Drought stress is seriously affecting maize production. To investigate the influence of calcium (Ca) foliar application on maize production and chemical composition of grains under drought stress, two experiments were carried out at Cairo University Research Station, Giza, Egypt, during the summer seasons of 2018 and 2019. The experimental design was split-split plot design with a completely randomized blocks arrangement with three replications. Water regimes were assigned to the main plots [100 (control), 75, and 50% of estimated evapotranspiration]. Calcium levels (zero and 50 mg/L) were assigned to the sub plots. Maize cultivars (SC-P3444, Sammaz-35 and EVDT) were assigned to the sub-sub plots. Three maize cultivars were sprayed with Ca solution concentration (50 mg/L) under normal and drought conditions. The control treatment (0 mg/L) was sprayed with an equal amount of distilled water for comparison. Results indicated a significant decrease in total yield and grain characteristics [protein, ash, total sugars, nitrogen (N), phosphorus (P), potassium (K), and iron (Fe) contents] as a response of drought. Calcium foliar application significantly increased maize yield, protein, ash, carbohydrates, starch, total sugars, and ionic contents of grains, except for manganese (Mn), under all irrigation levels. Based on the drought tolerance index (DTI), only cultivar SC-P3444 showed drought tolerance while cultivars Sammaz-35 and EVDT were sensitive to drought stress. Foliar application of Ca on SC-P3444 cultivar achieved the highest grain yield per hectare (8061 kg) under the water regime of 100% of the total evapotranspiration, followed by Sammaz-35 (7570 kg), and EVDT (7191 kg) cultivars. At the water regime of 75% of estimated evapotranspiration (75% irrigation), Ca foliar application increased grain yield by 16, 13 and 14% in SC-P3444, Sammaz-35, and EVDT, respectively. At the water regime of 50% of the estimated evapotranspiration (50% irrigation), Ca foliar application increased grain yield by 17, 16, and 13% in SC-P3444, Sammaz-35, and EVDT, respectively. In brief, Ca had a clear impact on productivity and grain quality with important implications for maize yield under normal and water stress conditions. Our findings demonstrate that foliar application of Ca enabled drought stressed maize plants to survive better under stress. The most water stress tolerant cultivar was SC-P3444 followed by Sammaz-35 and EVDT under drought stress.

To reduce the environmental pollution, this study was designed to test the effect of using compost and biostimulants as total or partial replacement for mineral nitrogen on productivity and grain quality of two wheat cultivars. Two field experiments were conducted in the Desert Experimental Station, Cairo University located at Wadi El-Natroon, Egypt during two successive seasons (2016/2017 and 2017/2018). A split-split-plot design in a randomized complete block arrangement was used. Four fertilizer treatments (100% mineral nitrogen as control, 100% compost, 75% compost + 25% mineral nitrogen and 50% compost + 50% mineral nitrogen). Four levels of biostimulants foliar applications (control, 0.75 L ha−1, 1.13 L ha−1 and 1.5 L ha−1). Treatments were tested on two wheat cultivars (Egyptian cultivar, Gemmiza-10 and Nigerian cultivar, LacriWhit-4). Results indicated that, the treatment of 50% compost + 50% mineral nitrogen fertilizer along with 1.5 L ha−1 of biostimulants (VIUSID® agro) significantly increased the grain yield of both wheat cultivars, LacriWhit-4 and Gemmiza-10 (4.44- and 4.53-ton ha−1, respectively). The increase of grain yield was 0.9- and 1.36-ton ha−1, respectively. The treatment of 100% compost significantly increased protein, crude fiber, total sugars, Mg and Mn contents in grain while the treatment of 100% mineral nitrogen fertilizer significantly increased ash, total phenols, P and Ca contents in grain. Replacing nitrogen fertilization with compost significantly increased ether extract and carbohydrates content of the Nigerian cultivar grains while N, K and Fe contents were increased in the grains of both tested cultivars. The foliar application of biostimulants (VIUSID® agro) at different levels significantly increased protein, carbohydrates, total sugars, P, K, Ca, Cu and Zn contents. It can be concluded that replacing mineral nitrogen fertilizer with a combination of compost and mineral nitrogen (50% compost + 50% mineral nitrogen) along with 1.5 L ha−1 of biostimulants (VIUSID® agro) is recommended for the enhancement of productivity and grain quality of wheat while reducing environmental pollution.

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