Influences of Seaweed Extract and Potassium Nitrate Foliar Application on Yield and Fruit Quality of Date Palms (Phoenix dactylifera L. cv. Sukary)

Advances in Agricultural Science 05 (2017), 03: 16-22

Influences of Seaweed Extract and Potassium Nitrate Foliar Application on Yield and Fruit Quality of Date Palms (Phoenix dactylifera L. cv. Sukary)

Alaa El-Din K. Omar 1,2*, Mahmoud A. Ahmed 2, Adel M. Al-Saif 2

1 Horticulture Department (Pomology), Faculty of Agriculture, Kafrelsheikh University, Kafr Sheikh 33516, Egypt.
2 Plant Production Department, College of Food and Agricultural Science, King Saud University,P.O. Box 2460, Riyadh 11451, Saudi Arabia.


This study was carried out during 2012 and 2013 seasons on date palms cv. Sukary, to study the effect of seaweed extracts and KNO3 spray (1 and 2%) on fruit yield and quality characters. Five spraying treatments were applied as follow: KNO3 at 1% and 2%, seaweed extracts at 1% and 2%, and the control (water). Results showed that both seaweed extracts and KNO3 at 2% level improved fruit yield and quality of Sukary dates. Spraying of 2% seaweed extracts resulted in the highest bunch weight, fruit yield, fruit and flesh weight, soluble solids content and reducing and total sugars content. On the other hand, spraying of 2% KNO3 showed the highest fruit volume, fruit diameter and fruit moisture. This study indicated that seaweed extracts improved fruit yield and quality as compared to KNO3.  In addition, seaweed extracts are more favorable to the consumer rather than chemical spray with KNO3.

Keywords: KNO3, Organic source, Safe products, Date Palm, Saudi Arabia


Date palm (Phoenix dactylifera L.) is one of the ancient domestic fruit trees in the Middle East countries and their fruit play an important role in the nutrition pattern of many people (Harhash and Abdel-Nasser, 2010 and Sarrwy et al., 2012). Saudi Arabia is the largest country of the Arabian Peninsula and occupies about 80% of its area Abdullah and Al-Mazoui 1998. In Saudi Arabia, the total dates yield is estimated to be 1.2 million tons (FAO, 2014). In recent years, chemical pesticides and fertilizers were extensively applied to maintain high crop yield (Sarker et al., 2012). Environmental pollution associated with hazardous chemical usage for crop protection and weed control have attracted the attention of scientists worldwide, because microbial diseases, insects and weeds have become more resistant to chemical pesticides and herbicides (Hegab et al., 2005; DeSouza et al., 2006). The excessive application of chemical nitrogen fertilizer not only accelerated soil acidification, but also contaminated groundwater and the atmosphere and weakened the roots of the plant making them vulnerable to several diseases (Ayed, 2002; Fornes et al., 2002). Seaweed extracts are rich and varied source of bioactive natural products which have been used for decades in agriculture (Crouch, 1990).  They are considered as potential biotical and pharmaceutical agents (Ito and Hori 1989; Ahmed and Ragab 2002). It has been reported that seaweed extracts enhance the growth of vegetables and fruits, and also can protect them from different pathogens either on the plant or in storage (Washington et al., 1999 and Khanzada et al., 2007). Moreover, seaweed extracts such as algae extract as a new bio-fertilizer improve crop growth through certain mechanisms, due to the high level of phytohormones (auxins, gibberellins, cytokinins and abscisic acid), macronutrients (N, P and K), certain micronutrients (Fe, Cu, Mo, Mn, Zn, Co, and Ni), and other secondary metabolites such as amino acids and vitamins (Challen and Hemingway, 1965; Fornes et al., 2002; Abd El-Migeed et al., 2004; Spinelli et al., 2009; and Haider et al., 2012). Potassium influences fruit quality (Geraldson 1985), since its nutrition is directly related to high yield, fruit size, long shelf life, high level of soluble solids and ascorbic acid in many horticultural crops (Lester et al., 2005, 2006). It is also related to fruit color and shipping quality (Usherwood, 1985; Rengel et al., 2008). The aim of this study was to evaluate the effect of foliar application with seaweed extract and potassium nitrate (KNO3) on yield and fruit quality of Sukary date palms grown under the conditions of Saudi Arabia.


Materials and methods

Plant materials and treatments

This experiment was carried out during two successive seasons (2012 and 2013) on 13 years old female date palms (Phoenix dactylifera L.) of Sukary cultivar, grown in the Agricultural and Research Station-Dirab, College of Food and Agricultural Sciences, King Saud University, Riyadh, Saudi Arabia. Fifteen uniform palms which were grown in sandy soil at 10 m apart and subjected to the same management and cultural practices (irrigation, pest and weed control), were selected for this study. Bunches were thinned to 10 bunches per palm and pollinated from one ‘Meghal’ male palm by placing 10 fresh male strands among female flower clusters in both seasons.  A commercial Seaweed extract (ALGA600; chemical analysis is displayed in Table 1), KNO3 at 1% or 2%, and control were applied twice (4 weeks after pollination and 4 weeks after the first spray). Bunches were sprayed using a small spraying motor, until run-off stage, with 1%Tween® 20 added to the spraying solution. Five treatments (three palms for each treatment) in each spray were applied as follow: 1% KNO3 (T1), 1% seaweed extract (T2), 2% KNO3 (T3), 2% seaweed extract (T4) and the control (water only, T5).


Measurements and determination

Bunch weight and total yield: To determine the total yield at harvest time (Tamr stage), each spathe was weighed separately using weighing balance and weight was expressed in kilogram (kg).

 Fruit quality: One hundred fruit per bunch were randomly collected; 50 fruits at Bisir stage to determine physical characteristics and 50 fruits at Tamr stage to determine chemical characteristics. The dimensions (length and diameter) 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 (AOAC, 2000). Each fruit was submerged in a container full of water and the volume of displaced water was measured using a 250 cm3 graduated cylinder. Water temperature during measurements was 27 °C (AOAC, 2000). The percentage of soluble solids content (SSC) was determined in fruit juice using a BRX-242 digital refractometer. Titratable acid- it was determined in juice by titrating with 0.1-N sodium     hydrox- ide     in     the     presence     of

Table 1. Chemical analysis of seaweed extracts (ALGA600 seaweed).


Analysis                                                                       (w/w)


Organic matter (%)                                                       40–50

Alginic acid (%)                                                              12

Total nitrogen (%)                                                          0.6

Phosphorus (P2O5) (%)                                                    6

Potassium (K2O) (%)                                                      20

Mannuronic acid (%)                                                        –

Amino acid (%)                                                                4

Mannitol (%)                                                                    3

Mg (%)                                                                             0.06

Ca (%)                                                                               0.4–1.6

Fe (%)                                                                               0.15–0.3

Cu (ppm)                                                                           25–45

S (%)                                                                                 1.0–1.5

I (ppm)                                                                             300–600

Soluble in water (%)                                                        100

pH                                                                                      9–10

Specific gravity (g cm23)                                               0.50–0.55

Odour                                                                          Seaweed-like

Appearance                                                             Brownish powder



Table 2: Effect of seaweed extracts and potassium nitrate (1 and 2%) spray on bunch weight (kg), yield (kg/tree), fruit and flesh weight (g) of ‘Sukary’ date palm fruit during 2012 and 2013 seasons.

Treatments Bunch weight (kg) Yield (kg/tree) Fruit weight (g) Flesh weight (g)
2012 2013 2012 2013 2012 2013 2012 2013
1% KNO3 14.00d 14.57d 140.00c 145.67d 14.83d 14.78c 13.01d 12.99c
1% seaweed extracts 14.23c 15.37c 142.33c 153.67c 15.34c 14.84c 13.53c 12.92c
2% KNO3 16.27b 18.2b 162.67b 182.00b 16.27b 17.32b 14.46b 15.48b
2% seaweed extracts 17.27a 19.03a 172.67a 190.33a 16.92a 18.48a 14.87a 16.51a
Control 9.17d 10.9e 91.67d 109.00e 10.52e 12.74d 8.65e 11.06e
LSD 0.5% 0.45 0.40 4.48 3.99 0.23 0.44 0.29 0.39

Means followed by a common letter in the same column are not significantly different by LSD 0.5% (P ≤ 5%)


Table 3: Effect of seaweed extracts and potassium nitrate (1 and 2%) spray on fruit length (cm), fruit diameter (cm), fruit and flesh weight (cm), fruit volume(cm3) and SSC (%) of ‘Sukary’ date palm fruit during 2012 and 2013 seasons.

Treatments Fruit length (cm) Fruit diameter (cm) Fruit volume (cm3) SSC (%)
2012 2013 2012 2013 2012 2013 2012 2013
1% KNO3 3.47a 3.46a 2.87b 2.72d 14.83c 14.83c 60.47ab 60.4b
1% seaweed extracts 3.52a 3.52a 2.90ab 2.78c 15.5bc 15.17c 63.33a 59.67b
2% KNO3 3.52a 3.45a 3.00a 3.01a 17.33a 18.67a 59.87ab 60.80b
2% seaweed extracts 3.51a 3.52a 2.98a 2.93b 16.33b 17.17b 62.4a 62.4a
Control 3.1b 3.1b 2.61c 2.73cd 11.00d 12.5d 57.67b 57.60c
LSD 0.5% 0.16 0.16 0.079 0.053 0.91 0.62 2.78 1.4

Means followed by a common letter in the same column are not significantly different by LSD 0.5% (P ≤ 5%)

phenolphthalein as an indicator and results were expressed as a percentage of maleic acid (Shaaban, et al., 2006). Reducing, non-reducing, and total sugars were determined according (AOAC 2000).


Experimental design and statistical analysis

The experiment was set in a randomized complete block design with three replicates per treatment. One-way ANOVA was applied using SAS program (SAS, 2000). Means were compared using least significant differences (LSD) at P≤0.05 (Snedecor and Cochran, 1977).



Bunch weight, yield, fruit weight and flesh weight

The highest significant values in bunch weight (19.03kg), yield (190.33kg/palm), fruit weight (18.48g) and flesh weight (16.51g) were recorded with 2% seaweed extract (T4) as compared with other treatments and the control during both seasons (Table 2). T3 (2% KNO3) followed T4 (2% seaweed extract) in terms of improving yield and the other fruit characteristics, as compared to other treatments. Control treatment recorded the lowest values during both seasons.


Fruit length, fruit diameter, flesh weight and SSC

The effect of seaweed extracts and potassium nitrate (1 and 2%) spray on some physical characters and SSC percentage during 2012 and 2013 are illustrated in Table 3.  T3 (2% KNO3) recorded the highest significant values of fruit diameter during 2013, and the highest fruit volume in both seasons.  T2 (1% seaweed extract) recorded the highest significant SSC during 2013 season only as compared to other treatments during both seasons.  Control recorded the lowest significant fruit length and volume in both seasons, the lowest diameter in 2012 season, and the lowest SSC content in 2013 season.

Acidity, reducing sugars, total sugars and fruit moisture

The control (T5) recorded the lowest significant values of total sugars (43.81 and 41.31) and fruit moisture content (13.58 and 14.66 %) during 2012 and 2013 seasons, respectively (Table 4). T 3 (2%KNO3) and T4 (2% seaweed extract) showed the highest significant reducing sugars content during 2013 season. T 3 (2% KNO3) showed the highest significant fruit moisture during 2013 season.



The link between food safety and human health is the major concern of the consumer. Natural sources (seaweed extracts, compost and yeast) have an important role in this regard (Kullk, 1995; Howgate, 1998; Massie, 2003; Fornes et al., 2005). Farmers are more interested in using natural sources (seaweed extracts) in agriculture as biocontrol agents for the nutrient formation of the foods (Verkleij, 1992; Fleet 2007; Hassan-Hoda, 2008). Results of some physical characteristics (fruit weight, flesh weight, bunch weight and total yield), as well as some chemical characteristics (SSC, reducing and total sugars) in both seasons of this study (Table 2, 3 and 4) showed that the application of 2% seaweed extract (T4) had a positive effect on these characteristics, while treatments 2% KNO3 and 1% seaweed extract had a positive effect only on some physical and chemical characteristics (Total and reducing sugars). All foliar applications with seaweed extract or KNO3 at 2% recorded a higher value in most characteristics than 1% KNO3and the control during both seasons.  The results of the present study confirmed similar findings by previous reports (Metting et al., 1990; Umer et al., 1999; Abd El-Migeed et al., 2004; Chouliaras et al., 2005; Fornes et al., 2005; Hegab et al., 2005; Spinelli et al., 2009; Elham et al., 2010; Hanafy et al., 2012). They study concluded that, the presence of some nutrients and growth regulators in seaweed extract, in addition to protein, carbohydrates, vitamins such as thiamine, riboflavin, vit-B12, folic

Table 4: Effect of seaweed extracts and potassium nitrate (1 and 2%)  spray on acidity (%), 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 (%)
2012 2013 2012 2013 2012 2013 2012 2013
1% KNO3 0.89a 0.81a 30.72b 29.47ab 50.73a 45.91c 17.67b 16.57c
1% seaweed extracts 0.83a 0.83a 34.10b 31.40a 54.08a 47.25c 17.13ab 17.63b
2% KNO3 0.81a 0.92a 37.10a 28.61b 53.70a 49.17b 17.67a 18.57a
2% seaweed extracts 0.87a 0.93a 37.40a 31.05a 55.08a 53.34a 18.07a 17.34b
Control 0.92a 0.95a 29.21b 27.79b 43.81b 41.31d 13.58c 14.66d
LSD 0.5% 0.109 0.034 3.98 2.25 4.67 1.78 0.92 0.62

Means followed by a common letter in the same column are not significantly different by LSD 0.5% (P ≤ 5%)

acid in seaweed extract spraying solution may have a positive effect on increasing fruit yield and improving fruit quality (physical and chemical characteristics) of Sukary dates. This may be due to the effect of such treatments on nutritional status of the palms, which has been reflected on fruit yield and quality.



Foliar application of seaweed extract twice (4 weeks after pollination and 4 weeks after the first spray) at 2% followed 1%, have a positive effect than KNO3, on yield and fruit quality of Sukary date palm grown under Saudi Arabia conditions. In addition, seaweed extract is very safe for human, animal and the environment in terms of less pollution and low soil salinity via the reduction of fertilization; in addition, it reduces the total production cost.



The authors would like to thank the Deanship of Scientific Research and Research Center, College of Food and Agricultural Sciences, King Saud University, KSA for funding this research.



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