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Lentil (Lens culinaris Medik) is an important component of the human diet due to its high mineral and protein contents. Abiotic stresses, i.e., drought, decreases plant growth and yield. Drought causes the synthesis of reactive oxygen species, which decrease a plant’s starch contents and growth. However, ACC-deaminase (1-aminocyclopropane-1-carboxylate deaminase) producing rhizobacteria can alleviate drought stress by decreasing ethylene levels. On the other hand, caffeic acid (CA) can also positively affect cell expansion and turgor pressure maintenance under drought stress. Therefore, the current study was planned with an aim to assess the effect of CA (0, 20, 50 and 100 ppm) and ACC-deaminase rhizobacteria (Lysinibacillus fusiform, Bacillus amyloliquefaciens) on lentils under drought stress. The combined application of CA and ACC-deaminase containing rhizobacteria significantly improved plant height (55%), number of pods per plant (51%), 1000-grain weight (45%), nitrogen concentration (56%), phosphorus concentration (19%), potassium concentration (21%), chlorophyll (54%), relative water contents RWC (60%) and protein contents (55%). A significant decrease in electrolyte leakage (30%), proline contents (44%), and hydrogen peroxide contents (54%), along with an improvement in cell membrane stability (34% over control) validated the combined use of CA and rhizobacteria. In conclusion, co-application of CA (20 ppm) and ACC-deaminase producing rhizobacteria can significantly improve plant growth and yield for farmers under drought stress. More investigations are suggested at the field level to select the best rhizobacteria and CA level for lentils under drought.

Objective: Biochar and a commercial humic acid-rich product, Humac (modified leonardite), represent soil amendments with the broad and beneficial effects on various soil properties. Their combination has been scarcely tested so far, although the positive impact of their interaction might be desirable. Materials and Methods: The dehydrogenase activity (DHA), microbial biomass carbon (Cmic), soil respiration (basal and substrate-induced), enzyme activities, total carbon (Ctot), and both shoot and root biomass yield were measured and compared in the short-term pot experiment with the lettuce seedlings. The following treatments were tested: the unamended soil (control), the Humac-amended soil (0.8 g&middot, kg&minus, 1), the biochar-amended soil (low biochar 32 g&middot, 1, high biochar 80 g&middot, 1), and the soil-amended with biochar + Humac. Results: The effect of both amendments on the soil pH was insignificant. The highest average values of Ctot and Cmic were detected in high biochar treatment and the highest average values of basal and substrate-induced respiration (glucose, glucosamine, alanine) were detected in the low biochar treatment. The phosphatase activity and fresh and dry lettuce aboveground biomass were the highest in the low biochar + Humac treatment. Conclusions: Even though the combination of both biochar + Humac decreased the microbial activities in the amended soil (Cmic, DHA, enzymes, substrate-induced respiration) at the low biochar dose, they mitigated the detrimental effect of the high biochar dose on respiration (all the types) and the enzyme (phosphatase, arylsulphatase) activities. In contrast to the previously published research in this issue, the effects could not be attributed to the change of the soil pH.

The high consumption of water in industries, domestic areas and increasing earth temperature are major hurdles for the optimization of maize yield. Being the third most widely cultivated cereal crop, improvement in maize yield is a big challenge under the limited availability of irrigation. As the water requirement for maize cultivation is high, it is time to introduce technologies that can mitigate drought stress and are environmentally friendly. The inoculation of rhizobacteria with &lsquo, 1-aminocyclopropane-1-carboxylate deaminase&rsquo, (ACCD) can play an imperative role in that regard by decreasing stress ethylene in plants. Biochar (BC) can also alleviate drought stress. Therefore, a field study was conducted, to examine the single and combined application of drought-tolerant plant-growth-promoting rhizobacteria (PGPRs) Achromobacter xylosoxidans and Enterobacter cloacae, with 15 Mg ha&minus, 1 of timber waste biochar (TWBC) at normal irrigation = 16 irrigations, mild drought = 14 irrigations and severe drought = 12 irrigation for maize cultivation. A significant improvement in shoot dry weight (28%), 1000-grains weight (19%), grain yield (27%), concentrations of N (43%), P (92%) and K (71%) in grains, rate of photosynthesis (33%), transpiration rate (55%), stomatal conductance (104%), chlorophyll A (33%), chlorophyll B (62%) and total chlorophyll (45%) of maize was noted under drought stress where E. cloacae + TWBC was applied. Likewise, the application of A. xylosoxidans + TWBC also significantly enhanced the plant height (24%) and cob length (9%) of maize under drought stress. In conclusion, E. cloacae is more effective than A. xylosoxidans, with 15 Mg ha&minus, 1 TWBC to increase maize yield under drought stress, due to the potential of higher &lsquo, 1-aminocyclopropane-1-carboxylate&rsquo, (ACC)-deaminase synthesis, better nutrient solubilization and indole acetic acid (IAA) production.