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Water scarcity is of growing concern in many countries around the world, especially within the arid and semi-arid zones. Accordingly, rationalizing irrigation water has become an obligation to achieve the sustainable developmental goals of these countries. This may take place via using deficit irrigation which is long thought to be an effective strategy to save and improve water productivity. The current study is a trial to evaluate the pros and cons of using 50 and 75 % of the irrigation requirements (IR) of wheat (deficit irrigations) versus 100 %IR, while precisely charting changes in wheat growth parameters, antioxidant enzymes in plant shoots and the overall nutritional status of plants (NPK contents). Accordingly, a field experiment was conducted for two successive seasons, followed a split-plot design in which deficit irrigations (two irrigations to achieve 50 % of the irrigations requirements (IR), three irrigations to attain 75 % IR, and four irrigations to fulfill 100 % IR) were placed in main plots while four different studied wheat cultivars were in subplots. Results obtained herein indicate that deficit irrigations led to significant reductions in growth parameters and productivity of all wheat cultivars, especially when using 50 % IR. It also decreased NPK contents within plant shoots while elevated their contents of proline, peroxidase, and catalase enzymes. On the other hand, this type of irrigation decreased virtual water content (VWC, the amount of water used in production on ton of wheat grains). Stress tolerance index (STI), and financial revenues per unit area were also assessed. The obtained values of grain productivity, STI, VWC and financial revenues were weighted via PCA analyses, and then introduced in a novel model to estimate the efficiency of deficit irrigations (ODEI) whose results specified that the overall efficiency decreased as follows: 50 %IR < 75 %IR < 100 %IR. In conclusion, deficit irrigation is not deemed appropriate for rationalizing irrigation water while growing wheat on arid soils.

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A comprehensive body of scientific evidence indicates that rhizobial bacteria and melatonin enhance salt tolerance of crop plants. The overall goal of this research was to evaluate the ability of Rhizobium leguminoserum bv phaseoli to suppress salinity stress impacts in common bean treated with melatonin. Treatments included bacterial inoculations (inoculated (RI) and non-inoculated (NI)), different salinity levels (non-saline (NS), 4 (S1) and 8 (S2) dS m-1 of NaCl) and priming (dry (PD), melatonin (PM100) and hydro (PH) priming) with six replications in growing media containing sterile sand and perlite (1:1). The results showed that the bacterial strain had the ability to produce indole acetic acid (IAA), ACC deaminase and siderophore. Plants exposed to salinity stress indicated a significant decline in growth, yield, yield components, nitrogen fixation and selective transport (ST), while showed a significant increase in sodium uptake. However, the combination of PM100 and RI treatments by improving growth, photosynthesis rate and nitrogen fixation positively influenced plant performance in saline conditions. The combined treatment declined the negative impacts of salinity by improving the potassium translocation, potassium to sodium ratio in the shoot and root and ST. In conclusion, the combination of melatonin and ACC deaminase producing rhizobium mitigated the negative effects of salinity. This result is attributed to the increased ST and decreased sodium uptake, which significantly reduced the accumulation of sodium ions in shoot.

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To cope with water crisis, wastewater reuse has been introduced as a potential source for irrigation. On the other hand, irrigation with wastewater may negatively affect the surroundings. In this study, reed plant (Phragmits australis) and its biochar were tested as low-cost treatments to enhance the efficiency of wastewater reclamation in wetlands within only 72 h. The investigated water was of low irrigation quality and exhibited high contents of BOD5 and fecal coliform. Moreover, this water contained high levels of soluble cations and anions; besides, being marginally contaminated with Cu, Mn and Cd. After 2 days in the sedimentation unit, wastewater was subjected to three reclamation treatments in parallel (each lasted for 24 h): (1) a "sand & gravel bed", (2) "reed plants grown on a sand & gravel bed" and (3) "biochar + a sand & gravel bed". The results showed that all treatments decreased BOD5, fecal coliform, total cations and anions, with superiority for the second and third treatments. The levels of the potentially toxic elements also decreased to values within the permissible levels. Although the aforementioned wastewater treatment processes upgraded the quality of this water, it remained in the poor grade. Biochar or reed plants grown on sand and gravel beds significantly improved wastewater quality to the medium quality grade, with superiority for biochar treatment. In conclusion, investigated treatments are guaranteed in wetlands for wastewater reclamation; yet, further protocols should be followed to achieve safe handling of this water and attain the sustainable goals.

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Soil organic carbon plays considerable roles in binding soil particles together forming aggregates. Carbon (C) incorporated within these aggregates is thought to be microbially processed; thus, investigating changes in microbial activities i.e. dehydrogenase, urease, catalase and phosphatase enzymes may explain, to some extent, the dynamics and probably mechanisms responsible of formation of these aggregates. Since, soil water content (SWC) may take part in stimulating/lessening activities of organic matter decomposers; thus, this study aimed at investigating the effects of rice straw as a source of organic C in combination with variable SWC on bioaccumulation of C within different soil aggregate size fractions (2000-250, 250-53 and < 53 µm) and hence formation of these aggregates. To achieve these objectives, a pot experiment was conducted for 90 days, including five water levels i.e. maintaining a water head 1 cm above the soil surface (W1), 100% of the saturation percentage, SP (W2), 80% of SP (W3), 65% of SP (W4) and 50% of SP (W5), beside of two rates of applied rice straw i.e. 0 and 15 g kg-1 (w/w). Results revealed that application of rice straw at a rate of 15 g kg-1 increased the activities of dehydrogenase, urease, neutral phosphatase and catalase enzymes within the first 60 days after application; thereafter, activities of the first three enzymes decreased considerably. Likewise, formation of soil macro- (2000-250 µm) and micro-aggregates (250-53 µm) increased by the end of the experimental period. The highest concentrations of soil carbon were incorporated within soil macro-aggregate, whereas the least C content was found within the "silt + clay" fraction. Increasing SWC resulted in significant reductions in activities of the aforementioned enzymes and consequent reductions occurred in soil aggregation. Carbon content within aggregates sized <250 µm were significantly correlated with the percentage of these aggregates in soil. Thus, soil aggregation is thought to be the byproduct of an aerobic biosynthetic microbial process in which more stable hydrophobic organic C existed mainly in macropores. This process probably occurred within the first 60 days after RS application.

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