Boosting nitrogen fertilization by a slow releasing nitrate-intercalated biocompatible layered double hydroxide-hydrogel composite loaded with .

Indiscriminate use of chemical fertilizers leads to soil environmental disbalance and therefore, preparation and application of environment-friendly slow-release multifunctional fertilizers are of paramount importance for sustainable crop production in the present scenario. In this study, we propose a slow-release multifunctional composite nitrogen (N) fertilizer, which possesses the ability to supply plant accessible N in the form of ammonium (NH ) and nitrate (NO ) to improve nitrate assimilation coupled with zinc (Zn, a major micronutrient for plants in the soil) after its degradation. For this purpose, NO -intercalated zinc-aluminum (Zn-Al) layered double hydroxide (LDH) was synthesized using a co-precipitation protocol. The prepared LDH was added as 25.45% of total polymer weight to a sodium carboxymethyl cellulose/hydroxyethyl cellulose citric acid (NaCMC/HEC-CA) biodegradable hydrogel. , commonly used nitrogen-fixing bacteria in soils, was added to the LDH-hydrogel composite along with LDH alone to augment the availability of NH and NO . Adjusting the pH under acidic (pH 5.25) and neutral (pH 7) conditions, the release pattern of NO from LDH and the composite was monitored for 30 days at normal temperature. The pH was selected based on the soil analysis data of North East India. The LDH-composite released 90% (w/w) and 85.45% (w/w) of intercalated NO at pH 5.25 and 7.00 respectively in 30 days. However, 100% (w/w) and 87% (w/w) of intercalated NO at pH 5.25 and 7.00 respectively were released in 30 days when only LDH was applied, which indicated the lower performance of LDH alone in comparison to the LDH-composite for the nitrate holding pattern. The pH of the bacteria-loaded system was observed to be acidic (pH = 5-6) during the study of nitrate assimilation and Zn release. improved nitrate assimilation and increased the NH ion concentration in the studied system. A significant increase in Zn release was observed from day 5 in the presence of in the LDH-composite compared with that in the absence of . In conclusion, the prepared LDH-hydrogel- composite fertilizer system increases the availability of plant accessible N form (both NO and NH ) and can potentially improve soil fertility with the addition of Zn and bacteria to the soil in the extended course.