Potassium solubilizing bacteria (PSB) are able to dissolve K from K-minerals and enhance plant growth and yield. A field experiment was carried out during 2017/2018–2018/2019 growing seasons in a randomized complete block design (RCBD) with three replicates. This study aims to assess the performance of bio-fertilization (Bacillus cereus) as PSB on the growth of potato (Kara Spp) and availability of N, P, and K. Potato plants were fertilized with K-feldspar and inoculated with PSB. The results showed that the PSB significantly increased the plant height (PH), branches number (BN), and shoot dry weight by about 15%, 27%, and 26%, respectively, compared to the untreated one. Soil available K increased by 42% as a result of PSB inoculation, moreover, K uptake by potato tubers increased by 62% in compassion with untreated plants. Leaf N, P, and K concentrations as well as the uptake were significantly increased in the plants inoculated with PSB compared to the un-inoculated plants. The graded weights of potato were increased by 20%, 26%, and 25%, for large, medium, and small size of tubers, respectively as a result of applying of bio-fertilizer. The bio-fertilization of potato with Bacillus cereus significantly increased the total yield of potato by 21% above the untreated plants. The application of K-feldspar (12% total K₂O) at a rate of 240 kg K₂O ha⁻¹ to potato inoculated with Bacillus cereus gave a total tuber yield of 40 ton ha⁻¹.

Soil amendments may increase the slate tolerance of plants consequently; it may increase the opportunity of using saline water in agricultural production. In the present pot trial, the effects of biochar (BIC) and compost (COM) on roselle (Hibiscus sabdariffa L.) irrigated with saline water (EC = 7.50 dS m⁻¹) was studied. Roselle plants were amended with biochar (BIC₁ and BIC₂) or compost (COM₁ and COM₂) at rates of 1 and 2% (w/w), as well as by a mixture of the two amendments (BIC₁+). The experiment included a control soil without any amendments. Biochar and compost significantly enhanced the soil quality and nutrients availability under saline irrigation. Compost and biochar improved the degree of soil aggregation, total soil porosity and soil microbial biomass. BIC₁ + COM₁ increased the soil microbial biomass carbon and nitrogen over the individual application of each amendments and control soil. BIC₁ + COM₁ increased the activity of dehydrogenase and phosphatase enzymes. Growth of roselle plants including: plant height, shoot fresh and dry weight, and chlorophyll were significantly responded to the added amendments. The maximum sepal’s yield was achieved from the combined application of compost and biochar. All the investigated treatments caused remarkable increases in the total flavonol and anthocyanin. BIC₁ + COM₁ increased the total anthocyanin and flavonol by 29 and 17% above the control. Despite the notable improvement in soil and roselle quality as a result of the single addition of compost or biochar, there is a clear superiority due to mixing the two amendments. It can be concluded that mixing of biochar and compost is recommended for roselle plants irrigated with saline water.

Exposure of banana plants, one of the most important tropical and subtropical plants, to low temperatures causes a severe drop in productivity, as they are sensitive to cold and do not have a strong defense system against chilling. Therefore, this study aimed to improve the growth and resistance to cold stress of banana plants using foliar treatments of chitosan nanoparticles (CH-NPs). CH-NPs produced by nanotechnology have been used to enhance tolerance and plant growth under different abiotic stresses, e.g., salinity and drought; however, there is little information available about their effects on banana plants under cold stress. In this study, banana plants were sprayed with four concentrations of CH-NPs—i.e., 0, 100, 200, and 400 mg L⁻¹ of deionized water—and a group that had not been cold stressed or undergone CH-NP treatment was used as control. Banana plants (Musa acuminata var. Baxi) were grown in a growth chamber and exposed to cold stress (5 °C for 72 h). Foliar application of CH-NPs caused significant increases (p < 0.05) in most of the growth parameters and in the nutrient content of the banana plants. Spraying banana plants with CH-NPs (400 mg L⁻¹) increased the fresh and dry weights by 14 and 41%, respectively, compared to the control. A positive correlation was found between the foliar application of CH-NPs, on the one hand, and photosynthesis pigments and antioxidant enzyme activities on the other. Spraying banana plants with CH-NPs decreased malondialdehyde (MDA) and reactive oxygen species (ROS), i.e., hydrogen peroxide (H₂O₂), hydroxyl radicals (^•OH), and superoxide anions (O₂^•−). CH-NPs (400 mg L⁻¹) decreased MDA, H₂O₂, ^•OH, and O₂^•− by 33, 33, 40, and 48%, respectively, compared to the unsprayed plants. We hypothesize that CH-NPs increase the efficiency of banana plants in the face of cold stress by reducing the accumulation of reactive oxygen species and, in consequence, the degree of oxidative stress. The accumulation of osmoprotectants (soluble carbohydrates, proline, and amino acids) contributed to enhancing the cold stress tolerance in the banana plants. Foliar application of CH-NPs can be used as a sustainable and economically feasible approach to achieving cold stress tolerance.

Enrichment of soils with organic amendments could increase the content of available nutrients, improve soil chemical characteristics and increase plant growth. In the current pots experiment, the influences of biochar (BC), humic acid (HA), and compost (CO) on barely growth were investigated under saline conditions. Barely plants grown on a clay loam soil and irrigated with saline water concentration of (EC = 13.8 dS m⁻¹) were amended with BC, HA and CO at a rate of 1 or 3% of soil weight. The results showed that BC, HA and CO treatments had significant effects on the soil salinity, pH, organic matter (SOM), and plant nutrients. The results showed that the high rate application of BC, HA and CO increased the SOM by 14, 75 and 58% respectively, above the control. Consequently, the total chlorophyll as affected by the treatments can be arranged in descending order: BC₃ > CO₁ > CO₃ > HA₃ > HA₁ > BC₁ > C. The high rates of BC, HA and CO increased the dry biomass by 28.0, 21.6 and 39.7% respectively, above the control %, respectively, above the control. The investigated organic amendments increased the nutrients availability and uptake and enhanced the synthesis of chlorophyll in the plant tissues and this may be the reason of increasing the ability of barley to tolerate salinity.