Physio-biochemical responses of rice to smart nitrogen fertilizer nano-hydrogel under drought stress and flooding alternation: An eco-friendly innovative approach to enhance the grain quality

Fertilizer nanohydrogels have been newly introduced to agriculture. Herein, we investigated the effects of smart nitrogen (N) fertilizer nano-hydrogel on rice's physio-biochemical traits and seed quality under different drought stress and flooding conditions. Therefore, a pot experiment was conducted with no N fertilizer delivery 0 g N/kg (NND), with conventional N fertilizer delivery 0.175 g N/kg (CND), and smart N fertilizer delivery 0.175 g N/kg (SND) using three irrigation options: flooding/moderate dryness (FMD, 90% saturation, 30 mm submerged), flooding/sharp dryness (FSD, 70% saturation, 30 mm submerged), and flooding/extreme dryness (FED, 50% saturation, 30 mm submerged). Results showed that rice root's active acquisition area and enzymatic activity were larger in FMD x SND than in FED x NND, as the former combination increased NH4+, NO3-, and TN contents in the soil while the latter reduced their availability. The optimal N nutrition improved the plant cell ultrastructure, and the catalase activity was higher in the FMD x SND (42.0 mg/min) compared to the FED x NND (25.2 mg/min), leading to the alleviation of oxidative cell injury, as verified by lesser radical oxidative sequences and lipid peroxidation. The leaf soluble protein (8.8 mg/g) and sugar (36.9 mg/g) were greater in FMD x SND than in FED x NND (5.3 mg/g), (10.4 mg/g), and (8.3 mg/g h), respectively. Moreover, a-amylase and glutamine synthetase activities were larger in the FMD x SND than in FED x NND. Meanwhile, the FMD x SND resulted in the highest milled rice (87.3%), amylose (17.6%), protein (12.4%), and fatty acids (11.1%). However, the combination of FED x NND led to the lowest milled rice (70.0%), amylose (5.6%), protein (5.3%), and fatty acids (6.6%). This study suggests that the FMD x SND can guarantee physio-biochemical improvements in rice, thereby increasing grain quality. (c) 2024 SAAB. Published by Elsevier B.V. All rights reserved.