Controlled-release Urea Fertilizers Research Articles

Assessing the Impact of Coated and Prilled Urea Fertilizers on Nitrogen Dynamics and Fodder Maize Yield in Alfisols

The study investigates the impact of different urea fertilizers on nitrogen mineralization, leaching losses, and growth, yield of fodder maize in Alfisols. Nitrogen is vital for plant growth but deficient in soils. Urea, a widespread nitrogen fertilizer, suffers from significant losses, prompting the development of controlled-release urea (CRU) fertilizers. This study assesses various urea formulations with coated urea and prilled urea. Laboratory incubation studies show that coated urea exhibits slower NH4+-N release, reducing losses and improving efficiency compared to uncoated urea. Nitrate content increases steadily periodically with coated urea, potentially enhancing nitrogen availability to plants. Greenhouse experiments reveal significant differences in plant height, leaf number, and leaf area among treatments. Coated urea formulations, chiefly CSPC @3%, demonstrate superior growth parameters (plant height-169.56cm, number of leaves-10.33 and leaf area-1850.59), yield (green fodder-328.25 gplant-1, dry fodder-198.61 gplant-1 and dry matter percentage-54.52) and quality parameters (crude protein-4.03, total ash content-3.82%) compared to prilled urea growth parameters (plant height-113.38cm, number of leaves-8.07 and leaf area-1670.98), yield (green fodder-246.26 gplant-1, dry fodder-116.35 gplant-1 and dry matter percentage-44.32) and quality parameters (crude protein-2.88, total ash content-2.75%), likely due to sustained nitrogen release. Higher nitrogen availability from coated urea leads to increased forage yield and quality. The findings suggest that coated urea fertilizers, specially CSPC @3% advocate improved nitrogen management, enhancing fodder maize productivity and sustainability.

Effects of Long-Term Controlled-Release Urea on Soil Greenhouse Gas Emissions in an Open-Field Lettuce System.

Controlled-release urea (CRU) fertilizers are widely used in agricultural production to reduce conventional nitrogen (N) fertilization-induced agricultural greenhouse gas emissions (GHGs) and improve N use efficiency (NUE). However, the long-term effects of different CRU fertilizers on GHGs and crop yields in vegetable fields remain relatively unexplored. This study investigated the variations in GHG emissions at four growth stages of lettuce in the spring and autumn seasons based on a five-year field experiment in the North China Plain. Four treatments were setup: CK (without N application), U (conventional urea-N application), ON (20% reduction in urea-N application), CRU (20% reduction in polyurethane-coated urea without topdressing), and DCRU (20% reduction in polyurethane-coated urea containing dicyandiamide [DCD] without topdressing). The results show that N application treatments significantly increased the GHG emissions and the lettuce yield and net yield, and DCRU exhibited the lowest N2O and CO2 emissions, the highest lettuce yield and net yield, and the highest lettuce N content of the N application treatments. When compared to U, the N2O emission peak under CRU and DCRU treatments was notably decreased and delayed, and their average N2O emission fluxes were significantly reduced by 10.20-20.72% and 17.51-29.35%, respectively, leading to a significant reduction in mean cumulative N2O emissions during the 2017-2021 period. When compared to U, the CO2 fluxes of DCRU significantly decreased by 8.0-16.54% in the seedling period, and mean cumulative CO2 emission decreased by 9.28%. Moreover, compared to U, the global warming potential (GWP) and greenhouse gas intensity (GHGI) of the DCRU treatment was significantly alleviated by 9.02-17.13% and 16.68-20.36%, respectively. Compared to U, the N content of lettuce under DCRU was significantly increased by 6.48-17.25%, and the lettuce net yield was also significantly increased by 5.41-7.71%. These observations indicated that the simple and efficient N management strategy to strike a balance between enhancing lettuce yields and reduce GHG emissions in open-field lettuce fields could be obtained by applying controlled-release urea containing DCD without topdressing.

Nitrogen Use Efficiency and Yield Levels Using Soluble and Controlled-release Urea Formulations in Tomato Production

This research study evaluated the suitability of controlled-release urea (CRU) as an alternate nitrogen (N) fertilizer source to conventional soluble urea (U) for tomato production under a humid, warm climate in coastal plain soils. Tomatoes are typically produced on raised plastic-mulched beds, where U is fertigated through multiple applications. On the other hand, CRU is applied once at planting, incorporated into soil before the raised beds are covered with plastic mulch. N source and management will likely impact tomato yield, N use efficiency (NUE), and apparent recovery of N fertilizer (APR). A 2-year field study was conducted on fall and spring tomato crops in north Florida to determine the crop N requirement and NUE in tomatoes (var. HM 1823) grown in sandy soils under a plastic-mulched bed system. In addition to a no N fertilizer treatment, three urea N sources [one soluble source and two polymer-coated CRU sources with different N release durations of 60 (CRU-60) and 75 (CRU-75) days] were applied at three N rates (140, 168, and 224 kg⋅ha−1). Across all N sources and N rates, fall yields were at least 20% higher than spring seasons. At the 140 kg⋅ha−1 N rate, APR and NUE were improved, especially when U was applied in fall tomato, whereas preplant CRUs improved N efficiency in spring tomato. Based on the lower APR values found in spring production seasons (0% to 16%) when compared with fall (57.1% to 72.6%), it can be concluded that residual soil N was an important source for tomatoes. In addition, the mean whole-plant N accumulation of tomato was 102.5 kg⋅ha−1, further indicating that reducing the N rate closer to crop N demand would greatly improve conventional vegetable production systems on sandy soils in north Florida. In conclusion, polymer-coated CRU and fertigation U applications were able to supply the N requirement of spring and fall tomato at a 38% reduction of the recommended N rate for tomato in Florida (224 kg⋅ha−1). Preliminary results show that adoption of CRU fertilizers can be considered a low-risk alternative N source for tomato production and the ease of applying CRU once during the bed preparation period for tomato may be an additional incentive.

Effects of straw returning combined with blended controlled-release urea fertilizer on crop yields, greenhouse gas emissions, and net ecosystem economic benefits: A nine-year field trial

Although straw returning combined with blended controlled-release urea fertilizer (BUFS) has been shown to improve wheat-maize rotation system productivity, their effects on greenhouse gas (GHG) emissions, carbon footprints (CF), and net ecosystem economic benefits (NEEB) are still unknown. Life cycle assessment was used to investigate a long-term (2013–2022) wheat-maize rotation experiment that included straw combined with two N fertilizer types [BUFS and (conventional urea fertilizer) CUFS] and straw-free treatments (BUF and CUF). The results showed that BUFS and CUFS treatments increased the annual yield by 13.8% and 11.5%, respectively, compared to BUF and CUF treatments. The BUFS treatment increased the yearly yield by 13.8% compared to the CUFS treatment. Since BUFS and CUFS treatments increased soil organic carbon (SOC) sink sequestration by 25.0% and 27.0% compared to BUF and CUF treatments, they reduced annual GHG emissions by 7.1% and 4.7% and CF per unit of yield (CFY) by 13.7% and 9.6%, respectively. BUFS treatment also increased SOC sink sequestration by 20.3%, reduced GHG emissions by 10.7% and CFY by 23.0% compared to CUFS treatment. It is worth noting that the BUFS and CUFS treatments increased the annual ecological costs by 41.6%, 26.9%, and health costs by 70.1% and 46.7% compared to the BUF and CUF treatments, but also increased the net yield benefits by 9.8%, 6.8%, and the soil nutrient cycling values by 29.2%, 27.3%, and finally improved the NEEB by 10.1%, 7.3%, respectively. Similar results were obtained for the BUFS treatment compared to the CUFS treatment, ultimately improving the NEEB by 23.1%. Based on assessing yield, GHG emissions, CF, and NEEB indicators, the BUFS treatment is recommended as an ideal agricultural fertilization model to promote sustainable and clean production in the wheat-maize rotation system and to protect the agroecological environment.

Controlled-release urea for use in sugarcane ratoons

Urea is the main solid N fertilizer used worldwide. Among its advantages are the high nutrient content, ease of handling and application, and low cost. Urea is subject to high losses through NH3 volatilization if surface-applied on soils. Therefore, ammonium nitrate is the preferred N source, especially in the ratoon cycles. Urea treated with the urease inhibitor NBPT and controlled-release fertilizers are options to replace ammonium nitrate. Controlled-release urea (CRU) is produced by coating the urea granules with resin or synthetic polymers so that the urea in the nucleus is not in contact with soil moisture. This study aimed to test CRU in sugarcane ratoons compared with ammonium nitrate (AN) and urea treated with urease inhibitor (UR-NBPT) at three rates: 60, 120 and 180 kg ha–1. Efficiency was also compared with two control treatments, the N control and the NPK control. Two field experiments were established and conducted in 2020 and 2021 in Sao Paulo state, Brazil. Sugarcane yield was evaluated in both experiments. N losses as NH3 volatilized were measured in the first experiment. All sources were equally efficient in promoting increases in sugarcane ratoon yield in both experiments. The relative yield obtained with N fertilizers and the control without N showed yield increases in the first experiment of 40, 54 and 68% for 60, 120 and 180 kg N ha–1 as AN, respectively; 29, 61 and 61% for 60, 120 and 180 kg N ha–1 as urea-NBPT, respectively; and 32, 62 and 67% for 60, 120 and 180 kg N ha–1 as CRU, respectively. Yields were higher in the second experiment, but increases in yield were lower compared to the first. Increases of 7, 10 and 16% for AN in three doses, 5, 12, 15% for UR-NBPT and 7, 9 and 14% for CRU were observed, respectively. N losses as NH3 volatilized were relatively low; CRU fertilizer showed good protection against NH3 losses by volatilization, protecting urea for about 30 days. This protection, however, did not affect yield. NH3 losses reached 13% of the N applied in the treatment with urea (about 16 kg N ha–1), 11% for Urea-NBPT (about 13 kg N ha–1) and 9% for CRU (about 11 kg N ha–1). Analyzing the results of both experiments CRU did not show an advantage in efficiency compared to AN and Urea-NBPT.

Evaluating How Enhanced Efficiency Nitrogen Fertilizers Improve Agricultural Sustainability: Greenhouse Multi-Phase Tracking System

The vast consumption of nitrogen-based fertilizers is a significant source of environmental pollutants in all phases. While enhanced-efficiency nitrogen fertilizers (EENFs) improve N-use efficiency and reduce environmental impact, their performance depends on local conditions. Here, we present a relatively simple soil–fertilizer–plants greenhouse setup for the multi-phase tracking of N species of the effects of EENFs. We compared the environmental and agronomic performance of three urea-based EENFs (urea embedded with urease inhibitors, 2-month, and 4-month controlled release urea) and the common split surface application of the granulated urea. We tested the fertilizer applications on basil seedlings for three consecutive growing cycles. The analyses carried out included nitrogen recovery in plant biomass, soil, drainage, and NH3 and N2O emissions. This multi-phase research indicates that tested EENFs perform better than the standard surface-applied urea. The four-month controlled-release urea fertilizer matched the basil N demand the best, significantly increasing yield and improving nitrogen use efficiency while reducing NO3− leaching and NH3 and N2O emissions. The presented soil–fertilizer–plants experimental setup provides a relatively easy-to-handle system for the comprehensive tracking of N dynamics, including plant response. It allows stakeholders to estimate and improve fertilization sustainability.

A Controlled-Release Nanofertilizer Improves Tomato Growth and Minimizes Nitrogen Consumption.

Minimizing the consumption of agrochemicals, particularly nitrogen, is the ultimate goal for achieving sustainable agricultural production with low cost and high economic and environmental returns. The use of biopolymers instead of petroleum-based synthetic polymers for CRFs can significantly improve the sustainability of crop production since biopolymers are biodegradable and not harmful to soil quality. Lignin is one of the most abundant biopolymers that naturally exist.In this study, controlled-release fertilizers were developed using a biobased nanocomposite of lignin and bentonite clay mineral as a coating material for urea to increase nitrogen use efficiency. Five types of controlled-release urea (CRU) were prepared using two ratios of modified bentonite as well as techniques. The efficiency of the five controlled-release nano-urea (CRU) fertilizers in improving the growth of tomato plants was studied under field conditions. The CRU was applied to the tomato plants at three N levels representing 100, 50, and 25% of the recommended dose of conventional urea. The results showed that all CRU treatments at the three N levels significantly enhanced plant growth parameters, including plant height, number of leaves, fresh weight, and dry weight, compared to the control. Additionally, most CRU fertilizers increased total yield and fruit characteristics (weight, length, and diameter) compared to the control. Additionally, marketable yield was improved by CRU fertilizers. Fruit firmness and acidity of CRU treatments at 25 and 50% N levels were much higher than both the 100% CRU treatment and the control. The vitamin C values of all CRU treatments were lower than the control. Nitrogen uptake efficiencies (NUpE) of CRU treatments were 47-88%, which is significantly higher than that of the control (33%). In conclusion, all CRU treatments at an N level of 25% of the recommended dose showed better plant growth, yield, and fruit quality of tomatoes than the conventional fertilizer.

水氮调控对根层土壤 Na+及耐盐水稻产量的影响

The cultivation of salt-tolerant rice (sea rice) along beaches has become an effective measure for the restoration and utilization of saline-sodic land, so this paper studies the effects of irrigation and nitrogen fertilization on soil Na+ in root zone and sea rice yield, and provides a scientific basis for planting sea rice. A pot experiment (two-factor split plot) of sea rice with salt stress (10 g NaCl/kg soil) was carried out. The main plot consists of three types of irrigation methods: flooding irrigation (F), intermittent irrigation (I), and controlled irrigation (C). The subplots are three types of nitrogen fertilizers: urea (U), controlled-release urea (R), and mixed fertilizer (M) with U and R. The results showed: (1) The soil water-soluble Na+ of MI was significantly smaller than that of other treatments with NaCl, but the Ca2+/Na+ and Mg2+/Na+ were opposite. (2) The nitrogen uptake and dry weight of rice of MI were significantly larger than those of other treatments with NaCl, and were respectively 23% and 32% higher than UI, 49% and 16% higher than MF, 56% and 38% higher than UF, 75% and 61% higher than RI, 76% and 50% higher than RF. (3) The sea rice yield of MI was increased by 105%, 154%, 262%, 338%, and 428% compared with MF, RF, UF, RI, and UI, respectively. Therefore, the MI can effectively reduce the Na+ and increase the Ca2+/Na+ and Mg2+/Na+ in root layer soil, and promote the nitrogen absorption and production of sea rice. So the article recommends that M and I methods should be adapted to plant sea rice on coastal saline-sodic soil.

Green Bio-composite Coating Film from Lignin/Pre-vulcanized Natural Rubber Latex for Controlled-release Urea Fertilizer

Green Bio-composite Coating Film from Lignin/Pre-vulcanized Natural Rubber Latex for Controlled-release Urea Fertilizer

A tunable controlled-release urea fertilizer coated with a biodegradable polyurethane-nanoclay composite layer

A tunable controlled-release urea fertilizer coated with a biodegradable polyurethane-nanoclay composite layer

Novel coating films containing micronutrients for controlled-release urea fertilizer: release mechanisms and kinetics study

Novel coating films containing micronutrients for controlled-release urea fertilizer: release mechanisms and kinetics study

Chitosan microspheres-based controlled release nitrogen fertilizers enhance the growth, antioxidant, and metabolite contents of Chinese cabbage

Agriculture lands have low fertilizer retention owing to porosity and irrigation, whereas a significant portion of fertilizer is lost through denitrification, volatilization, surface run-off, and leaching, causing losses of nutrients to air and ground/surface water. Urea fertilizer readily enhances the agricultural yield but also deteriorates the quality of fertile soils. To combat such problems, researchers are seeking to formulate controlled-release or slow-release fertilizers. We used chitosan microspheres as a carrier to encapsulate urea through emulsification and cross-linking techniques to reduce the wastage of urea fertilizer due to evaporation and water flow. Scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy were used to characterize chitosan microspheres and urea-loaded microspheres. Chitosan microspheres and urea-loaded microspheres were authenticated by FT-IR, showing 89% of urea successfully incorporated with chitosan microspheres. Then an experiment was run to compare the effects on plant growth, antioxidant and metabolite contents with and without added nitrogen fertilizer. Various amounts of urea per pot were applied to Chinese cabbage, including T1 0.5433 g, T2 0.6033 g, T3 0.8033 g, CK 0.00, while the same content of urea in chitosan microspheres as T4, T5, T6, and T0 (no urea), respectively. The results indicated that chitosan microspheres-based controlled release nitrogen fertilizers (Cm-CRNFs) had higher seed germination (96%), plant height (17.04 cm), number of leaves (11.00), and leaf length (110.19 mm) as compared to urea and control treatments. In addition, Cm-CRNFs treatment enhanced net photosynthetic rate, stomatal conductance, transpiration rate, fluorescence, dark respiration rate, total sugar, proteins, flavonoids, and polyphenols. Overall, Cm-CRNFs showed promising results in all treatments for all tested physiochemical and growth parameters. It is concluded that controlled release urea fertilizers based on chitosan microspheres can be developed with a simple process. The fertilizers are biocompatible, economically viable, and environment-friendly, and have the potential to prolong the release of macronutrients and micronutrients for plant growth.

Hydrogel Composite Based On Arrowroot Starch-G-Poly (Acrylamide-Co-Acrylic Acid)/Zeolite as Matrix of Controlled Release Urea Fertilizer

Agricultural yields can be increased through fertilization. Conventional fertilization by spreading fertilizer on agricultural land is very ineffective. As much as 40-70% of the nitrogen from urea given through conventional fertilization will be leaching. This problem can be overcome by implementing a new fertilization system, namely by applying controlled fertilizer release technology or Control Release Fertilizer (CRF). The CRF system is made by loading or mixing urea fertilizer at the time of synthesis of a composite based on Arrowroot Starch-g-poly (acrylamide-co-acrylic acid)/zeolite. Fertilizer will come off gradually during fertilizing the land. Synthesis of starch-based hydrogel composite Arrowroot Starch-g-poly (acrylamide-co-acrylic acid)/zeolite loaded or mixed with urea fertilizer, has been successfully carried out. The composite's structure characterized by IR spectroscopy and its ability as CRF has also been tested through swelling and urea release tests in distilled water, phosphate buffer pH 5, pH 7 and pH 9. The results show that the swelling capacity and urea release in distilled water > Buffer pH 7 > pH 9 > pH 5. The welling degree in distilled water, Buffer pH 5, pH 7 and pH 9 is 39.078; 18,719; 36,296 and 33,510 g.g-1 respectively and the release of urea is 2,129; 1,829; 2,110; and 2,091 mg.mL-1 respectively and they showed significant differences.

Effects of reducing and postponing controlled-release urea application on soil nitrogen regulation and maize grain yield

Controlled-release urea (CRU-N) fertilizer application is a solution to improve the utilization rate of nitrogen (N), reduce economic costs and improve crop yields. It is significant to study the effects of release CRU-N reduction and the combined application of conventional urea on soil N control and the large-scale maize planting system. In this study, the effects of controlled-release nitrogen fertilizer reduction and postponement on soil nitrogen components, enzyme activities, and yields were investigated. Seven treatments were set up in this study, including no N fertilizer (CK), 100% conventional urea (U), 100% controlled-release urea (S), 30% controlled-release urea (SU3/7), 50% controlled-release urea (SU5/5), 70% controlled-release urea (SU7/3) and Sodium Salt of Polyaspartic Acid (PASP)-N. The results showed that mixed CRU-N and urea increased yields and net benefits compared with conventional urea at the same application rate of N, and reduced N loss. The application of CRU-N at 70% for maize represented the best overall effects. Compared with U treatment, soil ammonium nitrogen (NH4-N), soil nitrate-nitrogen (NO3-N), and microbial biomass nitrogen (SMB-N) of CRU-N at 70% (SU7/3) increased by 35.00%, 15.53%, and 25.04%. However, soil nitrate reductase (S-NR) and urease (S-UA) were the best in SU5/5 and significantly higher than other treatments. The applications of CRU-N would effectively increase soil N; CRU-N in 50% proportion can promote the maize root growth and improve the efficient utilization of N by soil microorganisms. Like the yields (9186.61 kg/hm2), expertly in the proportion of 70% CRU-N (SU7/3) plays a vital role in a wheat-maize rotation system, which can potentially be used to improve the yields, nitrogen use efficiency, and net benefit with low N losses. In conclusion, using CRU-N fertilize effectively improves soil nitrogen, and various ratios of CRU-N can ensure the continuous release the nutrients during the growing period. And among the different proportions of CRU-N, it is optimal in SU7/3. Keywords: controlled-release urea, nitrogen regulation, maize grain yield, soil, reducing, postponing DOI: 10.25165/j.ijabe.20221501.6888 Citation: Ji P T, Peng Y J, Cui Y W, Li X L, Tao P J, Zhang Y C. Effects of reducing and postponing controlled-release urea application on soil nitrogen regulation and maize grain yield. Int J Agric & Biol Eng, 2022; 15(1): 116–123.

Effect of biodegradable polymer coated urea fertilizers for the growth and yield of hybrid maize (Zea mays L.)

Urea is an instantaneous fertilizer, releasing nitrogen (N) rapidly after application to soil as it is effectively lost as ammonia volatilization and nitrate leaching which causes nitrogen inadequacy around roots and in the long run causes a deficiency between nitrogen demand and supply. The nitrogen from controlled-release urea can be consumed by crops more congenial than the nitrogen from uncoated urea. A pot culture experiment was carried out to investigate the response of maize crop to controlled-release urea fertilizers. Three different coated materials were utilized to coat on urea viz., palm stearin, pine oleoresin, humic acid. Different thicknesses of coated urea were developed such as palm stearin coated urea (PSCU) 5, 10, 15%, pine oleoresin coated urea (POCU) 2, 4, 6%, and humic acid coated urea (HACU) 5, 10, 15%. The coated urea fertilizers impacted the growth and yield of maize and increment the yield from 26.7 – 33.5% over the uncoated urea. The most noteworthy rate augmentation of yield was seen in HACU 15% (33.5%) trailed by POCU 4% (32.4%) and PSCU 10% (32.1%). It was inferred that, better synchronization between the nitrogen Release from coated urea fertilizers and growth of maize throughout the growing season.

Mixture of controlled-release and conventional urea fertilizer application changed soil aggregate stability, humic acid molecular composition, and maize nitrogen uptake

Controlled-release urea (CRU) fertilizer application has been shown to improve crop yield and nitrogen (N) use efficiency. However, its effects when mixed with conventional urea fertilizer on soil aggregate stability, humic acid (HA) molecular composition and crop N uptake remain unclear. Soil and plant samples were collected from a long-term (2008–2019) experiment on field maize (Zea mays L., ‘Zhengdan 958’) which included two types of fertilizers [conventional urea fertilizer (CUF), blended CUF with CRU fertilizer (CRF)], four N application rates (0, 150, 300 and 450 kg ha−1), each in three replicates. The results showed that at 300 kg N ha−1, compared to CUF treatment, the CRF treatment significantly improved soil aggregate characteristics [aggregate content with particle size larger than 0.25 mm (R0.25) by 9.6%, mean weight diameter by 19.8%, and geometric mean diameter by 21.7%]. CRF treatment also increased HA content by 5.5%, fulvic acid (FA) by 5.5%, lignin-like molecules by 0.94 times, and protein-like molecules by 3.69 times. At grain-filling stage, CRF treatments significantly increased the sum of soil NH4+-N and NO3−-N content by 23.3–24.5%, sap bleeding rate by 12.8–18.2% and N delivery rate through bleeding sap by 60.6–87.7% compared to CUF treatments at the same N application rate. At the same rate of N application, the CRF treatments significantly improved the average yield during three growing seasons by 9.4–14.0% in contrast with CUF treatments. The regression equations showed that the maximum yield was 8294 kg ha−1 for CUF at the application rate of 312 kg N ha−1 while it was 9890 kg ha−1 for CRF at the application rate of 286 kg N ha−1. We conclude that the long-term application of CRF changed the HA molecular structure, enhanced the water stable aggregates, improved crop N uptake, and increased economically viable maize yield.

Optimization of Pan Coating Process for Increased Efficiency of Controlled-Release Urea Fertilizer

The goal of the research is to develop an experimental mathematical model of pan coating process effect on the biodegradable polymer and to determine optimal process parameters. The polymer solution was conducted with phosphated di-starch phosphate, polyvinyl alcohol, and polyacrylic acid and performed as material coating for the controlled-release urea fertilizer. The image analysis method has been used to determine the particle size distribution, Sauter mean diameter of the particle and layer thickness that is novel. The central composite rotatable design has been selected to determine the regression models of the process, which described the relationship between two objective variables as layer thickness, release time with angle of pan, spray flow, and coating time. The statistical analysis results indicate the fitness of model.

Empirical scale-up model of pan-coating process for controlled-release urea fertilizer production

An empirical scale-up model of the pan-coating process for controlled-release urea fertilizer (CRUF) was novel performed via a pan-coating process using the biodegradable polymer solution. The similarities in the geometry, kinetics, dynamics, and thermodynamics during the scaling-up of the pan-coating process were analyzed. The dimensionless numbers and a dimensionless number equation were determined and derived, respectively. The thickness of the formed coating related almost to the air velocity and the pan speed. This model showed the significant applications in the design and optimization of industrial particle-coating systems.

Reducing nitrogen leaching while enhancing growth, yield performance and physiological traits of rice by the application of controlled-release urea fertilizer

Controlled-release urea fertilizer (CRUF) consists of urea granules intercalated within the lattice of a superabsorbent composite to control urea release thereby improving nitrogen supply and minimizing environmental hazards. In this work, new formulations for controlled-release urea were prepared based on biodegradable polymers and agricultural waste. Following CRUF preparation, the release behavior of urea in aqueous medium was estimated, and the effect of medium pH on release behavior was also examined. A pot experiment was carried out on rice plants to examine the growth, yield performance and physio-biochemical traits (soluble proteins, amino acids, reducing and total free sugars, starch, proline and phenolics) of rice grains at different dosages (10, 25, 50, 75 and 100 kg ha−1) of CRUF under drought conditions (50% FC). Water stress adversely affected rice growth, membrane leakage and yield components (tiller length, filling ratio, grains mass and number per tiller). Drought exposure has influenced the physiological response of rice grains. Drought markedly increased proteins, amino acids, reducing and total free sugars and proline, but decreased starch and phenolic contents of rice grains. The application of CRUF mitigated water stress via improving the growth and yield parameters of rice plants. CRUF significantly decreased protein, amino acids, reducing sugars and proline contents but remarkably increased free sugars and starch contents of rice grains. Application of CRUF predominantly enhanced water and nutrients use efficiencies, contributing to improved metabolic machinery of droughted rice through reducing osmotic and oxidative stress levels by continued rhizophore moistening, extended urea nitrogen existence and enhanced soil characteristics.

Hydroxyapatite nanorods, hydrochar, biochar, and zeolite for controlled-release urea fertilizers

This study aimed to prepare, characterize, and investigate nitrogen (N) release pattern of urea-impregnated biochar (UB), hydrochar (UH), zeolite (UZ) as carriers, and urea-hydroxyapatite nanohybrids (U-HAP) in water and a calcareous waterlogged soil. The results indicated that the urea had interactions with carriers and hydroxyapatite nanorods which controlled the release of urea. The UH, UB, UZ, and U-HAP reduced the urea release by 4.5, 6.5, 9.0, and 11.5 times, respectively compared to the urea only. The kinetics of urea release from these fertilizers showed the best fit of the Korsmeyer-Peppas model following the Fickian diffusion law. Another experiment was carried out using 14 treatments including control, rice straw, hydrochar, biochar, and zeolite with and without urea application and UH, UB, UZ, and U-HAP fertilizers. The extractable-NH4+ was measured using 2 M KCl solution in different times (0, 0.5, 1, 3, 6, 12, 20, 30, 45, 70, and 100 days) after application of prepared fertilizers. The results showed that >85% of the applied urea was converted to NH4+ within 12 days in the urea-alone treatment. However, 20 days after the application of the UH, UB, UZ, and U-HAP in soil, 89.9, 76.5, 75.0, and 58.1 percent of urea was converted to NH4+, respectively. After the application of all controlled-release urea fertilizers, the extractable-NH4+ concentration increased initially but after 20 days decreased with time and the rate of reduction was lower in the UB, UZ, and U-HAP as compared to other treatments. Also, the kinetics of extractable-NH4+ showed the best fit to the Extreme model. The results showed that the UB, UZ, and U-HAP slowly released urea which may reduce N loss and increase its use efficiency in calcareous paddy soils.