Ammonia Volatilization Losses Research Articles

Microalgae biofilm in soil: Greenhouse gas emissions, ammonia volatilization and plant growth

Microalgal biofilm in soils represents an alternative fertilization method for agricultural sustainability. In the present study, greenhouse gas emission, soil ammonia volatilization, and the growth of Pennisetum glaucum were evaluated under the effect of a microalgal biofilm, commercial urea, and a control (without application of a nitrogen source). CH4 emissions were equal for the three treatments (p>0.05). CO2 emissions significantly increased in microalgal biofilm treatment (p<0.01), which was also responsible for the highest N2O emissions (p<0.01). The ammonia (NNH3) volatilization losses were 4.63%, 18.98%, and 0.82% for the microalgal biofilm, urea, and control treatments, respectively. The main differences in soil characteristics were an increase in nitrogen and an increase in cation exchange capacity (p<0.01) caused by the algal biomass application to the soil. The soil organic matter content significantly differed (p<0.05) among the three treatments, with the microalgal biofilm treatment having the greatest increase in soil organic matter. Significant differences were observed for shoot dry matter mass and nitrogen content in the plants from both treatments where nitrogen sources were applied. All treatments differed from each other in leaf dry matter mass, with the urea treatment increasing the most. Chlorella vulgaris was the dominant microalgal specie in the soil.

Combined Application of Concentrated Vinasse and Nitrogen Fertilizers in Sugarcane: Strategies to Reduce Ammonia Volatilization Losses

Ethanol is an alternative source of renewable fuel, but increasing production of vinasse as a by-product requires proper management. Combining concentrated vinasse (CV) and nitrogen (N) fertilizer into a single operation is increasing in Brazil. However, the chemical stability and potential for volatilization losses remain unknown. Our objectives were to characterize the chemical stability of CV and N fertilizer mixtures and to evaluate volatilization losses following application to sugarcane trash. In an initial study, we monitored variations in pH, total N and inorganic N content after a 22-day incubation of mixtures of CV and N fertilizer. In a second study, we evaluated N-NH3 volatilization losses following surface application to sugarcane trash. We used a medium-textured soil covered with trash (8 Mg ha−1), and measurements of N-NH3 losses were taken using acid traps in semi-static chambers during 40 days after mixture application. The addition of urea to the CV did not increase the pH and resulted in the maintenance of N in amidic form, demonstrating the chemical stability of the mixture. However, after application to sugarcane trash, N losses from urea added to the CV ranged from 29 to 35 % of the applied N. The addition of phosphoric acid and boron has the potential to reduce the N loss of 26 % of the applied N. The use of UAN mixed with CV had the lowest loss through volatilization (21 % of applied N) and is the suggested to use for application to sugarcane trash.

Ammonia volatilization following nitrogen fertilization with enhanced efficiency fertilizers and urea in loblolly pine (Pinus taeda L.) plantations of the southern United States

Ammonia (NH3) volatilization losses following surface application of urea and three enhanced efficiency nitrogen (N) containing fertilizers (EEFs) were compared in six thinned mid-rotation loblolly pine (Pinus taeda L.) stands across the southern United States. All fertilizer treatments were labeled with 15N (∼370‰, 0.5 AP) and applied during two different seasons (spring, summer) in 2011 to open chamber microcosms. Individual microcosms were sampled 1, 15 and 30days after fertilization to estimate remaining 15N. Losses of fertilizer N were determined using a mass balance calculation. Significantly less N loss occurred following fertilization with EEFs compared to urea after all sampling days for both seasons. Because root uptake was eliminated in the microcosms and there was no leaching of 15N below the microcosms, the most likely loss pathway of the 15N from the microcosms was NH3 volatilization. There were generally no differences among the individual EEFs. Following spring application, the mean NH3 volatilization during the 30day experiment ranged from 4% to 26% for the EEFs compared to 26–40% for urea. In summer, mean NH3 volatilization for EEFs ranged from 8% to 23% compared to 29–49% for urea. This research highlights the potential of EEFs to reduce loss of fertilizer N in forest systems, potentially increasing fertilizer N use efficiency in these pine plantations.

Nitrogen loss by volatilization of nitrogen fertilizers applied to coffee orchard

ABSTRACT Ammonia volatilization (N-NH3) is one of the main pathways of Nitrogen loss reducing nitrogen use efficiency in coffee orchard. This work aimed at quantifying ammonia volatilization (N-NH3) losses from N-sources to be used in coffee plantations fertilization in Brazil. The experiment was conducted in the field on a dystrophic red latosol (Ferralsol in FAO's classification) at the Coffee Research Sector, University of Lavras, MG, Brazil. The experimental design was of complete randomized blocks with three repetitions of the following treatments: conventional urea, ammonium nitrate and urea + 0.15% Cu and 0.4% B, urea + anionic polymers, urea + elementary sulfur (S0) + polymers, and urea + plastic resin. These N sources were split into three doses of 150 kg ha-1 and band applied. The N-NH3 losses by volatilization and variations of pH (H2O) were measured, before and after N application. The N-sources contributed to reduce the soil pH, measured after the third nitrogen fertilization. The N-NH3 losses by volatilization (average from three applications) was as follows: urea + anionic polymers (35.8%) &gt; conventional urea (31.2%) = urea + S0 + polymers (31.0%) &gt; urea + 0.15% Cu + 0.4 % B (25.6%) &gt; urea + plastic resin (8.6%) = ammonium nitrate (1.0%).

Adsorption and desorption of ammonium by maple wood biochar as a function of oxidation and pH

The objective of this work was to investigate the retention mechanisms of ammonium in aqueous solution by using progressively oxidized maple wood biochar at different pH values. Hydrogen peroxide was used to oxidize the biochar to pH values ranging from 8.1 to 3.7, with one set being adjusted to a pH of 7 afterwards. Oxidizing the biochars at their lowered pH did not increase their ability to adsorb ammonium. However, neutralizing the oxygen-containing surface functional groups on oxidized biochar to pH 7 increased ammonia adsorption two to three-fold for biochars originally at pH 3.7–6, but did not change adsorption of biochars oxidized to pH 7 and above. The adsorption characteristics of ammonium are well described by the Freundlich equation. Adsorption was not fully reversible in water, and less than 27% ammonium was desorbed in water in two consecutive steps than previously adsorbed, for biochars with a pH below 7, irrespective of oxidation. Recovery using an extraction with 2M KCl increased from 34% to 99% of ammonium undesorbed by both preceding water extractions with increasing oxidation, largely irrespective of pH adjustment. Unrecovered ammonium in all extractions and residual biochar was negligible at high oxidation, but increased to 39% of initially adsorbed amounts at high pH, likely due to low amounts adsorbed and possible ammonia volatilization losses.

Nitrogen management for zero till wheat with surface retention of rice residues in north-west India

In intensive rice–wheat systems of north-west (NW) India, surface retention of rice residues in wheat has been recommended instead of burning. Optimum nitrogen (N) management for zero till (ZT) wheat sown into rice residues may to differ from that of conventional practice (in-situ burning of residues followed by intensive tillage prior to sowing). Therefore, we conducted several on-farm and on-station field experiments in 2007–2008 to 2012–2013 to evaluate N management practices for ZT wheat sown into rice residues using the Happy Seeder. The optimum N rate for wheat planted into rice residues in fields with no or only a short history of rice residue retention was 120kgNha−1, the current recommendation for conventional practice. Short-term (up to 20 d) soil N mineralization was lower in undisturbed soil than disturbed soil, while the total amount of N mineralization was similar after 40d, suggesting that over the crop season, total soil N mineralization may be similar in tilled and non-tilled soil. Ammonia volatilization loss from urea broadcast over the residue covered surface, followed by irrigation, was low (<2kgha−1) regardless of time of urea application. Band placement of 20% of the fertilizer N as diammonium phosphate at seeding, and topdressing of the remaining 80% as urea in two equal doses before first and second irrigations produced higher grain yield and N use efficiency than other treatments. However, surface residue retention reduces the rate of soil drying and in some situations this delays the time of the second irrigation and thus N fertilizer application beyond the optimum time. Therefore, the effect of banding various proportions of the urea N between the rows at sowing was investigated. The results showed that, on a loam soil, up to 75% of the recommended N fertilizer can be applied at sowing, 24kgNha−1 as DAP with the seed and 66kgNha−1 as urea drilled between every second wheat row, without loss of yield. In conclusion, a better applied N management strategy for ZT wheat than currently practiced is drilling of 24kgNha−1 as diammonimum phosphate into the soil at seeding followed by two top-dressings of 48kgNha−1 each just prior to first and second irrigations.

Field-Scale Evaluation of Calcium Ammonium Nitrate, Urea, and Urea Treated with N-(N-Butyl) Thiophosphoric Triamide Applied to Grassland in Ireland

This study investigated the effects of nitrogen (N) source, rate, and timing of application on dry-matter yield (DMY), N responses, N uptake and N-use efficiency (NUE) in a grass crop. The experiment used three fertilizer treatments: calcium ammonium nitrate (CAN), urea, and urea treated with N-(n-butyl) thiophosphoric triamide (NBTPT), applied at 0 (control), 25, 50, and 75 kg ha−1 of N over eighteen application timings. Results showed relatively lower agronomic performance of urea compared with CAN when applied in early spring. Urea reported lower N responses, lower relative DMY (90 percent), and relative N uptake (85 percent), which translated in lower NUE (0.45 kg kg−1) compared with CAN (0.70 kg kg−1). In spring fertilizer applications, urea and NBTPT showed DMY and NUE values comparable to those obtained with CAN. However, NBTPT enhanced overall performance of urea, which was shown with increasing temperatures toward summer or increasing N application rates. For summer applications, the efficiency of urea was less (P < 0.05) than that of CAN or NBTPT in all measured parameters, suggesting greater ammonia volatilization loss in urea-treated grass. Nitrogen saved in volatilization improved uptake and responses in NBTPT-treated grass, and hence DMY was not affected compared with CAN in summer fertilizer applications. The results of this study are supportive of increased usage of urea-based fertilizers treated with NBTPT.

Do high nitrogen use efficiency rice cultivars reduce nitrogen losses from paddy fields?

Several high nitrogen use efficiency (high-NUE) rice cultivars have been developed to meet the increased food demand and urgent environmental concerns, but the effect of these cultivars on reducing N losses from paddy fields is not well documented. A two-year field experiment was conducted in the Taihu Lake region of China to evaluate the advantages of high-NUE rice on yields and N losses in 2011 and 2012. Two “high-NUE” rice cultivars and a conventional cultivar were compared at the same fertilizer N input of 200kgNha−1. Ammonia (NH3) volatilization, N2O emission, N leaching and runoff losses were monitored during the entire rice growing season within a rice–wheat rotation. The high-NUE rice cultivars Wuyunjing 23 (W23) and Zhendao 11 (Z11) achieved higher grain yields, and took up more N with a higher NUE than the conventional cultivar Wuyujing 3 (W3). There was a trend toward smaller N losses with the high-NUE cultivars W23 and Z11 (N leaching, N2O emissions and NH3 volatilization decreased by 12–23%, 5–10% and 2–8%, respectively), but the total reductions for the growing season compared to W3 were not statistically significant. Even though the high-NUE cultivars did not significantly decrease the absolute losses of N from the field, they did show lower N losses expressed on a yield-scaled basis than the conventional cultivar due to higher grain yields. Cultivars W23 and Z11 produced 21–27% less NH3 volatilization, 23–26% less N2O emission, 23–33% less N leaching, and 13–24% less N in runoff per ton of rice grain harvested than those of W3. Another cultivar Aoyusi 386 (A386), known to have a higher N uptake at early growth stages than W23 and Z11 was also planted in 2012. This cultivar significantly reduced N losses compared with the conventional variety. It was concluded that improving N uptake rate of high-NUE cultivars in the early stages of growth would be most effective in decreasing N losses and that the main part of N fertilizer applications should be later in the growing season than is currently practiced in the region.

Ammonia volatilization losses in Tanzania grass fertilized with urea

&lt;p&gt;Gaseous losses are the main factors affecting the efficiency of nitrogenous fertilizers in pastures. To evaluate NH&lt;sub&gt;3&lt;/sub&gt;-N volatilization losses in Tanzania grass fertilized with urea in autumn, spring and summer, a completely randomized design with repeated measurements over time and fifteen replicates was used. Plots were represented by urea levels (50; 100 and 150 kg ha&lt;sup&gt;-1&lt;/sup&gt; N) and subplots by time after fertilization (1; 2; 3; 6; 9; 12 and 15 days). The interaction between fertilization leveland time after urea application was significant for the accumulated NH&lt;sub&gt;3&lt;/sub&gt;-N volatilization. Urea application leads to higher percentage N losses in the first three days after application. The average cumulative NH&lt;sub&gt;3&lt;/sub&gt;-N loss for the three occasions (different seasons of the year) was 28%, 20% and 16% of N applied for fertilizer doses of 50; 100 and 150 kg ha&lt;sup&gt;-1&lt;/sup&gt;of N, respectively. The season of the year influenced NH&lt;sub&gt;3&lt;/sub&gt;-N loss pattern and volume, with the lowest values recorded in spring, followed by summer and autumn. The cumulative NH&lt;sub&gt;3&lt;/sub&gt;-N volatilization loss varies from 78 to 90% up to the third day after application of the total N-NH3 loss.&lt;/p&gt;

Comparison of Urease Inhibitors for Use in Rice Production on a Silt‐Loam Soil

In drill‐seeded, delayed‐flood rice (Oryza sativa L.), the large preflood application of nitrogen (N) is typically supplied as urea. Urea is susceptible to ammonia (NH3) volatilization loss if the flood is not established in a timely manner. Research studies investigated the effectiveness of two sources (Agrotain‐Ultra [AGR] and Arborite AG‐NT [ARB]) of the urease inhibitor N‐(n‐butyl) thiophosphoric triamide (NBPT) with different adhering technologies. The two sources were compared to untreated urea, in terms of preventing rice grain yield reduction attributed to N loss when urea‐N was applied at an optimal and suboptimal rate 10, 5, and 1 day prior to flooding (DPF). Sources were also compared to untreated urea in terms of urea‐N loss via NH3 volatilization. Grain yield, averaged across N source and application time, differed among N rates, where the yield from optimally N‐fertilized rice was 8208 lb/acre, suboptimal was 6692 lb/acre, and no N was 4996 lb/acre. Averaged across N sources and rates, rice fertilized 10 DPF produced a lower yield (7227 lb/acre) than urea applied 5 DPF (7673 lb/acre) or 1 DPF (7494 lb/acre), which did not differ. Yield from the two NBPT sources did not differ (7494 lb/acre and 7584 lb/acre) and were greater than untreated urea yield (7316 lb/acre). Results indicated that NH3 volatilization from urea (15%) was greater than from urea treated with either NBPT source (3%). Both sources of NBPT were similar in effectiveness and resulted in greater yields and decreased NH3 volatilization as compared to untreated urea.

Characteristics of ammonia volatilization on rice grown under different nitrogen application rates and its quantitative predictions in Erhai Lake Watershed, China

Ammonia (NH3) volatilization was measured with the continuous airflow enclosure chamber method under different urea application amounts using pots in paddy fields in Erhai Lake Watershed, China. Several factors, such as the urea nitrogen application amount, days after fertilization, NH4+-N concentration and pH of surface water, and climate, that could affect ammonia volatilization were also studied. The results indicated that ammonia volatilization loss increased linearly with increasing amounts of applied urea. The ratios of the ammonia volatilization loss to the applied nitrogen ranged from 16.59 to 18.43 % with different nitrogen application amounts. The ammonia volatilization loss peaked within the first 3 days after fertilization, which accounted for 65–82 % of the total ammonia loss in each period. We observed the following degree of the effects of various factors on ammonia volatilization: NH4+-N concentration of surface water > urea application amount > pH of surface water > days after fertilization > water temperature of surface water. The wind velocity and rainfall were the key factors affecting ammonia volatilization. The model of ammonia volatilization flux was established by using the measured dates from 2013 and was represented as Y = 0.008(x1 + x2 + x3) + e0.056x4−0.068x5−0.623 (R2 = 0.81, P < 0.0001). The model was verified by using the measured dates from 2012. The calculated values fitted well with the field observations. However, the model parameters need to be amended using the model to predict the ammonia volatilization flux in the rice season from other regions.

Maintaining yields and reducing nitrogen loss in rice–wheat rotation system in Taihu Lake region with proper fertilizer management

In the Tailake region of China, heavy nitrogen (N) loss of rice–wheat rotation systems, due to high fertilizer-N input with low N use efficiency (NUE), was widely reported. To alleviate the detrimental impacts caused by N loss, it is necessary to improve the fertilizer management practices. Therefore, a 3 yr field experiments with different N managements including organic combined chemical N treatment (OCN, 390 kg N ha−1 yr−1, 20% organic fertilizer), control–released urea treatment (CRU, 390 kg N ha−1 yr−1, 70% resin-coated urea), reduced chemical N treatment (RCN, 390 kg N ha−1 yr−1, all common chemical fertilizer), and site-specific N management (SSNM, 333 kg N ha−1 yr−1, all common chemical fertilizer) were conducted in the Taihu Lake region with the ‘farmer’s N’ treatment (FN, 510 kg N ha−1 yr−1, all common chemical fertilizer) as a control. Grain yield, plant N uptake (PNU), NUE, and N losses via runoff, leaching, and ammonia volatilization were assessed. In the rice season, the FN treatment had the highest N loss and lowest NUE, which can be attributed to an excessive rate of N application. Treatments of OCN and RCN with a 22% reduced N rate from FN had no significant effect on PNU nor the yield of rice in the 3 yr; however, the NUE was improved and N loss was reduced 20–32%. OCN treatment achieved the highest yield, while SSNM has the lowest N loss and highest NUE due to the lowest N rate. In wheat season, N loss decreased about 28–48% with the continuous reduction of N input, but the yield also declined, with the exception of OCN treatment. N loss through runoff, leaching and ammonia volatilization was positively correlated with the N input rate. When compared with the pure chemical fertilizer treatment of RCN under the same N input, OCN treatment has better NUE, better yield, and lower N loss. 70% of the urea replaced with resin-coated urea had no significant effect on yield and NUE improvement, but decreased the ammonia volatilization loss. Soil total N and organic matter content showed a decrease after three continuous cropping years with inorganic fertilizer application alone, but there was an increase with the OCN treatment. N balance analysis showed a N surplus for FN treatment and a balanced N budget for OCN treatment. To reduce the environmental impact and maintain a high crop production, proper N reduction together with organic amendments could be sustainable in the rice–wheat rotation system in the Taihu Lake region for a long run.

Effect of Split Variable Rate Fertilizationon Ammonia Volatilization in Wild Blueberry Cropping System

<abstract><title><italic>Abstract. </italic></title> Currently, fertilizer is applied uniformly in wild blueberry (Vaccinium angustifolium. Ait) fields, once in a two year production cycle, without considering substantial variation in soil/plant characteristics, topographic features, and fruit yield. The heavy rainfall, gentle to severe topography with high proportion of bare spots, and weed patches in wild blueberry fields emphasizes the need for variable rate split (VRS) fertilization to avoid environmental contamination. Two commercial wild blueberry fields were selected in central Nova Scotia to examine the impact of VRS fertilization on ammonia volatilization losses. Management zones (MZs) were delineated based on slope variation within the selected fields (steep slope (Zone-1), moderate slope (Zone-2), and low slope areas (Zone-3)). The fields were divided into two sections (VRS section and uniform rate (UR) section). Global positioning system (GPS) guided prescription maps based on slope variation were generated in ArcGIS 10 software to apply fertilizer in both fields. In VRS section, fertilizer was applied three times with commercial variable rate (VR) fertilizer spreader in Zone-1, Zone-2, and Zone-3 with fertilization rates of 66, 50, 33, and kg ha^-1, respectively. Single uniform grower’s fertilizer rate (200 kg ha^-1) was applied in UR sections of the selected fields for comparison. The ammonia volatilization trials were established under VRS and UR fertilized sections of the selected fields immediately following the fertilization. The ammonia volatilization samples were collected after each fertilization in VRS sections and once in UR sections. The samples were analyzed for ammonium nitrogen (NH₄⁺-N) concentrations. Leaf samples were collected in third week of July at tip-dieback stage and analyzed for leaf nutrient concentrations. The results of repeated measure analysis of variance showed ammonia volatilization losses were significantly (p < 0.05) lower in VRS sections as compared to uniformly fertilized sections of the selected fields. Secondly, the study found that the leaf nutrient concentrations were not reduced using VRS fertilization. Results of this study also indicated that the VRS fertilization improved the nitrogen use efficiency and reduced the ammonia volatilization in wild blueberry fields.

Hygroscopicity and ammonia volatilization losses from nitrogen sources in coated urea

Hygroscopic fertilizers tend to absorb moisture from the air and may have undesirable characteristics such as moistness, clumping and lower fluidity, hampering the application. The increasing use of urea is due to its numerous advantages, although this nitrogen (N) source is highly susceptible to volatilization losses, particularly when applied to the soil surface of management systems with conservation of crop residues. The volatilization losses can be minimized by slow or controlled-release fertilizers, with controlled water solubility of the urea-coating materials; and by stabilized fertilizers, which prolong the period during which N remains in the amide or ammonia forms by urease inhibitors. This study evaluated the hygroscopicity of and ammonia volatilization from urea coated with boric acid and copper sulfate or with sulfur. The hygroscopicity of the sources was evaluated over time after exposure to five levels of relative humidity (RH) and volatilization evaluated after application to the soil surface covered with sugarcane trash. Ammonium nitrate has a low potential for volatilization losses, but is highly hygroscopic. Although coating with boric acid and copper sulfate or elemental sulfur reduced the critical humidity level of urea, the delay in the volatilization process is a potential positive factor.

Effects of Poultry Litter Injection on Ammonia Volatilization, Nitrogen Availability, and Nutrient Losses in Runoff

Poultry litter is a common organic amendment in agricultural production, but nutrient losses can reduce its effectiveness as a fertilizer. Three experiments were conducted to evaluate ammonia nitrogen (NH3-N) volatilization, N availability, and runoff losses of nutrients by conducting a closed chamber volatilization study, a soil incubation, and a rainfall simulation. In all studies, poultry litter was applied at a rate of 6.7 Mg · ha−1 either on the surface or injected and compared with an unamended control. In the volatilization and soil incubation studies, Braddock Loam and Bojac Sandy Loam surface soils were compared. Of the ammonium N added, cumulative loss of NH3-N by volatilization was 3% from injected and 121% from surface applied poultry litter after 7 days in the Loam. In the Sandy Loam, cumulative loss of NH3-N was 9% from injected and 153% from surface applied poultry litter after 7 days. After a 40-day soil incubation, injection increased total inorganic N by 52% and 99% for the Loam and Sandy Loam soils, respectively, when compared with surface application. Injection reduced total Kjeldahl N by 59%, total Kjeldahl P by 53%, dissolved reactive P, dissolved nitrate N by 73%, and dissolved NH3-N in runoff by 99%, compared with surface application. Injection reduced NH3-N volatilization and nutrients in runoff to levels of the control. These studies show that injection increases plant available N while decreasing losses through volatilization and runoff.

Evaluation of ammonia volatilization losses by adjusted parameters of a logistic function

The dynamics of N losses in fertilizer by ammonia volatilization is affected by several factors, making investigation of these dynamics more complex. Moreover, some features of the behavior of the variable can lead to deviation from normal distribution, making the main commonly adopted statistical strategies inadequate for data analysis. Thus, the purpose of this study was to evaluate the patterns of cumulative N losses from urea through ammonia volatilization in order to find a more adequate and detailed way of assessing the behavior of the variable. For that reason, changes in patterns of ammonia volatilization losses as a result of applying different combinations of two soil classes [Planossolo and Chernossolo (Typic Albaqualf and Vertic Argiaquolls)] and different rates of urea (50, 100 and 150 kg ha-1 N), in the presence or absence of a urease inhibitor, were evaluated, adopting a 2 × 3 × 2 factorial design with four replications. Univariate and multivariate analysis of variance were performed using the adjusted parameter values of a logistic function as a response variable. The results obtained from multivariate analysis indicated a prominent effect of the soil class factor on the set of parameters, indicating greater relevance of soil adsorption potential on ammonia volatilization losses. Univariate analysis showed that the parameters related to total N losses and rate of volatilization were more affected by soil class and the rate of urea applied. The urease inhibitor affected only the rate and inflection point parameters, decreasing the rate of losses and delaying the beginning of the process, but had no effect on total ammonia losses. Patterns of ammonia volatilization losses provide details on behavior of the variable, details which can be used to develop and adopt more accurate techniques for more efficient use of urea.

Ammonia volatilization losses from paddy fields under controlled irrigation with different drainage treatments.

The effect of controlled drainage (CD) on ammonia volatilization (AV) losses from paddy fields under controlled irrigation (CI) was investigated by managing water table control levels using a lysimeter. Three drainage treatments were implemented, namely, controlled water table depth 1 (CWT1), controlled water table depth 2 (CWT2), and controlled water table depth 3 (CWT3). As the water table control levels increased, irrigation water volumes in the CI paddy fields decreased. AV losses from paddy fields reduced due to the increases in water table control levels. Seasonal AV losses from CWT1, CWT2, and CWT3 were 59.8, 56.7, and 53.0 kg N ha−1, respectively. AV losses from CWT3 were 13.1% and 8.4% lower than those from CWT1 and CWT2, respectively. A significant difference in the seasonal AV losses was confirmed between CWT1 and CWT3. Less weekly AV losses followed by TF and PF were also observed as the water table control levels increased. The application of CD by increasing water table control levels to a suitable level could effectively reduce irrigation water volumes and AV losses from CI paddy fields. The combination of CI and CD may be a feasible water management method of reducing AV losses from paddy fields.

Ammonia volatilization and nitrogen retention: how deep to incorporate urea?

Incorporation of urea decreases ammonia (NH) volatilization, but field measurements are needed to better quantify the impact of placement depth. In this study, we measured the volatilization losses after banding of urea at depths of 0, 2.5, 5, 7.5, and 10 cm in a slightly acidic (pH 6) silt loam soil using wind tunnels. Mineral nitrogen (N) concentration and pH were measured in the top 2 cm of soil to determine the extent of urea N migration and the influence of placement depth on the availability of ammoniacal N for volatilization near the soil surface. Ammonia volatilization losses were 50% of applied N when urea was banded at the surface, and incorporation of the band decreased emissions by an average of 7% cm (14% cm when expressed as a percentage of losses after surface banding). Incorporating urea at depths >7.5 cm therefore resulted in negligible NH emissions and maximum N retention. Cumulative losses increased exponentially with increasing maximum NH-N and pH values measured in the surface soil during the experiment. However, temporal variations in these soil properties were poorly related to the temporal variations in NH emission rates, likely as a result of interactions with other factors (e.g., water content and NH-N adsorption) on, and fixation by, soil particles. Laboratory and field volatilization data from the literature were summarized and used to determine a relationship between NH losses and depth of urea incorporation. When emissions were expressed as a percentage of losses for a surface application, the mean reduction after urea incorporation was approximately 12.5% cm. Although we agree that the efficiency of urea incorporation to reduce NH losses varies depending on several soil properties, management practices, and climatic conditions, we propose that this value represents an estimate of the mean impact of incorporation depth that could be used when site-specific information is unavailable.

Loss of ammonia from nitrogen fertilizers applied to maize and soybean straw

In Brazilian agriculture, urea is the most commonly used nitrogen (N) source, in spite of having the disadvantage of losing considerable amounts of N by ammonia-N volatilization. The objectives of this study were to evaluate: N lossby ammonia volatilization from: [urea coated with copper sulfate and boric acid], [urea coated with zeolite], [urea+ammonium sulfate], [urea coated with copper sulfate and boric acid+ammonium sulfate], [common urea] and [ammonium nitrate]; and the effect of these N source son the maize yield in terms of amount and quality. The treatments were applied to the surface of a soil under no-tillage maize, in two growing seasons. The first season (2009/2010) was after a maize crop (maize straw left on the soil surface) and the second cycle (2012/2011) after a soybean crop. Due to the weather conditions during the experiments, the volatilization of ammonia-N was highest in the first four days after application of the N sources. Of all urea sources, under volatilization-favorable conditions, the loss of ammonia from urea coated with copper sulfate and boric acid was lowest, while under high rainfall, the losses from the different urea sources was similar, i.e., an adequate rainfall was favorablet o reduce volatilization. The ammonia volatilization losses were greatest in the first four days after application. Maize grain yield differed due to N application and in the treatments, but this was only observed with cultivation of maize crop residues in 2009/2010. The combination of ammonium+urea coated with copper sulfate and boric acid optimized grain yield compared to the other urea treatments. The crude protein concentration in maize was not influenced by the technologies of urea coating.

Applied Model for Estimating Potential Ammonia Loss from Surface-Applied Urea

Ammonia loss from urea fertilizer is a major concern to farmers all over the world. Various environmental factors such as temperature, soil water content, wind speed, pH, rainfall, relative humidity, cation exchange capacity (CEC), soil organic matter, and others influence ammonia volatilization loss. The objective of this work was to establish a model for estimating ammonia loss utilizing published data. Also, using current day inputs (temperature, wind speed, and known soil pH) estimates could relate risk to producers considering surface applications of urea fertilizer without incorporation. Linear models for soil pH and ammonia loss, ambient temperature and ammonia loss, and wind speed and ammonia loss were determined based on more than 40 published articles. Final estimates of ammonia loss from surface applications of urea employed an additive effects model using inputs for pH, temperature, and wind speed. Web access to this model can be located at www.nue.okstate.edu/ammonia_loss.htm.