Why Are Seeds Treated Before Sowing
Treatment of seeds involves application of chemicals to the seeds, with an aim to provide them with insecticidal, fungicidal, nemotocidal and bactericidal properties. As much as it would be incredible to simply pop a seed in the ground and come back a week later to see a fully grown plant, nature sometimes needs a little hand. Growers don't only treat seeds with chemicals. There are other mechanical, chemical and electrical treatment methods designed to make sowing, germinating and yielding easier or faster. In terms of farming, the treatment of seeds is very important. oneHOWTO answers 'why are seeds treated before sowing?' and see how it helps the plant develop.
Methods of seed treatment
As we have mentioned, there are several ways in which seeds are treated. Each method has its own purpose, but some are more effective than others. Knowing which is the most effective is not easy to say and it often depends on the type of seed. One of the main reasons for treating seeds is that some species of seed, such as hairy bigleaf lupine, are somewhat rare or hard to find for sowing. Seed treatment is devised to ensure your seeds have the best chance of success.
The word for certain types of seed treatment is scarification. Scarification is when the outer shell of the seed is altered to help the seed on their way to germination. Scarification may be a little bit of a misnomer as it doesn't necessarily cut open the seed as would happen when something is scarred. Instead it is treated, usually mechanically, thermally or chemically. However, any type of seed treatment used to encourage growth is known as scarification. Here are the main type of seed treatment:
Seeds in small numbers can be scarified by cutting each seed with a knife or making a scratch with sandpaper. For seeds in large quantities, they can be pounded with sand, or rubbed against an abrasive surface. These methods improve the germination of the seeds and help them grow faster. They may need further treatment. When seeds are mechanically treated for tests, they chaff of the seed is removed and they are washed before further tests can occur.
There is also, unsurprisingly, machines which are used for these different parts of the mechanical seed treatment process. These include air-screen cleaners which separates the seeds by size, shape and density. As technology advances, these machines become more practical, but there are still some old machines which take up half the room. Cylinder separators remove the detritus away from the seeds through centripetal force.
Some seeds may be covered with hot water and then allowed to soak for a couple of days. The temperature is carefully regulated, between 115 ºF and 125 ºF. The length of treatment can vary. This treatment method is effective in improving their germination rate and enhancing their imbibitions. Unfortunately, even when a small amount of seed is infected, they can infect the rest.
Hot water seed treatment is one of the cheaper methods of treatment and is a good consideration for home growers. It is thought to be good for plant seeds such as tomato, pepper or brassicas (cabbage, broccoli, turnip, kale, etc.).
Dry heat treatment
In this method, dry heat of 60 to 80 ºC (140 to 176 ºF) is applied to the seeds for as long as 24 hours, with an aim to increase their imbibitions and improve their germination. However, extreme caution is required, as too much temperature or too long a period may be damaging to the seeds.
Dry heat treatment is often used when other treatment methods such as hot water treatment have proved ineffective. This is because some of the virulent strains of infestation might survive one process, but not the other.
Some seeds may be immersed for 12 hours in absolute ethyl alcohol. Some may be soaked in sulfuric acid for 15 to 30 minutes, with an aim to soften the seed coat and increase germination.
This treatment of seeds is usually for fungicides or insecticides. This is because, even if the seed is relatively clean as it is, there are pathogens which can be found in the soil. Protecting it with a chemical can also prevent pests from munching on them. This is one of the more controversial seed treatments as the chemicals used for chemical seed treatment have been banned in some countries and not others.
Sometimes, seeds may be exposed to radio frequency di-electric heating with electro-magnetic fields for increasing germination rates and breaking dormancy.
Reasons for treating seeds
Though there may be several contraindications to the process of treating seeds, there are also some advantages to doing so:
There are certain soil borne and seed borne diseases that seed treatment can control. Seeds can be treated with organo mercurial compounds or fungicides like agrosan, captain and cereson for keeping paddy blast under control. For instance, 3 gm of agrosan is enough to treat 1 kg of seed.
A disease crop can ruing the yield for the year, meaning a los of investment. However, they can also damage the soil and cause even more damage down the line. Seed treatment is a preventative measure to give the grower the best chance of a good yield.
Makes sowing convenient
Certain seeds have some characteristics due to which their sowing becomes somewhat difficult, especially seeds like fuzz of coriander seeds and cotton seeds, and tiny seeds of ragi, bajra and chili. For instance, coriander seeds need to be split by rubbing against a hard surface. Seeds of sesame, chili and bajra need to be mixed with soil or fine sand to make sowing easier.
Facilitates quick germination
Some seeds have a very thick coat due to which germination of seeds is unnecessarily prolonged. During the treatment process, such seeds are mixed with gritty coarse sand and pound or trampled in a mortar to break the thick coat. Some seeds like cotton seeds and paddy seeds are soaked under water before sowing, while indigo and Lucerne seeds are pounded with a pestle. With such treatment, seeds are germinated quicker, and yield crop faster.
With the demand on food supply, a faster growing crop can really put someone ahead of competition. It can also be used in countries where climates are harsh and any way to encourage growth might be helpful. This is particularly the case in areas where droughts and blights can ruin a crop.
Protects seeds against insects and pests
Some pests and insects like ants may be present in the soil which may attack the seeds and eat them. Sometimes, birds may also pick the seeds after sowing. This can be effectively avoided by treating the seeds with repellents such as kerosene, camphor, and insecticides like heptachlor and BHC.
The increased yield and better chance of germination means that even if you spend money treating the seeds, you will likely have a better ROI. In the long run, treating the seeds will save you money. It also creates an industry which can be good for employment.
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