Urea Granules Research Articles

Production and Characterization of Controlled Release Urea Using Biopolymer and Geopolymer as Coating Materials.

Synthetic polymers-based controlled release urea (CRU) leaves non-biodegradable coating shells when applied in soil. Several alternative green materials are used to produce CRU, but most of these studies have issues pertaining to nitrogen release longevity, process viability, and the ease of application of the finished product. In this study, we utilized tapioca starch, modified by polyvinyl alcohol and citric acid, as coating material to produce controlled release coated urea granules in a rotary fluidized bed equipment. Response surface methodology is employed for studying the interactive effect of process parameters on urea release characteristics. Statistical analysis indicates that the fluidizing air temperature and spray rate are the most influential among all five process parameters studied. The optimum values of fluidizing air temperature (80 °C), spray rate (0.13 mL/s), atomizing pressure (3.98 bar), process time (110 min), and spray temperature (70 °C) were evaluated by multi-objective optimization while using genetic algorithms in MATLAB®. Urea coated by modified-starch was double coated by a geopolymer to enhance the controlled release characteristics that produced promising results with respect to the longevity of nitrogen release from the final product. This study provides leads for the design of a fluidized bed for the scaled-up production of CRU.

Biodegradable oil-based polymeric coatings on urea fertilizer: N release kinetic transformations of urea in soil

Polymer coatings are used to control the rate of release of plant available nutrients from fertilizers as well as to reduce nutrient losses such as ammonia (NH3) volatilization. Although the literature presents several examples of materials used to coat urea, little is known about nitrogen (N) release properties such as the mechanism involved and phenomena (e.g., pore opening) in the polymer coating. Thus, this study investigated urea release from polyurethane (PU) derived from two renewable raw materials (castor oil and soybean oil), to explain how the oil structure and coating microstructure influence release and urea-N dynamics in soil. The results demonstrated that the profile of urea release and the urea-N mineralization in the soil could be controlled by altering the thickness of the coating on the urea granules. Coating by eco-friendly polymer was efficient in controlling urea release in soil to reduce volatilization of ammonia and increase the availability of N in the soil.

Agroecological efficiency of biomodified mineral fertilizers

To improve the elements of winter wheat cultivation technology in order to reduce the loss of nutrients from the soil, research was conducted. The results presented in the article show the effectiveness of the use of mineral fertilizers with the application of a biological preparation to the granules. The influence of the method of applying a biological preparation based on Bacillus subtilis H – 13 on urea granules was evaluated. The influence of bio mineral fertilizers on the dynamics of nitrogen accumulation by wheat plants is established. The results obtained are the scientific basis for the use of rhizospheric bacteria Bacillus subtilis H - 13 as an effective strain for expanding the range of mineral fertilizers by creating bio modified forms and subsequent use in agricultural technologies.

Sembradora para distribuir semillas a cuatro hileras en camas y captar agua de lluvia

Introduction: Planting bean and corn in multi-row beds, complemented with rainwater harvesting, has increased grain and dry matter yields. Objective: To design and evaluate a planter to distribute seeds in four-row beds. Methodology: The planter was created based on the design phases of mechanical engineering. Once built, the seed metering and fertilizer system was evaluated on a test bench. The first one was conducted under three conditions and ten operating speeds with bean and corn. The second one was performed under an operating condition with granulated urea. Subsequently, the planter was evaluated in agricultural soil with both species of seed and four forward speeds, and the horizontal distribution of the plants, planting depth and volume of the dikes formed in the soil were determined. Results: On the test bench, it was found that the number of seeds per linear meter of bean and corn was reduced in all three test conditions. In the field, it was observed that the variables evaluated were affected by the operating speed. Study limitations: The planter was only evaluated with corn grains and bean at a maximum speed of 7.5 km∙h-1 on a test bench and at 7 km∙h-1 in the field. Originality: The planter allows seeding four-row beds and, at the same time, forming dikes in the soil to store rainwater. Conclusions: The planter is a viable option to mechanize the corn and bean planting system in four-row beds, for irrigation and rainfed conditions.

Development and characterization of allicin using palm stearin as a binder on urea granules

The potency of allicin as a urease inhibitor has been discovered and the demand for using a biodegradable material as a coating is increasing. The loss of nitrogen can be reduced, and the efficiency of the fertilizer can be increased by utilizing a coating. The objective of this study was to determine the compatibility of allicin and urea with palm stearin as an adhesive agent in the coating process. Four treatments were used in this study; urea as the control, urea coated with palm stearin (UPS), urea coated with allicin and palm stearin (UPSA) and urea coated with NBPT (UNBPT). The treatments were analyzed for thickness, chemical structure, total N content, dissolution rate in water and hardness. Results from FT-IR and SEM images demonstrated that palm stearin was compatible with allicin and urea with smoother coated layer. The efficiency of coated urea with allicin and plam stearin was enhanced by reducing 70% of urea release in 24 hours as compared to the urea. The crushing strength was significantly improved by using palm stearin as the binder. Coating urea with palm stearin and allicin appears to increase the efficiency of urea.

Oil-based polyurethane-coated urea reduces nitrous oxide emissions in a corn field in a Maryland loamy sand soil

Urea is the most widely used N fertilizer due to its high N concentration (46%), cost effectiveness and ease of handling. However, urea is susceptible to loss as N2O, a greenhouse gas and catalyst of stratospheric ozone decline. Polymer-coated fertilizers may be effective in reducing such losses but the appropriate coating thickness for effective field performance is unknown. We prepared urea granules with polyurethane coating (PCU) based on castor oil at 2%–8% by weight. We tested the fertilizer value of these materials for maize (Zea mays L.) and measured field loss of N2O. Maize grain yield and N uptake were similar in treatments fertilized with urea (uncoated) and each of the coated materials. Cumulative N2O–N per unit of grain yield, however, was reduced by 80% with PCU8% compared with uncoated urea. Results indicate that polyurethane-coated urea performs similarly to uncoated urea for maize production while reducing soil N2O emissions up to 60–80%, with an efficiency factor twice as high as that suggested by the Intergovernmental Panel on Climate Change (IPCC) for N fertilizers. Our results indicate that urea with a polyurethane coating of 8% (PCU8%) had the best combined agronomic and environmental performance in a field study.

Effect of autumn nitrogen fertilization on winter oilseed rape growth and yield parameters

Autumn fertilization of winter oilseed rape with nitrogen was monitored in exactly delimited small field experiment in the period of 2013/14–2015/16. The cultivar used was DK Exstorm, sowing amount: 50 seeds/m<sup>2</sup> and fertilizer applied in autumn was Ureastabil – granulated urea with urease inhibitor (NBPT). The application period was at the end of October, doses 40 and 80 kg N/ha. Research results confirmed a statistically important effect of autumn fertilization on growth of the above-ground biomass and roots. Statistically important effect on seed yield was confirmed, too. The dose of 40 kg N/ha resulted in the highest seed yield, on average by 10.6% higher than reference (5.7–6.5 t/ha). On the other hand, the dose of 80 kg N/ha increased the seed yield only by 7.4% on average (5.4–6.3 t/ha).Fertilization effects on the oil content and one thousand seeds’ weight were statistically insignificant. The results show that considering the given local and weather conditions and low mineral nitrogen content in the soil, the most suitable nitrogen dose for autumn fertilization is 40 kg N/ha. This dose follows the nitrate directive rules, supports oilseed rape strengthening before winter and intensifies it for better seed yield.

Nitrogen availability and ammonia volatilization in biochar-based fertilizers

ABSTRACTIncreasing N use efficiency is an important strategy to intensify sustainable agriculture, optimize nutrient use, and reduce N loss to the environment via different routes. Owing to its physicochemical properties, biochar can be used as an additive to produce biochar-based fertilizers (BFs) with increased efficiency. We investigated N availability and ammonia loss from 17 BFs (3%–38% N). N availability and release from BFs were evaluated by water extraction experiments and soil column leaching. BFs (5%–10% N) had an average of 64% solubilized N after five extractions, whereas urea had 98% solubilized N. However, BFs produced with urea released N more slowly in soil, with the release rate 60% less than that of urea. Ammonia volatilization was evaluated using a 22-d experiment, where N was applied to soil surface (pH = 4.4). We compared urea, BF granulated with urea, and BF produced by coating urea granules with acidified or unacidified biochar. Compared to urea, biochar-based fertilizers granulated with urea and urea granules coated with acidified biochar significantly reduced (t-test at 5%) ammonia volatilization by 14%. The results demonstrated the potential of BFs as enhanced efficiency fertilizers. Therefore, BFs might be a good option to mitigate N loss.

Controlling nitrogen pollution via encapsulation of urea fertilizer in cross-linked corn starch

High fertilizer inputs augment the reactive nitrogen level in soil, air, and water. Unused reactive nitrogen acts as a pollutant and harms natural resources. This study focused on the thermal processing of corn starch into a coating material using disodium tetraborate and urea. The processed corn starch was coated over granular urea in a vertical bed coating reactor. The chemically modified starch, when compared with native starch, exhibited better stability and mechanical strength over time. The modified starch looked like a weak gel, and its loss modulus was dominated by the storage modulus. However, for native starch, the viscous component dominated the elastic component, especially at lower angular frequencies. The nitrogen release from the coated urea was remarkably slower than the uncoated one. A small difference in the peak and final starch viscosities in the presence of urea and borate revealed low thermal cracking of the starch molecules. The surface of the granular urea that was coated with chemically modified corn starch was uniform, dense, hard, and least porous. The uncoated urea granules became released into water in 6 min under gentle shaking, whereas the coated urea took almost 32 min to completely release.

Analysis of Wetting Behavior and Solidification Process of Molten Urea on a Superhydrophobic Surface and Its Application in Large Granular Urea Production

The wetting behavior of polar high-temperature melt on superhydrophobic surfaces is rarely studied, although water wetting process under normal temperature has been widely investigated. In this work, molten urea was considered as the typical polar melt substance, and its wetting behavior and solidifying process on a polytetrafluoroethylene (PTFE)-coated superhydrophobic stainless steel surface (PSSSS) were investigated. The results confirm the super-repellency of PSSSS on molten urea droplets with a static angle of over 155° and a rolling angle of 3.5 ± 1°, which is consistent with the Cassie–Baxter state. Such a superurea-melt-phobic state is ascribed to the high roughness of the PTFE-coated surface and high cohesive energy density difference between the urea and PTFE. The solidification process of the urea melt on PSSSS occurred from the outside to inside in 44 s at 18 °C to form a compact urea granule of large size and high mechanical strength. This occurrence provides a feasible and promising granulat...

Solvent-free mechanochemical polymerization of urea-succinic acid and urea-succinic acid-glycerol mixtures

Abstract Copolymers of urea and succinic acid (U/SA) and urea, succinic acid and glycerol (U/SA/GLY) were prepared through green mechanochemical reactions, without the use of solvents. A planetary ball mill was used for the polymerization operation and the effects of some of the polymerization conditions were investigated. The obtained samples were analyzed by Fourier Transform Infrared Spectroscopy (FTIR/ATR), Electrospray ionization mass spectrometry (IES-EM), Matrix- Assisted Laser Desorption Ionization Process (MALDI TOF), Nuclear Magnetic Resonance (1H NMR and 13C NMR), Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC), in order to study the structural, chemical and thermal properties of the obtained products. The results confirmed the occurrence of mechanochemical polymerizations of urea and succinic acid and of urea, succinic acid and glycerol. A relatively high yield of 83% (U/SA) and 75% (U/SA/GLY) and maximum degradation temperature of 290 °C were achieved using this novel solid copolymerization method. The method proved to be versatile, convenient and suitable for green and sustainable production of polymer materials, in particular for the coating of urea granules.

DESIGN OF AN EXPERIMENTAL DEVICE FOR THE MEASUREMENT OF THE COEFFICIENT OF RESTITUTION

In this work an experimental device was designed and built to measure the coefficient of restitution of particles of different type and size. The aim of the study is to analyze the dependence of the coefficient of restitution with the impact velocity, the shape and mass of the particles. Three types of particles of different origin and shape were used: lentils, urea granules and polyethylene pellets. Besides, two impact materials were evaluated: steel and polycarbonate. The images were captured with a high resolution camera, recording the moment at which the particles impact and bounce on the surface. Image processing software was used to obtain the position of the particle at the instants before and after the impact. The particle velocities before and after the collision were calculated and the coefficient of restitution of the particles were obtained. The experimental results showed the dependence of the coefficient of restitution with the studied variables, providing useful information about the energy dissipation for numerical simulations and a breakthrough in the study of gas-solid flow systems.

Effect of Biodegradable Binder Properties and Operating Conditions on Growth of Urea Particles in a Fluidized Bed Granulator.

Granulation is an important step during the production of urea granules. Most of the commercial binders used for granulation are toxic and non-biodegradable. In this study, a fully biodegradable and cost-effective starch-based binder is used for urea granulation in a fluidized bed granulator. The effect of binder properties such as viscosity, surface tension, contact angle, penetration time, and liquid bridge bonding force on granulation performance is studied. In addition, the effect of fluidized bed process parameters such as fluidizing air inlet velocity, air temperature, weight of primary urea particles, binder spray rate, and binder concentration is also evaluated using response surface methodology. Based on the results, binder with higher concentration demonstrates higher viscosity and higher penetration time that potentially enhance the granulation performance. The viscous Stokes number for binder with higher concentration is lower than critical Stokes number that increases coalescence rate. Higher viscosity and lower restitution coefficient of urea particles result in elastic losses and subsequent successful coalescence. Statistical analysis indicate that air velocity, air temperature, and weight of primary urea particles have major effects on granulation performance. Higher air velocity increases probability of collision, whereby lower temperature prevents binder to be dried up prior to collision. Findings of this study can be useful for process scale-up and industrial application.

Effects of copper content on microstructure and mechanical properties of open-cell steel foams

The effects of copper content on the microstructural and mechanical properties of steel foams are investigated. Spherical urea granules, used as a water-leachable space holder, were coated with a mixture of iron, ultrafine carbon, and different amounts of copper powders. After the mixture was compacted and the space holder was removed by leaching, a sintering process was performed under an atmosphere of thermally dissociated ammonia. Microstructural evaluations of the cell walls were carried out using optical microscopy and scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy. In addition, compression tests were conducted to investigate the mechanical properties of the manufactured steel foams. The results showed that the total porosity decreases from 77.2% to 71.9% with increasing copper content in the steel foams. In the foams’ microstructure, copper islands are mostly distributed in pearlite and intergranular carbide phases are formed in the grain boundaries. When the copper content was increased from 0 to 4wt%, the elastic modulus, plateau stress, fracture stress, and fracture strain of manufactured steel foams improved 4.5, 6, 6.4, and 2.5 times, respectively.

Release of urea from cellulosic hydrogel coated urea granule: Modeling effect of crosslink density and pH triggering

ABSTRACTUrea granules were coated with CMC-g-cl-PAA hydrogel by in situ spraying and polymerization technique with mean thickness of 0.24 mm. Water absorption capacity of hydrogel coated urea granules varied from 18.67 to 217.33 g/g depending on pH. Urea release was extended due to hydrogel coating and kinetic analysis at different pH (4.0, 7.0 and 9.2) revealed a sigmoid function as best fit model. The coated urea granules showed pH triggered release property with higher rate in alkaline medium and slower in acidic medium. The prepared hydrogel coated urea granules may find its application in integrated water and nutrient management strategies in agriculture.

Emissions of nitrous oxide and methane from rice field after granulated urea application with nitrification inhibitors and zeolite under different water managements

A field experiment was carried out to determine the emissions of nitrous oxide (N2O) and methane (CH4) and yield of rice grains under water management of continuously flooded (CF) and non-continuously flooded (NCF) systems and to find out those were affected by both input of water managements in combination with urea granulated with nitrification inhibitors (neem and dicyandiamide) and zeolite. Urea combined with zeolite and nitrification inhibitors (NIs) reduced the emission of N2O in both plots of CF and NCF compared with urea alone, while the release of CH4 was induced, especially at CF plot. However, no differences existed in the emissions of N2O and CH4 between the types of urea granulated with zeolite and NIs and urea treatments in both water input managements. A paired comparison between CF and NCF plots revealed fewer emissions of N2O and CH4 in NCF plot with urea granulated with zeolite and neem treatments. Urea with zeolite and NIs did not have any effect on improving rice grain yield different from the effect of urea alone. The nitrogen use efficiency employed in this study had little effect on delayed oxidation of NH4+ in the soil of both plots of rice field. The study showed that the water management or practice of irrigation promises to reduce the emissions of N2O and CH4 compared to nitrogen use efficiency application.

Evaluation of Commercial Additives Used with Granular Urea for Nitrogen Conservation

Core Ideas Urease and nitrification inhibitors can reduce N loss from granular urea. Agrotain Ultra functioned as a urease inhibitor, Nutrisphere‐N, and NZone did not. Agrotain Ultra reduced ammonia volatilization, Nutrisphere‐N, and NZone had little effect. SuperU and Instinct inhibited nitrification, Nutrisphere‐N, and NZone did not. ABSTRACTUrea is subject to loss by ammonia volatilization, and, after nitrification, by leaching and denitrification. This study evaluated commercial products marketed as fertilizer additives for granular urea for the purpose of reducing N loss. In a urea hydrolysis study, urea granules were applied to three soils, and hydrolysis measured for 10 d. The urea granules were untreated, or treated with Nutrisphere‐N (Verdesian Life Sciences, Cary, NC), NZone (AgXplore, Parma, MO), or Agrotain Ultra (Koch Agronomic Services, Wichita, KS). Agrotain Ultra was effective in slowing urea hydrolysis, but amending the granules with Nutrisphere‐N and NZone did not slow urea hydrolysis. In a ammonia volatilization study, the treatments were the same, two soils were used, and volatilization was measured over 14 d. Agrotain Ultra was effective in reducing ammonia loss compared to untreated urea granules, but amending the granules with Nutrisphere‐N and NZone had little effect. In a nitrification study, three soils were treated with urea granules, SuperU granules (Koch Agronomic Services, Wichita, KS), or urea granules treated with Nutrisphere‐N, NZone, or Instinct (Dow Agrosciences, Indianapolis, IN). The progress of nitrification was measured after 2 and 4 wk of incubation. SuperU granules, or granules treated with Instinct nitrified more slowly than untreated urea granules, amending urea granules with Nutrisphere‐N and NZone did not slow nitrification. The three experiments do not support the use of Nutrisphere‐N or NZone as fertilizer additives for granular urea, for the purpose of reducing N loss.

Impact of Using the Technology of Deep Placement of Super Granulated Urea in Rice Cultivation in the Senegal River Valley and the Anambé Basin

Impact of Using the Technology of Deep Placement of Super Granulated Urea in Rice Cultivation in the Senegal River Valley and the Anambé Basin

Development of a Polyacrylate/Silica Nanoparticle Hybrid Emulsion for Delaying Nutrient Release in Coated Controlled-Release Urea

Polyacrylate/silica hybrid emulsions were prepared by blending aqueous silica nanoparticles with polyacrylate emulsion, which were used for coating urea granules. After incorporating 1.0 wt.% silica nanoparticles into polyacrylate emulsion, preliminary solubility of CRU was decreased from 38.3% to 2.2%, and the release duration was extended from 8 to 27 days. The hybrid coating remarkably delayed the release of urea via improving wear-resistance due to the enhanced hardness, reducing water vapor permeability because of the tortuous diffusion pathway, and less breakage of CRU granules resulted from higher glass transition temperature. Meanwhile, the processibility was improved, which prevented particle agglomeration during coating. Therefore, aqueous silica nanoparticles have potential application in polymer emulsion coated controlled-release fertilizers.

Coating of urea granules by in situ polymerization in fluidized bed reactors

Abstract The main objective of the present work is to produce and characterize urea granules coated with polymers prepared with aqueous solutions of acrylic acid and glycerol. Both coating and drying of urea granules were performed in a fluidized bed reactor. Fourier transform infrared spectroscopy analyses indicated the presence of poly(acrylic acid) and acrylic acid / glycerol copolymers on the granule coating and the formation of chemical bonds between urea and the polymer coating. Scanning electron microscopy images showed that the original and coated urea granules presented different characteristics, reinforcing the idea that coating occurs in the fluidized bed. Finally, rates of urea release showed that the coated granules presented slightly slower rates of urea dissolution in water due to the presence of the coating layer. Therefore, it is shown that it is possible to produce coated urea granules through in-situ polymerization onto the granule surface using a fluidized bed.