Adopting foliar antiperspirants reduces the negative effects of water stress on crop production. In this study effects of chitosan (Ch) and potassium silicate (PS) on maize sowing at two sowing dates under irrigation water levels (100% of irrigation water applied −Ir00 and 70% of irrigation water applied −Ir70) were investigated. Thus, during the spring and fall seasons of 2020–2021, a field experiment of two similar experiments was conducted at the experimental farm of Water Studies and Research Complex (WSRC) station, National Water Research Center, Toshka—Abu Simbel City, Egypt, which the sowing dates were allocated in the main plot, then a strip-plot design with five replicates was used. It was found that sowing maize seeds in the fall season led to attaining a higher maize yield than in the spring. Moreover, the adoption of Ir70 provides better maize yield and water use efficiency than Ir100, particularly at the fall season sowing date. In addition, the adoption of the higher Ch concentrations in the spring, led to better improvements in maize yield particularly under Ir70, while the adoption of the higher concentrations of PS in the fall seasons, led to better maize yield. It was concluded based on present findings that applying chitosan as foliar applications with concentrations at 500 (mg l−1) under Ir70 in the fall had significant effects to maintain the higher maize yield, water use efficiency and irrigation water use efficiency in the arid regions as Toshka district and other similar areas.

Previous studies have demonstrated the impact of potassium humate (KH) and chitosan (CH) on ameliorating drought effects, but their combined applications in promoting these benefits are still unfound. Therefore, the current study aims to evaluate the efficacy of KH and CH on corn growth, yield, nutrient contents, and water productivity under full and limited irrigation conditions. Under the drip irrigation system, a split-plot experiment was performed with three replications in the second week of February in the seasons of 2021 and 2022. The main plot was equipped with a valve and a flow emitter to control the amount of the targeted irrigation levels (full irrigation and limited irrigation from the development stage onwards), as well as four foliar applications in the subplot (0, CH 500 mg l−1, KH 3000 mg l−1, and CH 500 mg l−1 + KH 3000 mg l−1). It was found that separate foliar applications of KH or combined foliar applications of KH + CH had a significant impact on the most examined traits. However, compared to the control, adopting limited irrigation and applying combined applications thereof have significantly increased iron, zinc, manganese, oil, protein, yield, and water productivity. In addition, this combination decreased proline, and the maximum reduction was observed for the combined application with adopting full irrigation. In arid regions, the researcher recommends treating stressed plants with combined foliar applications of KH + CH, which could help plants overcome the negative effects of drought and attain the highest yield and water productivity.

While previous studies have demonstrated the positive effects of low cobalt (CB) levels and chitosan (CH) on yield and nutrient status, information about their individual and combined applications on plants under stress is still lacking. Therefore, we conducted a study to investigate CB and CH impacts on mitigating water stress during growth stages and their effects on corn macronutrient uptake and yield. Four irrigation schemes were employed, including (1) control (full irrigation), (2) 70% of irrigation water during the vegetative stage, (3) 70% of irrigation water during the flowering stage, and (4) 85% of irrigation water during both the vegetative and flowering stages. The plants were treated with (7.5 mg l−1) CB injected into the irrigation water and CH foliar application (500 mg l−1), while distilled water was used as the control. Plants that were exposed to water stress during the flowering stage and treated with CB, or those subjected to water stress during the vegetative stage and treated with CH, showed increased macronutrient uptake and growth, which had a positive effect on yield and water use efficiency. However, when CB and CH were applied in combination, their potential to enhance these features depended on the pattern of water stress adopted. Overall, the application of CB and CH was effective in mitigating water stress, and their combined application was particularly effective when 70% of irrigation water was applied during the flowering stage. This approach resulted in the highest yield, macronutrient uptake, water use efficiency, and tolerance index.

Water stress is the most detrimental stress which has significantly affected the yield particularly in arid climates. It is quite important to provide peanuts with a suitable supplement that can enhance its resistance and yield. Therefore, the current study aims to study the efficacy of cobalt and zinc on peanuts growth, yield, nutrient contents, and water use under full and limited irrigation conditions. For this purpose, a split- split plot experiment was conducted in 2021 and 2022. Three levels of peanuts gross water requirements (GWR) (100, 80 and 60%) were allocated in the main plots. In the sub plots, the plants were treated with cobalt (0 and 7.5 mg l-1). While the sub-sub plots were divided to tested the impacts of chelated zinc as (foliar and soil applications). Under GWR60% we detected marked reductions in yield and it was found that the adoption of separate soil applications of zinc under these conditions or foliar applications of zinc under GWR100&80%, had a significant impact on the most examined traits. However, compared to the control, adopting GWR60% and applying separate cobalt application thereof have significantly led to a lowest decline in iron, copper, yield and water use. Moreover, it was found adoption of foliar zinc applications in a combination with cobalt under GWR60% improved yield. This study recommend adopting GWR60% and treating plants with combined applications of foliar zinc+ soil application of cobalt, which could help plants overcome the negative impacts of water stress and achieve the highest yield and water use.

Upper Egypt is characterized by high temperatures in summer and low temperatures in winter, which has a significant impact on the dates of planting maize in this region. The productivity of the maize crop as well as the efficiency of the use of water can be severely affected by planting dates and drought. Consequently, the optimum irrigation level and planting date must be determined based on local conditions. Two irrigation schemes were used: (1) control (full irrigation water applied), (2) 70% of irrigation water. Field experiments were conducted at the water studies and research complex station, National Water Research Center in Toshka to evaluate two irrigation levels (full irrigation water applied and 70% of irrigation water requirements) under five planting dates (early seeding (mid-February and March), normal (mid- June) and late planting (mid- August and September) in 2019 and 2020) to determine the optimum planting date and irrigation level. Early SD has increased the days between seeding and plant emergence. Late SD reduced the number of days until the plant matured and had higher grain yields and water use efficiency (WUE). The planting date in September under the irrigation level of 70% achieved the best productivity and the best water use efficiency, where the productivity was 7.01 Mg ha−1 and the water use efficiency was 0.72 kg/m3 The data confirm the general perception of farmers that the September sowing date under 70% irrigation levels is the best within the experimentation area.

Enhancing plant nutrition during critical periods of water stress is a paramount objective. As such, this study aims to examine the effects that arise from implementing water stress regimes during the sensitive growth phases of groundnut. Furthermore, we will explore the impact of applying cobalt and potassium humate individually or in combination, either through foliar application (KH-F) or soil amendments (KH-S), to mitigate the adverse effects on nutrient accumulation, yield, and irrigation water use efficiency (Iwue). A field experiment was conducted between 2021 and 2022 using a split-split plot design. In the main plots, an additional control of full irrigation requirement scheme (IR100) was implemented, along with three other schemes: the first involved applying 75% of the irrigation requirement during the development stage (IRD75), the second applied 75% during the flowering till pod stage (IRF75), and the third involved applying 85% from the development stage till the pod stage (IR85). In the subplots, cobalt was applied at rates of 0 and 7.5 mg l−1 to the plants. The sub-sub plots were further divided to investigate the effects of KH-F and KH-S. Plants that experienced water stress during the flowering stage were found to be more vulnerable. However, when treated with KH-S, there were significant improvements in yield compared to KH-F treatment. This effect was particularly pronounced under the IRF75 irrigation scheme. Interestingly, there was an antagonistic relationship observed between cobalt and iron or manganese, in contrast to other nutrients. When KH-S was applied in combination with cobalt, it showed the potential to enhance various characteristics and increase the uptake of iron or manganese. The highest yield, nutrient accumulation, and Iwue were achieved through the combined application of cobalt and KH-S, along with adopting the IR85% irrigation scheme.