Effect of foliar spraying with potassium dehydrogenase phosphate and yeast extract on yield and fruit quality of Sukary date palm (Phoenix dactylifera L.) in Saudi Arabia

Advances in Agricultural Science 06 (2018), 03: 25-32

Effect of foliar spraying with potassium dehydrogenase phosphate and yeast extract on yield and fruit quality of Sukary date palm (Phoenix dactylifera L.) in Saudi Arabia

Alaa El-Din K. Omar 1, 2*, Rashed S. Al-Obeed 1 and Mahmoud A. Ahmed 1

Plant Production Dept., College of Food and Agric. Sci., King Saud Univ., P.O. Box. 460, Riyadh 11451, Saudi Arabia.
Horticulture Dept. (Pomology), Fac. of Agric., Kafrelsheikh Univ., Kafr El-Sheikh 33516, Egypt.


As a natural bio-stimulant, bread yeast has an influence on growth, yield and fruit quality of many crops. This research was conducted during two successive seasons, 2013 and 2014, in order to study the effect of spraying with yeast and potassium dehydrogenase phosphate (KH2PO4) on yield, bunch weight and fruit quality of 13 year old Sukary date palm. Five spraying treatments were performed with control (water only), potassium dehydrogenase phosphate  at 1 and 2%, and yeast at 4 and 8%. These treatments were applied once at 4 weeks after pollination or twice at 4 week after pollination, repeated after another 4 weeks. All treatments with yeast or potassium dehydrogenase phosphate twice had a pronounced effect compared with the control fruit during both seasons.  Spraying Sukary date palms twice with potassium dehydrogenase phosphate (2%) was effective in improving yield, bunch weight and fruit physical characteristics, while spraying yeast (4 and 8%) improved soluble solids content (SSC), and total and reducing sugars.

Keywords: Date palm, Fruit quality, Potassium dehydrogenase phosphate, Yeast

How to Cite: Omar, A. E.-D., Al-Obeed, R., & Ahmed, M. (2018). Effect of foliar spraying with potassium dehydrogenase phosphate and yeast extract on yield and fruit quality of Sukary date palm (Phoenix dactylifera L.) in Saudi Arabia. Advances in Agricultural Science6(3), 25-32.    


Saudi Arabia is the largest country of the Arabian Peninsula, occupying about 80% of its area (Abdullah et al., 1998). The country lies between latitudes 16°21’58”’ and 32°9’57”’ N and longitudes 34°33’48”’ and 55°41’29” E (Wynbrandt and Gerges, 2004). Date palm (Phoenix dactylifera L.) is one of the most important fruit crops in the Arab world. Arab countries are the main source of dates in the world (Mohamed, 1982).

There are many reports on the effect of nutrient fertilization on date palm yield and fruit qualities (Atalla et al., 1999; Shawky et al.,1999). The efficient use of fertilizers is the most important goal in all agricultural systems to improve yield and to reduce the cost (Dong et al., 2005). It is very important to apply a proper fertilization program that matches the requirements of the trees to maximize nutrient uptake and minimize nutrients leaching. The ability of plant leaves to absorb nutrients (Swietlik and Faust, 1984) has resulted in the efficient uptake of nutrients by fruit trees through foliar rather than soil applications (Weinbaum, 1988).

Potassium (K+) has a great effect on fruit quality (Geraldson, 1985), since potassium nutrition is directly linked to increased yield, fruit size, shelf life, soluble solids and higher levels of ascorbic acid in many horticultural crops. It is also related to improved fruit color and shipping quality (Usherwood, 1985; Rengel et al., 2008). The impact of yeasts on the production, quality and safety of foods and beverages is intimately linked to their ecology and biological activities (Atawia and El-Desouky, 1997).

Bread yeast (Saccharomyces cerevisiae) as a natural bio-stimulant appears to induce growth and yield of many crops, since it has various basic functions including carbon dioxide production, and formation of alcohol, acids and esters (Martinez-Anoya et al., 1990). Spraying Valencia orange trees with active bread yeast either once in March or August or twice in both months improved growth, and fruit set, number, weight and volume, as well as yield and other fruit quality parameters (Hegab et al., 2005). Ahmed et al., (1995) reported similar findings on Picual olive trees. Bio-fertilization is very safe for humans, animals and the environment. It also reduces soil salinity and saves fertilization cost (Fathy and Farid, 1996; Hewedy et al., 1996; Mohamed et al., 1999). The aim of this study was to evaluate the effect of foliar spraying with bread yeast and potassium phosphate on yield and fruit quality of Sukary date palms grown under the conditions of Saudi Arabia.


Materials and Methods

Plant materials and treatments

This research was carried out during two successive seasons, 2013 and 2014, on 13 years old female date palms cv. Sukary, grown at the Agricultural Experimental and Research Station-Dirab, College of Food and Agricultural Sciences, King Saud University, Riyadh, Saudi Arabia. Thirty uniform palms (3 palms/treatment for once or twice spraying), grown 10 m apart in sandy soil and subjected to the same management and cultural practices (such as irrigation, pest and weed  control, etc.), were selected for this study. Bunches were thinned to 10 per palm and were pollinated from one cv., Meghal male palm by placing 10 fresh male strands among female flower clusters in both seasons.

Bread yeast, the composition of which is shown in Table 1 as reported by Nagodawithana (1991) and mono potassium phosphate (MKP, also potassium dihydrogenphosphate, KDP, or monobasic potassium phosphate, KH2PO4– Sigma-Aldrich Canada Ltd) treatments were applied individually by spraying once after 4 weeks of pollination or twice, 4 weeks after pollination and again after a further 4 weeks. Bunches were sprayed (15 litter/tree) using a small motor sprayer, until run-off, with a wetting agent Tween® 20 (1%) added to the spraying solution. Four treatments were applied, 1% potassium phosphate (T1), 2% potassium dehydrogenase phosphate (T2), 4% bread yeast (T3), 8% bread yeast (T4) and a water only control (T5).


Main agricultural practices

Fertilization: Nutrients requirements for a sufficient supply with composted organic materials (animal manure with other organic materials like dry leaves of date palm trees and other organic waste material).

Irrigation wells were used in drip irrigation system.

Integrated pest management and bio pesticide were used, bedside using hoeing weeds to get rid of the farm.


Measurements and determination

To determine the total yield at harvest time during Tamr stage, (Tafti and Fooladi 2006), each spathe was weighed    separately and the weight was expressed in kilograms.

 Table 1. Chemical composition of bread yeast (Nagodawithana, 1991).

8% Nucleic acids 47% Protein
4% Lipids 33% Carbohydrates
8% Minerals
Approximate composition if vitamins (mg/g)
1.3 Biotin 6-100 Thiamine
4000 Collin 35-50 Riboflavin
5-13 Folic acid 300-500 Niacin
0.001 Vit-B12 28 Pyridoxine HCl
70 Pantothenate
Approximate composition if minerals (mg/g)
8.00 Cu 0.12 Na
0.10 Se 0.75 Ca
0.02 Mn 0.02 Fe
2.20 Cr 1.65 Mg
3.00 Ni 21.00 K
0.04 Va 13.50 P
0.40 Mo 3.90 S
3.00 Sn 0.17 Zn
0.17 Li 0.03 Si


Table 2. Effect of potassium phosphate and yeast spraying and number of sprays on fruit weight (g), bunch weight (kg) and yield (kg/tree) of ‘Sukary’ date palm fruit during 2012 and 2013 seasons.

Treatments No. of


Bunch weight (kg) Yield (kg/tree) Fruit weight (g) Flesh weight (g)
2013 2014 2013 2014 2013 2014 2013 2014
KH2PO4 1% (T1) I 9.67c 11.33f 96.67h 129.33bc 11.37f 12.78e 9.55f 11.06e
II 10.37c 12.00e 103.67g 120.00bc 12.35e 12.92e 10.46e 11.05e
KH2PO4 2% (T2) I 14.80ab 16.2b 148.00b 162.00a 15.54a 15.5b 13.64a 13.80b
II 15.4a 16.67a 154.00a 166.67a 15.72a 16.3a 13.86a 14.51a
yeast 4% (T3) I 12.17abc 12.56d 121.67f 129.33bc 13.17d 13.26d 11.27d 11.59d
II 13.17abc 13.07c 131.67e 130.67bc 13.55c 13.34d 11.75c 11.48de
yeast 8% (T4) I 13.57abc 13.46c 135.67d 134.67b 13.85c 13.46d 11.99bc 11.62d
II 10.77bc 13.47c 141.00c 134.67b 14.26b 14.21c 12.29b 12.46c
Control (T5) I 9.17c 10.9f 91.67i 109.00c 10.52g 12.74e 8.74g 11.06e
II 9.17c 10.9f 91.67i 109.00c 10.52g 12.74e 8.74g 11.06e
LSD 5% 2.95 0.37 3.82 14.75 0.32 0.33 0.34 0.33

Means followed by a common letter in the same column are not significantly different by LSD (P ≤ 5%)


One hundred fruits per bunch were randomly collected; 50 fruits at Bisir stage (Tafti and Fooladi, 2006) to determine physical characteristics and 50 fruits at Tamr stage to determine chemical characteristics. The fruit lengths and diameters were measured using a digital caliper. Fruit and flesh weight were measured using a digital balance (AOAC, 2000). Fruit volume was measured using the water displacement method. Each fruit was submerged in a container full of water and the volume of displaced water was measured using a 250 cm3 capacity graduated cylinder. Water temperature during measurements was 27°C (AOAC, 2000). The soluble solids content (SSC), titratable acidity, total soluble sugars, reducing sugars and fruit moisture content were measured to determine fruit quality (AOAC, 2000).


Experimental design and statistical analysis

The experiment was designed as a split plot block model with three replicates (each tree as replicate) per treatment. One way analysis of variance (ANOVA) was performed using the SAS program (SAS, 2000). Means were compared using least significant differences (LSD) at p ≤ 0.05 (Schanderi 1970).



Bunch weight, yield, fruit weight and flesh weight

Treatment 2 (2%) (Potassium dehydrogenase phosphate) gave significantly the highest bunch weight (2014), yield (2013 and 2014), fruit weight (2013 and 2014) and flesh weight 2013 and 2014, respectively (Table 4). There were non- significant differences among treatments and control in bunch weight (2013), only. Control recorded the lowest significant value in yield (2013), fruit weight (2013) and flesh weight (2013).


 Fruit length, diameter flesh weight and SSC

Effects of potassium dehydrogenase phosphate and yeast treatments on some physical characters and SSC percentage during 2013 and 2014 were illustrated in Table 3.  Treatment 2 (twice spays) recorded the highest significant values in fruit diameter (2014), while treatment 4 (twice sprays) recorded the highest SSC in both seasons as compared with other treatments during both seasons. There were non-significant differences among treatments in fruit length and fruit volume during both seasons. Control gave the lowest significant fruit length (2014) and SSC content (2013 and 2014).


Acidity, reducing sugars, total sugars and fruit moisture

Control (treatment 5) recorded the highest (0.92 and 0.95%) significant in acidity content at single and twice sprays during 2013 and 2014, respectively, Table 4. While treatment 4 recorded the lowest significant acidity content during 2014. All treatments significantly decreased acidity content compared to the control in both seasons. Treatments 3 and 4 recorded the highest significant reducing sugars during 2013 only. Treatment 2 recorded the highest significant value (17.60%) during 2014 at twice sprays of fruit moisture %. While control recorded the lowest significant reducing sugars (2014), total sugars (2014), respectively and fruit moisture (2014), respectively.



Food safety and the link between diet and health are the major concern of the consumer, and yeasts have an important role in this context (Howgate 1998; Massie 2003). Farmers are more interested in using yeasts in Agriculture, as bio control agents, and for the nutrient formation of foods (Fleet 2007); however, food-associated yeasts could be a source of infections and other adverse health responses in humans (Umer et al., 1999). On the other hand, potassium is  one  of  the  major  macronutrients, contributing up to 6% of plant dry weight (Shabala, 2003) and it is considered to be a key factor for fruit quality (Hartz et al., 1999).

Table 3. Effect of potassium phosphate and yeast spraying and number of sprays on fruit length (cm),  fruit diameter (cm), fruit volume (cm3) and SSC  (%) of ‘Sukary’ date palm fruit during 2012 and 2013 seasons.

Treatments No. of


Fruit length (cm) Fruit diameter (cm) Fruit Volume (cm3) SSC (%)
2013 2014 2013 2014 2013 2014 2013 2014
KH2PO4 1% (T1) I 3.13b 3.20d 2.65d 2.70c 11.83bc 12.83ab 66.4b 63.20bc
II 3.17b 3.27cd 2.75c 2.73c 12.33abc 13.00ab 68.80b 64.00bc
KH2PO4 2% (T2) I 3.22b 3.33bc 3.02a 2.92b 13.00abc 12.83ab 64.80b 62.33c
II 3.30ab 3.36abc 2.95a 3.02a 13.67abc 13.33ab 65.60b 63.20bc
yeast 4% (T3) I 3.22b 3.27cd 2.75c 2.78c 14.17abc 13.93ab 78.8a 64.53bc
II 3.37ab 3.32bc 2.80bc 2.78c 15.00abc 14.33a 79.2a 64.80b
yeast 8% (T4) I 3.45a 3.38ab 2.82bc 2.77c 15.50ab 15.67a 79.2a 65.60b
II 3.52a 3.45a 2.80bc 2.87b 15.67a 16.33a 79.60a 69.60a
Control (T5) I 3.1b 3.10e 2.62d 2.73c 11.33c 12.50ab 60.40c 57.60d
II 3.1b 3.10e 2.62d 2.73c 11.33c 12.50ab 60.40c 57.60d
LSD 5% 0.17 0.077 0.077 0.06 2.35 2.33 1.98 1.64

Means followed by a common letter in the same column are not significantly different by LSD (P ≤ 5%)


Table 4. Effect of potassium phosphate and yeast spraying and number of sprays on acidity content (%), reducing sugars (%), total sugars (%) and fruit moisture (%) of ‘Sukary’ date palm fruit during 2012 and 2013 seasons.

Treatments Acidity (%) Reducing sugars (%) Total sugars (%) Fruit moisture (%)
2013 2014 2013 2014 2013 2014 2013 2014
KH2PO4 1% (T1) I 0.69bcd 0.63c 34.38c 32.58b 54.34bc 54.34e 14.16de 15.44d
II 0.78b 0.61c 40.56b 32.62b 54.34bc 56.24cde 14.79de 15.77cd
KH2PO4 2% (T2) I 0.79b 0.71b 33.24c 35.30ab 53.77bc 54.30e 16.63ab 16.48b
II 0.76bc 0.63c 36.43bc 35.41ab 58.36b 55.46de 16.96a 17.60a
yeast 4% (T3) I 0.68cd 0.61c 48.55a 32.90b 57.00b 57.00cd 14.93d 16.16bc
II 0.69bcd 0.53d 49.16a 33.24b 58.26b 58.26c 16.01bc 16.21bc
yeast 8% (T4) I 0.66d 0.49e 51.27a 34.36ab 70.74a 60.38b 15.79c 14.83e
II 0.63d 0.45f 48.87a 37.20a 70.75a 64.36a 17.12a 14.51e
Control (T5) I 0.92a 0.95a 32.54c 28.46c 50.48c 44.31f 13.91e 14.65e
II 0.92a 0.95a 32.54c 28.47c 50.48c 44.31f 13.91e 14.65e
LSD 5% 0.07 0.03 0.03 4.76 2.14 3.51 1.86 0.43

Means followed by a common letter in the same column are not significantly different by LSD (P ≤ 5%)


Results of treatments 4 and 8% yeast (T3, T4) had pronounced effect on SSC, total and reducing sugars either one or two sprays (Table 4), while the application of 2% potassium dehydrogenase phosphate (T2) had a good effect on fruit weight, bunch weight and total yield in both seasons of study (Table 2). All foliar application with yeast or potassium dehydrogenase phosphate at two sprays gets a higher value in most characteristics than one spray during both seasons.  These results are in agreed with previous reports (Gobara et al., 2002; Nomier, 2000; Abada, 2002; Abd-Elmotty and Fawzy, 2005; Hossain and Ryu, 2009; Spinelli et al., 2009). Yeast has a beneficial role in improving growth of vegetable (Fathy et al., 2000; Omer, 2003; Sarhan 2008). Abd El-Motty et al., 2010 reported that  spraying ‘Keitte’ mango trees once at full bloom with yeast at 0.2% was very effective in improving yield as number of fruit or fruit weight per tree (kg); increased fruit length (cm), fruit width (cm), fruit weight (g), pulp/fruit percentage; and enhanced total soluble solids (SSC). These effects of yeast extract may be due to that yeast is a natural component (safe and non-pollutant) contains many of the nutrient elements and cytokininis, also has a considerable amounts of amino acids; mineral elements, carbohydrates, reducing sugars, enzymes and vitamins B1, 2, 3, 12 that can improve physical and chemical characters  fruit (Fathy and Farid, 1996; Khedr and Farid, 2000). Moreover, it is a source of cytokinins and protein that enhance cell division and enlargement (Barnett 1990). Atawia and El-Desouky (1997) reported that foliar application with natural yeast extract at the full bloom stage of orange ‘Washington navel’ trees improves the fruit yield per tree as well as fruit quality.



Other approaches have been to try and identify effective natural chemicals, which may be more acceptable to consumers than those that are synthetically produced. Thus, through our results found that spraying bread yeast one time (4 weeks after pollination) or two times (4 weeks after pollination and 4 weeks after the first spray) has a positive effect on yield and fruit quality of ‘Sukary’ date palm grown under Saudi Arabia conditions.



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