Waste from crustaceans has adverse effects on the environment. In this respect, shrimp waste was valorized for producing chitosan nanoparticles as a source for eco-friendly nano-nitrogen fertilizer. The application of nano-nitrogen fertilizers is a valuable alternative approach in agriculture due to its potential for reducing the application of mineral nitrogen fertilizers and increasing yield quality and quantity, thereby helping to reduce the worldwide food shortage. Chitosan nanoparticles were foliar sprayed at three volumes (0, 7, and 14 L/ha) and compared with mineral nitrogen fertilizer (M-N) sprayed at three volumes (0, 120, and 240 kg N/ha) and their combination on two wheat cultivars (Misr-1 and Gemaiza-11) during two consecutive seasons (2019/2020 and 2020/2021) in order to evaluate the agronomic response. The synthesized chitosan nanoparticles displayed characteristic bands of both Nan-N and urea/chitosan from 500–4000 cm⁻¹. They are stable and have a huge surface area of 73.21 m² g⁻¹. The results revealed significant differences among wheat cultivars, fertilization applications, individual or combined, and their interactions for yield-contributing traits. Foliar application of nano-nitrogen fertilizer at 14 L/ha combined with mineral fertilizer at 240 kg/ha significantly increased total chlorophyll content by 41 and 31% compared to control; concerning plant height, the two cultivars recorded the tallest plants (86.2 and 86.5 cm) compared to control. On the other hand, the heaviest 1000-grain weight (55.8 and 57.4 g) was recorded with treatment of 120 kg Mn-N and 14 L Nan-N/ha compared to the control (47.6 and 45.5 g). The Misr-1 cultivar achieved the highest values for grain yield and nitrogen (1.30 and 1.91 mg/L) and potassium (9.87 and 9.81 mg/L) in the two studied seasons when foliarly sprayed with the combination of 120 kg Mn-N/ha + 14 L Nan-N/ha compared to the Gemaiza-11 cultivar. It can be concluded that Misr-1 exhibited higher levels of total chlorophyll content, spike length, 100-grain weight, grain yield in kg/ha, and nitrogen and potassium. However, Gemaiza-11 displayed higher biomass and straw yield values, plant height, and sodium concentration values. It could be economically recommended to use the application of 120 kg Mn-N/ha + 14 L Nan-N/ha on the Misr-1 cultivar to achieve the highest crop yield.

Two successive field trials were carried out at the experimental farm of the Agriculture Department of Fayoum University, Fayoum, Egypt, to investigate the sole or dual interaction effect of applying a foliar spray of Aloe saponaria extract (Ae) or potassium silicate (KSi) on reducing the stressful salinity impacts on the development, yield, and features of roselle (Hibiscus sabdariffa L.) plants. Both Ae or KSi were used at three rates: 0% (0 cm³ L⁻¹), 0.5% (5 cm³ L⁻¹), and 1% (10 cm³ L⁻¹) and 0, 30, and 60 g L⁻¹, respectively. Three rates of salinity, measured by the electrical conductivity of a saturated soil extract (ECe), were also used: normal soil (ECe < 4 dS/m) (S1); moderately-saline soil (ECe: 4–8 dS/m) (S2); and highly-saline soil (ECe: 8–16 dS/m) (S3). The lowest level of salinity yielded the highest levels of all traits except for pH, chloride, and sodium. Ae at 0.5% increased the values of total soluble sugars, total free amino acids, potassium, anthocyanin, a single-photon avalanche diode, stem diameter, fruit number, and fresh weight, whereas 1% of Ae resulted in the highest plant height, chlorophyll fluorescence (Fv/Fm), performance index, relative water content, membrane stability index, proline, total soluble sugars, and acidity. KSi either at 30 or 60 g L⁻¹ greatly increased these abovementioned attributes. Fruit number and fruit fresh weight per plant also increased significantly with the combination of Ae at 1% and KSi at 30 g L⁻¹ under normal soil conditions.

Spinach (Spinacia oleracea L.) is considered a nitrogen (N) intensive plant with high nitrate (NO₃⁻) accumulation in its leaves. The current study via a two-year field trial introduced an approach by combining N fertilization from different sources (e.g., ammonium nitrate; 33.5 % N, and urea; 48 % N) at different rates (180, and 360 kg N ha⁻¹) with the foliar spraying of molybdenum (Mo) as sodium molybdate, and/or manganese (Mn) as manganese sulphate at rates of 50 and 100 mgL⁻¹ of each or with a mixture of Mo and Mn at rates of 50 and 50 mg L⁻¹, respectively on growth, chemical constituents, and NO₃⁻ accumulation in spinach leaves. Our findings revealed that the highest rate of N fertilization (360 kg N ha⁻¹) significantly increased most of the measured parameters e.g., plant length, fresh and dry weight plant⁻¹, number of leaves plant⁻¹, leaf area plant⁻¹, leaf pigments (chlorophyll a, b and carotenoids), nutrients (N, P, K, Fe, Mn, Zn), total soluble carbohydrates, protein content, net assimilation rate, and NO₃⁻ accumulation, but decreased leaf area ratio and relative growth rate. Moreover, plants received urea-N fertilizer gave the highest values of all previous attributes when compared with ammonium nitrate –N fertilizers, and the lowest values of NO₃⁻ accumulation. The co-fertilization of N-Mo-Mn gave the highest values in all studied attributes and the lowest NO₃⁻ accumulation. The best treatment was recorded under the treatment of 360 kg N-urea ha⁻¹ in parallel with the combined foliar application of Mo and Mn (50 + 50 mg L⁻¹). Our findings proposed that the co-fertilization of N-Mo-Mn could enhance spinach yield and its quality, while reducing NO₃⁻ accumulation in leaves, resulting agronomical, environmental and economic benefits.

Drought stress and nutrient status are highly important for plant growth and productivity. Two field experiments were conducted during two consecutive seasons (2017–2018 and 2018–2019) at El-Molak, Abo-Hammad, Sharkia, Egypt. This work was conducted under sandy soil conditions to evaluate the effects of foliar application with growth regulators (PGRs) such as cycocel (CCC), applied at 0, 500, or 1000 mg L⁻¹, and/or salicylic acid (SA), applied at 0, 0.05, or 0.1 mM on the productivity as well as improving drought tolerance of three wheat cultivars, i.e., Gemmeiza 11, Misr 1, and Giza 171 under three irrigation intervals, i.e., 10, 15, and 20 days. Foliar spray was given at 35 and 50 days after planting (DAP). The obtained results showed that mean squares as a result of the main effect and first- and second-order interactions were significant (p ≤ 0.01) for all studied traits. The application of SA increased total chlorophyll content and flag leaf area (cm²) while the number of days to 50% heading was decreased; however, the number of spikes m⁻², protein and proline contents were increased with the application of CCC. The cultivar Misr 1 outperformed the other cultivars in the most studied traits. Estimates of heritability in the broad sense (h²b) were, on average, higher in five physiological traits than other agronomic traits, and the highest estimate of h²b (95.1%) was shown by the number of days to 50% heading followed by protein content (91.90%). Among the interactions between irrigation and growth regulators, the I₍₁₀₎ × SA_(0.1) recorded the highest flag leaf area (cm²), SPAD value, number of grains spike⁻¹, 1000-grain weight (g), and grain yield (t ha⁻¹). Among the interactions between irrigation and cultivars, the I₍₁₀₎ × Misr 1 recorded the highest flag leaf area (cm²), SPAD value, number of grains spike⁻¹, and grain yield (t ha⁻¹). Among the interactions among irrigation, growth regulators and cultivars, the I₍₁₀₎ × SA_(0.1) × Misr 1 recorded the highest flag leaf area (cm²), number of grains spike⁻¹, 1000-grain weight (g), and grain yield (t ha⁻¹). Correlation coefficient between grain yield (t ha⁻¹) and each of the number of days to 50% heading, flag leaf area, total chlorophyll content, number of spikes m⁻², number of grains spike⁻¹, and 1000-grain weight was positive and significant. Three main factors for the studied variables were created from the application of the factor analysis technique. Grain yield ha⁻¹ (Y) can be predicted by the method of forwarding stepwise through applying the automatic linear regression analysis. Besides, the best prediction equation of grain yield ha⁻¹ (Y) was formulated as: Ỷ = −14.36 + 0.11 number of grains spike⁻¹ (NGS) + 0.09 1000-grain weight (THW) + 0.04 number of spike m⁻² (NSm) + 0.03 days to 50% heading (DF) + 0.02 total chlorophyll content (TC) with adjusted-R² (87.33%).