Seed Technology

Seed Handling

Care should be taken when handling vegetable seeds as some seed is easily damaged by rough handling. Rough handling can result in a broken seed coat which allows the entry of pathogens, dirt and moisture and may in turn cause the seed to split.

Seed Storage

In order to extend the storage capability of seed it is necessary to first start with good quality seed. Quality seed can be obtained by purchasing your seed from a reputable seed company that details on its labels quality information of a seed lot, such as germination percentage and purity. It is also necessary that a seed lot number is detailed on the packaging label so that in the event of any issues the seed line is traceable and information can be accessed.

Seed is a perishable product and, as such, should be stored under the correct conditions to ensure optimum seed quality. Vegetable seeds should store on a shelf at room temperature for one year without appreciable decrease in germination. If storage is required for a longer period than this, say in the case where seed is leftover after a crop is planted, then it is necessary to take further steps to ensure seed viability. Seed moisture (ideally less than 8%) and storage temperature (a practical guideline is 15-17⁰C) are the most important factors in determining how long seed can be stored.

Some seed lasts longer than others depending on the crop and seed treatment. Seed which has been treated for thermodormancy or primed has a much reduced shelf life and more specific requirement of storage conditions. These seeds should be kept for a maximum of six months and require cooler conditions for storage.

Most of our vegetable seed is scientifically de-humidified before being hermetically sealed in foil, packs, cans or drums. Seed treated like this normally retains original germination potential much longer than seed which is not treated in this manner.

Seed Cleaning

The aim of seed cleaning is to remove any foreign matter from the seed lot thereby ensuring the seed lot is as pure as possible. Freshly harvested seed can contain a number of elements other than the seed variety cultivated. These elements include:

  • Other crop seeds
  • Weed seeds (especially herbicide resistant weeds)
  • Straw, soil, dust and other inert material
  • Immature, shrivelled, damaged, cracked, undersized or oversized seed

By removing all these elements it ensures the customer is getting only seed of the variety for which they want to purchase and they are not allowing weeds, diseased seed or other foreign matter into their production system.

Seed Grading

The aim of seed grading is to select only the best and highest quality seed for sowing.  Seed grading encourages consistency across seed lots and typically germination uniformity and final germination percentages are improved through the grading process. Uniformity of seed permits more even distribution of seed through the drill for precision sowing.

Seed Dormancy

Dormancy prevents seeds from germinating until the conditions are favourable for their growth. Temperature, light and naturally occurring chemical signals are variables that impact dormancy. There are three main types of seed dormancy:

  • Physical dormancy which occurs when seeds are impermeable to water or the exchange of gases thereby preventing moisture and oxygen from reaching the embryo. Impermeability is often caused by an outer cell layer that repels moisture or a hardened seedcoat. This can be overcome by mechanical scarification, the use of sulphuric acid, or soaking seeds in boiling water
  • Mechanical dormancy occurs when seed coats or other coverings are too hard to allow the embryo to expand during germination. As for physical dormancy this can be overcome by mechanical scarification
  • Chemical dormancy includes growth regulators etc… that are present in the coverings around the embryo. They may be leached out of the tissues by rainfall or irrigation, or by washing or soaking the seed. Or in the instance that the embryo is too immature to grow this can be overcome by allowing the seed time to mature before sowing

Dormancy is caused by the seed's need to grow to maturity, which requires it to wait until it is in the best conditions to grow before germinating. A dormant seed is not necessarily a low-quality seed. Dormancy is a normal process used by seeds to protect the embryo within the seed until conditions are optimal for growing.

Seed Thermodormancy

Thermodormancy is the sensitivity of a seed to temperature. Some seeds will only germinate at high temperatures while, more commonly, others will only germinate under cooler conditions, such as in the case of lettuce and celery seeds. Depending on cultivars, thermodormancy in lettuce seeds may be induced when germination temperatures exceed 28⁰C and for celery temperatures that exceed 25⁰C. Priming seeds is an effective method to overcome this dormancy.

Seed Priming

Seed priming is an effective method to improve the speed and uniformity of seed germination and optimise seed performance under extremes of temperature and moisture availability. Seed priming consists of soaking seeds under conditions that allow the seeds to imbibe water and initiate germination, but which do not permit radicle protrusion through the seed coat. This generally includes the use of an osmoticum, such as a salt solution and low temperature which assists the seed in taking up moisture. The duration of the soak is important in order to ensure that radicle protrusion through the seed coat does not occur. The seeds can then be dried and stored or planted with conventional equipment. Crops that may have primed seed include capsicum, celery and lettuce.

Seed Treatment

When seed is film coated, coated or pelleted it is possible to incorporate certain registered pesticides, fungicides and other biological agents like beneficial fungi and microbes. By incorporating these treatments into the coating it ensures uniform distribution of the product right where the seed is going to make the best use of it. Most vegetable seed is sold with standard fungicide treatments such Thiram, Ipriodione and/or Metalaxyl-M as a first cover protection against soil fungal diseases.

For untreated seed please see our organic seed information or look under the “Market Segment” heading on our product information sheets for details on whether the variety is available as untreated seed.

Film Coating

Film coating is the term used to describe the application of a thin polymer material onto the seed. Filmcoating does not change the seed size or shape but will change the seed count based on only a very slight weight build-up. Filmcoating bond a combinations of colour, fungicides and/or insecticides to the seed. The outer layer, containing the colour, encapsulates the seed and any chemicals, offering a very clean and dust free product, which contributes to the safety of the handler and the environment. Filmcoating makes the seed flow easily and aids in plantability.

Seed Coating

Seed coating involves a lighter weight coating of inert polymers to increase the seed size to achieve greater drilling accuracy and singulation when using pneumatic (vacuum) drilling equipment. The added weight from the coating helps to minimise the “seed bounce” and increase the accuracy of seed placement. When crops are direct sown into the soil, at speed from a precision planter, the uniformity of seed placement can result in a direct increase in the crop yields. Various chemicals such as fungicides, fertilisers and growth promoters can be incorporated into the coating that may assist seed emergence and crop establishment.

The seed coating will break down on contact with water, therefore it is recommended during warmer and drier periods to pay greater attention to watering by providing slightly more water and increasing the irrigation frequency during the first few days after sowing compared to raw seed. Coated seed is commonly used for crops such as carrot, onion and parsnip seed.

Seed Pelleting

Seed pelleting involves a heavier weight coating of inert polymers to increase the seed size and alter the seed shape to achieve greater drilling accuracy and singulation when using pneumatic (vacuum) drilling equipment. The added weight from the pellet helps to minimise the “seed bounce” and increase the accuracy of seed placement. When crops are direct sown into the soil, at speed from a precision planter, the uniformity of seed placement can result in a direct increase in the crop yields. Various chemicals such as fungicides, fertilisers and growth promoters can be incorporated into the pellet that may assist seed emergence and crop establishment.

The seed pellet will break down on contact with water, therefore it is recommended during warmer and drier periods to pay greater attention to watering by providing slightly more water and increasing the irrigation frequency during the first few days after sowing compared to raw seed. Pelleted seed is commonly used for crops such as carrot, onion and lettuce seed.