5. In this study, nitrogen stable isotope analyses and an atmospheric chemistry model were used to estimate the contribution of major NH3 sources to particulate NH4+ in Tianjin, a megacity in North China Plain (NCP). Our research has implications for investigations of NH3 emission sources and relevant pollution control in Tianjin and NCP. Rationale The North China Plain (NCP) has been identified as an NH3 emission hotspot. Source apportionment of NH3 is a prerequisite for controlling NH3 or NH4+ pollution. Nitrogen stable isotope (δ15N) analysis is a promising method for NH3 source apportionment but its accuracy is still in question. Methodology In this study, daytime and nighttime PM2.5 samples were collected from two sites in Tianjin, NCP, in autumn. Concentrations and δ15N of particulate NH4+ were then measured. Nitrogen stable isotope analyses and isotope mixing model (MixSIAR), and an atmospheric chemistry model (WRF-CMAQ-ISAM) were used to estimate the sources of NH3 in Tianjin. Results Results from the MixSIAR and WRF-CMAQ-ISAM models suggested that all the sources including livestock breeding, N-fertiliser application, fossil fuels, NH3 slip (especially from traffic), human waste and biomass burning (mostly from bioapplication) were non-negligible to NH3 and NH4+ in Tianjin. This high complexity is due to significant agricultural and industrial production and residential life in Tianjin and the surrounding regions. Our results indicate all NH3 sources need to be considered if we want to reduce NH4+ pollution in Tianjin in autumn.

Fertilization-induced greenhouse gas emissions partially offset carbon sequestration during afforestation

Newly-planted forests require careful management to ensure the successful establishment of young trees; this can include herbicide application, irrigation, fertilization, or a combination of these treatments. The global rise in nitrogen (N) fertilizer application in managed forest plantations is driven by policies aiming at rapid tree growth and carbon sequestration as a strategy to tackle climate change. However, the impact of N-fertilizer on production and consumption of greenhouse gases (GHG), such as carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) is poorly understood, particularly when combined with irrigation. As a result, assessing forest GHG balance is key to defining effective climate mitigation strategies through afforestation projects.This study assessed the response of GHG fluxes to irrigation and fertilization on recently afforested lowland arable land in central England, across loamy and sandy loam soils. The application of 180 kg ha−1 of N via an irrigation system, aimed at enhancing wood production and C sequestration, resulted in an increase of CO2 and N2O emissions for both soil types. Particularly, the N2O emission factors (EF; kg N2O/kg N applied) for loamy and sandy loamy soils were 3.9% and 2.1%, respectively, higher than the IPCC default estimate of 1% for agricultural and forest land. Furthermore, both sandy loam and loamy soils showed a distinct transition from being CH4 sinks to sources. Thus, the combined application of irrigation and N-fertilizer had a significant impact on the total Global Warming Potential (GWP), which increased by 34% and 32% for sandy loam and loamy soil, respectively, when compared to their controls. Despite a significant increase in tree growth under fertilized conditions, the offset potential was only partial, highlighting the net contribution to GHG emissions. The outcomes of this study emphasise the potential for significant “carbon-equivalent-debt” from afforestation supported in its early years by irrigation and fertilization.

Viability and agronomic efficiency of using Bacillus licheniformis to complement nitrogen fertilization and pre-treatment and storage of mayze seeds

The objective of the study was to evaluate the agronomic efficiency and viability of using the bacteria Bacillus licheniformis to complement nitrogen fertilization in top dressing and in the pre-treatment and storage of maze seeds. The study was conducted in the municipalities of Candói- PR and Lapa-PR (phase 1) and in the municipalities of Serranópolis do Iguaçu–PR and São Miguel do Iguaçu (phase 2). Inoculation with Bacillus licheniformis presents agronomic efficiency similar to nitrogen control and inoculation with Azospirillum brasilense during the harvest period. Inoculation with Bacillus licheniformis 90 days before sowing is capable of reducing the application of N-fertilizer by 25% without compromising the yield of maze grains in the second harvest period.

Optimizing fertilizer usage for source reduction of salt and fluoride ion runoff discharge from a soda saline-alkali paddy field

Planting rice is a beneficial strategy for improving soda saline-alkali soil, but it comes with the challenge of increased runoff discharge of salt and fluoride (F−) ions. The use of different nitrogen (N) fertilizers can impact this ion discharge, yet the specific characteristics of ion runoff under different N-fertilizer applications remain unclear. A field experiment was conducted in this study, applying five commonly used N-fertilizer types to monitor the ion runoff throughout an entire rice growing season. Salt ions and F− runoff discharge was significantly affected by N-fertilizer type, runoff event, and their interaction (p < 0.001). Regardless of N-fertilizer types, sodium (Na+) and bicarbonate (HCO3−) ions were consistently discharged from runoff in soda saline-alkali fields, constituting 20.55–25.06 % and 47.57–50.49 % of total ion discharges, respectively. Compared to no N-fertilizer (CK) and other N-fertilizer treatments, the organic-inorganic compound fertilizer (OCF) application significantly reduced Na+ and HCO3− runoff discharge, causing a decrease in the competitive adsorption capacity between HCO3− and F− (p < 0.05). The use of OCF and inorganic compound fertilizer (ICF) lowered pH in runoff water, resulting in reduced dissolution capacity of calcium fluoride in the soil and thereby decreasing total F− runoff discharge. In conclusion, OCF proves to be an effective N-fertilizer in mitigating salt ions and F− runoff discharge in soda saline-alkali paddy fields. Additionally, ICF demonstrates the ability to control F− runoff discharge.

Fertilizer Application Method Provides an Environmental-Friendly Nitrogen Management Option for Sugarcane

PurposeNitrogen fertilizer management is an important agricultural tool that must be optimized to promote sustainable practices since the nitrogen-fertilizer recovery by plants (NRP) is low, leading to nitrogen losses to the environment. In sugarcane, N-fertilization has been investigated over the years but little attention has been given to N-fertilizer application methods. Sugarcane crop production and environmental impact regarding N-fertilizer application methods (i.e., applied onto the sugarcane straw layer and incorporated into the soil) were investigated in the present study aiming to achieve an environmental-friendly cropping system.MethodsSugarcane yield and NRP, N2O emissions, relevant components of the soil microbiological community and N-fertilizer retention in soil layers were quantified. The experiment was carried out in field conditions where N-fertilizer application methods using 15N-labelled ammonium nitrate (15NH415NO3) were compared to a control treatment with no N-fertilization.ResultsIncorporation of N-fertilizer into the soil increased the sugarcane yield by 17% (two-year average) compared to N-fertilizer applied onto the sugarcane straw layer, which was similar to control treatment. There was an increase in NRP-fertilizer of 79% due to the application of N-fertilizer incorporated into the soil. Furthermore, soil incorporation of N-fertilizer decreased N2O emission by 22% with the fertilizer N emission factor reduced four-fold. The N2O emissions were mostly associated with ammonium-oxidizing bacteria (AOB).ConclusionsOur results show that application of N-fertilizer incorporated into the soil is an environmental-friendly N-fertilization management which will improve agricultural sustainability and reduce environmental impacts.Graphical

Assessing the impact of irrigation and nitrogen management on potato performance under varying climate in the state of Florida, USA

Optimizing irrigation and nitrogen (N) fertilizer management in irrigated potato crops grown on sandy soils in subtropical regions such as in northeastern Florida, USA is essential to sustain a high yield and to minimize leaching. N applications in this region typically occur at approximately 25–30 days prior to planting (Npre), at emergence (Neme), and at tuber initiation (Nti). However, recent studies suggest that applying N near planting (Npl) enhances fertilizer N use efficiency (FNUE). We combined experimentation with modeling to assess irrigation and N management options for potato in northeastern Florida. We first aimed to evaluate the DSSAT/CSM-SUBSTOR-Potato model using two-year irrigated field experiments conducted on sandy soils with variable N rates and application timings. CSM-SUBSTOR-Potato accurately simulated aboveground plus tuber dry weight [Relative root mean squared error (RRMSE) = 26.4%, Willmott’s index (d) = 0.98] and N accumulation (RRMSE = 28.6%, d = 0.97). Soil moisture and mineral N were captured well overall, but they were often underestimated due to a water table influence that is currently not considered in DSSAT. Subsequently, CSM-SUBSTOR-Potato was applied to simulate tuber yield, N leaching, and FNUE under scenarios of irrigation scheduling and N-fertilizer application (rate/timing) strategies, focusing on Npre versus Npl aiming to improve resource use efficiency. The simulations indicated that a target of 60% and 70% of the available soil water can be safely used as an irrigation strategy to achieve a high yield, while reducing irrigation water applied and N leached to the environment. Overall Npl increased crop N uptake by 10%, tuber yield by 7%, reduced N leached by 13%, and consequently increasing FNUE by 9%, compared to Npre across the irrigation treatments. Thus, Npl should be preferred in sandy soils and climate-risky subtropical environments, along with Neme and Nti as key timings to synchronize N supply with potato growth.

Dominant contribution of combustion-related ammonium during haze pollution in Beijing

Aerosol ammonium (NH4+), mainly produced from the reactions of ammonia (NH3) with acids in the atmosphere, has significant impacts on air pollution, radiative forcing, and human health. Understanding the source and formation mechanism of NH4+ can provide scientific insights into air quality improvements. However, the sources of NH3 in urban areas are not well understood, and few studies focus on NH3/NH4+ at different heights within the atmospheric boundary layer, which hinders a comprehensive understanding of aerosol NH4+. In this study, we perform both field observation and modeling studies (the Community Multiscale Air Quality, CMAQ) to investigate regional NH3 emission sources and vertically resolved NH4+ formation mechanisms during the winter in Beijing. Both stable nitrogen isotope analyses and CMAQ model suggest that combustion-related NH3 emissions, including fossil fuel sources, NH3 slip, and biomass burning, are important sources of aerosol NH4+ with more than 60% contribution occurring on heavily polluted days. In contrast, volatilization-related NH3 sources (livestock breeding, N-fertilizer application, and human waste) are dominant on clean days. Combustion-related NH3 is mostly local from Beijing, and biomass burning is likely an important NH3 source (∼15%–20%) that was previously overlooked. More effective control strategies such as the two-product (e.g., reducing both SO2 and NH3) control policy should be considered to improve air quality.

The effects of straw returning and nitrogen fertilizer application on soil labile organic carbon fractions and carbon pool management index in a rice–wheat rotation system

Straw returning and nitrogen (N) fertilizer application are important agricultural measures to improve soil carbon pool. However, the combined effect of various straw-returning amounts and N-fertilizer application rates on soil carbon pool is still unclear. Therefore, a field experiment with three straw-returning amounts and three N-fertilizer application rates was conducted for 4 years in central China. The results revealed that the addition of N fertilizer clearly enhanced the contents of soil organic carbon (SOC) by 2.2%− 2.7%, dissolved organic carbon (DOC) by 20.1%− 39.2%, microbial biomass carbon (MBC) by 37.9%− 44.2%, and easily oxidizable carbon (EOC) by 18.4%− 23.6%. Moreover, it also enhanced the activities of invertin by 33.4%− 46.4%, cellulase by 23.5%− 32.4%, and polyphenol oxidase by 20.5%− 27.1%, as well as the carbon pool management index (CPMI) by 21.3%− 27.6%. The CPMI increased gradually as the N-fertilizer application rate increased. However, straw returning did not significantly change the contents of SOC, EOC, and MBC; invertin activity, or CPMI. Based on the structural equation model, it was observed that N fertilizer application enhances MBC and subsequently improves CPMI by increasing EOC. This highlights the vital role of soil microorganisms in the soil carbon cycle and the significance of supplementing N to improve and sustain agricultural soil carbon reservoirs. Additionally, this study indicates that the combined application of N fertilizer and straw returning has a more positive effect on improving the soil carbon pool.

Growth and yield performance of wheat (Triticum Aestivum L.) As influenced by combined application of naa and n-fertilizer in two sowing time

Growth and yield performance of wheat (Triticum Aestivum L.) As influenced by combined application of naa and n-fertilizer in two sowing time

Roles of historical land use/cover and nitrogen fertilizer application changes on ammonia emissions in farmland ecosystem from 1990 to 2020 in China

In the past decades, China has witnessed significant changes in its land use/land cover (LULC) pattern. These changes have led to a direct impact on ammonia (NH3) emissions in soil background, and indirectly affected the total nitrogen fertilizer (N-fertilizer) application, crop planting amount and the resulting straw mass through the changes of cropland area. Great changes have also taken place in the amount and structure of fertilizer application in China, which affects the NH3 emissions from farmland ecosystems caused by N-fertilizer application. The aforementioned changes have led to significant alterations in NH3 emissions from China's farmland ecosystems over the past 30 years. The process of these changes remains to be analyzed, and the contributions of LULC changes and N-fertilizer application in this process are yet to be assessed. This study aims to investigate the NH3 emission changes and spatiotemporal variation characteristics from farmland ecosystems during 1990 and 2020 due to the LULC changes. Additionally, the study employs scenario analysis method to discuss the effects of LULC changes and N-fertilizer application changes on NH3 emissions in farmland ecosystems. Results indicate that there is evident spatiotemporal heterogeneity in China's LULC pattern, particularly in eastern China. The southeast region is predominantly characterized by the conversion of cropland into construction land. Moreover, some regions such as Northwest China and Northeast China have experienced the conversion of other land types into cropland, significantly influenced by national development policies. From 1990 to 2020, the national NH3 emissions from farmland ecosystem range from 3294.75 Gg to 4064.20 Gg. NH3 emissions and their interannual variation in farmland ecosystems exhibit significant differences across various regions. The regions with higher contributions to NH3 emissions in farmland ecosystems are East China, Central China, and North China, accounting for 25.32 %–37.26 %, 18.85 %–22.46 % and 11.24 %–18.50 % of the total emissions, respectively. NH3 emissions in each region are influenced by cropland area, N-fertilizer application, and regional development characteristics. Compared to LULC changes, changes in N-fertilizer application have a more pronounced impact on NH3 emission changes in farmland ecosystems. From 1990 to 2020, the contribution (increase or decrease) of N-fertilizer application changes to NH3 emission changes in farmland ecosystems in China ranges from 0.11 % to 16.61 %, while the contribution (increase or decrease) of LULC changes ranges from 0.47 % to 2.38 %. South China demonstrates a unique situation regarding the influence of LULC changes. This region has a relatively small cropland area, and fluctuations in cropland area significantly affect NH3 emissions in farmland ecosystems. The influence of policies is evident. From the changes in cropland area in Northwest China and Northeast China to changes in N-fertilizer application, policy changes have consistently impacted the changes in NH3 emissions in China's farmland ecosystems. From “soft policies” involving encouragement and guidance to “hard policies” encompassing the establishment of necessary targets, the degree of strictness in policy directly affects the timeliness of policies effectiveness. The results of this study indicate that reducing the application of N-fertilizers is the primary approach to reducing NH3 emissions in China's farmland ecosystems. In terms of policy guidance, compared to implementing structural and pathway adjustments, implementing clear total control of fertilizer usage is a timely and effective choice for reducing NH3 emissions.

Impact of Rice–Wheat Straw Incorporation and Varying Nitrogen Fertilizer Rates on Soil Physicochemical Properties and Wheat Grain Yield

Straw return (SR) is crucial for the comprehensive and efficient utilization of resources within agroecosystems; however, its impact on soils and wheat grain yield in the Jianghan Plain of the Yangtze River Basin, Hubei Province of China, is not fully known. Therefore, the present study was undertaken to assess the impact of returning rice–wheat straw, along with different nitrogen (N) fertilizer applications, on soil physicochemical properties and wheat grain yield. The Yangmai 23 wheat variety was cultivated in the Experimental Farms of Yangtze University in the Yangtze River Basin, with three rates of rice SR (0, 50 and 100%) and four N fertilizer rates (0, 33.3, 70 and 100%) with 180 kg/ha urea. The integrated use of SR- and N-fertilizer rates significantly altered soil nitrogen, nitrate, ammonium, phosphorus, potassium, pH and moisture within the 20 cm depth before the seeding, jointing and maturation stages of the wheat. The grain yields of 6408 ± 110 − 8290.00 ± 298 and 4726 ± 62 − 6758.00 ± 196 kg/ha were obtained in the 2021–2022 and 2022–2023 seasons, respectively. The studied soil physicochemical properties either before seeding, or at the jointing and maturation stages had a significant effect on final grain yield. These results underscore the combined effect of SR- and N-fertilizer application to improve wheat productivity in the Yangtze River Basin. However, further studies are ongoing to assess the impact of these treatments on the soil microbial community, as well as on wheat grain quality.

Nutrient runoff loss from saline-alkali paddy fields in Songnen Plain of Northeast China via different runoff pathways: effects of nitrogen fertilizer types.

The application of nitrogen (N) fertilizer aggravates the nutrient runoff loss from paddy, causing serious agricultural non-point source pollution, and leading to a serious decline in water quality. The global area of saline-alkali paddy has expanded, but the response of nutrient loss via runoff to N-fertilizer applications in saline-alkali paddy is still unclear. This study conducted a 147-day field experiment to evaluate the nutrient runoff loss from saline-alkali paddy with different N-fertilizer application strategies in Songnen Plain of Northeast China. Regardless of N-fertilizer types, the nutrient loss via rainfall runoff in the entire rice-growing season was significantly (p < 0.05) higher than that via artificial drainage. The N and phosphorus (P) concentrations in runoff water were correlated with salinity and alkalinity. Especially, pH had a significant positive correlation with total-P (TP) (r = 0.658, p < 0.01). In the entire rice-growing season, the TN runoff losses in urea (U), microbial fertilizer (MF), and inorganic compound fertilizer (ICF) treatments were significantly (p < 0.05) lower compared with carbon-based slow-release fertilizer (CSF) and organic-inorganic compound fertilizer (OCF), respectively. Meanwhile, the TP runoff losses in OCF and ICF treatments were significantly (p < 0.05) lower than U and MF, respectively. Overall, the application of ICF is a better choice to avoid N and P losses via runoff from saline-alkali paddy fields.

Tillage intensity and straw retention impacts on soil organic carbon, phosphorus and biological pools in soil aggregates under rice-wheat cropping system in Punjab, north-western India

The climate smart agricultural residue management practices which entail reduced tillage and in-situ crop residue managements are considered pre-requisite for improved soil health and ecosystems’ sustainability. The adoption of rice residue management practices help reduce the risk of soil nitrogen (N) depletion, while sequestering and conserving more carbon (C) in soils due to crop residues retention as compared to the conventional tillage characterized by more intense tillage and residue removal and/or burning. We therefore, quantified the impact of tillage regimes and residue return on soil C, phosphorus (P) and biological pools in the surface (0–15 cm) soil layer under rice-wheat cropping system in north-western India. We studied the medium term (5-years) impacts of fertilizer-N application (viz. N1 =75% and N2 =100% recommended fertilizer-N) as main plot treatments, and tillage regimes viz. conventional tillage, rotavator tillage and zero tillage, rice residue removal and retention under conventional and rotavator tillage and RT vis-à-vis zero tillage with partial and complete rice residue retention for wheat as sub-plot treatments in a split-plot design. Residue retention and/or incorporation significantly (p < 0.05) increased the proportion of macro-aggregates (>0.25 mm), aggregate diameter and aggregate ratio than the conventional tillage. Zero tillage significantly increased the macro-, meso- and micro-aggregate associated C by ∼22.2%, 25.7% and 18.6%, respectively than under conventional tillage. Macro-aggregates has higher concentration of very labile (by ∼37.8% and 153.1%) and labile C (by ∼29.7% and 80.4%) than the meso-aggregates (0.25–2.0 mm) as well as micro-aggregates (<0.25 mm). The passive C pool comprised the largest proportion of total organic C (TOC) pool; the highest in macro-aggregates (∼75.7% of TOC), while the lowest in macro-aggregates (∼64.4% of TOC). Macro-aggregates has higher dehydrogenase and alkaline phosphatase activity than the meso-and micro-aggregates; which was closely linked to soil related glomalin protein (R2 =0.798–0.828 *; p < 0.05). These results revealed that rice residue retention significantly increased the water soluble-P concentration by ∼60.1% and 57.9%, respectively in macro-aggregates compared to residual removal. The water soluble-P showed linear relationship with increased concentration of Fract. 1 in different sized aggregates (R2 =0.789–0.975). The inorganic P pool (NaHCO3-PI and NaOH-PI) increased with increasing organic P pool (NaHCO3-PO and NaOH-PO). These results suggest that reduced tillage and residue retention is highly beneficial for the overall improvement of C, P and biological pools in soils under rice-wheat cropping system.

The recovery of river chemistry from acid rain in the Mississippi River basin amid intensifying anthropogenic activities and climate change

Acid rain has degraded the environmental health of many regions worldwide since the Industrial Revolution. Signatures of river chemistry recovery from acid rain since the Clean Air Act and similar legislation have been reported extensively in small streams but are often subdued or masked in large rivers by complex, co-occurring drivers. Here we assess the recovery of river chemistry from acid rain deposition in the Mississippi River Basin (MRB), the largest river basin in North America. We combine analysis of temporal trends of acid rain indicator solutes with Bayesian statistical models to assess the large-scale recovery from acid rain and characterize effects of anthropogenic activities. We found evidence of river chemistry recovery from acid rain; however, the effects of other anthropogenic activities, including fertilizer application and road salting, and changing climate, are likely intensifying. Trends of pH, alkalinity and SO4 export suggest acid rain recovery at large in the MRB, with stronger evidence of recovery in the historically afflicted eastern region of the basin. The concentrations of acid rain indicators generally correlate positively to NO3 and Cl, indicating that N-fertilizer application may have significantly increased weathering, and possibly acidification, and road salt application likely increased cation loss from catchments and contributed to SO4 export. Temperature correlates positively with solute concentrations, possibly through respiration-driven weathering or evaporation. The concentrations of acid rain indicators correlate negatively and most strongly to discharge, indicating discharge as a predominant driver and that lower discharge during droughts can elevate concentrations of riverine solutes in a changing climate. Using long-term data, this study represents a rare, comprehensive assessment of the recovery from acid rain in a large river basin, taking into consideration the entangled effects of multiple human activities and climate change. Our results highlight the ever-present need for adaptive environmental management in a constantly changing world.

Response of Teff ((Eragrostis tef (zucc.) Trotter) to nitrogen and phosphorus applications on different landscapes in eastern Amhara

The dynamic nature of soil fertility status across different landscapes attracted research attention in Ethiopia and the globe. Teff [Eragrotis tef] is a major staple cereal crop in Ethiopia but yields are low due to inadequate nutrient supply and other constraints. A field study was conducted in 2020 and 2021 in the Habru district of Amhara Region to determine teff yield response to fertilizer-N and -P at hillslope, midslope, and footslope positions with slopes of >15%, 5–15%, and 0–5%, respectively. N and P fertilizer rates were factorially combined in randomized complete block design with three replications in each farmer's field. A linear mixed modeling framework was used to determine effects on grain yield due to N rate, P rate, slope, study sites, and years. Model fit was examined using Akaike's Information Criterion and Bayesian Information Criterion. Economic analysis was done with a quadratic response function to determine the economics of fertilizer. Yield response to fertilizer-P was affected by slope but the response to fertilizer-N was not affected. Teff yield increase with fertilizer-N application up to 92 kg ha−1 the economic optimum rate based on the yield response function for nitrogen fertilizer was 85.4 kg ha−1 to obtain maximum profit (86878.8 birr ha-1). Similarly, the optimum phosphorus fertilizer rate at the hill slope was 39.7 kg ha−1 to obtain a maximum profit of (96847.8 birr ha−1). But there was not a profitable response at the midslope and foot slope positions. Therefore, for Habru district and similar agroecologies85.4 kg ha−1 N and 39.7 kg ha−1 P in hillslopes and only 85.4 N kg ha−1 for midslopes and foot slopes are expected to give the most profitable returns to fertilizer applied for tef production.

Characteristics of annual NH3 emissions from a conventional vegetable field under various nitrogen management strategies

High N-fertilizer applications to conventional vegetable production systems are associated with substantial emissions of NH3, a key substance that triggers haze pollution and ecosystem eutrophication and thus, causing considerable damage to human and ecosystem health. While N fertilization effects on NH3 volatilization from cereal crops have been relatively well studied, little is known about the magnitude and yield-scaled emissions of NH3 from vegetable systems. Here we report on a 2-year field study investigating the effect of various types and rates of fertilizer application on NH3 emissions and crop yields for a pepper-lettuce-cabbage rotation system in southwest China. Our results show that both NH3 emissions and direct emission factors of applied N varied largely across seasons over the 2-year period, highlighting the importance of measurements spanning entire cropping years. Across all treatments varying from solely applying urea fertilizers to only using organic manures, annual NH3 emissions ranged from 0.64 to 92.4 kg N ha−1 yr−1 (or 0.07–6.84 g N kg−1 dry matter), equivalent to 0.05–5.99% of the applied N. At annual scale, NH3 emissions correlated positively with soil δ15N values, indicating that soil δ15N may be used as an indicator for NH3 losses. NH3 emissions from treatments fertilized partially or fully with manure were significantly lower compared with the urea fertilized treatment, while vegetable yields remained unaffected. Moreover, full substitution of urea by manure as compared to the partial substitution further reduced the yield-scaled annual NH3 emissions by 79.0–92.4%. Across all vegetable seasons, there is a significant negative relationship between yield-scaled NH3 emissions and crop N use efficiency. Overall, our results suggest that substituting urea by manure and reducing total N inputs by 30–50% allows to reduce NH3 emissions without jeopardizing yields. Such a change in management provides a feasible option to achieve environmental sustainability and food security in conventional vegetable systems.

Reaction of Peas to Nitrogen Fertilizer and Inoculation of Seeds with Ritorfin on Sod-Podzolic Soil of Different Degree of Cultivation

The results of the vegetative experiment on the establishment of the joint effect of the biological preparation Rhizotorphin and N-fertilizer (doses N0.05, N0.10, N0.15, N0.20, N0.25) on the formation of vegetative mass and the yield of seed pea grain when cultivated on weakly and medium cultivated sod-podzolic soil are presented. With an increase in the dose of N-fertilizer from N0.05 to N0.25, an increase in the yield of green mass of peas was observed by 3.4–22.2 g/vessel (on poorly cultivated) and by 10.3–35.5 g/vessel (on medium cultivated soil). The increase in grain yield from the use of Rhizotorphin on average in the experiment was 1.31 g/vessel on weakly and 1.66 g/vessel on medium cultivated soil. The application of N-fertilizer in medium cultivated soil conditions increased the responsiveness of seeded peas to inoculation to 1.70–1.87 g/vessel. When using Rhizotorphin and applying N-fertilizer, the accumulation of N in pea grain increased by 0.22 and 0.18% in accordance with the degree of cultivation of the soil. When using Rhizotorphin, N was accumulated in the roots, which positively affected the preservation of their activity and functioning at later stages of development, the intake and accumulation of N in the forming grain. The biological preparation Rhizotorphin influenced the accumulation and distribution of consumed N between the main and by-products of pea plants. Due to this, in the budding phase – the beginning of flowering, the dose increased to 0.83–0.88, and 38.0–65.5 mg N/vessel was additionally accumulated in the pea grain. With an increase in the dose of N-fertilizer over 0.05 g/kg on weakly and 0.20 g/kg on medium cultivated soil, the process of forming a symbiotic apparatus on the root system of peas was completely suppressed.

Effects of Different Irrigation Levels and Fertilizer Rates on Yield, Yield Components and Water Productivity of Onion at Adami Tulu Agricultural Research Center

Today’s agriculture sector faces a complex series of challenges to cope with the demands for sustainable management and production, which entails an increase in food production to ensure food security while using less water per unit of output and reducing nitrogen (N) fertilizer losses through leaching. The experiment was conducted at Adami Tulu Agricultural Research Center on-station to study the effect of different irrigation levels and N-fertilizer rates on plant height, bulb yield, bulb diameter, and bulb height and water productivity of onion. The treatments of the experiment had factorial combinations of three levels of watering and four N-fertilizer amounts. Results indicated that the highest plant height (53.07 cm), bulb height (6.13 cm), bulb diameter (6.21 cm), marketable bulb yield (241.39 qt/ha) and total bulb yield (252.89 qt/ha) were obtained from full irrigation and fully N-fertilized compared to the deficit conditions. The highest water productivity was recorded from 60% ETc irrigation level and 150 Kg/ha N-fertilizer application rate, but the reduction in water productivity with 80% ETc and 150 Kg/ha N-fertilizer application rate was not significant. Hence, if water is not limiting factor, 100% ETc irrigation level and 150 Kg/ha N-fertilizer could be suggested to apply. But if water becomes 232 limiting factor, 80% ETc irrigation level with 150 Kg/ha N-fertilizer would be more appropriate for growing onion in the study area. Therefore these can be used as one package of onion production technology and all growers better to apply.

The Influence of Nitrogen Applications and Low Rainfall Conditions on Yield of Mixed Grass-Legume Grassland for 2 Years

Mixed-species grassland containing legumes were suggested to increase yield compared to monocultures. Furthermore, some legumes were suggested to be able to sustain growth, even under drought conditions. The first aim of the current study was to measure if multispecies grassland with legumes is also more productive when their N input due to symbiotic N2 fixation is taken into account. Our second aim was to determine the benefit of grass–legume mixtures in terms of dry matter production under naturally occurring drought conditions. Mixed-species grasslands, consisting of monocultures and variable mixtures of (a) Trifolium pratense, (b) Trifolium. repens, (c) Lolium perenne, and (d) a mixture of drought-tolerant grasses (GSWT based), were assessed for their dry matter production over two years with contrasting weather patterns. The legume–grass seeding mixtures received either a fixed (180 kg N ha−1) or adapted N-fertilizer application (0–180 kg N ha−1), with the latter taking the assumed symbiotic N2 fixation by legumes into account. Mixed-species grassland showed improved yield compared to monocultures both in comparably humid and drought-affected years. The benefits of multispecies grass–legume mixtures were considerably more obvious under a fixed but still measurable under an adapted N-fertilizer regime. The species diversity effect appears to be significantly dependent on the additional N supply enabled by legumes’ symbiotic N2-fixation. Legumes and drought-tolerant grasses yielded equally well under drought conditions, although legumes showed major advantages during moderate drought and humid conditions. White and red clover, although both legumes, differed significantly in their persistence under elevated-N and their dry matter production under low-N fertilizer application, but were equal in their tolerance towards drought.

Content Variation and Potential Runoff Loss Risk of Nutrients in Surface Water of Saline-Alkali Paddy in Response to the Application of Different Nitrogen Fertilizer Types

As the saline-alkali paddy area continues to grow, the nutrient (e.g., nitrogen (N) and phosphorus (P)) runoff loss is becoming more serious in the world. The N-fertilizer application affects the nutrient runoff loss risk in paddy. Selecting suitable fertilizer types to reduce nutrient loss is beneficial to agricultural sustainability. However, the effects of N-fertilizer application in saline-alkali paddy are not clear. This study measured the N and P concentration of surface water in saline-alkali paddy, using various N—fertilizer treatments (i.e., urea (U), urea with urease—nitrification inhibitors (UI), organic–inorganic compound fertilizer (OCF), carbon—based slow—release fertilizer (CSF), and no N fertilization (CK)). Based on the structural equation model, both phosphate (PO43−-P) and total−P (TP) concentrations had a positive influence on total-N (TN) concentration regardless of N−fertilizer types applied. Potential risks of ammonia—N (NH4+—N) and nitrate—N (NO3−—N) runoff losses were reduced in UI treatment, but the TN and TP losses were increased. At the panicle-initiation fertilizer stage, the NO3−−N, TN, and TP concentrations in CSF and OCF treatments were lower than U. The CSF application can control the TP runoff loss risk during the rice-growing season. UI should not be suggested for the control of nutrient runoff loss in saline-alkali paddy.