Salinity impedes soil and crop productivity in over 900 million ha of arable lands worldwide due to the excessive accumulation of salt (NaCl). To utilize saline soils in agriculture, halophytes (salt-tolerant plants) are commonly cultivated. However, most food crops are glycophytes (salt-sensitive). Thus, to enhance the productivity of saline soils, gypsum (CaSO₄·2H₂O) as well as bio-organic (combined use of organic materials, such as compost and straw with the inoculation of beneficial microbes) amendments have been continuously recognized to improve the biological, physical and chemical properties of saline soils. CaSO₄·2H₂O regulates the exchange of sodium (Na⁺) for calcium (Ca²⁺) on the clay surfaces, thereby increasing the Ca²⁺/Na⁺ ratio in the soil solution. Intracellularly, Ca²⁺ also promotes a higher K⁺/Na⁺ ratio. Simultaneously, gypsum furnishes crops with sulfur (S) for enhanced growth and yield through the increased production of phytohormones, amino acids, glutathione and osmoprotectants, which are vital elicitors in plants’ responses to salinity stress. Likewise, bio-organic amendments improve the organic matter and carbon content, nutrient cycling, porosity, water holding capacity, soil enzyme activities and biodiversity in saline soils. Overall, the integrated application of gypsum and bio-organic amendments in cultivating glycophytes and halophytes is a highly promising strategy in enhancing the productivity of saline soils.

Mangrove (Avicennia marina) forests in the Red Sea cost have great concern from environmental, biological, economic, and social points of view. Therefore, assessing water contamination in this ecosystem is worth to be investigated. Consequently, here we aimed to examine the levels of salinity, acidity, and the total content of Fe, Mn, Cu, Zn, Cd, Cr, Ni, and Pb in water samples collected from the upper, middle, and lower part of three mangrove lagoons (i.e., Al-Shuaiba, Yanbu, and Jeddah), Red Sea, Saudi Arabia. The total metal content (µg L⁻¹) in water samples differed significantly among the studied areas and ranged from 286.2 to 4815.0 for Fe, 86.4–483.0 for Mn, 22.9–468.8 for Cu, 199.2–366.6 for Zn, 44.1–99.8 for Cd, 25.6–80.3 for Cr, 11.6–41.5 for Ni, and from 17.7 to 102.0 for Pb. The mean values of Cu, Zn, Cd, and Pb were higher than the WHO water quality standards for fisheries. Water samples in Yanbu were more contaminated and contained higher concentrations of all metals than Jeddah and Al-Shuaiba, due to the petrochemical industries in this industrial area. Our findings suggest that the high metal content in the water of these mangrove sites, particularly in Yanbu, should be considered due to the high potential environmental and human health risks in these ecosystems. These results may help for demonstrating effective approaches for the management of these lagoons. More studies will be carried out on the sediment and mangrove plants in this ecosystem.

The importance of inorganic fertilizers in squash crop productivity is enormous. However, the continuous use of inorganic fertilizers constitutes a serious problem to the environment and human health due to nitrate accumulation. Thus, two seasons (2020 and 2021) of field trials were carried out to investigate the effects of bio-organic amendments on squash under arid land conditions in Saudi Arabia. The bio-organic amendments were comprised of humic acid (HA) at three levels (0, 50 and 100 L/ha), inoculation of a cellulose-decomposing bacterium (CDB; Geobacillus stearothermophilus SSK-2018) and wheat straw at four levels (0, 20 and 30 t/ha and NPK 20:20:20 at 600 kg/ha as a positive control). A randomized split-split plot design replicated three times was used in laying out the field trials. The independent application of HA, CDB and wheat straw significantly (p ≤ 0.05) improved squash growth, yield and water-use efficiency in both seasons. Furthermore, HA significantly (p ≤ 0.05) reduced fruits’ nitrate content. HA (100 L/ha) reduced nitrate content in squash fruits by 87% and 71.6% compared to the control in 2020 and 2021, respectively. The application of 20 t/ha of wheat straw significantly (p ≤ 0.05) reduced nitrate accumulation in fruits compared to the positive control (NPK) by 5.9% and 13.6% in 2019/20 and 2020/21, respectively. Regression analysis shows that increased nitrate accumulation in fruits results in decreased squash growth and fruit yield. This study demonstrates the significance of bio-organic amendments in improving squash growth and yield while reducing nitrate accumulation in fruits.