Thesis (Ph.D.) - Cairo University - Faculty of African Postgraduate Studies - Department of Natural Resources

Drought and salinity negatively affect root nutrients uptake and consequently decrease yield. Adequate soil management under such conditions involves the use of silicate fertilizers for enhancing yield and plantation properties. A split- split plot experiment was conducted in Oraby Village, Maryout area, Alexandria in the most dried year (2009/ 2010) to obsess the effect of silicon as a beneficial nutrient element on winter wheat especially under combined salinity and drought stresses. Results revealed the following:positive response functions of silicon foliar application to root calcium, potassium, magnesium, nitrogen and silicon uptake but the opposite is true for sodium.Yield and plantation properties were maintained with silicon foliar application especially under environmental stress condition. Soil stress index exhibits the known hysteresis and relativity with the advance of connecting soil physical properties with yield and plantation under stress conditions.A direct relationship between the SSI and PSI was observed under drought and salinity stresses.The empirical equations between the latter two indices reverse that SSI is better than PSI in studying drought and salinity either alone or in combination. But the opposite is true in the case of other biotic and abiotic stresses because plant is the final receiver of all types of stresses.By comparing between SSI and PSI, the type of compensated water uptake could be distinguished.The role of silicon was better under stressed conditions than unstressed ones and potassium silicate is better than sodium silicate. A new model, SSIMOD, was discussed.

Issued also as CD