The agricultural industry prioritizes minimizing crop yield losses caused by pests, making it essential to develop effective, safe and sustainable pesticide formulations. Hydrogels are promising carriers for pesticide delivery, due to their high surface area, large pore volume, and pore size. In this study, we synthesized Cassia fistula (CA-g-AA) and its derivative carboxymethylated Cassia fistula-grafted polysodium acrylate hydrogel (CMCA-g-AA) using free radical polymerization, with N, N'-methylene bisacrylamide (MBA) as a crosslinker, for the ex-situ encapsulation of dinotefuran. Characterization was performed using FTIR, 13C CPMAS-NMR, SEM, TGA, rheology, and XRD. The maximum swelling capacity of hydrogels was investigated in distilled water. CA-g-AA and CMCA-g-AA hydrogels exhibited a dinotefuran loading percentage of 37 and 39% and released dinotefuran for 26 and 29 h, respectively. The dinotefuran release kinetics was analyzed by using the Korsmeyer-Peppas and Higuchi models. Under drought like conditions, CMCA-g-AA-treated soil sustained plant growth for 7 days, compared to CA-g-AA (5 days) and untreated soil (3 days). The novel hydrogel CMCA-g-AA enhanced soil water absorption and retention along with highlighting its potential for extended pesticide release. Thus, the developed CMCA-g-AA hydrogel is an efficient strategy for sustainable agriculture.

Bio-based polymers are a promising material with which to tackle the use of disposable and non-degradable plastics in agriculture, such as mulching films. However, their poor mechanical properties and the high cost of biomaterials have hindered their widespread application. Hence, in this study, we improved polysaccharide-based films and enriched them with plant nutrients to make them suitable for mulching and fertilizing. Films were produced combining sodium carboxymethyl cellulose (CMC), chitosan (CS), and sodium alginate (SA) at different weight ratios with glycerol and CaCl2 as a plasticizer and crosslinker, respectively, and enriched with ammonium phosphate monobasic (NH4H2PO4). A polysaccharide weight ratio of 1:1 generated a film with a more crosslinked structure and a lower expanded network than that featuring the 17:3 ratio, whereas CaCl2 increased the films' water resistance, thermal stability, and strength characteristics, slowing the release rates of NH4+ and PO43-. Thus, composition and crosslinking proved crucial to obtaining promising films for soil mulching.

The objective of this study is to explore the novel use of natural polymers like Humic acid, Lignin, and Lignite based hydrogels for the formulation of pesticides and fertilizers that would reduce the residues in soil and run-off water that pose a threat to human health and the environment. We synthesized hydrogels by grafting Humic acid, lignin, and lignite onto acrylic acid with N ' N-methylene bisacrylamide (MBA) for the ex-situ encapsulation of thiamethoxam, a common pesticide. Various characterization techniques including Fourier-transform infrared spectroscopy, Carbon-13 Solid-state Cross-Polarization Magic Angle Spinning Nuclear Magnetic Resonance, X-ray diffraction, Thermogravimetric Analysis, and Rheology were employed. The release kinetics of thiamethoxam in water from the developed formulations were analyzed using the Korsmeyer- Peppas model and the Weibull model. Humic acid and lignin-based hydrogels exhibited a long-sustained release for 49 hours, followed by lignite-based hydrogels (38 hours). According to ANOVA results, the change of biopolymer proved to be an effective factor in reducing the water evaporation rate, which decreased from 99 % to 72.85 % in the soil amended with synthesized hydrogels. In conclusion, the novel formulations of humic acid, lignin, and lignite exhibit potential as slow-release vehicles for pesticides and fertilizers. This study provides valuable insights for the research community, addressing the need to develop effective strategies for mitigating pesticide residues in soil and water bodies. Humic acid, lignin, and lignite grafted poly(sodium acrylate) hydrogels have been synthesized and characterized by 13C CPMAS NMR, FT-IR, XRD, SEM, TGA, and Rheology. The release kinetics of thiamethoxam is studied using the Korsmeyer-Peppas and Weibull models. This study will reduce the environmental influences of pesticide runoff into the water and bring humic acids, and lignite out of the traditional soil context by applying them in modern fields along with lignin. image

Controlled release of pesticides in response to environmental stimuli using hydrogels as carriers is a feasible approach to improve the effective utilization rates of pesticides. In this regard, modified carboxylated cellulose nanocrystal (CCNC)-based hydrogels with appropriate biocompatibilities and high specific surface areas have broad prospects. Accordingly, in this study, a pH -responsive hydrogel loaded with the pesticide thiamethoxam (TXM) (PEI-CCNC@A-MMT/TXM) was constructed by synergistically introducing CCNC modified with polyethyleneimine (PEI) into cost-effective acidified montmorillonite (A-MMT) via electrostatic self -assembly followed by combination with sodium alginate (SA) by emulsion - gel method via ionic crosslinking. PEI-CCNC@AMMT efficiently improved the mechanical properties of the SA hydrogel and ensured the stability and TXM loading efficiency of this hydrogel; however, the hydrogel stress increased from 9.48 to 41.44 kPa under 20 % compressive strain when the mass ratio of A-MMT to PEI -modified CCNC (PEI-CCNC) was increased from 0 to 0.8. PEI-CCNC@A-MMT/TXM exhibited significant controlled -release characteristics with the change in pH; specifically, with an increase in pH from 5.0 to 9.0, the cumulative release ratio of TXM increased from 53.62 to 94.86 wt % within 48 h of the addition of PEI-CCNC@A-MMT/TXM to the phosphate buffered saline solution. Fitting the six models to the release curves proved that swelling, dissolution, and diffusion acted together during TXM release, and release mechanisms for TXM under different pH conditions were proposed. The release behaviors of PEI-CCNC@A-MMT/TXM in soil indicated that this hydrogel effectively prolonged the release of TXM, and only 91.53 wt % TXM was released within 240 h after the hydrogel entered the soil. The bacterial activity revealed that the hydrogel did not destroy the microbial environment of the soil and demonstrated high biocompatibility. This study provides a promising strategy for regulating the pesticide release behavior, improving pesticide utilization, and reducing environmental pollution of pesticides via introducing low-cost AMMT and green CCNC into the SA hydrogel and applying this hydrogel as a pesticide carrier.

Meeting agricultural requirements without a significant impact on the soil-water ecosystem in terms of delivering agrochemicals for seed germination and plant growth necessitates the development of a sustainable and multifunctional controlled release fertilizer carrier. For this purpose, the current study aims at fabricating highly porous urea-biochar/PLA-based agro-augmenting bead-free electrospun mats (EM) with improved physicomechanical performance. The method involved the hydrothermal synthesis of walnut shell-derived biochar, followed by the ball milling, urea loading and subsequent incorporation of urea-loaded ball-milled biochar into porous PLA-based electrospun fibers. The impacts of ball milling and urea loading were evaluated by using morphological (FESEM and TEM), microstructural (FTIR and XRD), and physiochemical (BET and BJH) attributes. To enhance the surface hydrophilicity, PLA-based porous EM was fabricated by altering the concentration of cosolvent (DCM:DMSO) and relative humidity (20-80%). Bead-free and uniform urea/biochar-loaded PLA EM were fabricated by incorporating urea/biochar into PLA precursor solution, and the resultant EM showed improved surface hydrophilicity (with a contact angle of 98.4 degrees), water absorption (similar to 69.4%), retention capacity (similar to 17days), and effective release of urea in water (similar to 11.6%) and soil (similar to 5.67%). The thermal stability (degradation temperature from 334 to 413 degrees C) and mechanical properties (from similar to 9.6-13.56 MPa) are improved for PLA-based EM upon incorporating urea-biochar. The efficacy of developed EM for promoting plant growth was validated by conducting germination and growth assessments using green gram (Vigna radiata) plants. The results demonstrated a higher germination rate (59.33%), plant height (23.67 cm), root length (9.33 cm), dry weight (0.38g), and fresh weight (0.44g) for plants treated with the EM as compared to the control sample. Thus, the study established optimally designed uniform bead-free microfibrous electrospun constructs with tunable urea release, pointing at an agrotechnology not only enhancing crop yield but also ensuring environmental sustainability as undesirable nutrient-induced secondary complications such as eutrophication and soil quality deuteriation possibilities are largely mitigated.

The climate changes have caused more extreme precipitation and drought events in the field and have exacerbated the severity of wet-dry events in soils, which will inevitably lead to severe fluctuations in soil moisture content. Soil moisture content has been recognized to influence the distribution of heavy metals, but how temporal changes of soil moisture dynamics affect the release rates and lability of heavy metals is still poorly understood, which precludes accurate prediction of environmental behavior and environmental risk of heavy metals in the field. In this study, we combined experimental and modeling approaches to quantify copper release rates and labile copper fractions in two paddy soils from southern China under different moisture conditions. Our kinetic data and models showed that the release rates and lability of copper were highly associated with the soil moisture contents, in which, surprisingly, high soil moisture contents effectively reduced the release rates of copper even with little changes in the reactive portions of copper in soils. A suite of comprehensive characterization on soil solid and solution components along the incubation suggested that soil microbes may regulate soil copper lability through forming microbially derived organic matter that sequestered copper and by increasing soil particle aggregation for protecting copper from release. This study highlights the importance of incorporating soil moisture dynamics into future environmental models. The experimental and modeling approaches in this study have provided basis for further developing predictive models applicable to paddy soils with varying soil moisture under the impact of climate change.