1. SEEDS, SIGNIFICANCE OF SEED TREATMENT AND PLANTING METHODS
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2. ABSTRACT
Good quality seeds are the most important inputs in agriculture.
Seeds are treated before sowing for different purposes.
Seeds are treated with cow dung or red earth by the ancestors.
Cottons seeds are treated with cow dung, red earth, H2SO4 which makes easy during sowing.
Fungicides or insecticides are used to control the pest and diseases of crops and treating with small quantity may reduce the ill effects besides reducing the chemicals and spraying cost.
Seeds are treated with hot water or acid or hormones etc. to break the dormancy.
Planting methods vary with individual crops. Broadcasting is the most predominant method of sowing besides drilling, planting and transplanting.
Seeds are sown either wet or dry condition according to the type of crops.
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3. LEARNING OBJECTIVES
To study the importance of seed treatment and methods of treating seed and seedlings
To gain knowledge on methods of planting and their feasibility in crop production.
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4. INTRODUCTION
Plant propagation is made in two ways, Sexual (by seeds) and asexual (by vegetative means).
Biologically, seed is a ripe, fertilized ovule and a unit of reproduction of flowering plants.
Good quality seeds are pre-requisite for better crop.
Seed viability and vigour are the two most important characters determine the quality of seeds.
Seed treatment is an age-old practice followed all over the globe.
Ancestors treat the seeds with mud, red soil; leaf extracts etc. assuming that the crop performs well.
Nowadays, seed treatment is practiced in all the crops for different purposes.
They are convenience in sowing, control of pests and diseases, enhancing germination and for inoculating bio-fertilizer culture.
Crops are established using different methods in field condition.
There are about four methods of establishment of crops, viz., broadcasting, drilling, planting and transplanting.
These planting methods can be carried out either the seeds are wet or dry condition.
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5. I. SEEDS, SIGNIFICANCE OF SEED TREATMENT
Seeds are treated with chemicals, bio-agents, acids etc. for different purposes. Main purposes are as follows
1. Convenience in sowing
Difficulties are encountered in sowing of certain crops due to the special characteristics of the seed.
On existence of fuzz and lint on cotton seeds, it is difficult to sow either through drills or broadcast, as the seeds cling together.
In order to get over this difficulty, the seeds are treated so that the fluff becomes pasted on the seed, after which the seeds can’t adhere to each other, but, roll apart just like grains.
For this purpose, the seeds are rubbed together with a paste made of wet dung or earth or both and then dried.
The fluffiness can also be removed by treating the seeds with concentrated Sulphuric acid for two minutes, followed by repeated washing and drying thoroughly and sown.
(Cont)..
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6. The seeds can then be sown evenly.
The coriander seeds are prepared by splitting the two locules of which the fruit is made up, so that the seeds fall apart.
This practice is not only economic one, but also, ensures evenness of sowing.
In the case of garlic, the compound bulbs are to be split into individual cloves then sown reduces cost of seed material and better germination.
Earth or sand is mixed with seeds of finger millet, sesame, tobacco etc. at different ratios ranged from 5:1 to 20:1 (sand: seed) before sowing as the seeds are small.
This way we can obtain a larger quantity which can be handled more conveniently.
The seeds can then be sown evenly.
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7. 2. Pests and diseases control
Seeds of several crops contain tiny cracks developed during harvesting and threshing.
Disease causing organisms attack these seeds.
There are some seed borne or soil borne diseases.
To reduce attack from these diseases, the seeds are treated with fungicides like thiram, captan, mancozeb, carbendazim, captfol etc. at 2g to 4g per kg of seeds.
The seed treatment also ensures preventive measure of diseases for future.
Two gram of carbendazim or pyroquilon or tricyclozole is used for seed treatment in rice.
Chlorpyriphos or monochrotophos or 4 ml per kg of seeds are used as precautionary measure for insect pests in most of crops.
10 per kg of seeds are used to manage shoot fly incidences in millets.
Trichoderma 4g per kg or Pseudomonas 10g per kg of seeds are used to prevent disease incidences in field crops.
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8. 3. Seed hardening
Seeds are treated with certain chemicals or materials which results in drought tolerant in dryland areas and the process is called as seed hardening.
Seed hardening improves seed viability and water absorption, improves root development and increases relative water content of leaves.
Commonly used seed hardening materials in various
Crops are, KH2PO4 in sorghum and pearl millet, KCl in maize, cycocel or succinic acid in cotton, Cacl2 in groundnut and ash in pulses.
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9. 4. Breaking dormancy Scarification
The process of breaking, scratching, mechanically altering or softening the seed coats to make permeable to water and gases in known as scarification.
Mechanical scarification is generally done by pounding seeds in a large sized mortar with pestle.
Scarified seeds make injury to the seeds and induces susceptible to pathogenic organisms; hence, scarification is done at the time of sowing or a few days before sowing.
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10. Hot water treatment
Seeds are dropped in water of 75 to 100C. The ratio of water: seeds must be 4:1 or 5:1.
The seeds are soaked in the gradually cooling water for 12 to 24 hours.
After, the un-swollen seeds are separated from the swollen ones and treated again.
The seeds have to be sown within a few days after hot water treatment.
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11. Acid treatment
Dry seeds are placed in glass or earthenware or wood containers and concentrated sulphuric acid is added in twice the volume of seeds.
Continuous periodical mixing ensures uniform treatment of seed.
The duration of the seed treatment varies from 10 minutes to six hours or more depending on the thickness or hardness of seed coat.
The end point of seed treatment is known by examining the treated seeds.
The treatment is completed when the thickness of the seed coat is reduced.
At the end of the treatment period, the acid is poured-off and seeds are washed to remove the acid.
Further, seeds are mixed with large volume of water with a small amount of sodium bicarbonate (baking soda) to neutralize any adhering acid.
The extra acid can also be removed by washing the seeds in running water for minutes. The acid treated seeds can be sown immediately or dried and stored for subsequent use.
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12. LEACHING
The purpose of leaching is to remove germination inhibitors by soaking seeds in running water or by placing them in frequent changes of water. The length of leaching time is 12 to 24 hours.
Hormonal treatment
Treating the seeds with Gibberellic acid (GA3) at 500 ppm concentration for 1 hours period, breaks the dormancy of seeds caused by physiological reasons. Similarly, Cytokinins and Ethylene are also used to break dormancy.
Many crop seeds are soaked frequently in water for 24 to 48 hours to induce incipient germination as in rice.
American cotton is sown after soaking the seeds in water for 12 to 24 hours.
As germination involves hydration or imbibitions as the first step, soaking seeds helps in carrying out the initial steps of germination.
The most common soaking material is water and cow-dung extract is also found to improve germination.
Seed treatment, for purpose of hardening, consists of soaking seed for 12 hours (in most cases) and drying to original moisture.
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13. Extension of viability
Hydration midway during storage of seeds, followed by immediate drying back helps in extending its viability.
However, soaking and drying treatment doesn’t extend storage life of fresh seed (i.e. immediately harvested seeds).
5. Inoculation of bio-fertilizers
The symbiotic bacteria (genus) Rhizobium is capable of fixing atmospheric nitrogen and hence, treating the legume seeds with Rhizobium culture improves crop yields and reduces nitrogen requirement.
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14. Rhizobium species suitable for different legume crops
Suitable crops
R. leguminosorum
Peas, Lathyrus, Vicia, Lentil,
R. tripoli
Berseem
R. phaseoli
Kidney bean (Phaseolus)
R. lupini
Lupinus, Ornithopus
R. japonicum
Soybean
R. meliloti
Melilotus,
Cowpea miscellaneous
Cowpea, clusterbean, greengram, blackgram, redgram, groundnut, moth bean, Dhaincha, sunnhemp, Glyricidia, Acacia, Prosopis, Dalbergia, Albizzia, Indigofera, Tephrosia, Atylosia, Stylo
Separate group
gram
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15. The inoculums requirement ranged from 600g to 2.0 kg per ha of seeds.
The Rhizobium culture is mixed with jaggary solution and applied to the seed and shade dried.
The inoculums requirement ranged from 600g to 2.0 kg per ha of seeds.
Free living micro-organisms such as blue green algae (BGA), Azolla, Azotobacter and Azospirillum can fix the atmospheric nitrogen.
Of them, BGA, Azolla are mainly used under lowland conditions, where small quantity of inoculum is obtained from laboratories and multiplied in the field conditions.
Azotobacter chroccum is widely used in rice, cotton and sugarcane crops, and 3-5 kg per ha is required.
It can fix kg of nitrogen per ha.
Azospirillum is widely used in cereal crops.
Phosphobacteria is inoculated with seed as seed treatment to enhance the P availability to crops.
Now, Azophos is used to replace both Azospirillum and Phosphobacteria.
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16. 6. Controlling stored pests
Seeds quality is reduced by storage pests.
Fumigants are used for managing the stored pests effectively.
Some of the fumigants are, acrylonitrile ( g/m2), Carbon disulphide (24-32 g/m2), carbon tetra chloride ( g/m2), ethyl bromide ( g/m2), methyl bromide (32 g/m2) and phosphine (3- 6 g/t of seeds).
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17. Planting (crop establishment) methods
The various types of planting methods are as follows
Broad Casting
Drilling
Planting
Transplating
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18. BroadCasting
This is the most primitive, ancient and widely followed methods of sowing crops.
In broadcasting method, seeds are spread uniformly over well prepared land and are covered by light ploughing or planking.
Broadcasting has several disadvantages. The seeds fall at different depths resulting in uneven crop stand.
Seeds fallen at shallow depth emerge early if moisture is available and otherwise, later.
Seeds fallen deep in the soil may not germinate and even if they germinate, may emerge from the soil after considerable time.
The seeds fallen on the surface or more than 10 cm deep may not germinate at all.
At any given time, the plants stand may be at different height, size and age.
Thus, there is lot of wastage of seeds and necessarily high seed rate is to be adopted.
(Cont)..
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19. Rice is also sown by broadcasting on puddled soil.
Since seeds fall randomly in broadcasting method, there is no possibility of controlling weeds by inter-cultivation with bullock drawn implements.
Hand-weeding adopted in a broadcasting crop is expensive, time consuming and laborious.
Because of randomness of seed dispersal, the spacing available for individual plants varies considerably.
It results in excess competition at certain areas and no competition at all in some other areas of the field.
However, this method is still used for sowing fodder crops or crops where seeds are cheap or crops which can easily establish and suppress weeds.
Rice is also sown by broadcasting on puddled soil.
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20. Drilling
To overcome the problems of broadcasting, drilling the seeds in lines is practiced widely and specifically under dryland areas.
Crops can be sown in lines with seed drills.
Weeds can be controlled economically by inter- cultivation in line sown crops.
In addition, drilling or line sowing facilitates uniform depth of sowing resulting in uniform germination and crop stand.
Seed rate can be considerably reduced by drilling compared to broadcasting.
Tractor operated seed cum ferti drill
Drilling behind plough
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21. planting
When individual seed material is placed in the soil by manual labour, it is called planting.
Generally crops with bigger sized seeds and those needing wider spacing are sown by this method.
Planting is done for crops like cotton, maize, potato, sugarcane etc.
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22. transplanting
Due to shrinkage of cultivable land area, intensive cultivation (more than one crop is to be grown in a year on the same piece of land) is needed.
Under this situation, the time occupied by each crop has to be reduced.
The seedling growth in the early stages is very slow and need extra care for establishing in the field because of their tenderness.
Small seeded crops like tobacco, chilli, tomato etc. are to be sown shallow, can’t separate individual seeds and frequently irrigated for proper germination.
Taking care of the germinating seed or seedlings which are spread over large area is a problem with regard to water, weed and pest management etc.
(Cont)..
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23. Therefore, seeds are sown in a small area called nursery and all the care is taken to raise the seedlings.
When seedlings grow to certain stage, they are pulled out from the nurseries and transplanted in the main field.
The advantages of transplanting are saving in irrigation water, good stand establishment and increase in intensity of cropping.
For achieving good results from transplanting, the seedlings are transplanted at optimum age and at proper depth.
The thumb rule for the optimum age of seedlings is one week for every month of total duration of the crop.
However, young age of seedlings is always produces better yields in crops.
Ex. Rice seedlings are transplanted at 8-15 days under System of Rice intensification (SRI) and producing higher yield.
The depth of planting should be as shallow as possible for getting more number of tillers in tillering crops.
Transplanting of rice seedlings more than 2 cm deep results in poor tillering.
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24. Sowing types of seeds
There are two method of sowing types of seeds.They are as follows
Dry sowing
Wet sowing
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25. 1.Dry sowing
Dry sowing is followed widely in black soils where sowing operations are difficult to carry out once rains commence.
Field is prepared with summer rains and seeds are sown in dry soil around 7 to 10 days before the anticipated receipts of sowing rains.
The seeds germinate after the receipts of the rains.
By this method, the first drop of rainfall is efficiently utilized.
Pre-monsoon sowing weeks are identified for different areas and based on that dry sowing is followed.
Ex. Pre-monsoon weeks identified for Coimbatore and Erode districts of Tamil Nadu, India are weeks falls September
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26. 2. Wet sowing Wet sowing is the most common method of sowing crops.
The minimum amount of rainfall necessary for taking up sowing is 20-25mm.
Two or three days after soaking rain (depends on soil type), sowing can be taken and continued for two or three days.
Certain amount of moisture is wasted during the period between receipts of rainfall and sowing.
For better and uniform germination, about 10 mm of rainfall is needed after sowing.
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27. SUMMARY Quality seed is the most important input for crop production.
Seed treatment is one of the easy way to manage the pest incidences in crop production besides, serves purposes such as easiness in sowing, breaking dormancy, hardening the seeds, enhancing nitrogen fixation and solubilizing phosphorus.
Broadcasting, drilling, planting and transplanting are important crop establishment techniques followed in crop production.
Seeds are sown either dry (without soil moisture, i.e. before receipt of rainfall) or wet (after receipt of rainfall) and latter in the most important one.
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28. ASSESSMENT
Concentrated HCl is used to de-lint the cotton seeds (True/False)
Sesame seeds are mixed with sand to improve germination (True/False)
Carbendazim, a fungicide used as seed treatment material to prevent diseases (True/False)
Cacl2 is used to harden the groundnut seeds in dryland areas (True/False)
Gibberellic acid is used to break the dormancy in many crops (True/False)
Broadcasting is the most primitive and still widely practiced method of sowing in dryland areas (True/False)
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29. REFERENCES
Agarwal, R.L Seed Technology. Oxford and IBH Publishing Co. Pvt. Ltd., New Delhi.
Reddy, S.R Principles of Crop Production. Kalyani Publisher, Ludhiana.
Scott, J.M Seed coatings and treatments and their effects on plant establishment. Advances in Agronomy,42:
Subba Rao, N.S., A.W. Sen and K.R. Dadwal Rhizobium research in India. In: Review of Soil Research in India, Part I. Indian Society of Soil Science, I.A.R.I., New Delhi.
Yellamanda Reddy, T. and Sankara Reddi, G.H Principles of Agronomy. Kalyani Publisher, Ludhiana.
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