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.

This study aimed to use organic fertilizers, e.g., compost and manures, and a halophytic plant [wavy-leaved saltbush (Atriplex undulata)] to remediate an agricultural soil polluted with toxic elements. Compost or manure (1% w/w) was added to a polluted soil in a pot trial. The application of the organic fertilizer, whether compost or manure, led to a significant improvement in the growth of the tested plant. From the physiological point of view, the application of organic fertilizers to polluted soil significantly increased the content of chlorophyll, carotenoid, and proline and, furthermore, led to a clear decrease in malondialdehyde (MDA) in the plant leaves. The highest significant values of organic carbon in the polluted soil (SOC) and cation exchange capacity (CEC) were found for the soil amended by compost and planted with wavy-leaved saltbush. Manure significantly reduced the soil pH to 7.52. Compost significantly decreased Zn, Cu, Cd, and Pb availability by 19, 8, 12, and 13%, respectively, compared to the control. On the other hand, manure increased Zn, Cu, Cd, and Pb availability by 8, 15, 18, and 14%, respectively. Compost and manure reduced the bioconcentration factor (BCF) and translocation factor (TF) of Cd and Pb. Compost was more effective in increasing the phytostabilization of toxic metals by wavy-leaved saltbush plants compared to manure. The results of the current study confirm that the application of non-decomposed organic fertilizers to polluted soils increases the risk of pollution of the ecosystem with toxic elements. The cultivation of contaminated soils with halophytic plants with the addition of aged organic materials, e. g., compost, is an effective strategy to reduce the spreading of toxic metals in the ecosystem, thus mitigating their introduction into the food chain.

Biochar is one of the important recycling methods in sustainable development, as it ensures the transformation of agricultural wastes into fertilizers and conditioners that improve soil properties and fertility. In the current study, corn cob-derived biochar (CB) was used to reduce the negative effects of saline water on quinoa (Chenopodium quinoa cv. Utosaya Q37) grown on Aridisols and Entisols, which are the major soil groups of Egyptian soils. Quinoa plants were cultivated in pot experiment and were irrigated with saline water (EC = 10 dS m⁻¹). The experiment contained three treatments, including control without any treatment, biochar at a rate of 1% (w/w) (BC₁), and biochar at a rate of 3% (w/w) (BC₃). The findings of the current study showed that BC treatments realized significant effects on soil salinity, pH, soil organic matter (SOM), and plant availability and nutrients’ uptake in the two soils types. BC₃ increased the SOM in Entisols and Aridisols by 23 and 44%; moreover, the dry biomass of quinoa plants was ameliorated by 81 and 41%, respectively, compared with the control. Addition of biochar to soil increased the nutrients’ use efficiencies by quinoa plants for the two studied Egyptian soils. Biochar addition caused significant increases in the use efficiency of nitrogen (NUF), phosphorus (PUE), and potassium (KUE) by quinoa plants. BC₃ increased NUE, PUE, and KUS by 81, 81, and 80% for Entisols, while these increases were 40, 41, and 42% in the case of Aridisols. Based on the obtained results, the application of corn cob biochar improves the soil quality and alleviates the negative effects of saline irrigation on quinoa plants grown on Aridisols and Entisols Egyptian soils. Biochar can be used as a soil amendment in arid and semi-arid regions to reduce the salinity hazards.

Shortage of water in arid and semi-arid regions increases the need of applying efficient drip irrigation system. A two-year field study in the semi-arid region of Upper Egypt was carried in randomized complete block design with four replicates. Wheat plants were irrigated by 100 or 75% of water requirements (I₁₀₀ = 5,370 and I₇₅ = 4,027 m³ ha⁻¹). Irrigation of wheat by I₁₀₀ increased growth and uptake of nitrogen, phosphorus, and potassium compared to low irrigation level. I₁₀₀ caused 14 and 5% increase in straw and biological yield, respectively, compared to I₇₅. Grain yield and water use efficiency (WUE) were higher by 20 and 59% in the case of I₇₅ compared to I₁₀₀. The use of deficit irrigation in drip-irrigated wheat under arid conditions is an effective tool to maximize efficiency of water use; moreover, 4,027 m³ ha⁻¹ is the optimum irrigation rate for maximum WUE and grain yield.

Limited water availability in arid and semi-arid wheat production systems increases the need of applying efficient drip irrigation systems. However, there is little information available about the optimum level of nitrogen (N) fertilization for drip-irrigated wheat. A two-years field study in the semi-arid region of Upper Egypt was carried out in a randomized complete block design to investigate the response of drip-irrigated wheat to three levels of N fertilization (N₁₂₀ = 120, N₁₈₀ = 180, and N₂₄₀ = 240 kg ha⁻¹). N₂₄₀ increased the uptake of N, P, and K by 66.3, 48.6, and 43.5%, respectively, as compared to N₁₂₀. The application of N₂₄₀ increased the grain yield by 28.4 and 40.4% and water use efficiency by 27.6 and 41.8% the first and second season, respectively, as compared to N₁₂₀. Based on the obtained results, it is recommended to fertilize drip-irrigated wheat by 240 kg ha⁻¹.