Seed Production Techniques in Castor
Land to be used for seed production shall be free of volunteer plants. In addition the field should be well- drained and soil well aerated.
Castor is an often cross- pollinated crop. Cross-pollination by wind varies from 5 to 36 percent according to the prevailing climatic conditions. For pure seed production , the seed field must be isolated from other variety fields and of same variety not conforming to varietal purity requirements of certification at least by three hundred meters for foundation seed class, and one hundred and fifty meters for certified seed class.
Brief Cultural Practices:
1) Preparation of Land:
Castor is a deep-rooted crop. Therefore, deep ploughing has been found very useful. One deep ploughing followed by two to three harrowings is sufficient to bring the field to the desired tilth.
2) Time of Sowing:
The sowing time in most of the states is June to July. In Bihar ( Rabi Crop) castor sown in September to October. In Gujarat , planting is done in August to September and in Karnataka it is sown in April.
3) Source of Seed:
Obtain nucleus / breeder’s foundation seed for planting from source approved by a seed certification agency.
4) Method of Sowing:
The crop is planted in rows either by drill, or behind the plough in furrows. The depth of seedling is 7.5 to 10 cm.
Row to Row – 90 cm ( annual varieties )
Plant to Plant – 45 to 90 cm.
6) Seed Rate:
11 to 18 kg per ha , varies upon spacing, seed size and method of sowing. For rainfed crops a seed rate upto 33 to 44 kg is also practised.
The crop responds well to organic manures. The rate of fertilizer application varies considerably in different states and ranges from 20 kg to 80-100 kg per hectare for nitrogen , 10 to 40 kg Phosphorous and 10 to 40 kg Potash.
The number of irrigations required varies with the rain. Usually two to three irrigations during the entire crop season may be required. Adequate moisture in soil at the time of flowering is necessary.
The castor field must be kept weed-free for the first sixty days after planting. Two to three weedings / hoeings are sufficient to keep the field clean. Application of 2-4,D or triflurelin ( 3 to 4 kg per ha) is also recommended for controlling annual dicot weeds.
Nipping of auxiliary buds of all the branches gives increased seed yields, besides reduction in maturity period and uniformly maturity.
11) Plant Protection:
For control of semilooper , spray 0.35 percent thiodan or 0.03 percent Dimecron, for castor pod borer , spray thiodan ( 1200 ml per ha) and for caterpillar, dust 5 percent BHC dust or spray 0.04 percent Malathion solution. For control of Phytophthora blight and Cercospora, spray Bordeaux mixture ( 4:4:50) at 15 days intervals or spray 2 to 3 times o.25 percent Dithane M-45.
Remove all off types before flowering. The diseased plants affected by Phytophthora blight and Cercospora leaf spot should be rogued out as soon they are noticed, and preventive plant protection measures adapted immediately to check further spread.
Harvesting ad Threshing:
The fruit are ready for picking in November. The picking continues until April, because the capsules mature unevenly due to sequential development of racemes. The fruits should be gathered when they start turning light yellow and placed in piles to dry in the sun until they blacken. Later the seeds are beaten out with sticks, winnowed and screened to remove husks, dry skins and soil pebbles. Before storage, the seed must be dried to eight percent moisture content.
8-10 q/ha. High yielding varieties if managed well may give 15-20 qtl/ha seed yield under irrigated condition.
Production of Hybrid Castor Seed:
For production of single cross hybrid seed, lines giving a 1:1 ratio of pistil late and heterozygous monoecious plants are used. In the crossing plot the latter are rogued out one to five days before flowering begins. Female plants are then cross-pollinated by a selected male pollinator line, planted in every sixth or eighth row. As many as six roguings may be necessary to keep self- pollination to a minimum.
The hybrid seed can also be protected by the use of 90 to 100 percent pistil late lines, this estimates Roguing but hybrid seed so produced would not be entirely uniform.