This study was carried out during three successive seasons of 2010/2011, 2011/2012 and 2012/2013 in a private orchard at 76 km Cairo, Alex. Desert road  to investigate the effect of nitrogen and potassium fertilization treatments and shading with white net on yield, and fruit quality of three-years-old mango (Mangifica indica L.) cv. Keitt grafted on sucary seedling rootstocks planted at 2.5×2.5 meters apart grown in sandy soil under drip irrigation system with wells water .This experiment included nine treatments of fertilization: T1= N 80+ K2O 80 Kg/Fed., T2= N 80+ K2O 100 Kg/Fed., T3= N 100+ K2O 80 Kg/Fed., T4= N 100+ K2O 100 Kg/Fed., T5= N 120+ K2O 80 Kg/Fed., T6= N 120+ K2O 100 Kg/Fed.,T7= N 150+ K2O 80 Kg/Fed., T8= N 150+ K2O 100 Kg/Fed. and control (T9) = N 133+ K2O 90 Kg/Fed.. The results cleared that mango Keitt cv. trees grown under white net shading condition significantly increased yield (kg)/ tree, number of fruit set/ panicle, fruit weight, TSS and ascorbic acid content. Trees supplied with 150 Kg/Fed. nitrogen + 100 Kg/Fed. potassium exhibited the highest yield (kg)/tree, number of fruit set/panicle and  fruit weight under shade . Moreover, the best fruit peel color was achieved with trees received 100 kg/feddan of nitrogen +100 kg/feddan of potassium and grown under screenhouse conditions during the three studied seasons. The higher significant value of acidity and TSS were recorded in trees supplied by 120 units of nitrogen + 100 units of potassium during first and third season. Whereas, the control treatment attained a maximum ascorbic acid content.

An experimental field trial was conducted in seasons of 2015 and 2016 at Giza Experimental Station of Agricultural Research Centre (ARC), Egypt to evaluate the foliar spray effect with transpiration regulators (Potassium, Kaolin and Ascorbic acid) and three levels of irrigations (100%, 80% and 60% of Et0) on yield, its attributes, and water productivity of two sunflower cultivars (Giza 102 and Solala 120). The factorial treatments were arranged in split- split plot design with three replications. The irrigation levels (100%, 80% and 60% of Et0) were devoted for main plots, while subplots contained the three spraying treatments of transpiration regulators. (Potassium at 1%, Kaolin at 3% and Ascorbic acid at 100 ppm), in addition to control treatment (water spray). Sub-sub plots were occupied by the two sunflower cultivars (Giza 102 and Solala 120). Obtained results proved that, increasing irrigation levels up to (80- 100%) caused significant increase in all growth characteristics, photosynthetic pigments (total chlorophyll), relative water content (RWC %) and seed oil %. Also, yield parameters being head diameter, 1000-seed weight and seed yield) show significant reduction under water deficit. Foliar spray with (Potassium at 1%, Kaolin at 3% and Ascorbic acid at 100 ppm), positively affected all the growth and physiological criteria of the tested plants compared with control. Generally, under low irrigation levels, application of transpiration regulators effectively reduced the detrimental impact of drought stress on growth, yield and its components of the two used cultivars in the two seasons. While, foliar spraying of potassium under 100% of Et0 gave the best treatment in this respect. Concerning cultivars, WUE (water use efficiency) for Solala 120 was significantly higher than for Giza 102 in the two seasons. All interactions among factors under study due to WUE were not significant in 2015 and 2016 seasons.

A greenhouse pot experiment was carried out to investigate the effect of salinity and potassium at different levels alone or in various combinations on growth, mineral and proline content in leaves of plantlets of Phoenix dactylifera L. cv. Bartomouda (in vitro production, two years old from acclimatized them). The following treatments were applied: three levels of salinity Na Cl + Ca Cl2 w.w 2:1 (14000, 16000 and 18000 ppm.) and two levels of potassium (2000 and 3000 ppm) in addition to control (no salts or potassium used), salts and potassium were added in the irrigation water. In general, all levels of salinity significantly decreased various growth parameters such as plant height, number of leaves and roots, root length, fresh and dry weights of leaves than that of the control. These parameters were decreased with increasing salinity levels, whereas it, significantly increased Na, Ca and K contents in leaves with high content of proline. The treatment 18000 ppm salts gave the highest significant reduction of the growth parameters, while caused an increase in proline Na, Ca, and K contents compared to control treatment (no salts) . This was true in both seasons. The applications of potassium significantly increased the previous growth parameters as compared with the control treatment (without salts and potassium) the treatment 3000 ppm had the highest results. Moreover the applications of potassium gave high alleviated the negative effects of salt stress, the treatment 3000 ppm gave the best results on the growth parameters of date palm plantlets grown under salinity condition . Regarding the interaction the obtained data revealed that the interaction between treatment 3000 ppm potassium and 14000 salts produced the highest significant results. Generally, from the obtained results it can conclude that the plantlets of date palm produced by tissue culture can be tolerated salt stress by addition of potassium which can significantly ameliorate the harmful effects of salts, positive effects on the growth parameters of the plantlets was showed by potassium applications.