The effect of salinity on biomass production, nodule formation and root acetylene reduction activity (ARA) in alfalfa (Medicago sativa L.) was investigated under field conditions. Seeds of alfalfa cv. Batini inoculated with one of four different Rhizobium strains were planted in washed loamy sandfilled transparent PVC cylinders arranged concentrically in plastic pots embedded in soil with the rims just above the soil surface. Salinization of plants commenced one week after emergence up to 16 weeks. Nitrogen (N)-free nutrient solutions of different concentrations (full strength and 0.05 strength) were also applied during this period. Tap water (0.8 dS nr 1 ) served as control for the nutrient solution treatments as well as the salinity treatments which included 6.4 dS m 1 and 12.2 dSnr 1 prepared with NaCl. The Rhizobium 'Corresponding author. 489 strains were TAL 380, TAL 1372, TAL 1373, and Buraimi. Increased salinity was associated with reduced shoot dry weights, root nodulation and ARA. Of the four Rhizobium strains, the order of efficiency in nodulation was Buraimi > TAL 1372 > TAL 1373 > TAL 380. This order was maintained in biomass the production. The detrimental effects of salinity appeared to be ameliorated by application of nutrient solutions, with the full strength being more effective than the 0.05 strength.

Two field experiments were carried out at El-Areish Agricultural Research Station, North Sinai Governorate during the two winter growing seasons of 2005/2006 and 2006/2007 to study the effect of canola varieties (Serw 4 and Bactol) with superphosphate and rock phosphate at rates (15.5 and 31 kg P2O5 /fed.) on some yield components, seed yield and chemical composition of canola plant grown in calcareous soil. Results can be summarized as follows:1-Variety Serw 4 was significantly higher than Bactol one for plant height only in the first season. Also, the higher rate of P fertilizer in form of superphosphate was better than other treatments in the first season. 2-Variety Serw 4 gave the highest significant value of seed weight/ plant (g) and oil yield (kg/fed.) in the first season, and oil yield (kg/fed.) in the second season compared to Bactol one. In addition, higher rate of P fertilizer for both P sources was better than lower one for seed weight/ plant (g), seed yield (kg/fed.) and protein % in the first season as well as seed yield (kg/fed.), oil yield (kg/fed.) and protein % in the second season. Variety Serw 4 received any of both P sources at higher level produced significantly better yield and its components than those recorded by other treatments. 3-The treatment of superphosphate and rock phosphate at higher rate gave a significant increase in N-uptake of canola plants in comparison with the other fertilization treatments in both seasons. 4-N-Uptake of variety Serw 4 fertilized with superphosphate at a rate of 31 kg P2O5/fed. was significantly higher than those obtained by others treatments.

Representative disturbed soil samples of tow successive layers (0 -30 and 30 -60 cm) were collected from the permanent experimental plots at Bahtim to study the prolonged effect of permanent fertilization under two crop rotations namely, one and three years rotation on some soil chemical properties, i.e., electrical conductivity, soil reaction, soil organic matter content, total soluble ions and nutritional status (available N, P and K).The obtained results indicated that the plots of 3-year rotation recorded significantly higher values of EC, pH and OM content. Sodium ion was the dominant cation in soil followed by Mg ++ , Ca ++ and K + , respectively, while SO4 -was the dominant anion followed by Cland HCO3 -. Also, all soluble cations except K + , and anions as well as available N and P were relatively higher under the three-years rotation than the one-year rotation. The adverse trend was found for soluble and available K. Organic manuring resulted in significantly higher values of EC and appreciable values of OM content than the other mineral fertilizers or unfertilized one while the adverse trend was true for pH. Also, soluble cations and anions were relatively higher due to applying organic manuring than the other fertilizers except for NPK fertilizer, which gave the same soluble anions. Farmyard manuring improved nutritional status in the soil compared with the other mineral fertilizers, where available N, P and K were higher due to applying organic manuring. The soil surface layer contained significantly higher OM as well as available N, P and K than the subsurface one, while the adverse trend was found for soluble cations, also, no clear trend was noticed for pH and soluble anions with soil profile depth.No clear variation was occurred in the studied soil chemical properties such as available nutrients (N, P and K), soluble Ca ++ and Mg ++ , soluble anions and soil organic matter content with a relative increase of such property as a result of crop rotation and long-term fertilization throughout the last nineteen years. On the contrary, an adverse trend of EC and soluble Na + and K + was found due to fertilization and crop rotation while pH value took different trends due to crop rotation only. Also, the dominant soluble ions in 2007 differed from those in 1989 where Na + and So4 -were the dominant ions in 2007.