Effect of proline and humic acid application in salinity stress mitigation on some vegetables in hydroponics

The research aimed to find suitable solutions to reduce the salinity stress of irrigation water for some types of vegetables in hydroponics under two drip and mist irrigation systems. The different concentrations of NaCl for irrigation water, are 500, 1000, 2000, 3000, and 4000 ppm used. Proline (30 mg∙dm -3), humic acid (300 mg∙dm -3) and compared without any from them were used to study their effect on the yield, and water use efficiency. The results indicated that the highest spinach and courgette yield (4.657 and 5.153 kg∙m -2) was observed for the DP500 treatment, and the lowest yield (0.348 and 0.634 kg∙m -2) was observed for the SW4000 treatment, respectively. The use of humic acid led to an increased yield on average by about 16.8 and 19.3% for spinach, and 39.4 and 51.7% for courgette, under drip and mist irrigation, respectively. Using proline led to an increased average yield of about 32.9 and 33% for spinach, and 51.8 and 58.4% for courgette, under drip and mist irrigation, respectively. The highest water use efficiency (WUE) of spinach and courgette (43.1 and 51.5 kg∙m -3) was observed for the DP500 treatment, and the lowest (3.2 and 6.3 kg∙m -3) was observed for the SW4000 treatment. According to our study, the use of proline and humic acid could compensate for the adverse effects of salinity under mist spraying more than drip irrigation.