World Journal of Agricultural Sciences 19 (5): 189-203, 2023 ISSN 1817-3047 © IDOSI Publications, 2023 DOI: 10.5829/idosi.wjas.2023.189.203 Corresponding Author: Heba Y.A. Morsy, Soil, Water and Environ. Res. Inst., Agric. Res. Center, Giza, Egypt. 189 Nano-silica Synthesis, Characterization and Their Effects on Rice Production in the Presence of Calcium Humate under Salinity Soil Stress Heba Y.A. Morsy, Wafaa M.T. El-Etr, Gehan H. Youssef, Marwa A.H. Shady and Hanaa A. Zein El-Abdeen Soil, Water and Environ. Res. Inst., Agric. Res. Center, Giza, Egypt Abstract: Agricultural by-products have been repurposed to manufacture specific compounds through cost-effective technologies in order to maximize their use. These artificial substances are being utilized to augment the capacity of rice plants to tolerate salinity, thereby increasing their productivity. So, rice husk was used to synthesize Nano-silica (NSi), which was characterization by X-ray diffraction (XRD) and transmission electron microscopy (TEM), while calcium humate (CaH) was extracted from compost. Subsequently, a field experiment on saline soil was carried out at Sahl El-Hossinia Agric. Res. Station Farm in El-Sharkia Governorate, Egypt. The experiment was conducted throughout the summer season of 2022 to investigate the influence of NSi, CaH and their combination NSi+CaH at various concentrations on rice crop productivity and soil properties. Three NSi treatments (2, 3 and 4 mM) and other CaH levels (2,3 and 4 % as well as their combinations were tested in the experiment were used. The study reveals that the addition of NSi significantly increased the biological, straw and grain yields of rice crops by 45, 52 and 34%, respectively. Similar results of CaH increased biological, straw and grain yields of ricewith 7649, 4419 and 3229 kg fed . The NSi +CaH composite application 1 2 2 produced superior yields. The total content of N, P, K and Si in the straw and grains of the rice increased as compared to the control. Also, NSi or CaH reduced SAR and ESP, but the NSi+CaH treatment had no significant reduction. All treatments significantly improved the availability of N, P, K and Si in the soil compared to the control treatment. In conclusion, this study shows that individual applications of NSi or CaH can effectively mitigate salinity stress by reducing sodium toxicity more than their combination. Key word: Nano silica Calcium humate Salinity stress Rice crop Soil properties INTRODUCTION In an effort to address the issue of this agricultural Large amounts of agricultural waste can have a subject of multiple studies published in recent years [3]. negative impact on the environment and ecosystems, Silicon (Si) is a necessary component for plant growth. such as greenhouse gas emissions, the formation of It is generally known that Si can promote plant disagreeable odors and dangerous compounds that can development under salt stress. Due to silicon, certain enter water sources [1]. Rice husk (RH) is a byproduct of plant species, including wheat, barley and rice, is thought rice milling that accounts for approximately 20% of the to be less salt resistant. Several hypotheses have been weight of unhulled rice. Rice waste materials, as stated by proposed for Si-mediated salt stress alleviation, including [2], are one of the agricultural wastes that are increasing [1] the buildup of Na in rice and barley shoots following year after year. Therefore, rice waste is an appealing Si addition under salinity stress. [2] Reduced Na renewable resource for the production of nanomaterials as absorption at the root [4, 5]. an alternative to harmful chemicals. In some countries, Also, nanoparticles (NPs) are particles with a size in where rice is the main crop consumed by the bulk of the at least one dimension ranging from 1 to 100 nm. When population, this amount will be abundant. Consequently, compared to bulk materials, they can affect physio- managing the RH is necessary to obtain high-value chemical properties more favorably since their increased products and lessen the environmental issues it causes. surface area enhances solubility and surface reactivity [6]. waste's availability, silica extraction from RH has been the