Agricultural water rationalization expressed in irrigating the plants below their requirements became a significant strategy in crop water management. However, reduction in crop productivity under low water supply is realized. Therefore, the current study aimed to diminish sunflower yield losses associated with deficit irrigation using salicylic acid (SA). During two seasons of 2019 and 2020 at El Nubaria region, El Behaira Governorate, Egypt, combinations of three irrigation regimes (100, 85 and 70% of crop evapotranspiration, denoted WR_100%, WR_85%, and WR_70%, respectively), and three levels of SA (0.0, 0.5, and 1 mM. abbreviated as SA_0.0, SA_0.5, and SA_1.0, respectively) on sunflower plants performance were evaluated. Treatments were arranged in a strip–plot design with three replicates. Findings revealed that treated sunflower plants with WR_100% × SA_1.0 contained the highest amounts of total chlorophyll and carotenoids as well as the lowest proline content. Seed yield of WR_100% × SA_1.0 treatment was higher than that of WR_70% × SA_0.0 by 109.7% in the first season and 125.9% in the second one. As averages of the two seasons, SA_0.5 and SA_1.0 lowered the reductions in seed yield from 21.0% to 15.8 and 14.4% as well as 46.2% to 40.8 and 40.1% under WR_85% and WR_70%, respectively, compared to the farmer common practice (WR_100% × SA_0.0). WR_100% × SA_1.0 for iodine value as well as WR_100% × SA_1.0 and WR_100% × SA_0.5 for seed oil % were recorded the highest. Application of WR_100% × SA_1.0 and WR_100% × SA_0.5 were the effective combinations for ameliorating water use efficiency. In conclusion, involving salicylic acid in irrigation programs of sunflower became a decisive action to save water and alleviate the yield losses resulting from drought stress.

Under arid and semi-arid climates, adopting the appropriate tools for alleviating water deficit impacts is a critical factor that affects the physiological characteristics and yield of sunflower. Therefore, in order to find promising field practices in sunflower cultivation, the strip plots design in randomized complete block arrangement was used to examine the effects of two irrigation regimes as 100% (FI) and 85% (DI) of crop evapotranspiration and five antioxidant treatments on physiological and agronomic traits, yield response factor, and irrigation water use efficiency (IWUE) of sunflower. The antioxidant treatments involved two rates of ascorbic acid (150 and 300 mg L⁻¹) and two rates of citric acid (250 and 500 mg L⁻¹), in addition to the check treatment (tap water). The study was conducted for two growing seasons of 2019 and 2020 at the Experimental Farm of Ain Shams University, Egypt, located in a semi-arid environment. Findings showed that exogenous application of higher rate of ascorbic acid, i.e. 300 mg L⁻¹ with FI exhibited the highest increase of chlorophyll a, chlorophyll b and the lowest proline content compared to other interaction treatments. Seed yield was significantly higher with FI plus ascorbic acid 300 mg L⁻¹ and DI plus ascorbic acid 300 mg L⁻¹ treatments than with their counterpart check treatment in both growing seasons. Under DI, IWUE was improved with antioxidant-treated plants compared to untreated plants. Yield response factor as an indicator of crop tolerance to drought was higher than the unit (> 1) under all ascorbic acid and citric acid levels. It could be concluded that ascorbic acid and citric acids partially mitigated the reductions in growth and yield caused by low water supply. However, yield response factor demonstrated that the crop is still sensitive to drought. Thus, other applicable patterns should be adopted to increase the yield potential of sunflower for counteracting the adverse impacts of drought.

Barley (Hordeum vulgare, L.) is the fourth most important cereal crop in the world. Salinity decreases the productivity of plants grown under salinity conditions. It leads to deficiency and limited absorption of water and nutrients, ionic stress, oxidative stress, and osmotic imbalance. In saline soil, a field experiment was conducted to verify the effects of nine combinations among three levels of bio-fertilizers, i.e., control (without), arbuscular mycorrhizal fungi (AMF), and phosphate solubilizing bacteria (PSB), as well as three levels of phosphorus fertilizer recommended dose (RDP) on barley yield, its components and nutrients uptake, to evaluate the useful influences of these combinations to improve P management under salinity stress related to yield and its components as well as N, P, and K uptake in barley. Findings revealed that the combination AMF + 100% RDP improved plant height, length of spike, spikes weight, number of spikes plant⁻¹, weight of 1000-grain, straw yield, grain yield, uptake of nitrogen (N), phosphorus (P), potassium (K) in grain and uptake of nitrogen (N), phosphorus (P), potassium (K) in straw by 19.76, 33.21, 40.08, 33.76, 14.82, 24.95, 47.52, 104.54, 213.47, 168.24, 124.30, 183.59, and 160.84% in the first season, respectively. Meanwhile, the increase was 19.86, 29.73, 40.47, 39.94, 14.92, 24.95, 47.94, 104.73, 213.33, 168.64, 124.47, 183.86, and 161.09% in the second season, respectively. AMF showed greater efficiency and effectiveness compared to PSB in improving yield and its components for all studied traits. The results of principle component analysis indicated that all combinations except AMF + zero% RDP, PSB + zero% RDP, control + zero% RDP, and control + 66% RDP showed high scores on positive PC1, where all studied traits were high. Therefore, it is recommended to inoculate the soil with AMF or PSB with the addition of phosphate fertilizer at the recommended dose under salinity conditions, i.e., AMF + 100% RDP (T1) or AMF + 66% RDP (T2) or PSB + 100% RDP (T4). The use of bio-fertilizers has increased plant tolerance to salt stress, and this was evident from the increase in different traits with the use of treatments that include bio-fertilizers.