Seeds and Sowing Point Wise Notes for Competitive exam part-1

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Seed

Seeds are used for multiplication purpose.

• Grains are used for consumption purpose.

• Sugarcane is planted with stem cuttings known as setts.

• Forage grasses like napier grass, guinea grass, para grass etc. are mainly propagated by stem cuttings or rooted slips.

Rooted slips are basal two or three internodes of the stem with a few roots.

Tubers are used as seed material in potato.

Grafting, budding and layering methods are used for the propagation of horticultural crops.

Good quality seed is of prime importance in agriculture.

• Cultivar is a contraction for cultivated variety.

• Cultivar is synonymous with variety.

• A variety is a subdivision of a species with some special characteristics.

• A cultivar is a unique population of plants, artificially maintained by human efforts.

• A synthetic cultivar is composed of plants produced by combining a number of genetically distinct but phenotypically similar lines which have been allowed to cross-pollinate at random.

• A hybrid line is the F1 generation of the two inbred lines.

Breeders seed originates with the sponsoring plant breeder or institution and provides initial source of all other classes of certified seeds.

Foundation seed is the progeny of breeders seed and is so handled to maintain the highest standard of genetic identity and purity.

• Foundation seed is produced under direct supervision of technical persons.

• Registered seed is the progeny of foundation seed or sometimes from breeders seed.

Registered seed is produced under specified standards approved by the certifying agency.

• Certified seed is the progeny of registered seed, sometimes of breeders or foundation seed which is produced in largest volume and distributed to growers.

• Type of Pollination

Self pollinated : Rice, wheat, barley, oats, groundnut, soybean, cowpea

Self pollinated with certain amount of cross pollination : Cotton (Upland type), Cotton (Egyptian type), Tomato 

Cross pollination by insects :Millets

Cross pollination by wind : Grasses

• Separation of different cultivars is needed in production of self pollinated plants to prevent mechanical mixing of seed during harvest. Minimum distance usually specified between plots is 3m.

Viability and vigour are important characters of seed quality.

Viability can be expressed by the germination percentage which indicates the number of seedlings produced by a given number of seeds.

• Low germination percentage, low germination rate and low vigour are often associated.

Vigour is indicated by the higher germination percentage, high germination rate and quicker seedling growth.

• Germination percentage is the number of seeds germinated to number of seeds planted and is expressed as percentage.

• Germination rate is expressed in two ways

1. Number of days required to produce a given germination percentage

2. Average number of days required for radical or plumule to emerge

• Moisture content at harvest is in the range of 25-35% for most of the seeds.

• After harvest seeds are sun dried for 2-3 days.

• When the outside temperature is more than 40oC, seeds should be dried under shade to maintain viability.

• Seed vigour tests may be categorized as quick tests, standard germination and stress type germination tests.

• Quick tests can be performed within 24 hours.

• Standard germination and stress type germination tests require 7 to 12 days.

• Calcium assay is included as a quick method to assess quality since it is a critical nutrient for seed groundnuts.

Tetrazolium and electrical conductivity tests both evaluate aspects of tissue integrity.

• Standard germination test is indicative of seed vigour with > 85% germination considered strong vigour.

• Accelerated aging and cold germination tests are stress type tests that are good indicators of seed strength.

• Onion is propagated by bulbs.

• Gladiolus is propagated by corms.

• Potato is propagated by tubers.

• Sweet potato and Dahlia are propagated by tuberous roots.

Rhizome is a specialized stem.

• Sugarcane, banana and many grasses have rhizome structures.

• Soil moisture in the range of 50% available moisture to field capacity is sufficient to ensure good germination of seeds though 80% of soil moisture at field capacity gives best germination.

• Soil temperature of 10 oC for temperate crops and 20 oC for tropical crops is the minimum requirement for germination.

• Establishment of crop is difficult under zero tillage and in problematic soils like saline and alkaline soils.

• When soil sodicity is high transplanting gives better establishment of rice than drilling.

• Germination in wheat in saline soils with EC 13 dS/m can be improved by soaking seeds for 24 hours in gibberellic acid solution (200 mg/l).

• Soaking of seeds in thiamin solution (200 mg/l) reduces adverse effects of salinity on germination and seedling growth.

• In SRI method 10 days age rice seedlings are transplanted.

• In other methods 65 days aged rice seedlings are also transplanted.

• In general, younger the seedlings, better is the establishment and yield of crop.

• Sowing very early in the season may not be advantageous.

• Sowing rainfed groundnut in June may result in failure of the crop if there is prolonged dry spell from the second week of June to second week of July.

• However, in certain situations early sowing increases the yield.

• Advancing sowing of rabi sorghum from November to September-October, increases the yields considerably as more moisture would be available for early sown crop.

• The optimum time of sowing for tall varieties of wheat was October, for dwarf varieties it was second or third week of November.

• Rainfed sorghum yields are reduced due to delay in sowing beyond June.

• In rainfed groundnut, sowing beyond July reduced the yields of all varieties at Tirupati.

• Delayed sowing of redgram and soybean reduced yields due to early induction of flowering, unfavorable temperature and rainfall.

• Most of the tropical plants are short-day plants.

Day length starts falling from July onwards, but the reduction in day length is steep from October onwards.

Flowering is induced in short-day crops earlier due to absolute short days or relative reduction in day length.

• If sowing are delayed, there is very little time for vegetative growth leading to reduction in yield.

• Late sown crops are exposed to increased population of pests and diseases.

• Late sown sorghum is subjected to severe attack of shoot borer.

• Optimum time of sowing for most of tropical crops is immediately after the onset of monsoon i.e., June or July.

• Optimum time of sowing for temperate crops like wheat and barley is from last week of October to first fortnight of January.

• Optimum time of sowing for most of summer crops is first fortnight of January.

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