Seed enhancements help seeds germinate and seedlings emerge quickly and uniformly throughout the field.

Seed enhancement refers to various technologies used to increase the consistency of seed performance, thereby improving a crop’s harvested yield and quality. Seed enhancement technologies are gaining increasing attention for their potential to confer greater disease resistance in seeds, improve seed vigor and modify seed emergence capabilities.

Seed coating refers to the application of materials to the seed surface, often containing seed protectants such as fungicides. In recent years, film coating, in which the active ingredient is applied in a quick-drying polymer film around the seed, has gained popularity. A major advantage of film coating is reduced loss of active material from the seed during seed transport and handling.

Seed pelleting technologies are used to alter seed shape, surface properties, density and size to enable more precise seed singulation and placement in the planting tray or soil. Singulation eliminates clustering of seed that leaves too much or too little space between plants within a row. Seed pelleting is also used to deliver a range of beneficial additives, including micronutrients and plant protection agents.

Seed priming is used to increase germination rate (speed) and uniformity and overcome seed dormancy. In seed priming, seeds are hydrated in a controlled manner to provide enough water to initiate the metabolic* processes of germination, but not enough to allow germination to be completed. Subsequently, the seeds are dried, distributed and planted in the usual way. Primed seed usually exhibit more rapid and uniform emergence of seedlings from the soil compared to non-primed seed of the same seed lot. These differences are greatest under adverse environmental conditions in the field, such as cold or hot soils. Primed seed often has a shorter shelf life than non-primed seed, and should be stored under optimal conditions prior to planting.

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The primary way of enhancing seed performance is through the addition of chemicals to protect the seed from pathogens. These are generally fungicides, although insecticides and other protecting agents can also be applied in this way.

Until recently, these chemicals were applied mainly as a slurry that coated the seeds and then was dried. Disadvantages of this method are that it is difficult to get a uniform coating of the material on the seed and much of the material can be rubbed off the seed during transport and handling. This is wasteful of the chemicals, is hazardous for the workers planting the seeds, and in some countries, including the U.S., requires the disposal of the seed bags as a hazardous waste.

In recent years, film-coating methods have been developed to overcome these problems. In film coating, the chemicals are applied in a polymer that is sprayed on the seeds as they fall though a specialized machine. The polymer is rapidly dried, so that the seeds emerge with a complete, dry polymeric coating.

This coating does not rub off the seeds, greatly reducing worker exposure and waste. In addition, colors can be added to the polymers to code different varieties or seed lots. Large-scale units capable of treating large quantities of seeds have been developed, making it feasible to treat high-volume agronomic crops by this method as well.

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The seeds of many agricultural species are either small or irregularly shaped, making it difficult to singulate them for planting.

New types of planters, particularly vacuum plate planters, have largely overcome this problem. However, even if the seeds can be dropped individually to control spacing, it is difficult with small seeds to control the depth of planting.

Seed pelleting addresses both of these problems by coating seeds with clay or other materials to give them a uniform shape and size and increasing their size and density to allow more precise placement in the soil.

Pelleting is used most widely for small field-planted seeds such as lettuce and alfalfa, but small and valuable seeds, such as petunias or geraniums, are often pelleted to increase their size and facilitate their use in automatic planters in greenhouses.

Modern types of pellets split upon imbibition – when they absorb fluid and swell - freeing the seed from any impediment by the coating material.

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A physiological method of improving seed performance is known as seed priming. In seed priming, the basic metabolic reactions needed for the seed to germinate occur in a lab under high moisture and ideal temperature conditions.

The water supplied to the seed is controlled such that seed moistures are at a level just below what is needed for actual germination, but just enough to get the process going. Germination is subsequently temporarily arrested by drying the seeds, allowing them to be packaged, distributed and planted in the same way as untreated seeds.

Primed seed usually results in more rapid and uniform emergence of seedlings from the soil compared to non-primed seed of the same seed lot.

These differences are greatest under adverse environmental conditions in the field, such as cold or hot soils.

In addition, priming can overcome some types of environmental stresses, such as high temperature inhibition of lettuce seed germination.

Primed seed often has a shorter life span than non-primed seed, and should be stored under optimal conditions prior to planting.

However, further refinements of the priming process, particularly the handling of the seeds prior to dehydration, are able to mitigate this effect. 

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