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<p>Conventional agricultural practices are heavily dependent on nitrogen fertilizers, which can have negative impacts on the environment through ammonia volatilization and nitrous oxide emission. Previous studies have shown that the use of urease inhibitors or biofertilizers may help reduce such impacts.</p> <p>A field experiment was established by the Joint FAO/IAEA Centre at the experimental station of the University of Natural Resources and Life Sciences (BOKU) located east of Vienna (Austria) to determine the effect of urease inhibitor and biofertilizer on nitrous oxide (N<sub>2</sub>O) emission, in wheat cropping systems. A randomized complete block design including five treatments and four replicates was used in this study. The treatments were: T<sub>1</sub> (control treatment - without N fertilizer), T<sub>2</sub> (Urea only), T<sub>3</sub> (Urea+Urease Inhibitor (UI)), T<sub>4</sub> (Urea+Biofertilizer), T<sub>5</sub> (Urea+UI+Biofertilizer). All treatments received 50 kg N ha<sup>-1</sup> at tillering stage (GS 31), except T<sub>1</sub>. In this study N-(n-butyl) thiophosphoric triamide (nBTPT) or “Agrotain” was used as UI and <em>Azotobacter chroococcum</em> (“AZOTOHELP”) was applied as biofertilizer.<em> </em></p> <p>Soil N<sub>2</sub>O gas fluxes were measured using the static chamber method, eight times between 3 to 84 days after fertilizer application. Gas sampling was performed at the same time each day of measurement, between 8:00 and 10:00 h, to minimize diurnal variation and better represent the mean daily fluxes. A PVC chamber (24 cm height and 24 cm diameter) was inserted into the soil 5 cm deep. The chamber was composed of two separate parts joined together with an airtight rubber. Gas samples were taken at 0 and 30 minutes after closing the chambers using a 500 mL syringe. The gas sample was then immediately transferred from the syringe to a pre-evacuated 1L gas sampling bag with multi-layer foil. Nitrous oxide in the gas samples was analysed using off-axis integrated cavity output spectroscopy (ICOS, Los Gatos).</p> <p>The statistical analysis showed that UI and biofertilizer had a clear and significant effect on nitrous oxide emission. However, this effect was only observed during the first week after the fertilizer application. Further, the results showed that the highest N<sub>2</sub>O emission, within this week after adding urea fertilizer, was under the U+UI treatment, which was significantly higher by about 139, 91,79% compared to the Urea+Biofertilizer, Urea, Urea+UI+Biofertilizer treatments, respectively. No significant difference was observed between the other Urea, Urea+Biofertilizer and Urea+UI+Biofertilizer treatments in this period. Although not significantly (p < 0.05), N<sub>2</sub>O emission was higher in Urea+UI+Biofertilizer treatment compared to the Urea+Biofertilizer treatment.</p> <p>Due to the ability of UI to reduce ammonia volatilization, we assume that pollution swapping from ammonia volatilization to nitrous oxide emission occurred, explaining the stimulus of UI on nitrous oxide emission. The lower N<sub>2</sub>O emission in the treatments receiving biofertilizer, compared to the one with no biofertilizer, may be caused by the ability of <em>Azotobacter</em> to reduce N<sub>2</sub>O emission by N<sub>2</sub>O-fixation, N<sub>2</sub> fixation and reduction of N<sub>2</sub>O to N<sub>2</sub>.  </p>

<p>Ammonia volatilization (AV) is one of the main pathways of nitrogen fertilizer loss, resulting in reduced crop yields, and a negative impact on the environment. Therefore, reducing AV through proper fertilizer management is essential. We can, however, only provide appropriate management advice when based on accurate measurements, along with understanding the processes involved. For this purpose, the <sup>15</sup>N technique has a unique advantage over other methods to precisely identify the sources of ammonia production.</p> <p>A field experiment was established at the SWMCN laboratory in Seibersdorf on maize with four replications and 120 kg N ha<sup>-1</sup> was applied through two equal split applications at 20 DAP (Days After Planting) and 34 DAP. Two <sup>15</sup>N microplots inside each main plot were installed. In these microplots, <sup>15</sup>N-labeled urea replaced the unlabeled urea according to the time of fertilizer application. Each microplot for <sup>15</sup>N-labelled urea was 2.5 m by 2.5 m,<sup> </sup>and the buffer zone between microplots was 1 m to minimize <sup>15</sup>N contamination from adjacent microplot. For these microplots, <sup>15</sup>N-labeled urea was used with an enrichment of 5.23 atom% <sup>15</sup>N excess. The first microplot received <sup>15</sup>N-urea at 20 DAP and unlabeled urea at 34 DAP, the second microplot received <sup>15</sup>N-urea at 34 DAP and unlabeled urea at 20 DAP. Ammonia volatilization was measured with semi-static chambers and chambers were installed inside the <sup>15</sup>N microplots.</p> <p>The total cumulative NH<sub>3</sub> emissions from urea after the first and second split applications were 13.9 kg N ha<sup>-1</sup> and 18.0 kg N ha<sup>-1</sup>, respectively. This calculation is based on the difference in AV between experimental treatments and control treatment, assuming that AV in control plots indicates the amount of AV from the soil source, whereas AV of the fertilized treatments presents AV from soil and fertilizer sources. It also assumes that all nitrogen transformations, i.e., mineralization, immobilization, and other process in the case of nitrogen, are the same for control and experimental plots. Therefore, the amount of AV in urea treatment was subtracted from the amount of AV in control treatment. The cumulative NH<sub>3</sub> emissions from the control treatment (without nitrogen fertilizer) at the same time were 2.7 kg N ha<sup>-1</sup> and 3.6 kg N ha<sup>-1</sup>, respectively. Accordingly, about 20% of the ammonia volatilized from the soil source and the rest could be attributed to the added urea fertilizer.</p> <p>However, using the <sup>15</sup>N labelled fertilizer, it was found that the above assumption shows some flaws. The fraction of nitrogen in the ammonia samples derived from the soil is not constant but changes significantly due to nitrogen fertilizer application. The results show that the nitrogen in the ammonia derived from the fertilizer was 65% and 53% after the first and second split applications, respectively. Therefore, the fraction of nitrogen in the ammonia samples derived from the soil source was 35% and 47% after the first and second split applications. So, the use of the <sup>15</sup>N technique shows that adding nitrogen fertilizer likely increased the rate of mineralization by changing the ratio of carbon to nitrogen.</p>

<p>Agricultural production must increase by 50% to support about 9 billion people by 2050. Previous studies show that integrated crop-soil management strategies can improve cereal yield by 30% without increasing nitrogen use. Sustainable practices and the application of environmentally friendly technologies can help to reach this point by improving resource use efficiency and increasing yield. For this purpose, the effect of urease inhibitor and biofertilizer<strong> </strong>were evaluated in this study as environmentally friendly technologies that can increase cereal grain yield.</p> <p>In the spring of 2022, a field experiment was established at the experimental station of the University of Natural Resources and Life Sciences (BOKU), located in the east of Vienna, to determine the effect of urease inhibitor and biofertilizer on wheat production. A randomized complete block design including five treatments and four replicates was used in this study. Each main plot was 9 by 9 meters, and a buffer zone of 1.5 meters was implemented between each of the individual main plots. The treatments were: T<sub>1</sub> (control treatment - without N fertilizer), T<sub>2</sub> (Urea only), T<sub>3</sub> (Urea+Urease Inhibitor (UI)), T<sub>4</sub> (Urea+Biofertilizer), T<sub>5</sub> (Urea+UI+Biofertilizer). All treatments received 50 kg N ha<sup>-1</sup> at tillering stage (GS 31), except T<sub>1</sub>. In this study N-(n-butyl) thiophosphoric triamide (nBTPT) or “Agrotain” was used as UI and <em>Azotobacter chroococcum</em> or “AZOTOHELP” was applied as biofertilizer.<em> </em>To determine wheat yield (grain and straw), a 1.5 by 8 meter area was harvested in each main plot (9 by 9 meters). To measure other parameters including the number of tillers per square meter, 1000-grain weight (g), plant height (cm), spike length (cm) and numbers of grains per spike, a 1m-by-1m area was harvested within each main plot for all treatments.</p> <p>The highest grain and straw yields were observed in the Urea+UI+Biofertilizer treatment, with a grain yield of about 20, 11, 8% higher, compared to the Urea, Urea+UI and Urea+Biofertilizer treatments, respectively. However, a significant difference in grain and straw yields was only observed between Urea and Urea+UI+Biofertilizer treatments. The grain and straw yields in the Urea+UI and Urea+Biofertilizer treatments were not significantly different from both Urea and Urea+UI+Biofertilizer treatments. The number of grains per spike and the weight of 1000-grain in the Urea+UI+Biofertilizer treatment showed an increase of about 20 and 11% respectively, compared to the Urea treatment, but these increases were not significant. Plant height in treatments that received nitrogen fertilizer was not affected by fertilization treatments, but spike length was affected. This study suggests that the use of urea fertilizer coated with urease inhibitor in combination with biofertilizer is a promising way for sustainable crop production in the lowlands of Austria.</p>

<p>Nitrogen (N) fertilizer management is challenging due to the many factors and have low N use efficiency (NUE). Heavy N losses from soil reduce plant yield and have negative impacts on the environment. Nitrogen processes inhibitors, such as urease and nitrification inhibitors (UI and NI), are chemical compounds which reduce urea hydrolysis and nitrification respectively. By coating ammonium based chemical fertilizers with N process inhibitors allows N to stay in a more stable form of ammonium (NH<sub>4</sub><sup>+</sup>) thus minimising N losses as well as improving NUE and consequently enhancing crop yield.</p><p>A field experiment was established at the Soil and Water Management and Crop Nutrition Laboratory (SWMCNL) in Seibersdorf, Austria to determine the effect of different N fertilizers coated with N process inhibitors on maize yield in summer 2020. The field site is characterised by a moderately shallow Chernozem soil with significant gravel content. Three combinations of N fertilizer (urea or NPK) with N process inhibitors (UI and/or NI)) were tested and compared with a control treatment (without N fertilizer) and a urea application without any inhibitor. All treatments received 60 kg ha<sup>-1</sup> P<sub>2</sub>O<sub>5</sub> and 146 kg ha<sup>-1</sup> K<sub>2</sub>O. The amount of N added to each treatment receiving N fertilizer was 120 kg N ha<sup>-1</sup>. The inhibitors used were (i) UI (2-NPT: N-(2-nitrophenyl) phosphoric acid triamide), (ii) NI-1 (MPA: N-[3(5)-methyl-1H-pyrazol-1-yl) methyl] acetamide), and (iii) NI-2 (DMPP: 3,4-dimethylpyrazole phosphate). DMPP, a nitrification inhibitor, was used in combination with NPK fertilizer. A randomized complete block design with four replications was used in this study. Treatments were: T<sub>1</sub> (control treatment - without N fertilizer), T<sub>2</sub> (Urea only), T<sub>3</sub> (Urea + UI), T<sub>4</sub> (Urea + UI + NI-1), and T<sub>5 </sub>(NPK + NI-2). Urea was applied through two split applications in the T<sub>2</sub> treatment. In T<sub>3</sub>, T<sub>4</sub>, and T<sub>5</sub> treatments, N fertilizers were applied only once. Supplemental irrigation was only applied in the early stages of growth, to ensure that the crop could establish. Harvest was carried out at 98 days after planting.</p><p>The yield data showed that different fertilizer treatments had a significant (p ≤ 0.01) effect on maize yield (dry matter production). There was no significant difference between treatments 4 and 5, which had the highest yield followed by treatments 2 and 3. The comparison between T<sub>2</sub> and T<sub>3</sub> showed that the application of a urease inhibitor avoids the need for a split application of urea, which decreases labour costs. Adding NI-1 (under T<sub>4</sub>) further increases the yield. Also, the package of NPK, a common choice by farmers in Austria, in combination with the nitrification inhibitor NI-2 showed equally good results as urea combined with two inhibitors. Based on the yield results, it can be concluded that N process inhibitors play a significant role in enhancing maize yields.</p>