This study was conducted during 2015 and 2016 growing seasons at a private orchard at El-Nubaria region, El-Behira Governorate, Egypt. The objective of this study was to investigate the response of "Anna" apple trees budded on Malus rootstock to three amounts of irrigation water using drip irrigation system; I1 : like irrigation water amount the local farmers in the studied regions ( control, 15.584 m3/tree/year ) , I2 :75% from the control ( 11.657 m3/tree/year) and I3 :50% from the control (7.792m3/tree/year), foliar spray included four treatments :W (tap water without K and Mg ), K, Mg and K+ Mg, 4 times applications, starting after fruit set, and the others 15 days intervals (K added as potassium sulphateat rate 2g/L , Mg added as magnesium sulphate at rate 2g/L) and their interactions on vegetative growth, water relations, leaf chlorophyll and mineral contents, yield and fruit quality of "Anna" apple trees. The experimental trees had the same volume and shape and were grown in a sandy loam soil, spaced at 5x5 meters apart and received the normal culture practices commonly adopted for this region.
The main results can be summarized as follows:
Foliar application of investigated nutrients increased leaf area, specific leaf weight, leaf chlorophyll, leaf- N, P, K and Mg contents, fruit set, fruit weight, yield, fruit firmness, total soluble solids% and anthocyanin compared to the unsprayed trees in the two growing seasons. The application of K+Mg gave the highest values, the application of K alone was superior to the individual application of Mg. On the contrary, foliar spray with these nutrients didn't show a significant differences on fruit juice acidity in the two seasons. Also, it was observed that, K and (K+Mg) treatments significantly increased total water content and decreased water deficit percentage in leaves compared to Mg or control (W). Mg treatment decreased total water content compared to the control.
As for the effect of irrigation rates, the results revealed that (I1) treatment was superior for leaf area, total water content, leaf chlorophyll reading and leaf-N, P, K and Mg contents. Also, fruit set as well as yield and fruit weight as compared to the other treatments in the two seasons. I2 treatment recorded the highest values of specific leaf weight in the two seasons and total soluble solids in the second one. On the other hand, (I3) treatment gave the highest significant value of water deficit, fruit firmness and anthocyanin in the two seasons, and total soluble solids in the first season for "Anna" apple.
The interaction effects between the foliar application of investigated nutrient and different irrigation treatments revealed that, (K+Mg) xI1 gave the highest significant mean values of leaf area, total water content and leaf-P content in the second season, fruit weight in the first one, also, leaf-N and K contents as well as yield per tree and total yield (ton/fed) in both seasons, while the interaction between (K+Mg) and I3 gave the highest significant values of total soluble solids%, fruit juice acidity and anthocyanin in the first season, and fruit firmness in the second one.
It could be recommended from this study that, Potassium and magnesium fertilizers have improved vegetative growth, yield and fruit quality of "Anna" apple and increasing water use efficiency (WUE) under using a lot of water supply with no offering to water deficit condition. Sprayed "Anna" apple trees with Mg and K gave the best results as compared to the individual applications.