Seed Production Techniques in Sunflower
Select fields in which sunflower was not grown in the preveious year unless they were of the same variety and were of equivalent or higher class and were certified. In addition, the selected field should be well-drained and the soil deep, fertile and with neutral PH.
Sunflower is partially self-pollinated. The extent of cross –pollination varies from 17 to 62 %, according to insect activity. The seed fields must be isolated at least by 400 m for foundation seed class and 200 m for certified seed class from fields of other varieties, same variety not conforming to varietal purity requirements and wild sunflower.
I) Brief Cultural Practices:
1) Preparation of Land:
Usually one deep ploughing , two to three harrowings followed by levelling are adequate to prepare the field to the desired tilth.
2) Time of Sowing:
Sunflower, unlike most other crops are not season bound. Barring the periods of extreme freezing temperatures the sowing time can be adjusted as per availability of land for planting. However, sowing should be so adjusted that the maturity of the crop does not coincide with the rains. Since rains during maturity period adversely affects the seed quality.
3) Source of Seed:
Obtain nucleus/ breeder’s / foundation seed from the source approved by the seed certification agency.
4) Method of Sowing:
The crop should be sown in rows. The depth of seedling should be 2 to 4 cm.
Row to Row: 60cm
Plant to Plant: 20 cm.
6) Seed Rate:
8 to 10 kg per hectare.
The fertilizer required for raising a good sunflower crop is 80 kg nitrogen, 40 kg phosphorus and 40 kg potash per ha. At the time of planting 50 kg nitrogen and the full amounts of phosphorus and potash should be applied as a basal dose and the remaining 30 kg nitrogen at the time of earthing i.e after 40 to 45 days of crop growth.
Pre-sowing irrigation is necessary in the spring to summer season, and desirable for rabi sowing for uniform germination and better stand. Sunflower is comparatively drought tolerant and yields higher than oilseeds crops under moisture stress conditions.
In rabi and zaid planting two and four irrigations respectively, are necessary for higher yields. In kharif , if rainfall distribution is favourable, no irrigation may be required. One irrigation between the flowering and grain filling stages must be applied.
9) Weeding and Interculture:
One to two weedings during the first six weeks after germination are necessary. Thereafter growth rate is high and the crop covers the ground and smothere most of the weeds.
The sunflower plants may root lodge because of large heavy heads. Earthing, preferably before and, if needed , after irrigation around 48 days after sowing is highly desirable. 10 to 15 cm high earthing is sufficeient.
11) Supplementary Pollination:
Placing of bee-hives on the field periphery or on blank strips approximately at 200 meter intervals has been found beneficial for cross-pollination and seed set.
Hand pollination may also be resorted to Sunflower heads are gently rubbed with bare plant or covered with muslin cloth during the animals period between 7Am to 11Am an alternate days of about two weeks.
II) Plant Protection:
Alternaria blight may assures serious proportions in the rainy season and may reduce yields drastically. The dark brown and black coloured spots, if seen on any plant part, should be immediately sprayed with 0.25 % spray of Dithane M-45 or Dithane Z-78 at one to two weeks intervals.
Other diseases of minor importance are: Sclerotium wilt in July and August plantings. Sclerotinia wilt in winter, and charcoal rot in March plantings. The affected plants should be uprooted and burnt. Growing of sunflower in longer duration rotational cycles is recommended.
Pests and Birds:
No serious pest of sunflower has been noticed. The crop should be watched against attack by cut worms during the seedling stage, for head borer damage at the bloom stage and for jassid attack all the time. Mixing of 5% heptachlor dust in soil at 15 kg per hectare will control cut worms and one to two sprays of 0.025 % metasystox ( 25 E.C) will take care of the other two insects.
In lonely maturing fields of sunflower , birds may cause extensive damage, particularly when no other seasonal crop is in the grain stage. Bird watching in such cases is imperative. In plantings with or after the seasonal crops the bird damage is minimal.
Generally two roguing are needed. The first should be done at the pre-flowering stage
and the second at crop maturity. Before flowering, tall, very early, very late, branched as well as weak, wild and diseased plants should be rogued out. At the time of 75% crop maturity , wild , ornamental, diseased, damaged and all those plants which do not conform to the characteristics of the variety under seed production, should be rogued out in addition to these , plants affected by wilt, charcoal rot, blight , etc should also be removed from time to time as required.
Precautions in Roguing:
1. Sunflower head continues to develop and shed viable pollen even after removal from stalk. It is therefore, important that the heads after removal from stalks are turned down ( Face down on the soil) while throwing them on ground.
2. Sunflower is phototropic until the early stage of flowering. After ray flowers are fully developed, the heads generally faces the east. This features makes roguing inefficient , if the row direction is east-west. If the direction is north-south, this problem is eliminated. It is therefore important that roguing is always done looking westward at the heads.
Harvesting and Threshing:
The crop is ready for harvest when top leaves are dry and flowers are shrivelled. Heads may be removed with shears or knife. Heads after cutting are sun dried on the threshing floor. Hand threshing can also be done by rubbing seed heads on a metal sheet or beating with sticks. Threshed seed must be dried to eight to ten percent moisture before storage.
A good crop may given an average yield of 15 qtls per hectare.