A FIELD experiment was conducted during two successive seasons on a slightly saline sandy clay loam soil calcareous in nature at a newly reclaimed area comprising the desert zone of El-Fayoum district, El-Fayoum Governorate, Egypt, located between latitude 29°21′48″N longitude 30°44′45″E. The main target of this study was to identify the positive effects of applied elemental sulphur (i.e, at the rates of 0, 200, 350 and 450 kg fed-1, as soil application), seed bio-inoculation (i.e., P-dissolving bacteria of Bacillus megatherium var. phosphaticum) and seaweed extract (at the rate 1.0 kg fed-1 with 400 liter water as foliar application) either solely or combined treatments on sunflower (Helianthus annuns, c.v.Hysun 336). Growth criteria, i.e., plant height, the number of leaves/plant as well as dry matter weight/plant and leaf content of total chlorophyll were determined after 50 days of sowing. At harvest yield and yield components as head diameter, 100 seeds weight, seeds weight fed-1, seed oil, protein and nutrient contents were also determined. Some soil properties, i.e., soil pH, ECe, ESP and available macro and micronutrient contents were also taken into consideration. Samples of the plants rhizosphere were collected after 50 and 90 days of sowing to determine CO2 evolution, dehydrogenases activity and total bacterial counts.
Data showed a clear response for studied soil properties as well as soil nutritional status as a result of the applied treatments, particularly those treated with the highest rate of elemental sulphur in combination with bio-fertilizer and foliar seaweed extract. The best and achieved greatest values of growth and nutritional status of plants, particularly at the early flowering stage were associated with plants subjected to the combined treatments compared to the other solely ones, which positively reflected on seed yield and its quality (oil and protein content). In general, the values of plant parameters were optimized, for bio-inoculated, with increasing the applied elemental sulphur rate350 or 450 kg fed-1, with an insignificant difference.
The results also showed that inoculation with P-dissolving bacteria in the presence of different elemental sulphur levels combined with foliar seaweed extract encouraged the total bacterial counts, CO2 evolution and dehydrogenase activity at 50 and 90 days.
So that, it could be recommended that elemental sulphur, seed bio-inoculation with P-dissolving bacteria and seaweed extract as a foliar application may be used to alleviate the hazardous effects of saline soil calcareous in nature, on sunflower seed yield and its quality.