Mitigation of water stress in broccoli by soil application of humic acid.

The main challenge to plant productivity is water scarcity, which is predicted to get worse with climate change, particularly in arid and semi-arid areas. Humic acid could improve plant tolerance to mitigate drought damage, which is an effective strategy to improve crop production and agriculture sustainability under limited water conditions in these regions, but its effective application rates should also be established. Thus, two field experiments were carried out at the Qaha Vegetable Research Farm in Qalubia Governorate, Egypt, during the two seasons of 2020-21 and 2021-22 on clay soil. The present study investigated the effect of three rates of humic acid application (0, 4.8, and 9.6 kg ha-1) on growth, yield, and quality of broccoli cv. Montop F1 hybrid under well-watered and drought conditions. Drought was induced by missing alternate irrigation. Soluble humic acid as potassium-humate was applied three times with irrigation water at the time of the first three irrigations of drought treatment. Water-stressed plants had a decrease in growth, yield, leaf chlorophyll, and nutrient content, while they showed an increase in the contents of leaf proline and curd dry matter and total soluble solids as well as water use efficiency, in both seasons. Soil application of humic acid was effective in mitigating the adverse effects of water deficit stress on the growth and yield of broccoli. Water-stressed plants had the highest WUE value (9.32 and 9.36 kg m3-1 in the first and second seasons, respectively) when the maximal humic acid rate was applied. Humic acid at a high level (9.6 kg ha-1) had the most promising results and represents an opportunity that must be applied to improve broccoli yield and its production sustainability in arid and semiarid regions.

Effect of water stress and foliar application of chitosan and glycine betaine on lettuce.

The present study investigated the effect of foliar application of chitosan at 150 ppm and glycine betaine at 700 ppm on lettuce plants cv. Balady grown under well-watered and water deficit conditions in terms of growth, yield, quality, and water usage efficiency. The study was conducted in Qalubia Governorate, Egypt, during the two seasons of 2020/2021 and 2021/2022 on clay soil. Results indicated that water-stressed plants had a reduction in plant fresh weight, plant height, leaf area, and total yield, chlorophyll content and relative water content, while they exhibited an increase in total soluble solids, nitrate, and proline contents as well as water-use efficiency in both seasons. The foliar application of chitosan or glycine betaine to lettuce significantly improved plant performance under limited and normal irrigation conditions in comparison with untreated plants. The maximum positive effect was for chitosan foliar application. Overall, the results of this study indicated that foliar application of chitosan or glycine betaine was a substitute technology for improving the lettuce yield and quality as well as increasing water use efficiency under both irrigation regimes, but may be more efficient in lettuce plants subjected to a water deficit.