Urea Ammonium Nitrate Research Articles

Do crops' responses to sulfur vary with its forms?

AbstractThe most common formsof S fertilizers in the northern Great Plains are ammonium sulfate (AS), ammonium thiosulfate (ATS), and elemental S (ES). Among these, AS is preferred over the others because of its readily available SO42– form, and it can be blended with other dry fertilizer granules, but SO42– is prone to leaching. Recently, fertilizer industries introduced micronized (<100 μm) S (MS) fertilizer formulations to hope that the smaller elemental S particles would increase the rate of S oxidation. Across the Red River Valley of North Dakota and Minnesota, field trials were conducted to compare the response of corn (Zea mays L.), spring wheat (Triticum aestivum L.), and sugar beet (Beta vulgaris L.) to the application of different forms of S (AS, ATS, mono ammonium phosphate or MAP‐10S [5% ES + 5% AS], MAP + MS, AS + MS, muriate of potash [MOP] + MS, urea ammonium nitrate [UAN] + MS). Spring wheat only had a significant positive response to S forms, with ATS having the highest grain yield in 2019, significantly higher than AS and AS + MS. In 2020, UAN + MS had the highest grain yield, only higher than the control. Corn and sugar beet did not respond to addition of or to S forms. Corn, sugar beet, and spring wheat yields were indifferent to supply and forms of S in the Red River Valley.

Aquifer lithology affects shallow groundwater quality more than nitrogen fertilizer form and placement method in an Iowa agricultural field

AbstractExcessive nutrient loss threatens local and regional water resources, and many midwestern U.S. states are adopting nutrient reduction strategies to reduce export of N and P. A common practice to reduce N loss is improved fertilizer management. In this study, we used a strip trial design to assess the effects of split N application form (urea and urea ammonium nitrate [UAN]) and placement method (broadcast, coulter, Y‐drop) on corn (Zea mays L.) yields and shallow groundwater quality at an agricultural field at Kirkwood Community College in Cedar Rapids, IA. Twelve shallow monitoring wells were installed within the production field and sampled 14 times across a corn–soybean [Glycine max (L.) Merr.] rotation. Results showed that split application of UAN applied with either coulter injection or Y‐drop method produced approximately 8–11% higher corn yields than broadcast urea, but no statistically significant relation was found between groundwater quality and N form and placement method. Instead, we report that groundwater quality and levels were significantly influenced by variations in aquifer lithology. Groundwater within fine‐textured glacial till had significantly higher dissolved reactive P, SO4, and specific conductivity, whereas groundwater within the sand aquifer had a deeper water table and had higher NO3–N and dissolved oxygen. Study results suggest aquifer lithology can play a much larger role than varying the N form and application method on shallow groundwater quality in agricultural fields.

Improvements in corn production technology using liquid nitrogen fertilizers

The article is devoted to improvements in technology of corn production using liquid nitrogen fertilizers such as urea ammonium nitrate (UAN), in pure form UAN-32 or with the addition of sulphur UAN+S, with various methods of application before seeding or leaf-feeding dressings. This technology provides an increase in the corn yield with additional efficiency compared with the use of solid nitrogen mineral fertilizers like ammonium nitrate in conditions of insufficient moisture, which are typical of many regions of Russia and especially of the Volga region (Samara oblast).

Influence of Mineral Fertilizers and Other Agrotechnical Cultivation Methods on Yield and Grain Protein Content of Winter Wheat

It is established that in the conditions of the northern steppe of Ukraine to obtain comparable results in the amount of protein in winter wheat grain it is necessary after such predecessors as stubble and sunflower, to apply a higher dose of nitrogen in complete pre-sowing fertilizer, as well as in spring fertilization, than when growing on black fallow. In the case of fertilization at the end of plants tillering with nitrogen with a local dose of N₆₀, the yield after spring barley, depending on the variety of winter wheat increased by 0.66-0.82, and for black fallow - by 0.58-0.64 t/ha. Among winter wheat varieties Kokhanka, Misia Odeska and Pylypivka, the highest yields and grain quality were observed in Pylypivka variety. It was found that among nitrogen fertilizers (ammonium nitrate, Urea Ammonium Nitrate solution - UAN-32, and ammonium sulfate) the best results in protein formation in grain in most cases provided the introduction of UAN-32 and ammonium sulfate. Strong in grain quality, winter wheat varieties Niva Odeska and Uzhynok, both after sunflower and black fallow, outperformed Kokhanka variety in terms of protein content. It is established that the highest grain productivity of different varieties of winter wheat, both when grown after spring barley and black fallow, was observed at the optimal sowing date (September 22); the variety of durum wheat Burshtyn formed a higher protein content in the grain (13.5-14.6%) than varieties of soft wheat - Golubka Odeska (12.0-12.6%) and Lastivka Odeska 13.2-13.6%). It was found that in the research years the amount of protein in the grain of winter wheat depended more on crop fertilizer than on the sowing date.

Biostimulant Effects of Glutacetine® and Its Derived Formulations Mixed With N Fertilizer on Post-heading N Uptake and Remobilization, Seed Yield, and Grain Quality in Winter Wheat.

Biostimulants could play an important role in agriculture particularly for increasing N fertilizer use efficiency that is essential for maintaining both yield and grain quality in bread wheat, which is a major global crop. In the present study, we examined the effects of mixing urea–ammonium–nitrate fertilizer (UAN) or urea with five new biostimulants containing Glutacetine® or its derivative formulations (VNT1, 2, 3, and 4) on the physiological responses, agronomic traits, and grain quality of winter wheat. A first experiment under greenhouse conditions showed that VNT1, VNT3, and VNT4 significantly increased the seed yield and grain numbers per ear. VNT4 also enhanced total plant nitrogen (N) and total grain N, which induced a higher N Harvest Index (NHI). The higher post-heading N uptake (for VNT1 and VNT4) and the acceleration of senescence speed with all formulations enabled better nutrient remobilization efficiency, especially in terms of N mobilization from roots and straw toward the grain with VNT4. The grain ionome was changed by the formulations with the bioavailability of iron improved with the addition of VNT4, and the phytate concentrations in flour were reduced by VNT1 and VNT4. A second experiment in three contrasting field trials confirmed that VNT4 increased seed yield and N use efficiency. Our investigation reveals the important role of these new formulations in achieving significant increases in seed yield and grain quality.

Efficiency of Mineral Nitrogen Fertilization in Winter Wheat under Pannonian Climate Conditions

Improvements in nitrogen (N) use efficiency in crop production are important for addressing the triple challenges of food security, environmental degradation and climate change. The three fertilizers, calcium ammonium nitrate (CAN), urea (Urea) and stabilized urea (Ureastab), were applied at a rate of 160 kg N ha−1 with two or three splits to winter wheat (Triticum aestivum L.) in the Pannonian climate region of eastern Austria. On average, over all fertilization treatments, the grain yield (GY) increased by about a quarter and the grain N concentration (GNC) doubled compared to the control without fertilization. Consequently, the grain N yield (NYGRAIN) was increased with N fertilization by 154%. The GY increased due to a higher grain density with no differences between N fertilizers but with a tendency of a higher grain yield with three compared to two splits. Three splits also slightly increased the GNC and consequently the NYGRAIN of CAN and Ureastab in one year. The removal of N fertilizer with the NYGRAIN (N surplus) was higher than the amount of applied fertilizer. Fertilization decreased the N use efficiency (NUE), the N uptake efficiency (NUpE) and the N utilization efficiency (NUtE) but increased the soil mineral nitrate (NO3-N) at harvest and the apparent N loss (ANL). Three compared to two applications resulted in a higher NO3-N at harvest but also a lower N surplus due to partly higher NYGRAIN. Consequently, the ANL was lower with three compared to two splits. Also, the NUpE and the apparent N recovery efficiency (ANRE) were higher with three splits. The best N treatment regarding highest above-ground biomass yield with lowest N surplus, N balance and ANL was the three-split treatment (50 CAN, 50 CAN, 60 liquid urea ammonium nitrate). Three splits can, under semi-arid conditions, be beneficial when aiming high-quality wheat for bread-making and also for reducing the N loss. Whereas, two splits are recommended when aiming only at high GY, e.g., for ethanol-wheat production.

The distribution of soil nitrifiers and efficacy of 3,4-dimethylpyrazole phosphate changes with soil depth and calcium carbonate application

The nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) is used to limit nitrogen (N) losses incurred following nitrification of applied N fertilisers. Inhibitor efficacy changes with soil conditions including pH and organic matter (OM) content, both of which can be stratified down the soil profile. An incubation study was conducted using acidic soil that exhibited pH stratification. Soil samples were collected from the field in 2 cm depth increments to a depth of 10 cm. Two liming treatments were applied to each depth where the pHCa was raised above 6 or left in its initial acidic state. Nitrogen treatments (urea ammonium nitrate (UAN) with and without DMPP) were applied to each liming treatment per depth and incubated for four weeks. Destructive sampling for mineral N, DMPP concentration and pH occurred every week. The abundance of nitrifiers was determined using semi-quantitative real-time polymerise chain reaction (PCR) targeting the amoA gene at weeks 0, 1 and 4. Liming significantly increased nitrification rates and bacterial amoA gene abundance. Results showed the top 0–2 cm recorded the largest population of bacterial nitrifiers. Changes in pH influenced the composition of nitrifiers present in the soil. Bacterial nitrifiers were absent from the 8–10 cm soil layer in unlimed soils (pHCa 4.25) but liming caused an increase in gene abundance. Archaeal amoA gene abundance was highest in unlimed plots at 4–8 cm depth although populations decreased over the incubation period and also with lime application. DMPP effectively inhibited nitrification in limed plots, however no significant difference existed between UAN and DMPP treatments for unlimed treatments. DMPP successfully decreased bacterial amoA gene abundance in all depths that were limed but not in unlimed soils. Decreases in inhibitor concentrations occurred within one week in the 0–2 cm layer possibly due to bacterial decomposition associated with greater OM concentration at the soil surface. This study highlighted that DMPP use is more effective in relatively neutral soils and liming will change the abundance and distribution of nitrifiers within the top 10 cm of soil.

Nitrapyrin reduced ammonia oxidation with different impacts on the abundance of bacterial and archaeal ammonia oxidisers in four agricultural soils

The compound nitrapyrin can act as a potential nitrification inhibitor (NI) when applied with ammonium (NH4+)-based N fertiliser. The efficacy of nitrapyrin applications may be soil dependent however, being influenced by soil texture, organic carbon (C), and moisture. The objective of this study was to assess the effects of nitrapyrin on the nitrification process in soils of different physicochemical characteristics and resident microbial communities. Four agricultural soils were incubated in microcosms for five weeks, after which nitrapyrin effects were assessed for soil NH4+, nitrate (NO3−), the microbial functional genes ammonia-monooxygenase (amoA) and nitrite oxidoreductase (nxr), and bacterial and archaeal nitrifier genera using 16S rRNA sequencing. Nitrapyrin co-applied with urea ammonium nitrate (UAN) fertiliser inhibited nitrification, shown by increased retention of NH4+ in all four soils and a lower accumulation of NO3− in three of the four soils compared to UAN treated soil. These results are most likely due to the inhibition of growth of ammonia oxidising bacteria (AOB) as nitrapyrin plus UAN reduced bacterial amoA abundance in three of the four soils compared to the UAN treatment. This study is the first to report increased archaeal amoA abundance in response to the co-application of nitrapyrin and UAN in four soils, possibly due to reduced competition from AOB. The bacterial nitrifier genera Nitrosospira and Nitrospira and archaeal nitrifier genus Nitrososphaera were detected in all four soils using 16S rRNA sequencing. The effects of nitrapyrin on downstream N transformations were assessed based on nxr and Nitrospira abundance though no conclusive treatment effects could be discerned for the four soils. Our results provide evidence of the interplay of AOB, ammonia oxidising archaea (AOA) and nitrite-oxidising bacteria (NOB) in nitrapyrin and fertiliser treated soils and will be useful in developing strategies to improve the efficacy of nitrification inhibitors in future studies.

Biochar coupled with contrasting nitrogen sources mediated changes in carbon and nitrogen pools, microbial and enzymatic activity in paddy soil

There is limited information on changes cause by nitrogen (N) fertilizers and biochar (BC) application in soil carbon and nitrogen availability, leaching and microbial activity at different growth stages in rice. This is first comprehensive study conducted in early and late seasons during 2019 to evaluate efficiency of various traditional N fertilizers (i) Urea (ii) Ammonium nitrate and (iii) Ammonium sulfate (315 kg N ha−1) with or without biochar (30 t ha−1). Results illustrated that all N fertilizers sources applied with biochar significantly increased soil organic carbon (SOC) content by an average 48.44% and 50.63%, soil total nitrogen (Nt) by 4.56% and 4.94%, reduction in total nitrogen leaching by 42.63% and 76.16%, while dissolved organic carbon leaching (DOC) augmented by 39.87% and 38.38% than non-applied treatments in early and late season, respectively. Additionally, soil microbial biomass C and N progressively increased with growth stages and was found higher than non-applied treatments in both seasons. Furthermore, combined application of N fertilizers and biochar, facilitated soil N transformation and the net concentration of NH4+–N and NO3−–N was relatively higher than non-charred treatments. Similarly, in both early and late seasons, urease enzyme activity increased by an average 13.52% and 13.55%, β-glucosidase by 15.99% and 19.27% however, catalase activity decreased by 14.58% and 12.38%, correspondingly. Moreover, no significant difference (p < 0.05) was recorded among N fertilizers sources in both seasons.

The effectiveness of nitrogen fertilizers and nutrition systems for the winter wheat cultivation using no-till technology in the Stavropol Territory arid zone

The article presents materials on the effectiveness of nitrogen fertilizers in the nutrition system for the winter wheat cultivation using no-till technology in the Stavropol Territory arid zone for 2017-2019. As a result of the studies, it was found that all the studied doses of mineral fertilizers relative to the control option (without fertilizers) on average increased the content of nitrate (by 0.9-10.4 mg / kg) and ammonia nitrogen in the soil (by 0, 2-6.7 mg / kg) during the vegetation phases. The urea ammonium nitrate (UAN) application using Duport liquilazer contributed to an increase in the nitrate and ammonium nitrogen content in the soil layer of 0-20 cm in all phases of the winter wheat development in comparison with similar experimental options in which nitrogen fertilizers were applied using a sprayer. According to the two years research results, a steady advantage of the intra-soil application of UAN using Duport liquilazer was noticed and the difference in yield, depending on the variant, was 0.15-0.25 t / ha. However, the more effective option was the introduction of UAN N20 autumn + UAN N87 spring + water-soluble organic substance 20:20:20 (2kg / ha) + water-soluble organic substance 20:20:20 (2kg / ha) Duport liquilazer, which allowed to obtain a yield of 4.66 tons / ha.

Long-term diverse rotation alters nitrogen cycling bacterial groups and nitrous oxide emissions after nitrogen fertilization

Agriculture accounts for a majority of global soil nitrous oxide (N2O) emissions. Increased crop diversity can change soil nitrogen (N), physicochemical properties and alter belowground microbial communities, leading to changes in potential N2O emissions when inorganic N fertilizer is applied. Nitrification and denitrification are two main N cycling pathways under investigation due to their contribution to soil N cycling and production of N2O. The goal of this study was to understand the impacts of 35 years of crop diversification in shaping diversity and the community size and activity of nitrifier and denitrifier bacteria and N2O emissions after N fertilization in corn. In 2017, after fertilizer addition, N2O emissions were continuously measured using automatic chambers from a long-term experiment of simple (corn-corn-soybean-soybean) and diverse (corn-corn-soybean-wheat underseeded with red clover cover crop) four year rotations under second year corn. Soil was collected during peak N2O emissions using high frequency temporal sampling to capture shifts in 16S rRNA, amoA, nirS, nirK, nosZ1 and nosZ2 genes and gene transcripts in soil where urea-ammonium-nitrate (UAN) was applied. An N2O emission event occurred in both rotations following UAN application but was higher in the diverse rotation, which also had persistent higher total and denitrifying (nirK and nosZ2) bacterial abundance. Bacterial amoA significantly increased in both rotations shortly after UAN addition, but gene detection decreased significantly in the simple rotation and remained elevated in the diverse. Transcripts for atypical nosZ2 were consistently detected but higher after UAN addition. Total bacterial diversity did not differ between simple and diverse rotations, however, abundance of microbial pathways leading to soil N2O emissions, ammonia oxidizers and denitrifiers, were elevated in soil with a more diverse cropping history. Best management practices (BMPs) that include crop diversification need to consider microbial communities and greenhouse gas (GHG) production, in order to fully quantify the soil ecosystem services.

Ammonia volatilization, nitrous oxide emissions, and corn yields as influenced by nitrogen placement and enhanced efficiency fertilizers

AbstractEnsuring sufficient fertilizer nitrogen (N) for crops while minimizing N losses requires best management practices optimized for climate, crop, soil, and root zone hydrology. In Ontario, pre‐plant N fertilization of corn (Zea mays L.) is common; however, this practice extends the time between application and significant root interception of N by the plant, potentially increasing the risk of N loss through soil nitrous oxide emissions, ammonia (NH3) volatilization, and nitrate leaching. These losses contribute to greenhouse gas emissions, affect air quality (NH3), and are a substantial financial loss. This study compared three N placement methods (broadcast urea [BrUrea], broadcast incorporated urea [BrIncUrea], and injected urea ammonium nitrate [InjUAN]) and the presence or absence of N metabolite inhibitors (urease inhibitor [UI], urease plus nitrification inhibitor [UI+NI]). Fertilizer N was applied immediately before planting (150 kg N ha−1) to all treatments except for the control. Averaged over 3 yr (2015–2017), NH3 losses were reduced by 34% from BrIncUrea, by 42–55% from BrUrea+UI+NI and BrIncUrea+UI+NI, and by 99% from InjUAN relative to BrUrea (21 kg N ha−1). On average, N application increased corn grain yields by 83% relative to the control (6 t ha−1). There were no annual yield differences among N placement methods. It was concluded that incorporation or injection of N in soil and use of urease and nitrification inhibitors reduced NH3 emissions when N fertilizer was applied pre‐plant.

Cotton yield and lint quality responses to nitrogen rate and placement in the humid southeast

AbstractProper N management in upland cotton (Gossypium hirsutum L.) is essential to optimize yields. Information on proper N application rate and placement method is needed for coarse‐textured soils of the humid Southeast. The objective of this study was to measure strip‐tilled cotton performance in response to five N rate and placement application methods. Five N rates (0, 45, 90, 135, and 180 kg N ha−1) and three placement methods {broadcast (urea + ammonium sulfate [AMS], surface banded (urea ammonium nitrate [UAN] + ammonium thiosulfate [ATS]), and injected (UAN + ATS) were evaluated from 2016 to 2018 at five sites in Virginia and one site in North Carolina. Petiole NO3–N, lint yield, lint percent turnout, and fiber quality parameters were measured. Nitrogen rate and placement had a significant effect on lint yield but only N rate affected petiole NO3–N concentration. Quadratic plateau analysis of relative yield found that 133, 128, and 180 kg N ha−1 were the optimum N rates for injected, surface‐banded, and broadcast systems with relative yields of 95, 90, and 94%, respectively. A critical petiole NO3–N concentration threshold of 5600 mg NO3–N kg−1 at early bloom was calculated to reach 92% relative yield. Neither rate nor placement had an effect on fiber quality parameters. This study shows that both surface banding and injecting between 128 and 133 kg N ha−1 can produce 90% or more relative yield for a modern cotton variety in the upper southeastern coastal plain of the United States.

Carbon footprint of fertilizer imports to the East African Bloc and policy recommendations for decarbonization

Background: Almost all nitrogenous (N) fertilizers are fixed on an enormous scale using the Haber-Bosch ammonia synthesis process via a reaction of Nitrogen with hydrogen in the presence of a catalyst. This process is a leading global polluter, emitting 830 megatons of CO2 to the atmosphere annually. On the other hand, the global transport sector emits 7.5 gigatons of CO2 yet the fraction of emissions from freight transportation of N fertilizers from exporting countries to the East African (EA) Bloc is not known. This study examined the carbon footprint from freight transportation of N fertilizers. The findings are useful in the regions’ nationally determined contributions (NDCs) as per the Paris Agreement of December 2015 regarding downsizing emissions from the transport sector. Methods: The study area included five EA Community (EAC) countries namely, Kenya, Uganda, Tanzania, Rwanda and Burundi. Statistics of fertilizers were obtained from https://africafertilizer.org/. The carbon footprint calculator (CFC) for fertilizer production (obtained from https://www.fertilizerseurope.com/), certified by the Carbon Trust Standard, was used. Results: Over 93% of fertilizers imported to the EA Bloc are N fertilizers, leaving a carbon footprint of 4.9 megatons CO2-eq. Of these emissions, 1.1 megatons CO2-eq were contributed by imports from Saudi Arabia and 0.8 megatons CO2-eq from China. The ‘dirtiest’ of N fertilizers that accounted for the highest carbon footprint on the EA bloc were urea ammonium nitrate, calcium nitrate, nitrophosphates and ammonium sulphate. Conclusions: Every metric ton of N imported results in a carbon footprint of 4.5 metric tons CO2-eq. The Ammonia production process of exporting countries, freight distance, choice and number of N fertilizers imported are significant determinants of greenhouse gas emissions to East Africa’s NDCs. To reach net-zero emissions the EA community needs to invest in new processes, circular economy and decarbonization pathways.

Nutrient recovery from anaerobic digestion of food waste: impacts of digestate on plant growth and rhizosphere bacterial community composition and potential function in ryegrass

Global food wastage equates to about 1.3 billion tons per year, which causes serious environmental impacts. The objective of this study was to evaluate the influences of addition of digestate from food waste in comparison to a synthetic liquid urea ammonium nitrate solution on plant growth, rhizosphere bacterial community composition and diversity, and hyphal abundance of arbuscular mycorrhizal (AM) fungi. Plant and soil samples were collected at 25, 50, and 75 days after seedling emergence. Annual ryegrass growth was significantly increased by both liquid urea ammonium nitrate and digestate, and digestate was just as effective as liquid urea ammonium nitrate. Additionally, digestate (50 kg N ha−1) significantly increased AM fungal hyphae density. Liquid urea ammonium nitrate (50 kg N ha−1) significantly decreased AM fungal hyphae density compared with liquid urea ammonium nitrate (25 kg N ha−1) at DAE 75. Digestate and liquid urea ammonium nitrate applications significantly shifted the bacterial community composition and OTU richness and changed the abundance of microbial C and N-cycling genes, while application rates had no significant effect. Structural equation modeling showed that digestate and UAN addition both directly and indirectly affected bacterial, C and N cycling genes community composition; the indirect effects were related to increased soil NO3− content and reduced pH. This study showed that the use of digestate as a soil amendment can be environmentally effective and can provide a sustainable supply of nutrients that increases soil organic C. Moreover, the use of digestate can readily be incorporated into agricultural practices with potentially less impact on soil microflora diversity and function than conventional fertilizers.

Studies on nutrition supplementation for production of oyster mushroom (Pleurotus florida)

The present experiment entitled “Studies on nutrition supplementation for production of oyster mushroom (Pleurotus florida)” was under taken with the aim to determine the growth and yield of mushroom. There are different organic substrates i.e. wheat straw, Soybean straw, moong bean straw, urd bean straw, Sorghum stem (chopped), Maize stem (chopped), Pigeon pea stalk, Cotton stalk and Safflower straw and different supplementation; Wheat bran, Rice bran, Maize bran, Neem cake, Oil cake, Glucose, Dextrose, Ammonium sulphate, Ammonium nitrate Urea, and Poultry manure were used for production. The minimum days of spawn run (18.75) was recorded with moong bean straw substrate. While, the maximum number of primordial (177), number of pin heads (164.75), number of fruiting body (68.50), diameter of fruiting body (8.25 cm), stripe length (3.43 cm) and Yield (579.75 g) were recorded with wheat straw substrate. On the effect of carbon, nitrogen and cakes supplementation on wheat straw, the minimum days of spawn run was recorded with oil cake 5%. While, the different quantity parameters were recorded number of maximum primordial and pin head on maize bran 5%, maximum number of fruiting body and diameter of fruiting body on dextrose 5%, stripe length maximum on maize bran 5% and maximum yield significant on dextrose 5%.

Stability of stored N-(n-butyl) thiophosphoric triamide (NBPT) treated urea-based fertilizers

ABSTRACTThe effectiveness of N-(n-butyl) thiophosphoric triamide (NBPT) in reducing ammonia volatilization from urea-based fertilizers has been thoroughly investigated. However, the stability of this inhibitor during storage of NBPT treated urea and urea ammonium nitrate (UAN) needs further investigation. We compared ammonia volatilization from NBPT treated urea (360 mg NBPT kg−1 urea) and UAN (180 mg NBPT L−1 UAN) that were stored at room temperature for 6, 3 and 0 months. We measured ammonia volatilization with cylindrical chambers fitted with acid-charged discs at five times for 21 d. Total ammonia volatilization (measured as a % of applied nitrogen) was significantly greater in untreated urea and UAN (32% to 33%) than those in NBPT treated urea and UAN (6% to 12%). Reduction of ammonia volatilization was not significantly different among NBPT treated urea (73% to 81%) and UAN (63% to 73%) irrespective of storage time. This implies that farmers can mix their urea-based fertilizers with NBPT formulation 6 months prior to fertilization without compromising the ammonia volatilization reducing property of the NBPT.

Optimum rates of surface-applied coal char decreased soil ammonia volatilization loss.

Fertilizer N losses from agricultural systems have economic and environmental implications. Soil amendment with high C materials, such as coal char, may mitigate N losses. Char, a coal combustion residue, obtained from a sugar factory in Scottsbluff, NE, contained 29% C by weight. A 30-d laboratory study was conducted to evaluate the effects of char addition on N losses via nitrous oxide (N2 O) emission, ammonia (NH3 ) volatilization, and nitrate (NO3 -N) leaching from fertilized loam and sandy loam soils. Char was applied at five different rates (0, 6.7, 10.1, 13.4, and 26.8 Mg C ha-1 ; char measured in C equivalent) to soils fertilized with urea ammonium nitrate (UAN) at 200kg N ha-1 . In addition, there were two negative-UAN control treatments: no char (no UAN) and char at 26.8 Mg C ha-1 (no UAN). Treatment applied at 6.7 and 10.1 Mg C ha-1 in fertilized sandy loam reduced NH3 volatilization by 26-37% and at 6.7, 10.1, and 13.4 Mg C ha-1 in fertilized loam soils by 24% compared with no char application. Nitrous oxide emissions and NO3 -N leaching losses were greater in fertilized compared with unfertilized soil, but there was no effect of char amendment on these losses. Because NO3 -N leaching loss was greater in sandy loam than in loam, soil residual N was twofold higher in loam than in sandy loam. This study suggests that adding coal char at optimal rates may reduce agricultural reactive N to the atmosphere by decreasing NH3 volatilization from fertilized soils.

The effects of split application of enhanced efficiency fertilizers on non-winter nitrous oxide emissions from winter wheat

This study tested if non-winter cumulative nitrous oxide (N2O) emissions, emission factors, and yield-scaled N2O emissions were affected by split application of enhanced efficiency nitrogen fertilizers in a rain-fed winter wheat crop. Based on initial soil tests, fertilizers were applied at 84 kg N ha−1in year 1 and 72 kg N ha−1in year 2. Two trials were completed each year. Trial 1 applied (1) urea, (2) urea with nitrification inhibitor, (3) nitrification and urease inhibitors, and (4) polymer-coated urea as (1) 100% side-banded at planting, 30% side-banded at planting and (2) 70% surface-applied in late fall, or (3) 70% surface-applied in spring at Feekes growth stage 4 (GS4). Trial 2 applied (1) urea–ammonium nitrate (UAN), (2) UAN treated with nitrification inhibitor, (3) urease inhibitor, (4) a combination of both, (5) granular urea, and (6) polymer-coated urea, all applied 50% side-banded at planting and 50% surface-applied at GS4. Cumulative N2O emissions from fertilized soils ranged from 0.101 to 0.433 kg N ha−1. The emission factors for trial 1 were greater in year 1 than year 2 (P ≤ 0.05). There were no treatment differences in cumulative N2O emissions in trial 2. However, cumulative N2O emissions, emission factors, and yield-scaled N2O emissions from trial 1 were higher when fertilizer was split-applied in late fall compared with at GS4 (all P ≤ 0.05). This study demonstrates that under best management practices, it is better to apply the required rate in the form of conventional fertilizer at planting rather than split application.

Urea Ammonium Nitrate Solution Treated with Inhibitor Technology: Effects on Ammonia Emission Reduction, Wheat Yield, and Inorganic N in Soil

Urea is the most used fertilizer nitrogen (N), and is often applied as urea ammonium nitrate (UAN), which may be an ammonia (NH3) emission source after application. This study examined whether the addition of urease inhibitors reduced NH3 emission, and, in combination with nitrification inhibitors, enhanced fertilizer N crop uptake. In three experiments, NH3 emission was measured from plots (100 m2) to which UAN was added with and without inhibitors. In March and May, the plots were covered with Triticum aestivum L., Sheriff (var), and in July, the soil was bare. The inhibitor mixed with urea was N-(n-butyl) thiophosphoric triamide (NBPT) and a mixture of NBPT and the new nitrification inhibitor DMPSA (3,4-Dimethylpyrazole succinic acid). Ammonia emissions were negligible from all plots after the first application of UAN due to the wet and cold weather while an average of 7% of applied UAN was emitted after application of UAN in April, where no significant effect of additives was observed. The harvest yield was low due to drought from May till August. Yield was highest when UAN was mixed with NBPT and lowest for untreated UAN. The highest emission from the bare plots was obtained from untreated UAN (17% of N), in contrast to 11% of N from the plots with added UAN + NBPT (not significant) and 7% from the plots with added UAN + NBPT + DMPSA (significantly different). Under the conditions of the current study, urease inhibitors reduce NH3 emissions in periods where the risk of emission is high, and the combination of urease and nitrification inhibitors increased yields.