PREPARATORY TILLAGE
Sunflower requires a fine seedbed, free of weeds and clods, for proper germination and good crop stand. to bury the residues or previous crop, ploughing with disc harrow followed by 2-3 cultivations and plankings may be required. fields vacated by potato may not require much seedbed preparation. However, adequate soil moisture is essential forgetting good germination.
VARIETY
MSFH8, PSFH-67,GKSFH-2002, Jwalamukhi, Mega-363 and NSFH-592 have been recommended. These hybrids are medium tall with dark green leaves. their seeds are black in colour and mature in about 110-125 days mega-363 is a long duration hybrid and hence should not be selected for cotton areas. These hybrids have an average yield about 20 quintals per hectare with an oil content of 40.5 to 43.0 percent. In hybrids fresh seed is to be sown every time which adds to its cost of cultivation.
SOWING TIME
Spring season is the best for getting higher and stable seed yield sunflower. Sunflower being a cross pollinated crop depends on honey bees for pollination and seed setting. Availability of honey bees is abundant during spring season due to favourable. Planting during spring should be made after the soil temperature exceeds 100C at 10cm depth at 8 a.m. Earlier planting at lower temperature increases time of flowering without much earliness. Best results are obtained when crop is sown in the first fortnight of January which produces higher seed yield than later planting. Sowing of short duration hybrids like GKSFH-2002,PSFH-67 and nsfh-592, however, can be extendedupto second fortnight of January. Besides low yields, the late sowing may also face early mansoon rain at harvesting ans threshing causing difficulty in its management.
SEED RATE AND SEED TREATMENT
Use 5kg seed per hectare for hybrids to achieve the required plant stand. Low seed rate recommendation for hybrids is mainly because of smaller seed size and wider spacing for hybrids. Seed should be treated with Brassicol or Thiram @ 2 g per kg of seed to control seed and soil borne fungal disease.
METHOD OF SOWING
A spacing of 60*30cm for hybrids has beenfound to be an optimum. These spacings result in better development of head, more seed filling and less stem breakage.
CRUST BREAKING
Rain after sowing, results in crust formation, which hinders the proper emergence of seedlings. Thus it may be necessary to break the crust, which can be done with harrowing. Harrow as soon as possible after the crust has performed and if possible, before seedlings have emerged.
FERTILIZER MANAGEMENT
Fields studies have shown that hybrid sunflower responds well to nitrogen application upto 60 kg/ha. further increase in nitrogen results in lower seed and oil yield. Application phosphatic ferticizers @ 30kg P2O5/ha increase sunflower yield. sunflower responds to K application only on soils deficient in available potassium and it is recommended to be applied @ 30 kg K2O/ha on such oils.
Regarding application method, drilling the fertilizers besides the seed row has been found to be more beneficial for getting higher seed yield. Application of fertilizers below the seed was found to be injurious to germinating seeds and reduced seed emergence count and seed yield.
Entire dose of N, P and K should be applied at the same time of sowing. Prefer single superphosphate for P application as it also contains sulphur to which sunflower responds favourably. If single superphosphate is not available apply gypsum @ 25-30 kg/ha at sowing time. A suppllementary dose of nitrogen @ 25-30 kg/ha may be top dressed a month after sowing sunflower if the crop exhibits symptons of nitrogen deficiency.
Nitrogen deficiency appears as yellowing of the older leaves, which die prematurely. Leaves are also fewer and smaller. Plants with a severe deficiency are yellow and stuned, while young plants are of purplish colour. Plants are slender with longer internodes. The flower head is small with many unfilled seeds and the oil content is reduced.
Phosphorous deficiency results is delayed flowering, stuned growth and small leaves which prematurelydie back from the leaf tip. Phosphorous deficiency is shown in small dark green leaves later turning pale with necrosis. Growth is restricted with short stiff stems, flowers are small, stuned malformed. Ripening is delayed, oil content and yield are reduced.
Potassium deficient plants are squat with a proportionately greater reduction in stem length then in leaf size. Initially leaves are dark green but turn yellow at the edges and die except the lower leaves. Potassium deficient plants have restricted growth with a rosette arrangement of the younger leaves. later the leaves develop dark brown necrotic patches.
WATER MANAGEMENT
Sunflower can withstand moderate drought because of its deep root system. However, it responds favourably to irragation and its seed yield can be increased subtantially by sustantially by sustaining adequate moisture insoil by timely irrigations besides improvements in oil content. sunflower is highly moisture sensitive plant and its broad leaves exhibit wilting with slight moisture deficiency.
First irrigation to sunflower should be applied a month after sowing and interval during the subsequent months be reduced to 2-3 weeks during March and 8-10 days during the hots months of Apriland May. Irrigation should be stopped about 12-14 days before harvest. Sunflower is a tall growing plant with heavy head, therefore , irrigation at flowering and thereafter should be given on clam days to avoid lodging. The incidence of Sclerotinia stem-rot is more under irrigated conditions especially where the soil drainage is poor. Excessive and frequent irrigations on fine textured soils should be avoided.
WEED MANAGEMENT
Mechanical methods such as hoeing at 3-4 weeks after sowing followed by earthing up before flowering has been found to be effective in checking weeds. Use of tractor drawn implements before the crop attains 60-70 cm height has also been found effective. for better efficiency of manual weeding an improved 3 tine wheel hand-hoe could also be used.
Removal of weeds through mechnical/manual means means quite effective but expensive. Moreover, often timely labour is not available. The studies initiated to find effective herbicides for weed cintrol in sunflower, revealed that pendimethalin (STOMP @2.51/ha) as pre-emergence application gave effective weed kill.
HARVESTING AND THERSHING
The crop is ready for harvesting when the back of flower heads turn lemon yellow or yellowish brown near the stalk and the discs start drying. At this stage the seeds give a blakish look and are fooly ripe. the shadding of disc-flower residues from undamaged heads also indicate psysiological maturity. Promptly harvesting seed after psysiological maturity has many advantages ; seed is least exposed to bird and rodent attack; the crop cycle is shorter resulting in more time to prepare for the next crop ; reduces harvest seed losses ; provides high quality seed and reduces exposures to bad weather.
The harvested heads are mildly dried and threshed by beating or trampling with tractors or sunflower threshers.The sunflower thershers are more efficient and economical. After threshing the produce should be throughly dried before storing otherwise in storage it gets affected by fungus and decomposes.
ALLELOPATHIC EFFECTS OF SUNFLOWER
Researches show that sunflower depresses the growth and productivity of succeeding crops. The reason postulated are the allelochemicals being secreted by sunflower crop. Decomposing residues of sunflower could also bring about allelopathic effects. Phytotoxic compounds released into the soil rhizosphere have been observed to cause varying degree of allelopathy/autotoxicity in crop. Field studies conducted in the department of Agronomy, Punjab Agricultural University, Ludhiana on the allelopathic effect of spring sunflower on succeeding Kharif crops revealed that maize, sorghum, cowpea, pearlmillet, pigeonpea, mungbean and sesamum suffered 41.7, 36.7, 27.6, 28.8, 23.0, 10.8 and 9 percent reduction in yield, respectively, as compared to these when grown after wheat. Studies in allelopathic effects of different plant parts of sunflower indicated that sunflower roots reduced pigeonpea, cotton and mungbean yields the most followed by roots plus shoots treatment. Sunflower shoots did not have any harmful effect on growth of these crops.
Bioassay studies involving use of aqueous sunflower extract, decomposing plant residue and soil from area in proximity of sunflower crop revealed inhibition of gemination and growth of cotton, pigeonpea, sunflower and mungbean. These studies further showed that effect of leaf extract/residue was more than roots. The allelopathic effect of sunflower plant residue persisted upto 24 days after incorporation and beyond this period the effect was rather meagre.
Chromatograhic and physico-chemical analysis of allelochemicals in sunflower parts showed the presence of chlorogenic and isochlorogenic acids in both stems and leaves besides these some unidentified phytotoxins were also observed. The concentration of these was more in leaves than in stems. Further studies revealed that total phenolics was more in leaves followed by in roots and shoots. Sunflower raised under moisture stress conditions had higher phenolics as compared to the raised without any moisture stress.
Cut worm (Agrotis spp.)
It is polyphagous pest adn cuts off the tender stalks, near ground, of young crop plants during night. During day time the caterpillars remain hidden in the soil. It is more serious during March_april when sunflower follows potato. When flat sowing is practised, apply 5 liters of Dursban/Radar 20 EC (Chlorpyriphos) per hectare before sowing. These insecticides should be mixed in 25 kg fine soil and broadcast uniformly after last ploughing but before planking.Sow crop on ridges to avoid cut worm damage in the early stages.
Tobacco caterpillar (Spodoptera litura)
The polyphagus pest remain active throughout the year feeding on one or the other crop. The newly hatched caterpillar is pale-greenish with a black head and feeds on the outer epidermis of leaves. It poses a serous threat during April-May and defoliates the plants.
Cabbage Semi-looper (Plusia orichalcea)
This insects feeds on many crops including the sunflower. The newly hatched caterpillars defoliate the crop and cause severe damage to it during April-May.
Bihar hairy caterpillar (Spilosoma obliqua)
It is also called Bhabbu Kuta. This is highly polyphagous and voraciousfeeder. The nefarious pest causes severe damage and plants looke denuded. Newly hatched larva is bright brown and its body is covered with hair and legs are brown. At the older stage it is much darker and with dark brown hair of almost uniform length. these insects feed gregariously and should be collected along with the plant and buried deep in soil.
For the control of above mentioned pests, spray 1.125 L. Folithion/Sumithion 50 EC (fenotrothin) or 1.225 L. Thiodan 35 EC (endosulfan) or 500 ml Nuvan 100 EC (dichlorvos) in 250 litres of water per hectare. Repeat after two weeks, if necessary.
Head borer (Helicoverpa armigera)
Head borer or American boll worm has become the noxious polyphagous pest in India adn also causes heavy losses in sunflower. Newly hatched larva is green yellow which changes its colour with every instar.
The full grown caterpillar is brownish green having grey longitudinal streaks on it. The adults lay eggs on the flower buds. After hatching the larvae feed on developing seeds and make tunnles through them.
Head borer can be controlled by spraying 2.5 Kg of Sevin 50 WP (Carbaryl) or 2.0 litres of Asataf 75 SP (Acephate) or 2.125 litre Folothion 50 EC (Fenitrothion) or 2.5 litres of Dursban 20 EC (Chlorpyriphos) or Thiodan 35 EC (Endosulfan) or 1.25 litre of Nuvacron 30 SI (Monocrotophous) in 375 litres of water per hectare. Repeat after two weeks if necessary. Endosulfan is comparatively safe for honey bees. Spray when honey bee activity is minimum i.e. early morning or late evening.
Precautions for spraying insecticides
- Spraying during flowering should be avoided to protect the pollinators.
- Spray in the afternoon when pollinators are less so that there is a time gap till morning or mid day when their activity is more.
- Spray only when pest incidance is observed in abundance.
- Spray on calm day to avoid drift.
- Precautionary measures are advisable if pest outbreak is observed every year.
