Slow-release Urea Fertilizer Research Articles

Development and characterization of slow release N and Zn fertilizer by coating urea with Zn fortified nano-bentonite and ZnO NPs using various binders

The fertilizer use-efficiencies particularly of nitrogen (N), phosphorus (P), and zinc (Zn) in alkaline soils are often seriously low. The surplus N released from the conventional fertilizers pollutes the environment and causes climate change. Slow or controlled release N fertilizer can improve its use efficiency and decrease its environmental impacts. Previously, we have shown that the ZnO nanoparticles (ZnO NPs) has higher use efficiency than the conventional Zn fertilizers. In this study, we focused on the development of Zn coated slow-release urea fertilizer. For this purpose, ZnO NPs and Zn fortified nano-bentonite were coated on urea by using various binders. The coated fertilizers ZU1& ZU2: nano-bentonite (4%) & ZnO NPs (2%) + vegetable oil respectively, ZU3 & ZU4: nano-bentonite (4%) & ZnO NPs (2%)+stearic acid+ paraffin oil+ paraffin wax respectively was prepared. The coated granules were characterized by using SEM, XRPD techniques. Zn and N release was evaluated in a soil incubation experiment. The results showed that ZU4 and ZU2 released higher amounts of Zn (3.9 and 3.42 mg kg −1) respectively while the prolonged release of Zn (>30 days) was observed from ZU3 and ZU4. Similarly, a significant reduction in N release from ZU3 and ZU4 (15 days) was observed while the rapid release of N from ZU1, ZU2, and control (first 5 days) was recorded. It was concluded that coated urea with ZnO NPs and Zn fortified nano-bentonite using stearic acid, paraffin oil, and paraffin wax as binder can act as an efficient slow-release macro micronutrient fertilizer.

Impact of UREAStable on Soil Property, Nitrogen Use Efficiency and Yield of Durum Wheat under Balanced Fertilizer Application

Wheat requirement of nitrogen for plant growth, and crop yields and quality depends upon substantial N inputs. Therefore, a field experiment was carried out at Gimbichu district in 2017 and 2018 main cropping season with the objective of evaluating the overall performance of applying slow-release/UREAstable fertilizer over the conventional urea fertilizer for durum wheat production, and to determine optimum rates of slow-release urea fertilizer for wheat productivity. The treatments consisted of Control, 90 kg N ha-1 from conventional urea applied in split, 90 kg N ha-1 from UREAstable applied once at planting, 90 kg N ha-1 from UREAstable applied in split, 45 kg N ha-1 from UREAstable applied once at planting, 45 kg N ha-1 from UREA stable applied in split form, 135 kg N ha-1 from UREA stable applied in split form, 135 kg N ha-1 from conventional UREA applied in split form and 135 kg N ha-1 from UREAstable applied once at planting. The results revealed that plant height, spike length, Tiller number, grain yield, biomass yield, harvest index and grain and straw uptake were significantly (P<0.05) affected by the application of slow release and conventional urea fertilizer. The highest spike length (3.8cm), Tiller number (2.1), grain yield (2205 kg ha-1), biomass yield (6968 kg ha-1) and nitrogen grain straw uptake (35.6 kg N ha-1) were recorded from 135kg N ha-1 urea stable fertilizer applied in split form followed by application of 135 kg N ha-1 conventional urea fertilizer applied in split form. While, maximum straw nitrogen uptake was obtained from application of 135 kg N ha-1 conventional urea fertilizer applied in split form. Therefore, taking the findings of the present study consideration it may be concluding that farmers can use 135 kg N ha-1 UREAstable fertilizer to improve nitrogen use efficiency and productivity of wheat in the study area in addition to conventional urea fertilizer. However, further research may be required at various locations to come up with an inclusive recommendation.

Formulation and characterization of water retention and slow-release urea fertilizer based on Borassus aethiopum starch and Maesopsis eminii hydrogels

Environmentally friendly slow-release fertilizers (SRF) based on Borassus aethiopum starch (BAS-SRF) and Maesopsis eminii (ME-SRF) hydrogels were formulated by encapsulating urea into biomaterials using borax as a binder. The SRFs were characterized by FT-IR, SEM and XRD techniques. The gel ratios of the hydrogels were found to be 71.27 ± 0.31 and 57.43 ± 2.27 for BAS-SRF and ME-SRF respectively. Swelling and water retention capacity of the SRFs in distilled water, NaCl, CaCl2, and FeCl3 solutions were evaluated. The water retention ratio at 4 days was similar 14.76% for both BAS-SRF and ME-SRF in soil and 4.67% for soil without the SRFs. The swelling ratio of the SRFs in solution, followed the order Water > NaCl > CaCl2>FeCl3. The swelling kinetics fitted with Scott's second order swelling kinetic model. The fertilizer release of the standard urea (un-capsulated) in distilled water revealed a cumulative release of about 97% within an hour. Whereas the formulated BAS-SRF and ME-SRF (encapsulated) had a cumulative release of 76% and 68% at 24 h and 96 h respectively. Interestingly, a sustained cumulative urea release was observed in soil; about 95% and 92% at 36 days for BAS-SRF and ME-SRF respectively.

Slow release fertilizer prepared with lignin and poly(vinyl acetate) bioblend

Controlled or slow release fertilizers have been recommended to enhance crop yield, while minimizing environmental and economic issues related from current fertilizer applications. However, alternative biodegradable and non-toxic coating material should be suggested to produce biocoated fertilizers. Here we propose the use of lignin and poly(vinyl acetate) (PVAc) as biocoating materials for preparing slow release urea fertilizer. The blend of PVAc and lignin at a mass ratio of 75:25 improved the characteristics of the formed film and increased the nitrogen release time if compared to the pure polymers. The nitrogen release time from urea granules coated with a polymeric layer of 154.3 ± 5.5 μm formed by lignin and PVAc was 36 times greater than from bare urea. The increase in the polymeric coating from 52.6 ± 5.2 to 80.2 ± 6.1 μm decreased the curvature of the nitrogen release data by a factor of at least 1.7, while the curvature was decreased in at least 1.3 with the increase in the polymeric coating from 80.2 ± 6.1 to 158.9 ± 10.6 μm. The adjustment of nitrogen release data to the Peppas-Sahlin model indicated the Fickian diffusion is more predominant than relaxation contributions, since the used polymers did not present considerable swelling. Thus, the blending of PVAc and lignin at 25 wt% of lignin and 75 wt% of PVAc is suggested as a biocoating material for producing slow release fertilizers.

Biodegradable hydrogels of cassava starch-g-polyacrylic acid/natural rubber/polyvinyl alcohol as environmentally friendly and highly efficient coating material for slow-release urea fertilizers

Biodegradable semi-IPN hydrogels of cassava starch (CSt)-g-polyacrylic acid (PAA)/natural rubber (NR)/polyvinyl alcohol (PVA) at different NR/PVA ratios were developed as low-cost coating membrane for improving slow-released fertilizer with low negative impact on environments. The effect of NR/PVA ratios on mechanical properties, swelling behavior, water retention and biodegradation of the semi-IPN hydrogels was evaluated. The biodegradable hydrogel wax coated urea (BHWCU) was produced by coating urea particles with semi-IPN hydrogel and wax as inner and outer layers, respectively. Results revealed that the higher NR/PVA ratios caused the significant decrease in water swelling, modulus, water-retention and biodegradation of the hydrogels. The BHWCU/9:1 formulation exhibited an excellent slow-release N nutrient in both water (47.5% at 168 h) and soil (38.5% at 30 day), relating well with the lowest surface area (1.95 m2/g) and pore volume (3.75 × 10−3 cm3/g). The release kinetics of BHWCUs in both water and soil followed the Korsmeyer-Peppas model. The released nutrient from the BHWCU/9:1 was strongly depended on the pH, temperature and ionic strength. The growth of chili plant was effectively facilitated by the BHWCU/9:1 having 4–5 times lower production cost (80.36 Baht/kg) than commercial slow-release fertilizer. Thus, the BHWCU formulations could be extensively applicable in sustainable agriculture.

Synthesis of a novel superabsorbent with slow-release urea fertilizer using modified cellulose as a grafting agent and flexible copolymer

In this work, a number of glucose unites in polymeric structure of cellulose was converted to 2,4-dihydroxy-3-(1-hydroxy-2-oxoethoxy)butanal (cellulose containing di aldehyde units (CCDAUs)) by oxidation with sodium periodate, followed by condensation with acetone to produce 5,7-dihydroxy-6-((1-hydroxy-4-oxopent-2-en-1-yl)oxy)hept-3-en-2-one unites (cellulose containing di ene units (CCDEUs)). This modified cellulose was characterized by different methods and applied as a copolymer and grafting agent to synthesize an eco-friendly (CCDEUs-g-poly(AA)/urea) superabsorbent with slow-release urea fertilizer. The created double bonds in C2 and C3 positions of β-d-glucose units increased the linkage between cellulose and acrylic acid, leading to the formation of a strong network for slow-release urea fertilizer. Also, this modification created an expanded network for storage a high amount of water by increasing the cellulose flexibility. The reaction conditions for modification and synthesis of the superabsorbent, the oxidation degree value of glucose units, kinetics models, the effect of different saline solutions, various pH and reswelling time on the water absorbency, water retention capacity, reusability, biodegradability, and slow-release property were investigated. Also, the effect of synthesized CCDEUs-g-poly(AA)/urea on plant growth was tested and excellent results were obtained.

DESIGN AND EXPERIMENT OF ADJUSTABLE SOCKET-WHEEL PRECISION FERTILIZER APPARATUS FOR DRY DIRECT-SEEDING RICE

To solve problems of non-adjustable fertilizer and low fertilization precision in the precision hole fertilization of dry direct-seeding rice, an adjustable socket-wheel precision hole fertilizer apparatus for rice was designed. The basic structure and working principle of the fertilizer apparatus were expounded, the structural parameters of key components were determined. The numerical simulation experiments based on the discrete element method were carried out by using sulfurized urea as the research object. Selecting the rotation speed of the socket-wheel, the length of the trough, the depth of the socket as the experimental factors, and taking the average amount of fertilizer discharging and the coefficient of variation of fertilization uniformity as evaluation indicators, the orthogonal rotation combined experiments with three factors and five levels were carried out. A multi-objective optimization method was used to determine the best parameter combination under the constraint of the target value of the hole fertilizer discharging of 1.500 g. The simulation results show that the coefficient of variation of fertilizer uniformity was the smallest and the coefficient of variation was 15.80% when the rotation speed of socket-wheel was 26.57 r/min, the length of the trough was 5.36 mm and the depth of socket was 5.64 mm. By using slow-release urea, sulfurized urea and bio-organic fertilizer as test materials, the bench test and field test was carried out on the fertilizer apparatus and the reliability of the simulation results and the adaptability of the fertilizer apparatus were verified.

Biochar Based Slow-Release Urea Fertilizer: Production and Assessing the Effects on Growth of Lowland Rice and Nitrogen Dynamics in an Alfisol

Use efficiency of N fertilizers in lowland rice cultivation is very low. Biochar can be used to modify the N releasing rates of fertilizers and increase their efficiency. Maximum amount of urea that can be intercalated into biochar (BC) and the effects of biochar based slow-release urea fertilizer (SRF) on soil solution N contents and growth of rice (<em>Oryza sativa</em>) were investigated. Two feedstock materials (sawdust and tea waste) were slow pyrolysed at 500°C to produce BC and N were intercalated into BC using urea solutions with seven concentrations (U1=0% &lt;U2&lt;U3&lt;U4&lt;U5&lt;U6&lt;U7=100% w/v). The maximum intercalated N contents in sawdust BC and tea waste BC were 28% and 22%, respectively. Five treatments: two SRFs at 17.25 mg N kg^–1 soil (75% recommended N) and three urea levels (0, 75, and 100% N) were applied to rice plants (Bg 251) in a pot experiment. Application of SRF significantly improved the greenness and growth of rice plants when compared with 0% N control and were comparable with 100% urea-N treatment. The apparent recovery of N (ARN) was significantly (p&lt;0.05) improved in SRFs (60-71%) compared to urea only treatments (38-52%). Nitrate-N contents in soil solution were not significantly different (p&lt;0.05) among treatments while NH4⁺-N content in 100% urea treatment was significantly (p&lt;0.05) higher throughout. Based on urea intercalation efficiency and the ARN, we concluded that SRF made using sawdust biochar is having a higher potential than SRF made using tea waste biochar to improve the efficiency of urea in lowland rice cultivation.

Rice productivity and profitability with slow-release urea containing organic-inorganic matrix materials

Applying slow-release fertilizers is possible means for reducing nitrogen (N) loss in rice production. Matrix-based fertilizers represent novel slow-release fertilizers. To date, there is little consensus about the effect of combined addition of organic and inorganic matrix materials on rice production. We developed a slow-release urea fertilizer with selected organic and inorganic matrix materials. The study aimed to: i) determine the effect of the slow-release urea on rice yield, profit, and agronomic efficiency and ii) elucidate its possible mechanisms. A two-year field experiment was conducted during 2015–2016. Besides, laboratory experiments were conducted to determine the potential N loss risk. Three treatments were set up: control without N application (CK), regular urea treatment (RU, 150 kg N ha–1), and slow-release urea treatment (SU, 150 kg N ha–1). The results showed that rice biomass and grain yield were significantly higher in SU than in RU (P < 0.05). The higher panicle density in SU was largely responsible for the greater grain yield. Net profit in SU was ≥ US$450 ha–1, higher than in RU. Agronomic efficiency was significantly greater in SU than in RU (P < 0.05). Rice height, root area, leaf chlorophyll, leaf nitrate reductase activity, and leaf glutamine synthetase activity were larger in SU than in RU. Less N loss and greater soil N availability were partly responsible for the improvements in rice growth traits and physiological parameters in SU. Overall, the slow-release urea is a promising fertilizer for rice production.

Urea fertilizer with precisely regulable slow-release performance by complexing with random copolyester

Slow-release fertilizers have been widely used to promote agricultural production with less losses to the environment. However, further achievement of fertilizer with precisely regulable release performance is still full of challenges, especially for the most used nitrogen fertilizer – urea. In this study, we provide a strategy for regulating performance of slow-release urea fertilizer (SRUF) based on inclusion complexation between biodegradable copolyester and urea via simply changing chain composition. The units of butylene adipate (BA) are copolymerized into the main chains of poly(butylene succinate) (PBS) to obtain a series of random copolyesters of poly(butylene succinate-co-butylene adipate) (PBSA). The crystallizability of PBSA declines with increasing BA content, leading to the longer slow-release time for corresponding PBSA/urea inclusion complex fertilizer. The monotonous, nearly linear relationship between chain composition and the slow-release performance of SRUF has been demonstrated, revealing the great potential to design SRUF with precise slow-release time. Consequently, pot trails in the lab are employed to evaluate the promotion effect of SRUF on Brassica chinensis L.. The growth indexes of plants significantly increase with increasing BA content in PBSA chains used in SRUF of inclusion complex. The plants reach about twice of dry weight in optimized group by referring to neat urea group when the SRUF shows a release duration closely matching to the growth cycle of Brassica chinensis L.

Slow-Release Urea Prills Developed Using Organic and Inorganic Blends in Fluidized Bed Coater and Their Effect on Spinach Productivity

The application of urea-based fertilizers in developing countries has gained significant momentum over time. urea usage is to meet demand and supply gap of food resources as world population is increasing at a fast pace. urea contains largest content of nitrogen (46%) among all the solid nitrogenous fertilizers. However, main drawback of urea is its higher dissolution rate. After soil application, most of urea nitrogen is lost through a leaching, runoff, nitrification-denitrification and ammonia volatilization. To tackle urea related environmental pollution, development of slow-release urea fertilizer is a need of the hour and this would also increase product use efficiency in terms of crop productivity and its N uptake. We studied the usage of polymeric materials in combination with inorganic substances like sulfur and plaster of Paris as effective and biodegradable coating substances for urea prills. For coating on urea prills, fluidized bed coater was used whereas paraffin wax and molasses were used as binding agents. The urea was coated with four different formulations, i.e., C-1: PVA 5% + plaster of Paris 10% + sulfur 5% + paraffin wax 2%, C-2: PVA 5% + starch 10% + sulfur 5% + paraffin wax 2%, C-3: gelatin 5% + plaster of Paris 10% + sulfur 5% + paraffin wax 2% and C-4: PVA 5% + starch 10% + sulfur 5% + paraffin wax 2.5% + molasses 2.5%. Each formulation along with uncoated urea prills (C-0) were evaluated for characterization and N release kinetics. All the formulations along with uncoated urea were applied to spinach crop in pot experiment. A control (No N: untreated) was also kept. Spinach biomass yield and N uptake were determined. The formulation C-1 yielded highest urea-N release efficiency and spinach N uptake of6.87% and 1.93 g N/pot, respectively. Themodified Schwarz and Sinclair formula gave the excellent representation of release of nutrient-N from coated urea prills. It is concluded that coating urea prills with organic and inorganic blends is better option to slow down N release kinetics and improve spinach productivity. Therefore, by using coated fertilizers, farmers can improve agro-environmental value of urea, worldwide.

Preparation of a Mesoporous Ceramic Adsorbent Based on Iranian Domestic Kaolin to Utilize as Slow-Release Urea Fertilizer Medium

Preparation of a Mesoporous Ceramic Adsorbent Based on Iranian Domestic Kaolin to Utilize as Slow-Release Urea Fertilizer Medium

Year-to-year climate variability affects methane emission from paddy fields under irrigated conditions.

A field experiment in Yangtze River delta of China was conducted to investigate the effects of four treatments (conventional chemical fertilizers (CF), chemical fertilizers incorporated with wheat straw (CF-WS), slow-release urea fertilizer incorporated with wheat straw (SCF-WS), and no fertilizers (Non-F)) on methane emission, rice grain yield, and straw biomass in three (2013, 2014, and 2015) consecutive growing seasons. Similar air temperature and precipitation were recorded in 2014 and 2015 normal seasons; however, the 2013 season with a 2.1-2.3°C higher mean air temperature and a 61-64% lower precipitation than the normal seasons was considered as a warm-and-dry season.No significant differences in seasonal total methane emissions across all treatments were observed in 2014 and 2015 seasons. Seasonal total methane emissions were 58-294% higher in 2013 season compared to 2014 and 2015 seasons, which suggests that higher ambient temperatures increase methane emissions from paddy fields. The enhanced methane emission was seen mainly during the mid-to-late growth stages after mid-season drainage. CF-WS and SCF-WS significantly increased methane emissions before mid-season drainage relative to CF, and thereby enhanced methane emissions in both normal and warm-and-dry seasons in a seasonal scale.While rice grain yield in each treatment in 2013 season was close to or lower than that in 2014 and 2015 seasons, straw biomass in CF, CF-WS, and SCF-WS in 2013 season were significantly higher than those in 2014 and 2015 seasons, by both 29%, 33-41%, and 15-16%, respectively. Enhancements in methane emissions at higher air temperatures were significantly correlated to its greater straw biomass. Furthermore, combination of slow-release urea fertilizer and straw by ploughing can significantly increase above-ground biomass yields and nitrogen use efficiency in both normal and warm-and-dry seasons.

Starch-g-poly(acrylic acid-co-acrylamide) composites reinforced with natural char nanoparticles toward environmentally benign slow-release urea fertilizers

Loss control of nutrients and water has been considered as a global challenge of agriculture because it faced with concurrent management of these two necessities of crop production. Herein, a bio-based slow-release fertilizer (SRF) has been developed using reinforcement of starch-g-poly(acrylic acid-co-acrylamide) superabsorbent polymer with natural char nanoparticles (NCNPs). Incorporation of urea in the matrix of nano-biocomposite resulted in the efficient SRF formulation with remarkable water absorbency (215.1 g/g). Variables including starch, monomers, cross-linker, and nano-filler dosages were optimized using screening the urea release behavior of samples in various pHs (3–10) and salt solutions (NaCl, CaCl2, and FeCl3). NCNPs acted as physical cross-linker as well as nano-filler and formed H-bondings between the oxygenated groups of the polymer and nanoparticles. Urea release measurements in water indicated a well slow-release property of SRF formulations, 70 % of nitrogen released during 21 days. The release time was prolonged with increasing the amount of NCNPs because the favorable interfacial polymer-filler interactions resulted in slower nitrogen diffusion and consequently, slower release rate at neutral and basic pHs. The water-retention of soils containing two different SRFs (with and without nano-filler) showed that NCNPs could double the water-retention compared with the neat polymer. While nitrate leaching rate in the soil for pure urea was measured to be 591.8 mg/L, the starch-g-poly(acrylic acid-co-acrylamide)/NCNPs/Urea decreased the leaching loss of N up to 49.5 mg/L. The soil burial degradation test indicated that the presence of NCNPs in the network of polymer could facilitate the degradation process of the SRF samples.

Degradable polyester/urea inclusion complex applied as a facile and environment-friendly strategy for slow-release fertilizer: Performance and mechanism

Most manufacturing technologies of slow-release urea fertilizers are solvent-assisted and consequently complicated. Therefore, the development of a solvent-free and facile approach has been actively pursued. Herein, the inclusion complexes (ICs) of environmentally degradable polyester and urea prepared by one-step blending are developed as slow-release urea fertilizers for the first time. Three kinds of polyesters, poly(butylene succinate) (PBS), poly(ethylene succinate) (PES) and poly(propylene succinate) (PPS) are involved. Compared with neat urea, the IC fertilizers exhibit much lower and more adjustable release rates, which can decrease from tens to thousands of times by varying factors such as granular size, compactness and polyester species. Interestingly, the crystallizability of polyester is demonstrated to play an important role in controlling the slow-release performance, the weaker crystallizability of polyester chains results in the longer release time of IC fertilizer. Analysis of release profiles reveals that the urea component in IC fertilizers displays a second-order release process first and then a zero-order behavior at the late stage. Microstructure assay suggests that the insoluble polyester chains freed from urea frameworks crystallize and sheath the rest of IC upon contact with water. Consequently, a sophisticated release model of urea from IC fertilizer is proposed. The degradation of polyester component and the promotion effect of IC fertilizer on maize growth are also studied in the lab.

Slow-release urea fertilizer from sulfur, gypsum, and starch-coated formulations

To address nitrogen (N)-related environmental pollution, development of an economical, slow-release urea fertilizer is the need of the hour. A study was conducted on the reduction of nitrogen released from granular urea fertilizer by applying sulfur, gypsum, bentonite, and starch as coating material. Paraffin wax was used as a binder. The dissolution rates were studied by changing the composition of coating mixture using high-performance liquid chromatography. SEM was used to study the morphology of coated urea in terms of smoothness and uniformity. The ultraviolet spectroscopy analysis further authenticated the release behavior of coated urea in terms of nitrogen concentration. Coating material reduced the release rate of nitrogen from urea fertilizer, significantly. Mixture of sulfur and gypsum coating on urea gave slowest release rate of nitrogen from urea fertilizer, i.e., 37%, as compared to uncoated urea and thus seems to be the most promising binding material for product development.

Slow release urea fertilizer synthesized through recrystallization of urea incorporating natural bentonite using various binders

Abstract In this study, various slow release urea fertilizers (SRUFs) were prepared by incorporation of urea into local natural bentonite with various binder i.e. corn starch and hydroxypropyl methylcellulose (HPMC). In the preparation, a binder was added to a mixture of natural bentonite and melted urea. Then, the admixture was put into a mould and extruded to obtain SRUF in the form of pellets. The SRUF was dried at 50 °C for 8 h before use. Urea desorption mechanisms of the SRUF was examined through static release experiments. The structural properties of SRUF was characterized through scanning electron microscopy with energy dispersive x-ray (SEM-EDX) analysis and Fourier-transform infrared spectroscopy (FTIR). It was found from static release experiments that the SRUFs more slowly released urea in water than conventional urea fertilizer. After 500 min of the experiment, the slowest release of urea was achieved by SRUF using corn starch. Meanwhile, conventional urea fertilizer completely released urea in water after less than 50 min. Release mechanisms of the SRUF using corn starch and SRUF using HPMC were anomalous transport and Fickian diffusion, respectively.

Biodegradable IPN Hydrogels Based on Pre-vulcanized Natural Rubber and Cassava Starch as Coating Membrane for Environment-Friendly Slow-Release Urea Fertilizer

Biodegradable interpenetrating polymer network (IPN) hydrogels based on pre-vulcanized natural rubber (NR) and cassava starch (St) using sulphur (S) and glutaraldehyde (GA) as crosslinkers were developed in a solution form as a coating membrane for slow-release nitrogen fertilizer. The NR/St ratios affecting water swelling, water permeability and biodegradation were investigated. Results revealed that water swelling, water permeability and biodegradation of IPN NR/St hydrogels decreased with increasing NR content. The wax was used as outer coating shell to further improve the release characteristic of the coated urea. The urea bead (UB) coated with IPN NR/St and wax layers (W-IPN-CUB) exhibited exceptional release behavior up to 24 days in soil compared to native UB (3 days). The release mechanisms of W-IPN-CUB in both water and soil environments were a non-Fickian diffusion with n = 0.88 and 0.85, respectively, relating to the diffusion through porous membrane. Also, the W-IPN-CUB was able to slow the leaching of urea fertilizer and significantly improve the performances of corn and basil height compared to native UB (P < 0.05). Thus, the W-IPN-CUB material proved to be a good candidate material for slow release fertilizer which could be widely used in agricultural and horticultural applications.

Environmentally Friendly Slow-Release Urea Fertilizers Based on Waste Frying Oil for Sustained Nutrient Release

Novel biobased polyurethane (PU) was synthesized by using waste frying oil-based polyol (WFOP) and isocyanate for slow-release fertilizers (SRFs). Epoxy resin (EP) was used to modify PU to synthesize the interpenetrating network (IPN) for improving the properties of the coating film. Nine polymer-coated nitrogen (N) fertilizers were prepared from these composite coating materials. The N release characteristics of the PU-coated urea (PCU) in water and soil were determined. Degradation behavior of coatings in the soil was evaluated. Results showed that 20% EP in the coating increased the cross-linking density by 77.9%, reduced the coating porosity by 28%, and thus slowed the nutrient release from the PCU significantly. Because of its compact structure, the water absorption rate of the EP-modified PCU shell was slower than that of the unmodified ones. All the PCUs, especially the EP-modified ones, showed excellent slow N release behaviors. In addition, the biopolymers derived from waste frying oil also displ...

Influence of growing measures on weed interference and water status in maize

Growing modern hybrids in narrow plant spacing together with nitrogen and herbicide application gives an advantage to maize crops over weeds. The aim of the present investigation was to evaluate the effect of nitrogen form, maize row spacing and herbicide treatment on weed and maize biomass and water usage, as well as maize yield. The investigation was conducted at the Maize Research Institute Zemun Polje, Belgrade during 2014-2016. A field experiment was set up as a split-split-plot block design with four replications. The maize hybrid ZP388 was planted, and a standard and a slow-release form of urea were applied. For each N source, maize was grown at two row spacings: narrow of 50 cm, and standard of 70 cm, while weed control treatments included: C - without herbicide application, T - application of a pre-emergence mix of herbicides. Sowing was done in the second decade of April, 2014, 2015 and 2016. Six weeks after herbicide application, the fresh biomass of weeds uprooted from 1 m2 and aboveground biomass of ten crop plants per plot were measured together with dry matter after drying in a laboratory oven. Water content (%) in weed and maize plants was calculated as a relation between fresh and dry biomass. Maize yield was measured at the end of each growing season and calculated with 14% of moisture. All data were processed by ANOVA. The fresh and dry biomass of weeds were significantly (P&gt;0.05) higher in untreated control than in the treated variant, while differences in water content were not significant between the two treatments. Row spacing and urea form did not cause significant differences in weed parameters. Related to this, maize fresh and dry biomass, as well as water content, were higher in herbicide-treated variants than in control but differences were insignificant. Maize biomass was somewhat higher in 50 cm rows and after application of the slow-release urea fertilizer. Yield was higher from 70 cm rows and after application of the slow-releasing urea and the herbicides.