Effect of Source and Rate of Nitrogen on Photosynthesis Pigments, Proline, Soluble Sugar, Sodium and Potassium in Purslane (Portulaca oleracea) Irrigated by Saline Water

The trend of saline water utilization in agricultural production is increasing. In order to evaluate the effect of source and rate of nitrogen on physiological characteristics of purslane (Portulaca oleracea L.) irrigated by saline water, a factorial experiment was conducted in a completely randomized design with three replications in the greenhouse conditions. Treatments included five levels of saline water (distilled water as the control, natural saline water with EC of 2.2 dS/m, three levels of saline water prepared by addition of NaCl (2.2, 4.4, and 6.6 dS/m) and four levels of fertilizer (control, 40, 80, and 120 g/kg soil) in the form of poultry manure and chemical fertilizer. The results showed that an increase in salinity increased chlorophyll a and chlorophyll b and then decreased them at 6.6 dS/m. An increase in salinity levels increased the amount of sodium and decreased the amount of potassium. The maximum amount of chlorophyll a and chlorophyll b were observed with 4.4 dS/m treatment. The interaction of salinity level × nitrogen source × nitrogen rate was not significant for any of the measured parameters. Results of poultry manure were better than those of chemical fertilizer, because chlorophyll content, soluble sugar, proline, sodium, and potassium in purslane plant were higher. Thus, the plants fertilized with poultry manure or those irrigated with natural saline water experienced salinity stress, but their higher uptake of potassium alleviated the stress effects and made it tolerable for the plant.