Soil salinity poses a significant challenge to agricultural productivity, particularly in arid and semi-arid regions. This study explores the effect of compost, elemental sulfur (ES), sulfur nanoparticles (SNPs), and their combinations, i.e., compost + ES and compost + SNPs, to improve soil properties and maize productivity across a range of salinity levels (EC1 = 3.68, EC2 = 6.15, EC3 = 8.34, and EC4 = 12.18 dS/m). We hypothesized that integrating compost with ES or SNPs would enhance soil quality and maize performance more effectively than individual treatments. Results validated this hypothesis, showing that compost increased soil organic matter (SOM) by 1.33 times, reduced sodium adsorption ratio (SAR) by 33%, and boosted maize grain yield by 40% in moderately saline soils (6.15 dS/m). ES and SNPs lowered soil pH by 0.8–1.2 units and improved phosphorus availability by 25–30%. The compost–SNP combination delivered the most significant improvements, enhancing infiltration rate by 60%, total porosity by 15%, and straw yield by 50% in highly saline soils (12.18 dS/m). Additionally, plant height, cob length, and chlorophyll content increased by 20%, 22%, and 40%, respectively, with combined treatments. These findings highlight the efficacy of integrated amendments in alleviating salinity stress, offering a promising strategy for sustainable agriculture in saline environments.

Aims: Saline sandy soils severely constrain sugar beet ( Beta vulgaris L.) productivity due to low nutrient retention, high salinity, and micronutrient imbalances, particularly boron deficiency. Although humic substances, glauconite, and boron fertilization have individually or pairwise improved crop performance, no previous field study has evaluated their ternary, dose-optimized integration as a multifunctional soil–plant management strategy under saline sandy conditions. Methods: This study investigated, for the first time, the combined application of soil-applied humic acid (600 kg/ha), glauconite (1100 kg/ha), and graded foliar boric acid (0, 1900, and 3800 g/ha) to test the hypothesis that their complementary physicochemical and physiological mechanisms would generate synergistic improvements in soil quality, crop performance, and sugar productivity beyond additive effects. Field experiments were conducted over two consecutive growing seasons (2021–2022) in West Minya, Egypt, using a split-plot design. Results: The integrated high-dose treatment (HG3800) significantly enhanced leaf area index (by 75%), chlorophyll content (46–71%), and net photosynthetic rate (40–128%) relative to the control. Root yield increased by 27% (reaching 56.7 ton/ha), while sugar yield rose by up to 79% (11.5 ton/ha). Sucrose concentration reached 20.4%, with reduced impurity indices and improved extractable sugar percentage (up to 90%). Based on fermentable sugar yield, the HG3800 treatment corresponded to a substantial increase in theoretical bioethanol output potential per hectare. Concurrently, soil electrical conductivity declined by 24%, soil organic matter increased, and bulk density decreased, reflecting improved soil structure and salinity mitigation. Conclusions: The ternary, dose-optimized integration of humic acid, glauconite, and foliar boron represents a novel agronomic strategy that simultaneously enhances soil physicochemical properties, physiological efficiency, and fermentable sugar production. By directly linking yield gains to increased bioethanol feedstock potential, this approach offers a scalable and multifunctional pathway for sustainable bioenergy-oriented sugar beet production in salt-affected sandy soils.