Sowing Of Seed – Seed Treatment
Seed treatment: It is a process of application of chemicals or protectants (with fungicidal, insecticidal, bactericidal or nematocidal properties) to seeds that prevent the carriage of insect or pathogens in or on the seeds.
Objects of seed treatment: Some seeds need treatment with some specific objectives before sowing.
1.To control disease: There are some seed borne or soil borne diseases, seeds are treated with fungicides or organo mercurial compounds like Thirum, captain, carbendazim, agrosan, cereson, etc. E.g. to control paddy blast, seed is to be treated with agrosan @ 3 g per kg (3g/kg) of seed).
2.To have convenience in sowing: Difficulties are encountered in sowing certain crops due to special characteristics of the seed like fuzz of cotton seeds, coriander seeds, small seeds of chilli, ragi, bajara, etc. E.g.: coriander seed is to be splitted by rubbing it against hard surface. Seed of chilli, Sesamum, bajara are mixed with fine sand or soil.
3. To have quick germination: Germination of certain leguminous crops is delayed due to thick seed coat which restricts water absorption. Such seed coats are broken to some extent by mixing them with coarse gritty sand & trampling or pounding it lightly in a morter with a wooden pestle for breaking the thick seed coat. Sometimes seeds are soaked in water for a specified time. E.g.: cotton seed or paddy seed is soaked in water before actual sowing. Seed of Lucerne and Indigo is pounded with pestle
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4. To increase nitrogen fixation in legumes: Legume seeds are inoculated with a particular Rhizobium culture. This is mixed with jaggery solution & applied to seed and dried in shade. It increases nodulation & thereby N fixation.
5. To protect the seed against insect pests: There are some insect pests like ants, white ants, in the soil which attack on seed and eat. Sometimes, seed may be picked up by birds after sowing. To avoid this, seed is treated with repellents like campor, kerosene or soil drenching with insecticides like BHC, heptachlor, etc. E.g.: the carbofuran treatment in Jowar.
6. To induce earliness (Vernalization treatment): This is an important for breeding programme by vernalization treatment. As a result of this, life span is reduced. In this, seed is soaked in water & incipient germination is induced in the form of awakening of the dormant embryo & commencing the changes favoring germination in the endosperm. Such seeds are kept in cold storage for a specified time in which germination power remains intact but the process of germination is temporarily halted. Thus, the plant spends part of its vegetative period or phrase in the form of sprouted seed and the seed so treated as a dormant plant. The period from sowing to flowering is thus greatly reduced & with such adjustment, a variety which is normally a long duration one, can be made to flower early.
7. To induce variation: Seed is treated to induce variation in its morphological & general structure by ‘X’ ray treatment. It changes the genetical make up & helps in selection of desired types.E.g. Sonora, a wheat variety, is the result of Sonora-64 treated with gamma rays.
8. To break dormancy: Some crops are having seed dormancy in fresh harvested produce. Dormancy is the state of rest period of a seed in which it does not germinate even if all the favorable conditions are available for germination. Due to dormancy of seed we cannot use the fresh harvested produce for sowing. It is desirable if the crop get rains at maturity. E.g.: groundnut varieties. This dormancy is broken by treating seed with chemicals. E.g. Thiourea 1% treatment to potato tubers.
9. Seed treatment for special purpose: In vegetatively propagated crops, planting material is treated with growth promoting hormones like colchicines, Gibberellic acid (GA), Indole acetic acid (IAA), Seradix, sometime cattle urine. These promotes sprouting & growth of plant. E.g.: onion bulbs or potato tubers are treated with Malic Hydrazine (MH) for avoiding sprouting and growth of sprouts and thereby reducing losses due to sprouting.
Seed treatment in important crops:
1) Sorghum: Thirum or 300 mesh sulphur: Seed is coated in seed dressing drum or earthen pot @ 3.4 g/kg seed against smut disease.
2) Bajara: Brine solution treatment is given @ 20% against eat got and to discard light & diseased seed.
3) Paddy: Seed is treated with brine solution @ 3% against blast of paddy and to discard unfilled seed.
4) Cotton: a) Cow dung slurry treatment: Seed is rubbed with cow dung slurry in 1:1 proportion of dung and soil for convenience in sowing or Seed is delinted by treating the seed with conc. H2SO4 for 2 min. for convenience in sowing. b) Seed is treated with organo mercurial compound like ceresin, agrosan @ 3 g or Thirum @ 5g against seed borne disease like anthracnose.
5) Coriander & Garlic: Seed is rubbed to split the seed for even sowing.
6) Small seeded crops like Sesamum, bajara, tobacco, etc: Seed is mixed with fine sand or soil for even sowing of seed in the field.
7) Potato: a) Seed is dipped in 1% Thiourea solution for breaking the seed dormancy.
b) Seed is dipped in streptomycin solution @ 200 g in 100 lit. Water for 1 hour against Ring rots disease.
8) Legume crops like Mung, Udid, Soybean, Etc.
a) Seed is treated with Thirum @ 3 g/kg seed against seed borne disease.
b) Seed is treated with Rhizobium culture @ 250g/10kg seed for ‘N’ fixation & better nodulation.
9) Sugarcane: a) Hot water treat (500C) or hot air treat. (540C) is given to sets for 2 hrs. Against grassy shoot & other diseases.
b) Sets are treated with OMC 6% @ 500g in 100 lit. Water by dipping for 5 min. against smut & increase germination.
Or Bavistin @ 200g in 100 lit. For 5 min.
10) Wheat & Oilseed crops: Seed is coated with Thirum or Bavistin @ 5 g/kg seed against seed borne diseases.