Integrated SA-CMC hydrogel formulation with the NAA hormone, ZnO nanoparticles, and potassium chloride: a sustainable approach to enhance flowering and crop yield in the short-term crop chili (Capsicum annuum)†

Abstract

Rising food demand due to population growth and the low nutrient use efficiency (NUE) of conventional fertilizers necessitate environmentally friendly, effective agrochemical delivery systems. Hydrogels are innovative materials, and an integrated hydrogel formulation encapsulated with zinc oxide nanoparticles (ZnO NPs), potassium chloride and naphthalene acetic acid (NAA) was synthesized in this study to increase the flowering and crop yield of the short-term crop chili. ZnO NPs were synthesized via the co-precipitation method and characterized via XRD, SEM and FTIR techniques. The synthesized hydrogels were characterized using SEM and FTIR techniques. The swelling capacity of the hydrogels peaked at 202.04% on day 14, and they exhibited biodegradation by day 20, with a weight loss of 99.98%. Biodegradation findings were corroborated by optical microscopy pictures. Atomic absorption spectrometry was used to study the release of potassium and zinc nutrients from the hydrogels on days 1, 7, 14, and 21, suggesting the slow-release behavior of the hydrogels. UV-VIS spectrophotometry was used to study the NAA hormone, which revealed a higher encapsulation efficiency of 92.53% with a sustained, slow-release profile over a 21-day period. The exponential phase of the NAA-release profile matched well with the Higuchi model (R² = 0.97). The parameters plant height, number of branches, flowers, pods and yield at first plucking were statistically analyzed using the analysis of variance (ANOVA), and significant differences between each sample were analyzed using Tukey pairwise comparison at a significance level of 0.05. Significant enhancements observed in flowering and yield were attributed to the synergistic effect of the encapsulated agrochemicals in the hydrogels. The ability to biodegrade and improve NUE positions this integrated hydrogel formulation as a sustainable alternative for modern agriculture.