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Influence of Sowing Date on Growth and Yield Components of Sunflower (Helianthus Annuus L.) in Semi-Arid Zone
The main objective of this study was to quantify the influence of sowing date on growth and yield components of hybrid sunflower (Hysun33) cultivar in semi-arid zone. This experiment was conducted during the seasons 2014/2015-2015/2016 at the farm of the College of Agricultural Studies, Sudan University of Science and Technology, Shambat, Khartoum- Sudan. The experiment was arranged in randomized complete block design (RCBD) with four replications and three treatments. Different parameters were considered including plant height, leaf area index (LAI), filled sees number/head, head diameter, dry weight and yield components. The collected data were statistically analyzed. The results revealed that crop sown in May and July showed significant increase in plant height, LAI, head diameter, dry weight, field seed number/head, weight of 100 seeds; yield; and yield components; compared to crop sown in March. However, crop sown in the second season showed an increase in growth and yield components compared to the crop of the first season.
The economic importance of this crop is that the fresh green plant can be used as silage or fodder to feed livestock. The seed can be eaten raw or roasted, and it can be used in salads, cooking, margarine, lubricant, paint varnishes and soap production. The seed contains about 36 to 45 % oil depending on the variety 3.
The crop is categorized as a low to medium drought sensitive 4. It shows adaptability to different regions, climatic conditions and sowing dates due to its high genotype and ambient interactions 5. Therefore it can be grown twice a year 2. Nevertheless, despite the ability of the crop to high water use, and the ability to withstand short periods of severe soil water deficit of up to 15 atmosphere tension, the long periods of severe soil water deficit, particularly at water-sensitive growth stages, causes significant reduction in seed yield 6.
It is noticed that good cultural practices and drainage are required for sunflower production 7. However; several studies reflected that sunflower can be grown at a wide range of dates. Most cultivars are early maturing. In areas where no winter, sunflower can be grown at any month of the year to obtain satisfactory yields 8, 9.
It is reported that yield differences between hybrids with regard to sowing time and density are remarkable. These differences are determined on one hand by the hybrid characteristics and environmental conditions, and on the other hand, on by plant population, soil fertility and land preparation 8, 9.
Researchers 10 showed that when sunflower sown in December; it flowers between March and April, at a time when the honeybee activity is maximum, resulting in better pollination and consequently good seed setting.
Seed setting and filling problem is one of the most important constraints in sunflower production, especially under rain-fed; where the heavy rains wash the pollen grains, and often considered to be a major reason for low productivity 11.
This experiment was conducted at the farm of the College of Agricultural Studies, Sudan University of Science and Technology, Shambat, Khartoum - Sudan, during the seasons 2014/2015 and 2015/2016. Where the climate is described as semi-arid region. The area receives an average annual rainfall in summer, during July to September, ranging from 100 to 160 mm/annum, and relative humidity ranges between 31-51% during the wet season and 12-27% during the dry season. The average maximum and minimum temperature is about 41.7 0C and 15.3 0C respectively. The winter season begins in November and ends in March. It is relatively cool and dry 12.
The soil of study area is classified as silt, clay loam with non saline at surface, but slightly sodic at the subsurface.
The adopted experimental design was the randomized complete block (RCBD); with four replications and three treatments (sowing dates (March, May and July)) which referred as S1, S2 and S3 respectively.
The land was cleared, well prepared by using disc plough, disc harrow, leveler and moldboard. Then the area was divided into equal plots. Each plot size is 4 X 4 m2, with 5 rows. The spaces between rows are 70 cm. Following the randomization, seeds of sunflower (Hysun 33) were sown on rows, 70X15 cm apart. The recommended cultural practices by the Research Centre in Sudan were followed.
The data of the studied parameters were collected. Where three plants were randomly selected from each plot for measuring the following parameters: plant height (cm), leaf area index (LAI), plant dry weight (g), and yield components including head diameter, 100 seeds weight (g), number of seeds/head, yield (t/ha). The collected data were subjected to statistical analysis using statistic 8, Version 2.0 UK.
|Plant height (cm)||Leaf area Index (L. A I)||Filled seed No. /head|
|Sowing date||100 seed Weight (g)||Head diameter (cm)||Plant dry weight (g)||Yield t/ha|
Considering Table 1, and Figure 1, the results of data analysis of this study showed variation in plant height for the different sowing dates in the same season as well as between the two seasons. In the first season, crop sown in May (S2) has significantly increased plant height (136.55 cm) compared to January (132.15 cm) and July (128.46 cm), while in the second season plant heights for the different sowing dates were 125.50 cm, 135.84 cm and 129.49 cm for January, May and July respectively. It is clear that sowing date in May (S2), produced the highest plant height in both seasons. A researcher 13; reported that plant height decreased significantly with delay in sowing from first January, to first April. This result disagrees with the results obtained in this study. This variation may be due to difference in climatic conditions and cultural practices.
As far as the leaf area index (LAI) concern, in the first season, the sowing date S3 produced bigger LAI (106.13 m2) compared to 94.45 cm2 and S1 59.45cm2 for S1 and S2 respectively. While in the second season; S2 produced the biggest LA I 137.31 m2, followed by S3 and S1 respectively (Table 1, Figure 2).
For filled seed number/head, the data reflected S1 produced the highest number of seed filling/head (235.54), followed by S3 and S2 (152.75) in the first season (Table 1, Figure 3), where in the second season the highest number was obtained by S3 (316. 19) compared to S2 (289.38) and S1 (240.04) (Figure 2). Similar result was obtained by one of the researcher 14.
For seed weight (100 seeds weight), the sowing dates S3 (4.38g.) and S2 (4.2 g) produced higher seed weight in the first season compared to S1 (3.89 g.). While in the second season; the S1 produced more seed weight compared to S3 and S2 (Table 2, Figure 4).
In regard to head diameter, S2, and S3 appeared to be the suitable sowing dates for sunflower in this area (Table 2). However, the head diameters for the different sowing dates in different seasons were as follows: for the first season, S2, and S3 produced similar head diameter (9.46 cm, 9.42 cm), while S1 produced head diameter of 8.38 cm. For the second season, S2 (12.38) considered the best sowing date followed by S3 (11.19) and S1 (8.85) (Figure 5).
The data of the dry weight of the first season reflected that treatment S2 showed higher dry weight (435 g) compared to treatment S2 and S3 375.13 and 365 respectively. While treatment S3 produced more dry weight (262.5 g) compared to treatments S2 (205 g) and S1 (201.85 g) respectively (Table 2, Figure 6).
As far as the yield concern, the data displayed variation between and within the two seasons. The yield of the first season exceeded the second season. In the first season; crop sown in July produced higher yield, while in the second season; crop sown in May produced higher yield (Table 2, Figure 7).
Sunflower can be cultivated year a record in different region in the world. The performance of sunflower is largely affected by adverse conditions, cultural practices and sowing date.
This Study showed that the optimum sowing dates in the study area are May (S2) and July (S3), when the highest plant height, leaf area index (LAI), number of seed setting/head, weight of 100 seed, head diameter, dry weight were a obtained.