Improving water use efficiency of crops for sustainable agriculture in dry lands

Improving water use efficiency in agriculture especially in dry countries is the dire need of the day. Oman has limited groundwater and in many places it is saline water. Therefore, various approaches could be used to improve plant productivity in saline dry lands. One approach to overcome the limitation of plant growth due to shortage of water and soil drying could be to promote root growth for efficient uptake of water from greater soil volume. Ethylene is a plant hormone that is involved in the regulation of many plant physiological responses especially under stress conditions. Water stress has been extensively associated with elevated release of endogenous ethylene by the plant which results in root growth inhibition dramatically. Therefore, there are certain plant growths promoting rhizobacteria (PGPR) which contain a unique enzyme that decreases ethylene in the inoculated plant roots. The main aim of this project was to isolate and evaluate plant growth promoting rhizobacteria for increasing plant growth and water use efficiency of crops. Moreover, different compost could enhance the growth of bacteria and save water for better growth. For this purpose, different bacteria were isolated from saline soil of Barak, Oman. The best bacteria that gave better growth in saline media were selected. The best two bacteria were reproduced and used for field trials. They were compared with two bio-stimulants (Stimpo and Regoplant) and grown in three different composts (Kala, Growers and Al-Mukhasib). The study was done in greenhouse using radish and okra plants grown in pots and irrigated with freshwater and saline (4 dS/m) treated waste water. Plant showed the best growth under freshwater irrigation compared with saline water. This happened due to salinity stress that affected water and nutrients movements from the soil to the plant. All used composts positively affected plant growth. However, Kala compost gave the best growth and productivity even under saline irrigation. The most important thing was how bacteria and bio-stimulants could improve plant growth and give significant effect especially under saline conditions. It was observed that Regoplant was good and gave better results for plant growth (plant height, fresh weight and fruit weight) with freshwater irrigation compared with saline condition. Whereas, Stimpo and bacteria showed positive effect under saline condition and they supported plant growth much better than Regoplant. However, Stimpo is still chemical compound and could have some side effects with long-term applications. Therefore, bacteria could be the best option for improving plant growth under saline conditions because it is from nature and could adapt with soil-water-plant conditions. Using these bacteria under Oman saline condition will improve the growth and productivity of different plants that could not survive under saline conditions.