Highly Porous Agro-Augmenting Urea-Biochar/Polylactic Acid-Based Microfibrous Electrospun Mats as Sustainable Controlled Release Fertilizer Carriers

Abstract

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°), water absorption (∼69.4%), retention capacity (∼17days), and effective release of urea in water (∼11.6%) and soil (∼5.67%). The thermal stability (degradation temperature from 334 to 413 °C) and mechanical properties (from ∼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.