EFFECT OF POTASSIUM FERTILIZATION LEVELS ON GROWTH , YIELD AND QUALITY OF SUNFLOWER CULTIVARS ( Helianthus annuus L . )

The study included two field experiments for sunflower crop conducted during spring growing season of 2008 in two locations. The first was in AL-Rashidia (20 km) west north Mosul city, the second ones was in AL-Hamdanea (30 Km) east of Mosul city. The main objective was to find out the effect of potassium fertilization levels on growth, yield and quality of three sunflower cultivars. Each experiment was conducted according to factorial experiment in a randomized completely block design with three replications. It included three levels of potassium (0, 30 and 60 kg k per hectare -1 ) were applied to the soil during the sowing period, with three cultivars of sunflower crop (Saturn, Gordis and Majak). The results could be summarized as follows: The cultivar Gordis gave a high level for most growth, yield and quality parameters in both locations. Application of 30 kg K per hectare -1 led to a significant increase in plant height, leaf area, disc diameter, number of seeds per head, weight of thousand seed, seed yield, oil percentage and oil yield, while increasing concentration of potassium up to 60 kg K per hectare -1 caused a significant increase in protein percentage in AL-Rashidia and AL-Hamdanea locations. The interaction between the cultivars and potassium fertilization levels was significant in some growth, yield and quality parameters, the Gordis cultivar with potassium application to the soil with concentration 30 kg k.ha -1 was superior and gave highest values for plant height, stem diameter, leaf area, number of seeds.head -1 , weight of thousand seed, oil percentage, oil yield, protein percentage and protein yield in AL-Rashidia location only, while the interaction between cultivars and potassium fertilization levels was significant in number of seeds per head and weight of thousand seed in ALHamdanea location only.


INTRODUCTION
Sunflower (Helianthus annuus L.) is an important edible oil crops, ranking next to soybean (Khan, 1999).It is a drought tolerant and short duration crop and has a wider range of adaptability.Therefore, more care should be given to this crops to improve the productivity to meet the shortage of vegetable oil (Ibrahim et al., 2003).Its seed contain high oil content ranging from 40-50 percent and it is rich in protein 23 percent (Mohamed et al., 1992 andSangoi andKruse, 1993).Moreover, its oil quality is better due to higher percentage of linoleic acid and low percentage of linolenic acid which is the most desirable character, lacking in other oils (Annaduri et al., 1994).Nitrogen, phosphorous and potassium are major elements essential for plant growth and development.To date the use of chemical fertilizers has been confined mainly to the application of nitrogen, phosphorous and potassium.There role are well documented in photosynthesis, increasing enzyme activity, improving synthesis of protein, carbohydrates and fats, translocation of photosynthetic, enabling their ability to resist pests and diseases.Potassium also plays key role in increasing crop yield and improving the quality of product (Tisdale et al., 1985 andSoleimanzadeh et al., 2010).
In addition to the other factors that are responsible for increasing yield per hectare, is the application of potassium which plays a remarkable role in boosting up production (Blamey et al., 1979).The effect of potassium application on sunflower plant growth, yield and quality was reported by some investigators, who found that increasing potassium level led to a significant increase in plant height (Sirbu and Ailincai, 1992), no. of leaves, leave area and head diameter (Lewis et al., 1991).Response of sunflower to potassium application was studied by many investigators : Carter, (1978); Shinde et al., (1993) ;Khan, (1999) and Ahmad et al., (2001) who reported that the application of 150 kg potassium.ha -1 increased sunflower no. of seeds.head - , weight of thousand seed, fertility, and total yield.
So, the objective of this trial was to study the effect of three potassium fertilization levels on growth, yield and certain quality traits of three sunflower cultivars.

METERALS AND METHODS
Tow filed experiments were carried out during 2008 season at the experimental farm, the first was in AL-Rashidia 20 km west north Mosul city, the second was in AL-Hamdanea 30 Km east of Mosul city at Nineveh province, to investigate the effect of three levels of potassium fertilization (0, 30 and 60 kg k hectare -1 ) on the growth, yield and certain quality traits of three sunflower cultivars (Saturn, Gordis and Majak).Each experiment included nine treatments comprising the combinations of three cultivars and three potassium levels with three replications.
Seeds of these cultivars were obtained from the crops industrial company, Baghdad.The experimental design was factorial experiment in a Randomized Completely Block Design with three replications according to Steel and Torrie, (1980).Then Duncan's multiple range test (Duncan, 1955) was used to compare among means (SAS, 2001).A representative soil sample (0-30 and 30-60cm) was taken before planting, (table1) to study some physical, chemical and nutritional properties using the methods described by Black, (1965) ;Jackson, (1973); Page et al., (1982) and Tandon, (1999).
Seeds were sown in April 2 nd and 6 th and harvested in August 4 th and 8 th for 2008 season for the two locations respectively, in hills 30 cm apart on ridges 40 cm apart to attain a plant density of 83.333 plants.ha - .Super phosphate 120 kg per hectare -1 (45% P 2 O 5 ) and potassium levels (48%K 2 O) were applied to the soil during the sowing period, Nitrogen fertilizers was applied in the form of urea 80 kg.hectare -1 (46% N) in two equal doses, prior to the first and second irrigation.Each plot 14.4 M 2 (6*2.4)included six rows and six meters long.thinned to one plant per hill 14 days after sowing.The external two rows were left as border.Two of the remaining rows were devoted for estimating plant growth and some characteristics.The first irrigation was applied after 5 days from sowing and then irrigation was scheduled at about four days intervals.Normal cultural practices of growing sunflower were conducted in the usual manner followed by the farmers of the district.At heading, the heads of the two inner rows were bagged early to seed development to avoid birds damage until maturity.The following data were recorded: plant height (cm), stem diameter (cm), leaf area, and head diameter (cm).At harvest, ten plants were taken randomly from the two inner rows of each experimental plot and left for two weeks until fully air dried, then the following data were calculated; number of seeds per head, weight of thousand seed, hulls percentage, fertility percentage, yield and oil yield (ton.hectare -1 ).Oil seed content was determined using Soxhlet method (Anonymous , 1980) and seed nitrogen concentration was measured by microkjeldahl method, then protein percentage was calculated via multiplying the nitrogen percentage by the converting factor 6.25 (Agrawal et al., 1980).2) revealed that Gordis cultivar had taller (114.10,115.87 cm) and thicker (2.11, 2.56 cm) plant then those of Saturn and Majak in both locations AL-Rashidia and AL-Hamdanea respectively.The result of leaf area showed that Gordis cultivar significantly exhibited higher leaf area (3160, 3298 cm 2 .plant)than those of Majak and Saturn cultivars in the two locations respectively.The differences among the three cultivars in the leaf area may be attributed to the general varietals differences in the plant height and number of internodes per plant (Mohamed et al., 1992;Sangoi andKruse, 1993 andAbd EL-Samie et al., 1995).In this concern, Salama (1996) showed that taller cultivars had more leaves and leaf primordial than the others sunflower cultivars.It can be also noted that the head diameter of Gordis cultivar was greeter than Saturn and Majak cultivars at both locations.Mean values of seed yield, yield components and some related traits for the three tested cultivars are presented in revealed that Gordis cultivar surpassed Saturn and Majak cultivars in the head characteristic (head diameter, no. of seeds.head - , weight of thousand seed), Moreover, Saturn surpassed Majak in those traits in both locations.This means that Gordis plants were more efficient to accumulate dry mater in their head.Regarding to the seed characters studied i.e. weight of thousand seed, hulls, fertility and oil percentage, data showed that there were a significant variations among the three tested sunflower cultivars in both locations.Gordis cultivar surpassed significantly Saturn and Majak cultivars in no. of seeds.head - (1152.66,1181.00),weight of thousand seed, yield and oil yield (2.89, 2.82, 1.25, 1.23 ton.hectare -1 ) in both locations, respectively.However, fertility seeds percentage showed fluctuated direction in the two locations, where Gordis cultivar was the highest in both locations.On the other hand, Majak cultivar was the medium in both locations.The superiority of Gordis cultivar in the most seed characters may be due to that Gordis cultivar had better vegetative growth and hence photosynthetic area which led to more carbohydrates which was translocated from the source (leaves and stem) to the sink (seeds) (Carter, 1978 andMengel andKirkby, 1982).The results showed that the number of seeds per head, weight of thousand seed and yield, oil yield (ton.hectare -1 ) were always significantly higher for Gordis than that for Saturn and Majak varieties.2-Effect of potassium fertilization: Data presented in table (3) showed that increasing potassium level from 0 to 30 (Kg k ha -1 ) significantly increased stem diameter, leaf area and head diameter at the both locations, While these traits appeared to have negative response to 60 kg k ha -1 .This could be attributed to the highly available potassium in the experimental site in both locations (table 1) also showed that the available potassium in the soil is in the average of medium level which is ranged from 128-141ppm, and these results are in agreement with the classification of Bergmann, (1965), although sunflower required a high quantity of potassium, this reflected the response of the crop to this element when increasing the concentration from 0 to 30 kg k ha -1 .The beneficial effect of potassium on plant height may be due to its role in enhancing photosynthesis.In this concern, increasing potassium fertilizer levels increased plant height as was found by Sirbu and Ailincai, (1992) and Shinde et al., (1993).The leaf area was increased significantly by adding potassium fertilizer up to 30 kg k.ha -1 as compared to the check and the high level of potassium in both locations.However, increasing potassium level up to 60 kg k ha -1 had low significant effect on these traits.These results means that potassium application up to 30 kg k ha -1 was enough to increase the leaf area.These findings confirmed the results obtained by Shinde et al., (1993); Annaduri et al., (1994) and Khan, (1999) who found that the application of 150 kg k ha -1 increased sunflower area.plant - and number of leaves per plant.The stimulatory effect of potassium in sunflower plant may be due to its role in enhancing metabolic process.These results are in harmony with those obtained by Pervaiz et al., (1999); Ahmad et al., (2001); Karim and Hassain, (2002) and Mohammad et al., (2008).Data reported in table (3) demonstrated that the number of seeds per head significantly increased by increasing potassium application levels from 0 to 30 kg k ha -1 in both locations.Many researchers concluded that increasing potassium application rates increased number of seeds per head (Shinde et al.,  and Ahmad et al., 2001).The obtained data showed that weight of thousand seed, hulls, fertility, total yield and oil yield were increased significantly as the potassium application levels was increased from 0 to 30 kg k hectare -1 in the two locations.These results are in agreement with those reported by Roga et al., (1984); Lewis et al., (1991) ;Harmati, (1993); and Annaduri et al., (1994) who reported that potassium application increased seed yield to 40%.Soleimanzadeh et al., (2010) found that the increases in yield through potassium application may be due to its key role in increasing crop yield and improving the quality of product and hence, the transport of nutrients is essential to metabolism in active areas.Similar results were obtained by Ahmad et al., (2001) who found that head diameter, weight of thousand seed and oil yield were increased with increasing potassium application rates from 0 to 150 kg k ha -1 .On the contrary, the fertility percentage and seed oil percentage were decreased with increasing potassium application up to 60 kg k. ha - 1 .The decrease in the fertility seed may attributed to more light translocation to the seeds by increasing potassium level.However, the decrease in seed oil contents by potassium fertilizer may be due to the increase in seed protein content (Chitdeshwari et al., 2002).In this concern, Many researchers reported that the potassium application to sunflower caused a reduction in seed oil percentage (Nazakat et al., 2003).

3-Effect of interaction between cultivars and potassium fertilization:
Interaction between the studying factors (cultivars and potassium fertilization) showed significant effects on some growth characters, yield components and quality in both locations as illustrated in table (5).The interaction between the cultivars and potassium fertilization for the other investigated traits were not statistically significant in both locations, therefore the data were excluded.
Data illustrated in table (4) show generally that Saturn, Gordis and Majak cultivars appeared to be clearly affected by increasing rate of potassium fertilization levels up to 30 kg k ha -1 for the traits of plant height (120cm), stem diameter (2.4cm), leaf area, number of seeds.head - , weight of thousand seed, oil percentage (43.7%),oil yield, protein percentage and protein yield only in AL-Rashidia location, while the interaction between cultivars and potassium fertilization levels was significant in number of seeds.head - and weight of thousand seed only in AL-Hamdanea location, while they appeared to be little response to 60 kg k ha -1 for those traits.On the other hand, Gordis cultivar reflected the greatest response to potassium fertilization levels up to 30 Kg k ha -1 for these traits, with this regard, Prunty, (1981);Faizani, et al., (1990) ;Sarmah, et al., (1994); Conley and Barta, (2003) and Khan, (1999) found that fertilization with 150 kg k ha -1 produced maximum weight of thousand seed (53.71g) and seed yield (4153 kg ha -1 ).On the other hand, the response rate of Saturn and Majak cultivars to potassium fertilizer was low with increasing potassium fertilization levels more than 60 kg k ha -1 for the most of these traits.It could be concluded that the tallest cultivars i.e.Gordis responded positively to high potassium fertilization levels compared with the shorter cultivars Saturn and Majak.(Osman and Abolila, 1984;Ibrahim et al., 2003;Govt 2004;Brar, 2007 andRathika et al., 2008).The insignificant effect between cultivars and potassium fertilization levels on other characteristic showed that each of these two factors acted independently on these traits.

Table ( 1
): Physical and chemical characters of soil experiments at both locations.

RESULTS AND DISCUSSION 1-Effect of cultivars
: Data in table ( table (2).The data

Table ( 2
): Means number of some growth characters, yield components and quality as affected by cultivars in both locations.The mean values within column followed by the different letter are significant at 0.01 and 0.05 probability levels, respectively.

Table ( 3
): Means number of some growth characters, yield components and quality as affected by potassium fertilization levels in both locations.

Table ( 4
): Means number of some growth characters, yield components and quality as affected by interaction between cultivars and potassium fertilization levels in both locations.The mean values within column followed by the different letter are significant at 0.01 and 0.05 probability levels, respectively.

Table ( 5
): Analysis of variance F values for some growth characters, yield and yield components and quality in AL-Rashidia and AL-Hamdanea locations.Significant at the 0.05 and 0.01 probability levels, respectively.and n.s.not Significant.