Effect of plant density on yield and yield components of two sunflower (Helianthus annuus L.) hybrids under rain-fed conditions

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1 Standard Scientific Research and Essays Vol (): 52-58, April 2 Research Article Effect of plant density on yield and yield components of two sunflower (Helianthus annuus L.) hybrids under rain-fed conditions Salah Balla M. Ahmed * and Omer A. Salam Nafea 2 Faculty of Agricultural and Environmental Sciences, University of Gadaref, Gadaref, Sudan. 2 Gadaref Agricultural Research Station, Gadaref, Sudan. *Corresponding author salahballa72@yahoo.com Received 26 January 2; Accepted 2 February Abstract A field experiment was conducted for two rainy seasons, 29/2 and 2/2 at Gadarif University Farm to study the effect of six plant densities 25, 62, 4,, 25 and 2 ( plants) ha - on yield, yield components and other growth attributes of two sunflower hybrids (Hysun and Panar 75). A randomized complete block design with four replicates was used for laying out the field experiment. Data were collected on plant height, leaf area index, stem diameter, head diameter, number of seeds/head and seed yield/ha (kg). A scatter graph was drawn for the data averaged over the two seasons to study the effect of the plant densities on plant height and leaf area index for each genotype. The results showed that, although the performance of both hybrids for all characters in the first season was quite different from the second one, the response of the two hybrids under the different population densities was more or less similar in both seasons for most of the studied parameters. In both seasons and for both Hybrids, stem and head diameters were affected significantly by the population density, whereas, the number of seeds/head and the seed yield (kg) ha - were affected by the plant densities in the first season for Panar only. Higher seed yield and its related components were recorded under low plant densities and the reduction in seed yield under high population densities for both hybrids was due to smaller leaf area, thinner stem size, shorter plant heights, smaller head size and lower number of seeds/head produced, and thus, greater number of heads produced under higher densities was not enough to compensate for the reduction of seed yield obtained under the higher densities. The optimum plant density for the highest yield for both hybrids was achieved at 2-25 plants/ha. Key words: Plant density, sunflower, hybrids, effect, growth attributes, yield, rain-fed.

2 Stand. Sci. Res. Essays Ahmed and Nafea 5 INTRODUCTION Sunflower (Helianthus annuus L.) is the second most important edible oilseed crop in the world after soy bean. It is grown on an area of 6. million hectare with a production of about 22. million metric tons in the world (Ramanthan, 24). Sunflower originated in south and Central America (Heiser, 976). China and Spain were the main producing countries. They produce about 9% of the world production (Ishag, 988). Commercial cultivation of sunflower in Sudan was in the rain-fed sectors at the Blue Nile and Gedarif States, and under irrigated condition at Rahad and Gezira schemes. Sunflower oil is used for industry. In addition to this, it is used in soap making, (Karaaslan et al., 24). Oil content of sunflower seed is between 25 and 48% (Mohamed 2). Naturally, sunflower oil is better and more stable than soy bean oil (Ahmed et al., 2). It is used in cooking and margarine making (Khidir, 997). Plant density is one of the most important cultural practices that affect yield and other important agronomic attributes of the crop. Numerous research studies for different climates have shown that plant density influences growth, seed yield and quality of sunflower (Sterjo, 989; Getmanets et al., 99; Harmati, 992; Patil et al., 992). Studies by Narwal and Malik (985) showed that as plant density increased, head diameter, number of seeds per head and -seed weight decreased. Also the reduction in percentage of empty seeds per head may be attributed to the reduction in head diameter and to the greater leaf area index under high plant densities. The reduction in seed weight was associated with substantial increase in the percentages of empty seeds. Fisal et al. (26) Degenhardt and Kondar (98), Morrison et al. (99) and Van Denze et al. (992) reported that low plant densities increased production of biomass and grain per plant, because of reduced competition among individual plants with associated benefit of improved canopy radiation interception. Increasing plant densities decreased head diameter (Rao and Reddy, 982). The smaller head diameter of closer spacing may be due to the competition of plants for nutrients, moisture, light and carbohydrates (Ahmed et al., 2). Lazim (985) reported that moisture stress reduced disc size of the crop. Wider spacing resulted in larger head and higher seed number per head (Steer et al., 986; Ahmed et al., 2). Few researches dealt with suitable cultivars, optimum plant density for the rain-fed areas, hence the objectives of the current study are to evaluate two sunflower hybrids at six plant densities for some growth attributes, yield and yield components, under rain-fed conditions. MATERIALS AND METHODS A field experiment was conducted for two consecutive rainy seasons 29/2 and 2/2 at the Farm of the Faculty of Agriculture and Environmental Sciences, University of Gedarif, Tawawa, Gedarif state, Eastern Sudan ' longitude and 6 ' East and 2 4' and5 46' North, elevation 592 masl. The soil is classified as vertisol with dark heavy cracking clay, with low organic matter and low nitrogen contents,.7 and.% respectively (Blokhuis, 99). The experimental area was ploughed by wide level disc and then ridged for two rainy seasons, the rain showers as recorded in the Experimental Farm Station, were and 5 mm/annum during the two seasons, respectively. In each season a randomized complete block design with four replications was used for laying out the field experiment. Each block was divided into 2 plots, to which six population densities 25, 62, 4,, 25 and 2 ( plants ha - ) designated later as (D, D2, D, D4, D5 and D6) respectively, for each of the two hybrids namely, (Hysun-and Panar-75) were assigned randomly. The plot size was m 2, each genotype was represented by four rows.8 m apart. Seeds were sown manually along the ridge bottom; sowing date was on 27 th of July 29 for the first season and on 2 rd of July 2 for the second season. The plants for each genotype were thinned to the aforementioned densities three weeks after emergence; the experimental area was kept free of weeds in both seasons. Nitrogen in the form of Urea was added as recommended for the rain-fed area. The data were collected on the following parameters: (PH) and leaf area index (LAI) were measured after 4 days from sowing and then every 5 days interval, stem diameter (cm) (SD), head diameter (cm) (HD), number of seeds per head (NSPH) and seed yield (SY kg/ha). The analysis of variance was carried out for the data using the computer program MSTAT-C,99 in each season to test the effect of the two hybrids and the six plant population densities on yield, yield components and other growth attributes, according to the methods described by Gomez and Gomez (984) for the randomized complete block design. A scatter graph to show the effect of the population densities on plant height and the leaf area index for each genotype was drawn, Abscissa was presented by the number of days after sowing (days), whereas, the

3 Ahmed and Nafea 54 Ordinate by the plant height (cm) and then by the leaf area index (data were combined over the two seasons for each graph). RESULTS, DISCUSSION AND CONCLUSION The performance of both hybrids in the first season for all characters was quite different from the second season (Table ), and this may be due to the differences in the rain showers between the two seasons. In both seasons, stem and head diameters showed highly significant differences (P.) between the two hybrids. Number of seeds/head was not affected by the hybrids in both seasons whereas; seed yield was affected only in the second season. Both hybrids scored higher means in the first season than in the second one. Hysun exceeded Panar in number of seeds by and 7.7 seeds in the first and second seasons, respectively, whereas, Panar -75 outyielded the overall mean yield by 6.87%, and this is in line with the results reported by Solmon and Eshete (987), and Kaya et al. (26), who attributed this to the fact that Panar is an early maturing hybrid. Table. Effect of hybrids on stem diameter (SD), head diameter (HD), number of seeds per head (NS/H), and seed yield (SYkg/ha) in 29/2 and 2/2 seasons. Hybrids SD(cm) (29/2, HD(cm) (29/2, NS/H (29/2, SY(kg/ha) (29/2, Hysun-.58 b.77 a 7.8 b 6.5 a a b.54 c b Pan-75.9 c.66 b 7.22 c 6.56 a a 85.8 b 2.58 c a G-mean l Sign. Level *** *** * N.S N.S N.S N.S * C.V% S.E *, *** Significant at.5 and. probability levels, respectively. N.S Not-significantly different. Means within the column or row for each character, sharing similar letters are not significantly different at 5% according to Duncan s multiple range test. The graphical presentation for the effect of the population densities on the plant height for the two hybrids is shown in Figures and 2, whereas the effect of the population densities on leaf area indices for both hybrids is depicted in Figures and 4, respectively, (the data averaged over the two seasons). As shown in the graphs, the plant height for both hybrids increased with progress in time of the development of the plant, and then declined towards the end of the season, following the normal growth curve. Similar trends of development for plant height were followed by the leaf area indices. From the graphs, as the plant density decreased, heights of the plants increased, while the leaf area indices decreased at the different stages of the plant development. The increase in plant height under low plant density found in this study may be due to the fact that under low densities, inter plant competition decreases, therefore, sufficient amount of water is available per individual plant to elongate at low density, while the decrease in the leaf area index under low density may be attributed to the fact that, fewer number of plants even with large leaves size per unit area under low densities may not compensate for the greater number of leaves needed for increasing the leaf area. Again limited amount of water under rain-fed condition impairs plant growth and development under high densities. For both hybrids, most of the studied characters were affected significantly at least in one season by the plant density. For example, the stem and head diameters for both hybrids and in both seasons were affected significantly by plant density. The highest mean values for both characters were recorded at lower plant population density, whereas the lowest values were scored at higher densities. The highest means for the stem and head diameters were scored under the lowest density (D 6 ) whereas, the lowest ones were scored under the highest density (D ) (Tables 2 and ). Number of seeds/head and seed yield (kg/ha were not affected by the density in both seasons for Hysun-, but they were affected significantly in the first season only for Panar. Again for both hybrids and in both seasons, the highest seed number and yield were recorded at lower plant densities, whereas the lowest values for both characters were recorded at higher plant densities. For example, highest seed number for Hysun in the first and the second seasons were and 92.5 seeds recorded at D5 and D6 respectively, whereas, the lowest ones were and seeds scored at D2 and D respectively. On the other hand, highest seed number for Panar

4 Ahmed and Nafea Fig.Effect of population Fig.Effect of population density density on on plant height sowing (cm) (cm) of sunflow of er sunflow (Hysun ) er (Hysun ) grown under grown rain-fed under rain-fed condition condition (data averaged averaged over the over two seasons the two ) seasons ) Figure. Effect of population density on plant height (cm) of sunflower (Hysun ) grown under rain-fed condition (data averaged over the two seasons) Fig 2.Effect of poulation density on plant height (cm) of sunflow er (Panar) grownunder rain-fed condition (data Days averaged after sow over ingthe two seasons ) Fig 2.Effect of poulation density on plant height (cm) of sunflow er (Panar) grow nunder Drain-fed D2condition D (data D4averaged D5 over D6 the tw o seasons ) Figure 2. Effect of population density on plant height (cm) of sunflower (Panar) grown under rain-fed condition (data averaged over the two seasons).

5 Leaf area index Leaf area index Leaf area index 4 2 Ahmed and Nafea Days 4after sow6ing 8 Fig.Effect of population density on plant height (cm) of sunflow er (Hysun ) grow n under rain-fed condition (data averaged over the tw o seasons ) Fig. Effect of population density on leaf area index of sunflower (Hysun ) grown under rain - fed condition (data averaged over the two seasons) Figure. Effect of population density on leaf area index of sunflower (Hysun ) grown under rain-fed condition (data averaged over the two seasons) Fig4. Effect of population 2 density on leaf 4 area index of sunflower 6 (Panar) 8grown under rainfed condition (data Days averaged after over sowing the two seasons) Fig4. Effect of population D density D2on leaf area D index D4 of sunflower D5 (Panar) D6 grown under rainfed condition (data averaged over the two seasons) Figure 4. Effect of population D D2 density on Dleaf area D4index of D5sunflower D6 (Panar) grown under rain-fed condition (data averaged over the two seasons). in the first and second seasons were and 97.5 seeds scored at D6 and D4, respectively, and the highest seed yield for the same genotype in the first season was 72.5 kg scored at D6 whereas the lowest one was 7. kg scored at D2 (Tables 2 and ). Generally, increasing the number of plants per unit area increases competition among plants for light, nutrients and soil moisture, and this might explain the significant effect of plant densities on most of the parameters measured in the present study and at the same time interpret the reduction in seed yield and its components for the two hybrids at higher densities. Similar results were obtained by many researchers, Narwal and Malik (985), Sterjo (989), Killi and Ozelemir (2) and Rao and Reddy (982) who reported that, at higher plant densities along with limited moisture contents, the yield of the crop and its components were substantially reduced. In the present study, in addition to the interplant competition at higher plant densities, the insufficient amount of water during the two rainy seasons ( mm/annum) in 29/2 and (5 mm/annum) in 2/2 of the experiment resulted in the

6 Ahmed and Nafea 57 reduction of yield and its components for both hybrids. From the results of this study, it could be concluded that higher seed yield and its related components were recorded under low plant densities and the reduction in seed Table 2. Means of 4 parameters in Sunflower (Hysun-) as affected with 6 plant population densities grown under rain fed conditions during the two seasons (29/2 and. Plant densities (plants/ha) SD(cm) (29/2, HD(cm) (29/2, NS/H (29/2, SY(kg/ha) (29/2, G.mean Sign level *** ** *** ** N.S N.S N.S N.S C.V% S. E **, *** Significant at. and. probability levels. N.S Not significant. Table. Means of 4 parameters in Sunflower (Panar-75) as affected with 6 population densities grown under rain fed conditions during the two seasons (29/2 and. Plant densities SD(cm) (29/2, HD(cm) (29/2, NS/H (29/2, SY(kg/ha) (29/2, (plants/ha) G.mean Sign level *** * *** * ** N.S * N.S C. V.% S. E.,7.4, *, **, *** Significant at.5,. and. probability levels, respectively. N S not significant. yield under high population densities for both hybrids was due to small leaf area, thin stem, shorter plant heights, smaller head sizes and low number of seeds/head produced, and therefore, greater number of heads produced under higher densities was not enough to compensate for the reduction of seed yield obtained under the higher densities. References Ahmed M E, Mahmoud F, Ahmed A (2). Effect of irrigation intervals and intra-row spacing on vegetative growth characteristics in Sunflower (Helianthus aunns.l) hybrids in Shambat soil. Sudan, J. Appl. Sci. Res. 6(9): and oil yield of Sunflower hybrids. No um ve ac nytermele ac s,(99) 4(6): Blokhuis W A (99). Vertisols in the Central Clay Plain of the Sudan. Dissertation no.58. Wageningen Agricultural University, Wageningen, Netherlands crop net work at Njoro, Kenya January. Degenhardt F, Kondara Z P (98).The influence of seeding date and seeding rate on seed yield and components of five hybrids of Brassica napus Canadian J.Plant Sci. 6: density and nitrogen. J. Agric. Sci.4: 95 97

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