Role of compost, biochar and sugar alcohols in raising the maize tolerance to water deficit conditions

Now, it is known that people in Egypt are under the water poverty limit a long time ago due to climate change and the shortage of water resources. These conditions hamper agricultural development in Egypt. Thus, a practical solution must be undertaken for confronting the water scarcity that hindered agricultural development in Egypt. So, two field trials were executed to assess different irrigation techniques [(100, 75 and 50 % of irrigation requirements (IR)] as main plots. While different soil conditioners [without (control), biochar (at rate of 24 Mg ha-1) and plant compost (at rate of 24 Mg ha-1) in addition to both of them as combined treatment (at rate of 12 Mg ha-1 for each conditioner)] were evaluated as subplots. Also, the foliar application of glycerol and sorbitol (0.0, and 500 mM L-1) represented the sub-sub plots. Maize was used as an experimental plant. Findings illustrate that water deficit treatments (75 and 50 % of IR) led to a raise in the production of enzymatic antioxidants in maize leaves at the stage of 60 days after sowing. While the studied soil amendments (either solely or in combination) and the sugar alcohols led to a decline the values of these enzymatic antioxidants. On the contrary, at the period of 90 days from sowing (growth advanced stage), the grown plants without the studied substances (soil conditioners and sugar alcohols) cannot continue producing these enzymatic antioxidants under water deficit treatments. Also, the deficit irrigation (75 and 50 % of IR) caused a significant decline in the performance and productivity of maize compared to traditional irrigation (100 % of IR). For example, the highest values of the studied growth criteria e.g., fresh weight (951.64 and 965.61 g plant-1, for 1st and 2nd seasons, respectively), leaf area (620.25 and 628.56 cm2 plant-1, for 1st and 2nd seasons, respectively) and chlorophyll content (40.55 and 41.42 SPAD for 1st and 2nd seasons, respectively) were realized under traditional irrigation (100 % of IR) followed by those values achieved under deficit irrigation treatment (75 % of IR), while the lowest one were recorded with deficit irrigation treatment (50 % of IR). Regarding the soil conditioners effect, the compost and biochar either solely or in combination improved the plant performance and productivity compared to the corresponding plants grown without soil conditioners. The highest values of growth criteria and productivity were realized with the combined treatment of compost and biochar followed by compost alone then biochar alone and lately control treatment (without soil conditioner). Concerning sugar alcohols, the exogenous application of sorbitol was the superior treatment, while the glycerol came in the second order and lately control treatment (without sugar alcohols). Generally, it can be concluded that a combination of compost and biochar may hold enough amounts of irrigation water and nutrients and release them as required by the maize plant, thus enhancing plant growth performance with the limited supply of irrigation water. Also, sugar alcohols have a vital role in raising maize tolerance to water deficit conditions.