Methods of Seed Treatment Before Sowing for Maximum Germination Potential

Maintaining the quality of seed is dependent on many environmental factors, some of which are moisture, temperature, humidity, and storage conditions.

Even though these factors are properly accounted for, seed quality may still be reduced by certain seed-borne diseases or destroyed by insects and other pests.

Research has shown that treating seeds with one or more pesticides is the most economical and efficient way to protect seeds from these pests and improve seed quality.

Since pesticides are poisonous, extra care and safety precautions must be taken when applying them and in handling seeds after it has been treated.

The term “treated” means “to give an application of a pesticide or subject seed to a process designed to reduce, control or repel disease organisms, insects, or other pests which attack the seed or seedlings.”

Treatment methods of seed before sowing

It is the treatments given to the seeds before sowing to improve the germination and vigour potential and as well as to maintain the health of the seed.

Pre-sowing seed treatments include the following;

Chemical treatments to improve germination and vigour potential.
Insecticidal and fungicidal treatment.
Special treatments

Chemical treatments to improve germination and vigour potential

Soaking/treating the seeds with nutrients vitamins micronutrients etc.

Seeds can be soaked in 1 % KCl solution for 12 hours to improve the germination and vigour potential.

Sorghum: Seeds could be soaked in NaCl2 (1 %) or KH2PO4 (1%) for 12 hours to improve the germination and vigour potential.

Seeds can be soaked in ZnSO4, MgSO4 and MnSO4 100 ppm solution for 4 hours to improve the germination and vigour potential.

Insecticidal and Fungicidal treatments

Seed health is an important attribute of quality seed.

Though a seed lot meets high standards of germination, vigour and purity if it is contaminated with seed-borne pathogens and insect pests, may be useless to farmers because it may result in severe yield loss or even crop loss in an entire area.

Benefits of the insecticidal and fungicidal treatments:

Prevents the spread of plant diseases
It protects the seed from seed rot and seedling blights.
It improves the seed germination
It protects from storage insects.
It controls the soil insects.

Seeds may be affected by viruses, bacteria, fungi, nematodes and insects.

Seed pests and diseases of which the seed is a victim (e.g., grain weevils, Trichoderma spp., and storage pathogens such as Aspergillus flavus) should be distinguished from seed-borne diseases of which the seed is the vehicle of pest and pathogen dissemination (e.g., bunt of cereals, Tilletia spp.).

Seed Treatment with Fungicides

Fungicides are applied to seeds before planting to provide effective protection against many seed and soil-borne plant pathogens.

Chemical (fungicide) treatment guards against the various seed rots and seedling blights that occur during storage or after planting. It is not usually a “cure-all” and will not provide disease protection throughout the growing season after the plants become self-sufficient.

An exception to this would be the control of loose smut by seed disinfection.

Fungicidal seed treatment may be divided into three categories, depending on the nature and purpose of the treatment.

These categories are:

seed disinfection,

Disinfection is the elimination of a pathogen which has penetrated the living cells of the seed, infected it and become established example, loose smut of barley and wheat.

seed disinfestation,

Disinfestation is the control of spores and other forms of pathogenic organisms found on the surface of the seed.

and seed protection.

Seed protection is a chemical treatment to protect the seed and young seedlings from pathogenic organisms in the soil.

A given fungicide may serve in one or more of these categories

Seed treatment materials are usually applied to seed in one of four forms:

dust;
slurry (a mixture of wettable powder in water);
liquids;
and planter-box formulations.

Based on composition, seed treatment fungicides may be organic or inorganic, metallic or non-metallic, and, until recently, mercurial or non-mercurial.

Before the cancellation of the ‘volatile mercurial, fungicides for treating seed were generally classified as volatile and non-volatile.

With the elimination of the volatile mercurial, most fungicides now approved for use on seed are classified as non-volatile.

When using this type of material, complete coverage of the seed is necessary to obtain effective control.

Some of the systems, a fairly new class of pesticides, may now be used as seed treatment materials.

The desirability of having materials that would move inside the seed or plant and control the pest has long been recognized.

Such materials are called “systemic.”

When used according to the manufacturer’s recommendation (see label), a systemic move through the host plant controls or retards the growth of certain fungi and insects without affecting the host’s metabolic system.

Seed Treatment Insecticides

Insecticides are often applied to seeds to control or reduce insect damage to seed during storage and, to a lesser degree, to prevent damage from such insects as wireworms and seed corn maggots in the soil.

Since some pesticides are selective in their control of pests, many times two or more compounds are combined in the treater tank, or an extra tank may be used, to give the spectrum of control needed.

The manufacturers of pesticides are now making combinations available to seed processors, but should a processor blend two or more pesticides, the compatibility of the materials must be determined, since some combinations of materials may seriously reduce seed germination.

Also, when applying two or more pesticides, even at different times, the sequence of application may be very important.

Whether a single pesticide or a combination is to be applied to the seed, read the label and follow the manufacturer’s directions carefully.

Formulation of fungicides/insecticides

Fungicides/insecticides are available in the form of dust, wettable powders and liquids.

Dusts:

It is usually applied @ 200-250 gms/quintal of seed. The main disadvantage is dusty conditions will prevail during the seed treatment and after handling.

Slurry:

This type of fungicide is applied to the seed along with soap-like water suspension which can be mixed with the seed by using a special slurry treater.

Liquids:

The use of a liquid solution is known as the “quick wet ‘ method. Here a volatile fungicide is applied to the seed and it is thoroughly mixed with them.

e.g. Chemicals like panogen, mercurian, etc. can be applied by this method.

Safety

There is a general tendency to use chemicals that are safe for users and the environment. Very toxic substances, such as organic mercurian (Ceresan and others) and very persistent fungicides, such as Hexachlorobenzene ((HCB), are being replaced by new chemicals,

In the past, these chemicals have caused severe cases of poisoning, some resulting in death.

Most if not, all occurred because the treated seed was used for human consumption or livestock feeding instead of for planting.

Even with the new, less toxic chemicals, the following safety precautions must be taken.

Treated seeds must be clearly labelled and under no circumstances be used for feed or food.
Seed treatment should be carried out in a well-aerated area. Contact with chemicals through breathing of dust and skin contact must be avoided. Protective clothing should be worn.
As with all pesticides, empty containers should be properly disposed of and never reused in a household or on the farm.

Special treatments

Seed hardening treatment

Seeds can be hardened for 2 purposes;

Drought tolerance
Cold tolerance

The treatments are imposed on the seeds mainly to tolerate initial drought and cold.

Cold tolerance treatment is given to germinated seeds, such treatments are given only to temperate crop and tree seeds.

The most important factors to be considered while seed hardening are

Seed: solution ratio (1:1)
The duration of soaking
Method of drying.

The effectiveness of the treatment depends upon the conduct of the seed-hardening process.

The solution amount never be higher than the amount of the seeds.

All solution added should be imbibed by the seeds.

There should not be any leftover solution as it causes a leaching effect.

Once the seeds imbibe water, the germination process takes place.

At the end of the soaking period, the seeds should be dried back to their original moisture content.

These seeds when sown the germination will be completed earlier whereas in non-hardened seeds the process of germination takes a longer period.

Chemicals used: CaCl₂, KCl, KH₂PO₄,

Seed fortification

The main aim is to supply nutrients to seeds. The main objective is to achieve the high vigour to overcome unfavourable soil reactions. eg.) seed fortification with MnSO₄ @ 0.5 to 1 %. will improve the oxidation-reduction potential of seeds, which ultimately leads to higher germination.

Moist sand conditioning

It is a need-based treatment the concentration can be increased up to 2-4 %. The amount of solution should be a 1:1 ratio or a slightly excess amount of water can be used. Proteinaceous seeds should not be soaked in water (e.g.) soybean, etc. For these seeds, mix the seeds with moist sand @ 5 to 10% MC. It should be kept for a specified period. The method is known as moist sand hydration.

Seed pelleting

Here the nutrients are coated on the seeds. This technique is very much adopted in forest tree seeds.

Importance

Normally in small seeds this technique is adopted.
By pelleting we can increase the size of seeds and we can make it a free-flowing one.
Through this we can able to reduce the seed rate.
It is also important for aerial sowing (gum arabica) in tree seeds.

Seed infusion

Infusion of nutrients and growth-promoting substances with organic solvents like acetone and dichloromethane. The organic solvents, slowly increase the chemicals in the seed. In this method, there is no need for drying the seed materials to bring back the original moisture content of the seed. The organic chemicals are evaporative after the infusion is over, just we have to keep the seeds as such for 5 to 10 minutes in dry conditions the organic solvents will evaporate during this time and we can perform sowing. Seed infusion can also be used for breaking the seed dormancy.

Osmotic priming

It is very expensive but it is a required process, particularly for large-seeded legumes like peas, and beans etc., They have high protein content and large embryos and are susceptible to soaking injury. High-protein seeds are hygroscopic and hydrophilic.

Osmotic priming is nothing but making the seeds imbibe water very slowly. Osmotic solutions used are (PEG) (poly ethylene glyster). Maintol is highly toxic. PEG is inert and will increase very slowly the water into seeds. By preconditioning through osmotic priming, the seeds are invigorated which results in uniform, early and higher field emergence and higher seedling vigour.

Fluid drilling

This is a technology evolved for the mechanical sowing of seeds, particularly the germinated seeds. The seeds are coated with a jelly material called guar gel. It is to have a buffer action to avoid damage to the germinated seeds during sowing.

Separation of viable seeds

It is a new concept, particularly for groundnuts. This is a good method to get desired seed germination and plant population. In the case of groundnut, the actual population requirement is 30 plants / m². The actual seed multiplication rate in groundnut is 1:8. There are about 30-40% of dead seeds and if such dead seeds are eliminated, then we will be able to maintain the required plant population in the field. This is the base for evolving this technology.