Application Of Urease Inhibitors Research Articles

Nitrous oxide emissions are driven by environmental conditions rather than nitrogen application methods in a perennial hayfield.

Agricultural best management practices (BMPs) intended to solve one environmental challenge may have unintended climate impacts. For example, manure injection is often promoted for its potential to reduce runoff and nitrogen (N) loss as NH3 , but the practice has been shown to increase N2 O, a powerful greenhouse gas, compared to surface application. Urease inhibitor application with N fertilizer is another BMP that can enhance N retention by reducing NH3 emissions, but its impact on N2 O emissions is mixed. Thus, we measured N2 O, CO2 , soil mineral N availability, soil moisture, soil temperature, and yield in a 2-year perennial hayfield trial with four fertilization treatments (manure injection, manure broadcast, synthetic urea, and control) applied with or without a urease inhibitor in Alburgh, VT. We used linear models to examine treatment effects on daily and cumulative N2 O emissions and a boosted regression tree (BRT) model to identify the most important drivers of daily N2 O fluxes in our trial. While fertilization type had a significant impact on N2 O fluxes (p<0.05), our treatments explained an unexpectedly small amount of the variation in emissions (R2 =0.042), and urease inhibitor had no effect. Instead, soil moisture was the most important predictor of daily N2 O fluxes (39.7% relative influence in BRT model), followed by CO2 fluxes, soil inorganic N, and soil temperature. Soil moisture and temperature interacted to produce the largest daily N2 O fluxes when both were relatively high, suggesting that injecting manure during dry periods or during wet but cool periods could reduce its climate impacts.

Ammonia mitigation campaign with smallholder farmers improves air quality while ensuring high cereal production.

Reducing cropland ammonia (NH3) emissions while improving air quality and food supply is a challenge, particularly in China where there are millions of smallholder farmers. We tested the effectiveness of a tailored nitrogen (N) management strategy applied to wheat-maize cropping systems in 'demonstration squares' across Quzhou County in the North China Plain. The N-management techniques included optimal N rates, deep fertilizer placement and application of urease inhibitors, implemented through cooperation between government, researchers, businesses and smallholders. Compared with conventional local smallholder practice, our NH3 mitigation campaign reduced NH3 volatilization from wheat and maize by 49% and 39%, and increased N-use efficiency by 28% and 40% and farmers' profitability by 25% and 19%, respectively, with no detriment to crop yields. County-wide atmospheric NH3 and fine particulate matter (with aerodynamic diameter <2.5 μm) concentrations decreased by 40% and 8%, respectively. County-wide net benefits were estimated at US$7.0 million. Our demonstration-square approach shows that cropland NH3 mitigation and improved air quality and farm profitability can be achieved simultaneously by coordinated actions at the county level.

Chamomile plant material effects on soil nitrogen dynamics and ammonia-oxidizers to mitigate greenhouse gas emissions from maize fields

Commonly, agricultural practices utilize urea as a nitrogen (N) source, which can lead to N losses to the environment. Application of urease inhibitors (UIs) or nitrification inhibitors (NIs) can mitigate these losses to some extent but not completely. A preliminary study showed that 2-Cyclopenten-1-one (CCO), an organic compound derived from chamomile (Chamomila recutita L.) can inhibit soil urease activity and also nitrification and therefore has the potential to act as a dual-function inhibitor for decreasing fertilizer-induced N losses and increasing N use efficiency. In this study, a field experiment was conducted to evaluate the effect of CCO on N transformations and NH3, N2O and CH4 emissions from soil, and monitor changes in the ammonia oxidizer amoA gene abundance. Three replicates of five fertilized treatments were included: Urea (fertilizer only), thiophosphoric triamide (NBPT) (a urease inhibitor), dicyandiamide (DCD) (a widely used synthetic nitrification inhibitor), NBPT combined with DCD, and CCO, along with an unfertilized control.The results indicated that, the ability of CCO to reduce N losses and improve maize yield was potentially superior to DCD, NBPT, or the combination of DCD and NBPT. Compared with the urea treatment, the addition of CCO significantly reduced urease activity and nitrification, which subsequently increased the content of NH4+-N and decreased the content of NO3--N in the soil during the maize growth period. Moreover, the cumulative NH3 and N2O emissions, global warming potential (GWP) and greenhouse gas intensity (GHGI) of the maize field were lowest from the CCO applied plots during the growth season, decreasing by 32.5 %, 21.94 %, 7.69 % and 20.92 %, respectively, compared to urea treatment. Notably, CCO application significantly reduced the abundance of ammonia-oxidizing archaea and bacteria in soil. These results suggest that CCO is effective for suppressing urease activity and the nitrification rate in soil and has the potential to be a novel naturally sourced dual-purpose inhibitor.

Urease inhibitor and biochar independently affected N&lt;sub&gt;2&lt;/sub&gt;O emissions from Camellia oleifera soils

Nitrous oxide (N2O) is a long-lived greenhouse gas that impacts climate change. Agricultural soils with intensive nitrogen (N) application are the main source of N2O emissions. Reducing N2O emissions from N-fertilised soils is, therefore, important for climate change mitigation. The application of urease inhibitor and/or biochar provides the potential for mitigating N2O emissions. However, the interactive effect of urease inhibitor and biochar on N2O emissions remains limited. In this study, an incubation experiment was performed to investigate the gradients of urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) (0, 0.08, 0.16, and 0.24%) and biochar additions (0, 2.5, and 5%) on N2O emissions from urea-fertilised Camellia oleifera soils. Results showed that urease inhibitor decreased, but biochar increased cumulative N2O emissions. No significant interactive effects were observed between urease inhibitor and biochar on the cumulative N2O emissions, but cumulative N2O emissions were decreased by NBPT under a 2.5% biochar addition rate. Soil N2O emission rates were negatively correlated with net ammonification and N mineralisation rates and positively correlated with net nitrification rates. This study indicates that NBPT, with the characteristic of delaying urea hydrolysis, can be better than biochar in mitigating N2O emissions from urea-fertilised soils of C. oleifera plantations.

Nitrogen transformation genes and ammonia emission from soil under biochar and urease inhibitor application

Ammonia (NH3) volatilization is the main pathway, by which nitrogen (N) losses from calcareous and alkaline soils occur, and is responsible for economic losses and environmental hazards. We hypothesize that the application of biochar and urease inhibitor (NBPT) can mitigate NH3 production from urea by reducing its hydrolysis and the abundance of related microbial genes. To clarify this hypothesis, soil N fluxes and the genes controlling hydrolysis and nitrification were investigated under the combined application of urea (0, 75, 150, 225 and 300 kg N ha−1), biochar (7.5 Mg ha−1) and NBPT (2 %) for maize under field conditions. Soil moisture, temperature, pH, mineral N, NH3, urease activity (UA) and N cycle related genes (ureC, amoB and amoA) were quantified each 6–17 days during two growing seasons. The combined application of NBPT and biochar reduced NH3 by 13% of the control, which is twofold higher than the separate additions. All investigated parameters were raised with increasing N rate except pH, which was reduced. Biochar and NBPT mediated these effects of N fertilizer by increasing the soil pH, genes abundance, ammonium and nitrate contents, and reducing urea hydrolysis. Biochar maximized the ammonium and nitrate contents one week and three weeks following the N urea application, respectively. Accordingly, NH3 and UA peaked directly after N fertilization; nevertheless, NBPT delayed the peaks for three weeks and reduced their intensity by 24 % and 36 %, respectively, under the addition of 300 kg N ha−1. NBPT reduced ureC and amoB genes abundance by 14 % and 8 %, respectively, and increased amoA by 3 %. Biochar increased amoA and amoB abundance and nitrate content, while reduced the ureC gene. Biochar and/or NBPT reduced the negative effects of the soil pH on ureC gene. NBPT mitigated the reduction effects of pH on the amoB and amoA genes. In conclusion, NBPT mitigated NH3 emission by decreasing the ureC gene and UA, whereas biochar had a synergistic effect with NBPT by increasing amoB and amoA abundance and accelerating nitrification.

Biological nitrification inhibitor co-application with urease inhibitor or biochar yield different synergistic interaction effects on NH3 volatilization, N leaching, and N use efficiency in a calcareous soil under rice cropping

Nitrogen management measures (NMMs) such as the application of urease inhibitors (UIs), synthetic nitrification inhibitors (SNIs), and biochar (BC) are commonly used in mitigating nitrogen (N) loss and increasing fertilizer recovery efficiency (FRE) in agriculture. Calcareous soil under rice cropping is characterized by high nitrification potential, N loss risk, and low FRE. Application of SNIs may stimulate NH3 volatilization in high pH soils and the effects of SNIs on FRE are not always positive. BNIs have many advantages over SNIs. Whether combined application of BNI, UI, and BC that can result in a synergistic effect of improving FRE and decreasing N loss in a calcareous soil under rice cropping worth investigating. In this study, we conducted pot experiments to investigate the effects of single and co-application of BNI (methyl 3-(4-hydroxyphenyl) propionate or MHPP, 500 mg kg−1 soil), UI (N-(n-butyl), thiophosphoric triamide or NBPT, 2% of urea-N), or BC (wheat straw, 0.5% (w/w)) with chemical fertilizer on NH3 volatilization, N2O emission, N leaching, crop N uptake, and FRE in a calcareous soil under rice cropping. Our results demonstrated that those NMMs could mitigate NH3 volatilization by 12.5%–26.5%, N2O emission by 62.7%–73.5%, and N leaching loss by 17.5%–49.0%. However, BNI might have a risk of increasing NH3 (5.98%) volatilization loss. Among those NMMs, double inhibitors (BNI plus UI) yielded a synergistic effect that could mitigate N loss to the maximum extent and effectively improve FRE by 25.4%. The mechanisms of the above effects could be partly ascribed to the niche differentiation between the abundance of AOA and AOB and the changed community structure of AOB, which could further influence nitrification and N fate. Our results demonstrated that co-application of BNI and UI with urea is an effective strategy in reducing N loss and improving FRE in a calcareous soil under rice cropping.

Ammonia Volatilization from Fertilizer Urea—A New Challenge for Agriculture and Industry in View of Growing Global Demand for Food and Energy Crops

The growing world population and the necessity to meet its nutritional needs despite the limited area of agricultural land pose a serious challenge for agriculture. Agriculture is responsible for 80–95% of total ammonia emissions to the atmosphere, but at the same time it has great potential to reduce them. Fertilisation with mineral nitrogen (in particular urea) is responsible for 19.0–20.3% of total ammonia emissions emitted from agriculture. Ammonia emissions have a negative impact on the environment and human health, therefore it is important to minimize the volatilization of ammonia and increase fertiliser efficiency. This is important due to the need to mitigate the negative impact of anthropopressure on the environment in terms of air pollution, negative effect on soils and waters. The application of urease inhibitors during fertilisation with nitrogen fertilisers is one method to reduce ammonia emissions from plant production. Another option to achieve this goal is to reverse the global trend toward maximizing the production of energy crops (intensive fertilisation inevitably increasing ammonia emissions to the environment) for the production of biofuels, which is growing rapidly, taking up arable land that could be used for food production. The aim of the review is to identify the impact of recently introduced technologies for reducing ammonia emissions from urea on agricultural productivity, environment, and crops. It is of importance to reconsider optimization of crop production in arable land, possible owing to the progress in the production, modification, and application of mineral fertilisers and changes in crop structure. A broad debate is necessary with policymakers and stakeholders to define new targets allowing introduction of technologies for conversion of energy crops into energy with a minimal impact on food production and environmental issue.

Effects of Enhanced-Efficiency Nitrogen Fertilizers on Soil Microbial Biomass and Respiration in Tropical Soil Under Upland Rice Cultivation

While over-use of N fertilizers can suppress microbial biomass, application of urease inhibitors is known to be a potential way to rebuilt microbial diversity and improve soil functions. However, the hypothesis of this study is that the application of N fertilizers regardless of the source would increase soil microbial biomass and reduce soil respiration. A two-year field experiment was conducted to assess the effects of enhanced-efficiency N sources on soil microbial biomass, and soil respiration. The experiment was set up in a randomized block design in a 3 &amp;times; 4 + 1 factorial scheme, with four replicates. Treatments comprised three sources (conventional uncoated urea, NBPT (N-(n-butyl) thiophosphoric triamide)-treated urea, and polymer-coated urea) and four rates (30, 60, 90 and 120 kg ha-1) of N, in addition to a control treatment (no fertilizer application). Microbial biomass C (MBC) and microbial biomass N (MBN), and soil respiration (C-CO2 and qCO2) were determined in upland rice rhizosphere in each crop season. Responses of soil microbial properties to N fertilization were dependent on the N rates, but no significant effect of the N sources was observed. All measured parameters, except MBC in the first season and C-CO2 in the second season, were increased with increasing N rates. However, the application of N higher than 60 kg ha-1 suppressed soil microbial biomass, as well as soil respiration. &amp;nbsp;Therefore, the lack of response by added urease inhibitors to the N sources indicate that optimizing N rates for upland rice production is a far more effective option for improving soil microbial community than using enhanced-efficiency N sources.

Effect of urease inhibitor application on urease activity in three different cubicle housing systems under practical conditions

The reduction of ammonia emission from animal husbandry is required due to detrimental and harmful effects on environment, health and fertilizer value. Nevertheless, practicable measures with a high ammonia mitigation potential, which can be implemented in existing dairy housing systems without significant constructional changes, are still rare. A possible reduction option, not previously used in practice, is the application of urease inhibitors on floor surfaces in dairy houses. Urease inhibitors inhibit the enzyme urease, which is responsible for the release of ammonia. It can, therefore, be assumed that a reduction of the urease activity always results in ammonia mitigation. Cubicle housing systems for dairy cattle differ in technical, climatic and organizational conditions. Consequently, tests on three different housings in three seasons have been carried out in the current study to evaluate the use of urease inhibitor in practice. The effect of the urease inhibitor was investigated based on detection of urease activity. A significant correlation of floor surface temperature and level of urease activity was observed. The current study shows that the application of a novel urease inhibitor resulted in overall average reduction of urease activity of 80% at dairy housing systems and at different seasons.

Short term physiological implications of NBPT application on the N metabolism of Pisum sativum and Spinacea oleracea

The application of urease inhibitors in conjunction with urea fertilizers as a means of reducing N loss due to ammonia volatilization requires an in-depth study of the physiological effects of these inhibitors on plants. The aim of this study was to determine how the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) affects N metabolism in pea and spinach. Plants were cultivated in pure hydroponic culture with urea as the sole N source. After 2 weeks of growth for pea, and 3 weeks for spinach, half of the plants received NBPT in their nutrient solution. Urease activity, urea and ammonium content, free amino acid composition and soluble protein were determined in leaves and roots at days 0, 1, 2, 4, 7 and 9, and the NBPT content in these tissues was determined 48 h after inhibitor application. The results suggest that the effects of NBPT on spinach and pea urease activity differ, with pea being most affected by this treatment, and that the NBPT absorbed by the plant caused a clear inhibition of the urease activity in pea leaf and roots. The high urea concentration observed in leaves was associated with the development of necrotic leaf margins, and was further evidence of NBPT inhibition in these plants. A decrease in the ammonium content in roots, where N assimilation mainly takes place, was also observed. Consequently, total amino acid contents were drastically reduced upon NBPT treatment, indicating a strong alteration of the N metabolism. Furthermore, the amino acid profile showed that amidic amino acids were major components of the reduced pool of amino acids. In contrast, NBPT was absorbed to a much lesser degree by spinach plants than pea plants (35% less) and did not produce a clear inhibition of urease activity in this species.

Efficacy of urease inhibitor to reduce ammonia emission from poultry houses

As the poultry industry has grown, so have concerns about the environmental management aspects of these industries, including air and water quality. Poultry operations continue to expand and are large contributors to farm income. There is increased concern related to ammonia emission from poultry operations. Various abatement methods, including dietary manipulation, chemical amendment of litter, and improvement in ventilation system management have been used to control ammonia concentrations from livestock facilities, but these methods are perceived to be too expensive, to impair bird growth, or to add to pollution in some other form. Alternative strategies include reduction of ammonia emissions by arresting N in the litter. An alternative approach to decrease ammonia emissions in poultry facilities is to block the enzyme activity in the litter because ammonia is the by-product of a 5-step enzymatic degradation of uric acid. Our preliminary study with layer feces, which were allowed to accumulate on a layer of broiler litter, indicated that a commercially available urease inhibitor resulted in a significant reduction in equilibrium ammonia concentration over time. Based on the results of the preliminary experiment, further studies were conducted to study the effect of the urease inhibitor on broiler litter and layer feces directly. The results showed that the urease inhibitor did not have any effect on equilibrium ammonia concentration when applied to drier broiler litter. The reduced moisture content in the broiler litter may have inhibited urease inhibitor activity. With layer feces, urease inhibitor reduced equilibrium ammonia concentration. The effect of the first application lasted for 1 wk, after which the equilibrium ammonia concentration in the treated trays rebounded to exceed that of the control trays. Upon a second application of urease inhibitor, the effect lasted for 14 d. The difference in the effect of the urease inhibitor on equilibrium ammonia concentration upon first and second application could have been influenced by a change in manure characteristics over time. Layer manure is a dynamic environment with continued change; therefore, more research is warranted in the area of stored layer manure.

Influence of urea fertilization and urease inhibitor on the size and activity of the soil microbial biomass under conventional and zero tillage at two sites

Fertilizers are frequently used in agriculture to enhance crop yield and quality. Increasingly, microbial and enzyme inhibitors are being used to enhance the efficiency of fertilizer nitrogen use. The assumption being made is that the impact of these compounds is short-term or localized and thus does not adversely impact soil quality. This study investigates the implications of urea fertilizer with and without urease inhibitor [N-(n-butyl) thiophosphoric triamide, NBPT], conventional and zero tillage systems, and soil types on the soil biological characteristics including N mineralization. Microplot studies were conducted in clay loam and fine sandy loam soils in Manitoba. Soil type had a significant effect on the soil organic C but tillage did not have any significant effect. Soil microbial biomass C content ranged widely (131–1215 µg g−1 soil). The clay loam soil generally tended to contain higher biomass C than the sandy loam soil. The potential soil mineral N production (N0) was higher in clay loam soil (92.6 µg g−1 soil) than sandy loam soil (40.2 µg g−1 soil). Tillage systems, urea and urease inhibitor application had no significant impact on the soil biomass C, N0, arylsulfatase or acid and alkaline phosphatase content. At these sites considerable fluctuations occurred in the microbial and biochemical properties due to the variation of soil type. In general, these fluctuations were mainly related to soil organic matter and soil moisture content. Tillage system, urea with and without NBPT application did not contribute any notable impact on the soil biological properties reported in this study. Key words: Soil biological quality, soil type, urease inhibitor, conventional tillage, zero tillage

Urea N uptake efficiency of ryegrass (Lolium perenne L.) in the presence of urease inhibitors

A greenhouse experiment was conducted to study the comparative efficiency of urea as an N fertilizer with and without the addition of different urease inhibitors. Ryegrass (Lolium perenne L.) was used as the test plant and the N balance technique with 15N was applied. Three urease inhibitors, hydroquinone, phenyl phosphorodiamidate (PPDA), and N-(n-butyl) phosphorothioic triamide (NBPT), were evaluated for their effects on urea-N uptake as well as on grass yield. The addition of urease inhibitors, except for hydroquinone in the later growth period, did not significantly influence the dry matter weight. Throughout the whole growth period, only NBPT significantly increased the total urea-N uptake. In the uninhibited system, the major fertilizer N loss occurred during the first period of grass growth, presumably via NH3 volatilization, since the environment did not favour the other pathways of N loss. However, an appreciable amount of urea N was lost during the later growth period in all inhibited systems, especially in the hydroquinone-treated system. This indicates that the application of urease inhibitors could not eliminate the urea N loss. The greater N loss in the hydroquinone-treated soil appears to be related to the inhibition by hydroquinone of nitrification.