Facile Fabrication of N-Slow Release Fertilizer Hydrogel Beads by Alginate-Based Composites

A novel slow-release N-fertilizer hydrogel beads were developed using sodium alginate (SA) and alginate-talcum (ST) composite as N-absorbent. In this work, the hydrogel composite were fabricated by simple method and low cost. N-fertilizer hydrogel beads were prepared two types, for SA types, which were different sodium alginate (1(SA1), 3(SA3), 5(SA5), 7(SA7), and 10(SA10) wt%). And, for ST types, sodium alginate and talcum were vary ratios to 1:0.5(S1T0.5), 1:1(S1T1), and 1:2 (S1T2). The chemical structure of hydrogel composite beads were characterized via Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The release behavior were investigate by Zero-order kinetic model, First-order kinetic model, Higuchi model and Korsmeyer-Peppas model. We have found that the N-fertilizer release constants in Korsmeyer-Peppas model were decrease with increase SA content for 1-5 wt% in SA hydrogel beads. However, SA contents were more than 5 wt% which rapidly enhanced fertilizer release. In addition, to add talcum in ST hydrogel beads significantly reduced fertilizer release rate. The N-fertilizer hydrogel beads exhibits significantly slow release behavior. These results indicates that the development of slow-release fertilizer hydrogel beads can be improve the effectiveness of N-fertilizer.

A Theoretical Multifractal Model for Assessing Urea Release from Chitosan Based Formulations

This paper reports the calibration of a theoretical multifractal model based on empirical data on the urea release from a series of soil conditioner systems. To do this, a series of formulations was prepared by in situ hydrogelation of chitosan with salicylaldehyde in the presence of different urea amounts. The formulations were morphologically characterized by scanning electron microscopy and polarized light microscopy. The in vitro urea release was investigated in an environmentally simulated medium. The release data were fitted on five different mathematical models, Korsmeyer–Peppas, Zero order, First order, Higuchi and Hixson–Crowell, which allowed the establishment of a mechanism of urea release. Furthermore, a multifractal model, used for the fertilizer release for the first time, was calibrated using these empirical data. The resulting fit was in good agreement with the experimental data, validating the multifractal theoretical model.

Synthesis and Characterization of Ionically-Crosslinked κ- Carrageenan/Sodium Alginate/Carboxymethyl Cellulose Hydrogel Blends for Soil Water Retention and Fertilizer Release

Providing enough water in farming has become a challenge in the Philippines due to insufficient irrigation and escalating drought conditions, thereby decreasing agricultural productivity. The impact of this problem can be lessened through efficient water usage: by reducing water wastage in runoff or evaporation and improving soil water retention. Hydrogels can be used for this purpose due to their water absorption capabilities. In this study, a novel, biodegradable agricultural hydrogel was developed from κ-carrageenan, sodium alginate and carboxymethyl cellulose, crosslinked with Ca2+ and K+ ions. Scanning electron microscopy analysis confirmed the successful crosslinking while swelling tests revealed them as superabsorbent hydrogels, with maximum absorption reaching 2000%. Soil amended with 2% (w/w) hydrogel showed reduced water-depletion rate and improved field capacity by a maximum of 17.6% and 17.4%, respectively. Fertilizer release test also showed the potential of these hydrogels as fertilizer carriers.

Slow-release of fertilizer in soil using pectin/calcium-bentonite hydrogel

<p>Plant survival and growth are greatly affected by moisture and nutrient loss around root zones. Water and nutrient retaining agents such as hydrogels have been gaining popularity to solve this problem, but most commercial hydrogels are composed of non-biodegradable and synthetic components.  In this study, we successfully prepared hydrogels made of biodegradable pectin and naturally-occurring calcium bentonite. The synthesized hydrogels contained varied loadings of fertilizer (equivalent to 0, 0.2, 0.6, and 0.85 g NPK L<sup>-1</sup> soil). We characterized the hydrogels in terms of morphology (scanning electron microscopy/SEM), nutrient P and K concentration (X-ray fluorescence/XRF analysis), and degree of swelling in water (gravimetric method). We also determined the nutrient retention capacity and release of the hydrogels using a soil column leaching setup coupled with periodic monitoring of conductivity and total dissolved solids of column leachate. </p><p>SEM indicates the porous structure of the hydrogels, while XRF confirms the successful loading of fertilizer in the hydrogels. The hydrogel at 0.2 g NPK L<sup>-1</sup> soil has the highest degree of swelling in the water at 692.5%. The nutrient retentions of soil columns containing fertilizer-loaded hydrogels (0.2, 0.6, and 0.85 g NPK L<sup>-1</sup> soil) are greater by 35.5, 11.5, and 20.1%, respectively, compared to the control (soil column without hydrogel). Our measurements of fertilizer release rate also indicate that the presence of hydrogel in the soil column slows down the release of fertilizer as detected in the column leachates. We conclude that the pectin/calcium-bentonite hydrogels are effective in retaining water and reducing the release of fertilizer from the soil. With the biodegradability of pectin and natural occurrence of calcium bentonite, the hydrogel has the potential for sustainable management of slow-release fertilizer systems. </p>

Evaluation of morphological, mechanical, and rheological properties of vulcanized styrene–butadiene rubber/modified corn starch blends

The starch-filled styrene–butadiene rubber (SBR) was prepared using a laboratory-sized two-roll mill. Starch was modified by yeast fermentation for 1 day before it was blended with SBR. The hydrophilicity of SBR was enhanced by grafting with modified starch (MST) by utilizing tetramethyl thiuram disulfide as a catalyst. The effect of modified corn starch loading on morphological, mechanical, and rheological properties of vulcanized SBR blends was investigated. Scanning electron microscope result revealed that the adhesion between the MST and SBR was weak, and the starch pulled out due to poor interfacial bonding. The lowest ultimate tensile strength, elongation at break, and tensile modulus of the SBR- g-MST were found in the sample containing 150 phr of starch. The variation of the percentage elongation of neat rubber and MST/rubber composites was 91.34%. The significant decrease in cure times was observed with the loading of MST in all blends up to 100 phr starch, while no significant change in scorch time was observed. The maximum torque, minimum torque, and cross-linking density increased as the starch loading increases up to 100 phr MST. The water absorption by the composite increases with immersion time and MST loading, although the rate of absorption decreases with increased time. The current product could be especially advantageous in agricultural and horticultural applications as a good controlled fertilizer release and for water retention.