Urea Granules Research Articles

Mitigation of ammonia volatilisation from urea with micronised sulfur applied to common bean

Urea with micronised sulfur (S) in granules may result in lower nitrogen (N) depletion through ammoniacal N (NH3-N) loss than conventional urea due to the acidification reaction of S near urea granules in soil, and the addition of S to the urea may provide a limiting nutrient in tropical soils. The research objectives were to (1) verify whether urea containing micronised S (urea+S) can mitigate NH3-N volatilisation in comparison to conventional urea, ammonium nitrate, and ammonium sulfate; and (2) evaluate the efficiency of N and S sources for common bean (Phaseolus vulgaris L.) grown on coarse-, medium-, and fine-textured soil. The results showed that ~90% of NH3-N volatilisation occurred during the first 14 days after application. The blend of elemental sulfur and sulfate in urea reduces the loss of N by NH3-N volatilisation compared with regular urea but not enough to achieve the low volatilisation as observed for ammonium nitrate and ammonium sulfate application. Despite the differences in the leaf N and S concentration and bean yield components, no differences were observed among N sources in grain yield in general.

Tunable thermo-physical performance of castor oil-based polyurethanes with tailored release of coated fertilizers

In this work, castor oil-based polyurethanes were prepared through rotating-drum coating technology as encapsulating coating materials for slow-release fertilizers. The physico-chemical properties and microstructure of the polyurethanes were tailored by selection of diisocyanates, control of the hydroxyl number of castor oil used, and controlling the hydroxyl/isocyanate molar ratio. The effect of the microstructures and the composition of the resulting polyurethanes on the controlled release behavior of coated urea granules were evaluated by measuring the N release characteristics of the system in water under laboratory conditions. In addition, the critical mechanisms underlying the polyurethanes' structures and properties are clarified and discussed. The results show that isophorone diisocyanate, and 2,6-diisocyanatotoluene as the hard segment are not suitable for production of slow-release fertilizers while polymethylene diisocyanate does. The N release longevity of SRFs coated with only 5.0 wt% of polyurethane can be tuned from 20 days to 140 days, constituting the widest range reported in the literature to date. The high hydroxyl number of castor oil and high content of NCO in the polyurethanes prepared lead to a high crosslink density, hydrophobicity, and compact micro-structure, resulting in a material that exhibits low water and nutrients permeabilities, and therefore slow release. This work offers a simple and effective method to create slow release fertilizers that is cost-effective and environmentally friendly.

Encapsulation of urea with alkyd resin-starch membranes for controlled N2 release: Synthesis, characterization, morphology and optimum N2 release

Abstract Nitrogen released into soils from uncoated urea granules is lost continuously due to volatilization, leaching, denitrification, nitrous emission, water eutrophication and surface run-off. Reducing the release rate can increase its efficiency of use and reduce nitrogen pollution. In this research, granular urea fertilizer was encapsulated with alkyd resin-starch bio-composites as materials of biodegradable and regenerative resources to obtain controlled release coated urea (CRCU). Different bio-composites were synthesized from each of castor seed oil and rubber seed oil based alkyd resin (modified with sorbitol, maleic and phthalic anhydride) and cassava starch. Effects of sorbitol, maleic anhydride and pthalic anhydride on the release kinetics of the CRCU were evaluated. Optimum nitrogen release characteristic of the CRCU was evaluated as a function of coating thickness, release time and pH. Structural and morphology elucidation of the raw urea and encapsulated ureas were established using FTIR and SEM instrumental analysis, respectively. Nutrient release kinetic of the different coated urea was determined using Kjeldahl method. FTIR result confirmed the esterification reaction and hydrogen bonding integrity of the alkyd resins and starch. The SEM images of the raw urea appears rough and have fine openings while that of CRCUs possess a seemingly decrease in membrane porosity and ordered uniform layer. 31.66 and 48.61% cumulative nitrogen release were obtained with coating thickness of 6.4(mm), time of 24 days, pH of 8 and 2.2(mm), time of 24 days, pH of 8 for RSO-St-S and CSO-St-S encapsulated urea, respectively. The encapsulated ureas perfectly satisfy the requirements of European Standard EN 13,266 for CRFs. It can be concluded that the synthesized CRCU efficiently retard nitrogen release.

Parameters Affecting Coating Uniformity of Alkali -Activated Material Coated Fertilizer

The establishment of Controlled Release Urea (CRU) in agriculture industry has given a great significant outcome towards the development of economy while preserving the environment. As it is developed through a coating process, it does not only help to increase fertilizer’s efficiency, but also minimize the loss of nutrients into the soil and environmental pollution. There are many types of coating materials that have been extensively studied as well as applied in everyday life from pharmaceutical industry to engineering industry such as in pharmaceutical tablet, road construction and corrosion control of steel structures like offshore platforms. In this research, the alkali-activated material composite has been developed as a new coating material and is introduced as the main coating material for the CRU. In term of environmental friendliness, alkali-activated material (AAM) is considered better than sulphur and polymer. However, the combination of fly ash and sodium hydroxide (NaOH) solution producing the AAM paste needs further research since it can be categorized as a novel coating material for CRU. It is also to ensure the suitability of it to be used as a coating material on urea fertilizer. A significant coating thickness along with good hardness strength can produce promising coated urea granules characteristics. Two parameters have been studied for this research to identify its effect towards coating thickness and hardness strength of coated urea granules which are inlet air pressure and spraying rate. These two parameters are identified to be crucial in enhancing the characteristics of coated urea granules.

Nitrogen Recovery and Loss from Kentucky Bluegrass Fertilized by Conventional or Enhanced-Efficiency Urea Granules

Easy handling and low unit N cost make prilled urea (46-0-0) a popular fertilizer. While incomplete recovery of granular urea applications by turfgrass is documented, field evaluations of NH3 volatilization mitigation by coatings or bioinhibitor efficiency enhancements are limited. Meanwhile, NH3 emissions reduce air quality and contribute to nutrient loading of water resources. Our objectives were to quantify 3- and 6-d ammonia emission and 9-week turfgrass recovery of unincorporated granular fertilizer application to turfgrass. In 2014 and 2015, commercial urea-N fertilizers were broadcast over a mature Kentucky bluegrass (Poa pratensis L. ‘Midnight’) lawn at 43 kg ha−1. Treatments included conventional urea and three enhanced-efficiency fertilizers; a blended fertilizer with 25% of its urea-N supplanted by polymer- and polymer-/sulfur-coated prills, or two stabilized urea fertilizers both amended by N-(n-butyl) thiophosphoric triamide (NBPT) and dicyandiamide (DCD) inhibitors. Using a 51% ‘trapping-efficiency’ flux chamber system under the field conditions described, 23.1 or 33.5% of the conventional urea-N was lost as NH3 over the respective 3- or 6-d period following application. Alternatively, dual amendment by NBPT and DCD resulted in approximately 10.3 or 19.6% NH3-N loss over the respective 3- or 6-d periods, and greater fertilizer-N recovery by the turfgrass over the 9-week experiments.

Effect of Filler Treatment on the Release Properties of Coating on Urea Granules

ABSTRACTPolyurethane composite coatings on urea granules were prepared by SBA-15 mesoporous silica (in as-synthesized and calcined forms) as a pseudo-crosslinker without any other chain extenders. The calcination of mesoporous silica leaded to reduction of hydroxyl groups and increase of mesopores. The composite coating containing calcined SBA-15 showed enhanced controlled release properties compared with the other two coatings. At the loading content of 1 wt%, the initial release rate and release duration of urea coated by polyurethane/calcined SBA-15 composite were 0.08% and 83 d, respectively. It is shown that the calcination played an important role in controlling the properties of composite coating.

Enhanced efficiency fertilizers (EEFs) do not increase nitrogen retention in Pacific Northwest Douglas-fir forest soils four weeks post-fertilization

Enhanced efficiency fertilizers (EEFs) are used to minimize gaseous losses of applied nitrogen (N). Higher N retention resulting in increased uptake by plants is intended to offset the additional cost of these EEFs. Pacific Northwest Douglas-fir forests are N limited and assumed to have high N retention rates. Assuming N retention rates are high can lead to the over application of fertilizers which is both economically inefficient and detrimental to ecosystem health. We tested the hypothesis that EEF-fertilized plots have the highest ecosystem N recovery rates by tracing four urea-based fertilizers for four weeks after application in five commercially managed Douglas-fir forests in Oregon and Washington. Three EEFs, Environmentally Smart Nitrogen (ESN), N-(n-butyl) (NBPT), and Arborite coated urea fertilizer (CUF), were tested along with unformulated urea granules. These three particular EEFs are designed to reduce volatile losses of ammonia (NH3(gas)). Fertilizers were enriched with 15N, which facilitates the tracing of N as it moves between ecosystem pools. Retention rates were calculated for the forest floor and mineral soil to a depth of 20 cm. Retention rates were not significantly improved with the use of EEFs. On average, 30.2% of the applied N was lost from the system after four weeks. The lack of improvement in N retention with EEFs suggests that volatilization may not be a substantial loss pathway at these sites and therefore the application of these higher cost EEFs is not warranted.

Synthesis and characterization of zinc-coated urea fertilizer

ABSTRACTThe research was focused on the synthesis and characterization of zinc (Zn)-coated urea fertilizer. Zinc oxide (ZnO) particles were coated on urea granules through two different coating techniques, i.e., slurry coating and wet coating, and the release rate of the coated Zn was measured up to 24 hours. Slurry coating technique showed better Zn release rate and morphology of coated urea granules as compared with wet coating technique using different binders, i.e., water, molasses, paraffin oil, and the combined mixture of honey bee wax and gum arabica. Urea granules synthesized through wet coating technique have a low amount of Zn as compared with slurry-coated urea granules. Urea granules coated through slurry coating technique and molasses, paraffin oil, and water (MPW) as a binder were the best in term of coating efficiency, uniform size distribution of ZnO-coated particles, granule's morphology, and release rate of Zn from coated formulations.

The study of dissolving urea granules based on the generalized dimensional analysis

The study of dissolving urea granules based on the generalized dimensional analysis

The effect of binder concentration in fluidized-bed granulation: Transition between wet and melt granulation

According to the binder nature, fluidized-bed granulation (FBG) is usually classified as wet or melt granulation. In particular, the industrial urea granulation performed in fluidized beds, is often called “melt granulation” because a highly concentrated urea solution is used as binder (between 95–97wt%) (Cotabarren et al., 2012). However, plant disturbances can cause changes in binder urea concentration and thus granulation can shift from melt to wet granulation and vice versa.In a previous investigation, the granulation system urea (seeds)–urea (binder) was extensively studied in a pilot-scale batch fluidized-bed granulator (Veliz Moraga et al., 2015). Besides, the effect of seed size, bed temperature, binder flowrate and fluidization and atomization air flowrates on process variables as well as on product properties were studied. The aim of this work is to analyze the effect of the binder urea concentration on the urea granulation performance and product properties. This concentration was varied from 87.5wt% to 98wt%, while the fluidization air velocity, urea melt flowrate, bed temperature set-point and atomization air flowrate were kept constant. The product properties (percentage of agglomerates and coated particles, crushing strength and moisture content) and granulation efficiency are discussed in terms of the transition from wet to melt granulation. The critical urea content was experimentally found; indeed, urea concentrations lower than the critical one dramatically affect the product quality. Finally, the criterion proposed by Villa et al. (2016) for predicting agglomerates formation is used to determine the minimum allowable binder urea concentration. The prediction is consistent with the trends experimentally observed, indicating the good capacity of the criterion to identify the boundary for agglomeration occurrence.

Preparation and characterization of slow-release fertilizer encapsulated by biochar-based waterborne copolymers

To enhance the effectiveness of polyvinyl alcohol (PVA) coated fertilizers, a novel slow-release fertilizer was developed using biochar and waterborne copolymer of PVA and polyvinylpyrrolidone (PVP) as coating materials. The effects of botanical origins and doses of biochar as well as copolymer concentrations on biochar-copolymer structures and properties were investigated. Our results indicated that the water absorbency of blend films differing in biochar origins showed different responses to these three factors. Generally, biochar decreased water absorbency of copolymer with an increased degradability, and contributed to improving the slow-release property of coated urea. In particular, rice biochar-based copolymer (S5 film) had less hydrophilic OH bonds and encapsulated urea granules more compactly and densely. The urea particles coated with rice biochar-based copolymer (S5 film) exhibited an excellent release behavior of 65.28% nutrient leaching on the 22th day. Therefore, this work has demonstrated the potential of biochar-based copolymer from different botanical biochar for improving the effectiveness of fertilizers.

Optimization of Fluidised Bed Granulation Process Parameters for Urea Granule Manufacturing Using the Response Surface Method

Fluidised bed technology is commonly applied in the pharmaceutical, agricultural and food production technology. The aim of this work is to identify the optimum process parameters in order to gain the best hardness and density values for the urea granules from the fluidised bed granulation. The layout of the experiments are based on Central Composite Design of Response Surface Method. The analyzed data shown that the optimize value for each of these parameter are 0.10MPa, 32.11Hz, 50% w/w, 42.250C for spray pressure, fan speed, urea solution concentration and inlet air temperature with 1.71 kgf/granule hardness and 1.85 g/cm3 density were predicted. Experimentally, using the predicted optimize input parameter, the hardness and density observed were 0.20 kgf/granule and 1.30 g/cm3 respectively.

Green coatings from renewable modified bentonite and vegetable oil based polyurethane for slow release fertilizers

A series of modified bentonite (MBT)/polyurethane (PU) composites were synthesized from MBT, isocyanate, and soybean oil‐based polyols byin‐situpolymerization to coat urea granules for slowing nitrogen (N) release. Bentonite (BT) was modified by intercalation of polyethylene glycol inside the interlayer space, expanded the BT layer spacing and improved the performance of composites. The MBT and MBT/PU composites were characterized in terms of their structure, thermal stability, mechanical strength, surface wettability, and the urea slow‐release performance. With the addition of 5.0 wt% MBT, its tensile strength is 13.53 MPa and breaking elongation is 20.66%, increased by 27.52% and 67.97%, compared with pure PU, respectively. The release duration of the PU‐5%‐MBT composites coated urea was 74 days. The results indicated that the modified films are suitable for the slow release fertilizers. POLYM. COMPOS., 39:4355–4363, 2018. © 2017 Society of Plastics Engineers

Development of control release urea fertilizer model for water and nitrogen movement in flooded rice

Application of control release fertilizer in rice cultivation is a smart way to reduce the environmental nitrogen contamination and enhance the nitrogen use efficiency. The effect of coating thickness and radius of urea granule on nitrogen release rate was modelled, but their effect on nitrogen transformation in soil was not modelled for any crop. In this study, a simple rice water and nitrogen balance model was integrated with a nitrogen release rate model and the effect of coated urea on nitrogen transformations was studied in the CRF-applied flooded rice. The simulated nitrogen release during urea hydrolysis was verified with literature data for uncoated, polymer-coated and mix urea (polymer-coated + uncoated) cases. The integrated model successfully predicted the lag, linear and decay periods of nitrogen release, and peak nitrogen concentration during urea hydrolysis and declining trend during nitrogen transformations. The integrated model could be used as a management tool for determining optimum coating thickness and urea radius for which the nitrogen loss to environment is minimum.

Hybrid brown coal-urea fertiliser reduces nitrogen loss compared to urea alone

Synthetic nitrogen (N) fertilisers, such as urea, are susceptible to rapid dissipation from soil. More gradual release of mineral N from fertiliser may reduce the off-site movement of mineral N, thereby enhancing N supply to crops and minimising negative off-site impacts. We hypothesised that granulation of urea with humified brown coal (BC) delays mineral N release and maintains higher concentrations of N in soil than conventional urea granules. Four different brown coal-urea granules, with C:N ratios of 1‐10, were prepared by pan granulation. Advanced spectroscopic and X-ray powder diffraction (XRD) techniques confirmed loading of urea-N into the BC structure. Nitrogen-release from BCU granules was slower than from urea, resulting in higher N retention over a longer period for increasing growth and N uptake by crop plants. This trend increased with higher loading of BC, emphasising the significant role of BC in N retention. These findings support the hypothesis that BC is suitable for developing slow release N fertilisers.

Additives incorporated into urea to reduce nitrogen losses after application to the soil

Abstract: The objective of this work was to develop urea-based fertilizers with internal incorporation of urease inhibitors and other additives in the granule. The effects of the incorporation of NBPT, copper (Cu+2), boric acid (H3BO3), elemental sulphur (Sº), and a clay mineral from the zeolite group in powder urea - with ten different combinations of these additives - were evaluated as to N losses by volatilization and leaching. The losses in laboratory-developed formulations were compared with those of commercial fertilizers coated with the same additives (Super N, FH Nitro Mais, and FH Nitro Gold). The evaluations were made in greenhouse conditions, using a Ultisol accommodated in PVC columns. Nitrate and ammonium leaching was evaluated in the solution percolated through the soil columns. Ammonia volatilization was measured with a semi-open static chamber. The incorporation of urease inhibitors (NBPT, H3BO3, and Cu+2) into the urea granules was efficient to reduce N volatilization. Ammonia volatilization in the laboratory-developed ureas was lower than in commercial fertilizers coated with the same additives, while ammonium sulfate losses by leaching were similar. The addition of zeolite does not reduce N volatilization. Mineral N leaching in the soil profile is not affected by urease inhibitors.

Bacterial impregnation of mineral fertilizers improves yield and nutrient use efficiency of wheat.

The fertilizer use efficiency (FUE) of agricultural crops is generally low, which results in poor crop yields and low economic benefits to farmers. Among the various approaches used to enhance FUE, impregnation of mineral fertilizers with plant growth-promoting bacteria (PGPB) is attracting worldwide attention. The present study was aimed to improve growth, yield and nutrient use efficiency of wheat by bacterially impregnated mineral fertilizers. Results of the pot study revealed that impregnation of diammonium phosphate (DAP) and urea with PGPB was helpful in enhancing the growth, yield, photosynthetic rate, nitrogen use efficiency (NUE) and phosphorus use efficiency (PUE) of wheat. However, the plants treated with F8 type DAP and urea, prepared by coating a slurry of PGPB (Bacillus sp. strain KAP6) and compost on DAP and urea granules at the rate of 2.0 g 100 g-1 fertilizer, produced better results than other fertilizer treatments. In this treatment, growth parameters including plant height, root length, straw yield and root biomass significantly (P ≤ 0.05) increased from 58.8 to 70.0 cm, 41.2 to 50.0 cm, 19.6 to 24.2 g per pot and 1.8 to 2.2 g per pot, respectively. The same treatment improved grain yield of wheat by 20% compared to unimpregnated DAP and urea (F0). Likewise, the maximum increase in photosynthetic rate, grain NP content, grain NP uptake, NUE and PUE of wheat were also recorded with F8 treatment. The results suggest that the application of bacterially impregnated DAP and urea is highly effective for improving growth, yield and FUE of wheat. © 2017 Society of Chemical Industry.

EFFECT OF ANHYDROUS-AMMONIA INJECTION ON PLANT AND SOIL MICRO-ORGANISMS BIOLOGICAL ACTIVITIES

Agricultural practices such as seedbed preparation systems and fertilization especially Anhydrous-Ammonia had a great impact on plant and soil microbial community which were sensitive indicators of changes in soil. A field experiment was carried out at the research farm of Rice Mechanization Center (RMC), Meet El-Deyba, Kafr El-Sheikh Governorate, during growing the winter wheat season 2015-2016 to study the interaction effect of anhydrous-ammonia injection and seedbed preparation systems on wheat growth/yield and soil micro-organisms biological activities. Anhydrous-Ammonia was injected in soil with two levels, of 75 Kg N/fed (A.A.1), and 94 Kg N/fed (A.A.2) which represent 100% and 125% of nitrogen recommended dose and granulated urea, (control) 46.5% at three doses according to agronomy recommendations. While, the applied seedbed preparation systems were Heavy system, HS (Moldboard plough one pass followed by Chisel plough twice and laser leveling), Moderate system, MS (Chisel plough one pass followed by Rotary twice and laser leveling) and Conventional system, CS (Chisel plough twice and wooden leveling). However, the used different wheat cultivars were Gemmiza 11and Shandweel. Soil micro-organism biological activity, wheat plant growth activity and wheat yield and its components were measured and determined to realize the objective of this investigation. The Soil micro-organism biological activity and wheat plant growth activity were done at different three times of 4 days, 1 month after Anhydrous-Ammonia injection and after wheat crop harvesting. The obtained results indicated that: The population and activity of soil micro-organisms increased as the length of time increased compared with applied Urea fertilizer. Approximately, one month after A.A.1 injection, the populations of a bacterial group were increased by an average of 57.8 and 58.6% while, the fungi group was increased by an average of 53.5 and 55.2% compared with 65.1 and 66.0% for actinomycetes group during growing Gemmiza 11 and Shandweel wheat cultivars, respectively. Using MS seedbed preparation system gave the highest values of the total grain yield of 18.5, 29.6 and 24.1 Ardb/Fed. were obtained for Gemmiza wheat cultivars compared with 17, 24.8 and 20.3 Ardb/Fed. for Shandweel wheat cultivars under applied fertilizer levels of Urea, A.A.1 and A.A.2, respectively. Finally, from mentioned above and analyses of yield and its components, the authors recommended the wheat farmers in Egypt using MS seedbed preparation system and applied fertilizer level A.A.1 to get high wheat yield and maintain the soil in a good biological state.

New Preparation, Characterization and Application for Coated Urea using Aswan Red Clay

To enhance the effectiveness of urea fertilizers, a new coated slow-release fertilizer was developed using Aswan Red Clay (ARC) and a binder material called chitosan a biodegradable polymer was used to improve the property of urea. Characterizations of slow release of the urea granules were made using Scanning Electron Microscopy technique and energy dispersive X-ray analysis. Refractive Index method used for determine the rate of releasing. Ammonia volatilization was estimated by using the forced-draft technique. The static release experiment showed that the urea coated by Aswan Red Clay (ARCCU) gave a release of 9.78% at the first day and 95.36 at 24 day, in the same condition. The results of ammonia that volatized during 6 weeks showed that the total losses of ammonia gas for uncoated urea( UCU) and coated urea was 59.54% and 43.33%, respectively which main that the coating of urea is most costly in application.

Inverse Modelling for Prediction of Coating Material Diffusivity and Lag Time of Controlled-Release Coated Urea Granule

Controlled release fertilizer (CRF) has attracted a lot of interest because of its advantages for ecosystem in terms of enhancement of nutrient utilization and reducing nutrient loss from leaching and volatilization, etc. While a number of research studies on novel coating material to control the release of nutrients, modelling has a significant role in predicting release behaviour and determining good CRF design that matches the nutrient requirement from the plants. The present study proposes a solution to predict coating material parameters based on multi-diffusion model and preliminary experimental results using inverse simulation technique. In addition, the solution showed an advantage in prediction the release of nutrient, i.e., the reduction in experimental time which plays an important role in investigation novel coating material and designing of CRFs which are matched the nutrient uptake from plants. Hence, this solution reduces experimental cost and time to researchers, who investigated novel CRFs.