All About/Crops
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SunFlower |
Sunflower Production Technology
Seedbed preparation
As sunflower has a well-developed root system, deep ploughing with a mouldboard plough or sardheri plough is necessary. Secondary tillage implements like a disc harrow or tines should be used to level the field for planting and subsequent irrigations. It is important that the soil around the seed remain moist during germination. With light soils, the soil must be pressed during planting to make good contact between the seed and moist soil, as well as to reduce loss of moisture from the soil. This technique is especially important in dry rainfed areas.
Manuring
Sunflower has a low harvest index and is considered an inefficient converter of plant nutrients. Exact determination of nutrient requirements is very essential. Generally, 100 kg sunflower seed contains 6, 2, and 18 kg of N, P2O5 , and K, respectively. About three-fourths of the P2O5 absorbed is found in the seed. Balanced application of NPK is essential, otherwise N along reduces grain yield and oil content of the seed. Generally, application of N should not exceed 50-80 kg/ha. N is responsible for increase in the size of flower heads and the proportion of sterile seeds in the centre of the head. A basic dose of 40-60 kg/ha , P2O5 is sufficient. Increasing levels of phosphate increases seed size but adversely affects seed composition. However, deficiency of phosphate decreases the oil content of the seeds. Generally, the amounts of , P2O5 and K applied should be equal. The doses of fertilizer recommended by the Pakistan Agriculture Research Councils are 35-45 kg N, 30-35 Kg , P2O5 , and 15 kg K2O/ha in irrigated areas; and 30-40 kg N and 20-25 kg , P2O5/ha in barani areas. Half of the N should be applied at the time of planting, and half during earthing up when the plants are about 30 cm tall.
Time of planting
Sunflower is a new crop, and is unlikely to compete with the replace the already established crops with their established technology and markets. However, it is highly adaptable and fits very well into the cropping system. Throughout the country sunflower is grown in two seasons; spring and summer. Table 14.1 shows the times for planting spring and summer crops in different areas.
Table Time of planting spri8ng and summer sunflower crops in different areas
Locality
Time of planting
Spring
Summer
South Sindh
Jan 15-Feb.2
July 15-Aug. 30
North Sindh
February
July 15-Aug 20
Bahawalpur, Multan Div.
Jan.25-end of Feb.
July 20-Aug.15
Lahore, Sargodha Div.
Feb. 1-March 5
July 10-Aug.15
Rawalpindi Div. (rainfed)
Feb. 10-March 5
July
D.I.Khan
Feb.10-March 5
July 5-Aug 10
NWFP plain + mountainous tracts
March 1-30
July 1-Aug. 15
Source : PARC (1988:304)
Seed rate and plant population
Sunflower cultivars differ in seed size, plant size, and height. Therefore, it is necessary to determine the specific seed rate and plant population for the cultivar being planted. Present commercial sunflower cultivars are single-stemmed and single-headed, and unlike other crops like soybean, wheat, etc are not able to compensate or adjust plant population by regulating the number of branches/tillers or number of pods/spikes. The required seed rate can be calculated by the following formulas developed by Weiss (1983:430)
Seed No. /ha = desired population/ha x 100
Expected germination percentage
Seed required (kg) = seed number/ha x area sown (ha)
Seed number/kg
Seed number required/10 m row = seed number/ha x row width (mm)
1,000.000
Throughout the world seed rate varies from 3 to 8 kg/ha depending upon the size of the seed and spacing. The present cultivars available in Pakistan should not be planted with more than 5-10 kg seed/ha. The recommended seed rate in Sindh is 10 kg/ha. On light, sandy soils with low soil moisture content, the seed rate should be increased proportionately.
The recommended plant population in irrigated lands is 75,000-85,000 plants/ha, and under rainfed conditions from 37,000-50,000 plants/ha. In order to suppress weeds and facilitate interculturing, the plant-to-plant distance should be 25-30 cm in rows spaced 70-75 cm apart. Table 14.2 shows the exact combination of row-to-row and plant-to-plant spacing to obtain the desired plant population.
Table Sunflower sowing guide: plant-to-plant distance (cm) for various population densities (plants/ha) and row spacing (cm).
Desired plant population (plants/ha)
28,000
32,000
40,000
50,000
75,000
Row spacing (cm)
Plant-to-plant distance (cm)
35
75
66
53
43
28
45
60
51
41
33
21
53
50
44
35
28
19
60
44
39
31
25
16
68
40
35
28
21
15
70
37
33
26
21
14
85
36
31
25
20
13
83
33
29
23
18
13
88
30
21
16
11
11
90
29
25
20
16
11
100
27
24
19
15
10
Seed should be planted 3-8 cm deep using a cotton drill. Sowing can also be done by the kera method using a desi plough. The effects of using different types of ploughs and different methods of planting need to be investigated.
Interculture and weeding
Thinning is one of the operations essential in order to maintain the desired plant population. For this purpose weak or abnormal seedlings should be uprooted before the first irrigation is given. Control of weeds during the first four weeks after emergence is crucial. Up to 65-75% of potential yield can be lost because of damage during this period. The seedlings at this stage compete poorly with weeds and the root system is easily damaged by mechanical cultivation. Hand tools like the kudla, bar harrow or tripali should be used to suppress weeds. In order to avoid damage to the developing roots, mechanical weeding should be discouraged. Sunflower plants grow rapidly and cover the ground early, thus reducing weeding requirements. However, if weed are not sufficiently controlled and plant growth and spacing allow the use of machinery, a harrow should be used to control weeds.
Sunflower plants are extremely susceptible to hormone herbicides, and such compund should not be used. A number of pre-sowing or pre-butralin, nitralin, and profluralin are promising. For post-emergence application there are few recommendations. In fact, at present there is no practical substitute for manual weeding or directed spray to control weeds. Dalapon, for example, can be applied as directed spray.
When all interculturing operations are completed and the plants are about 30 cm tall, the soil from the centre of the rows should be pulled to the bottom of the plants. This operation is called earthing up. It helps in uprooting weeds and supporting the plants to avoid lodging. This operation can be done manually or by ridgers drawn by bullocks or a tractor.
Intercropping and rotation
Sunflower is a tall-growing plant with large, dropping leaves, significantly shading the companion crop. Intercropping with sugarcane is not recommended. However, intercropping with short statured crops like groundnut and mung bean increased the monetary value of the companion crops by 23 and 30% and land equivalent ration by 1.73 and 1.53, respectively, compared to sunflower alone (Chaudhry et al. 1986).
Sunflower, being a short-duration crop (90-110 days), fits very well into the prevailing cropping system. It is easily grown between the two major crops without disturbing them. Moreover, it can be grown either as a spring or a summer crop and can therefore be fitted easily into one of the seasons. The most common rotations are:
Cotton - Sunflower - Cotton
Rice - Sunflower - Rice
Sunflower - Wheat - Sunflower
Sugarcane - Sunflower - Maize
It is rainfed areas the following rotations are followed.
Sunflower - Wheat - Groundnut
Sunflower - Wheat - Soybean
Several other rotations could be followed depending upon locality and environmental conditions.
Irrigation
Sunflower is generally considered drought-resistant, but significant reduction in yield has been observed due to water stress. This is because the water requirements of sunflower are higher than for other crops; for example, water use by sunflower is twice that of sorghum at any stage of growth. In sunflower, water stress symptoms do not appear as quickly and recognizably as in other cultivated crops. It is therefore unwise to use visual symptoms as a guide for scheduling irrigation. However, the effects of water stress on seed characteristics are obvious at maturity.
On the other hand, excess water is also detrimental to sunflower, and the damage caused is proportional to the period of flooding or waterlogging. The number of irrigations required depends upon environmental conditions, particularly rainfall and the rate of evaporation. Generally, spring plantations require at least four irrigations. The first irrigation should be given 15 days after emergence, the second at the completion of vegetative growth, the third at head formation, and the last one at the time of seed filling. However, for summer planting, because most of these stages take place during the cooler months, the number of irrigations can be reduced to three. In both cases, the first and the last irrigation are considered the most crucial.
Harvesting and threshing
Spring-planted sunflower usually matures in May-June, and the summer-planted crop matures in the last week of November. At maturity the heads are often attacked by birds, especially parrots; thus delayed harvesting allows greater damage by birds as well as by shattering. The heads are ready for harvesting when the back of the flower heads turns yellow and the leaves become greyish white. At this stage the moisture content of the seed is 30-35%. The heads are cut with a sickle from the standing crop and spread in the open to dry. To avoid rotting of the heads and seed, if the heads are collected in heaps should be small and the heads should not remain stacked for very long. It is easy to moist. The seed can also be separated from the heads with threshers and combine harvesters. If threshing is done manually, the seed can be separated with winnowers.
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