Farm-saving seed is a valuable way of minimising seed costs, but it doesn’t necessarily mean scrimping on quality. Tom Allen-Stevens reports

Many factors contribute to the quality of farm-saved seed, but size is one of the most important when it comes to getting an oilseed rape crop off to a good start.

Work carried out by the National Association of Agricultural Contractors (NAAC) suggests bigger seed grows with far more vigour than smaller seed.

“It’s always been our belief that it’s more about seed size,” says Nigel Day from mobile seed treatment specialist Anglia Grain Services.

NAAC set about proving this by growing seeds of different sizes on paper and sand and measuring the seedlings after seven days. The seeds came from the same sample, but were sorted by diameter. At seven days the seedlings from the larger seeds had produced two-and-a-half times more dry matter, had visibly thicker stems and wider cotyledons (see table).

The results should encourage farmers to farm-save oilseed rape and ensure the mobile seed processor sieves out the boldest seed from the sample, says Mr Day.

When farm-saving, growers can boost seed size in cereals through the use of an ear spray. With oilseed rape, drilling on the thin side (less than 40 seeds/sq m) will encourage production of larger seed, says Mr Day.

Weeds/disease

Weeds and disease control is also critical for seed quality and Mr Day recommends growers earmark a fertile, well-drained and clean area. “Use the rotation to achieve a volunteer and disease-free crop.”

The most important weeds to avoid with oilseed rape are charlock, wild radish, and cleavers. For cereals, the key ones are wild oats and sterile brome. To ensure the crop is weed-free growers should rogue if necessary, he adds.

At harvest, growers should allow crops to ripen naturally or desiccate using diquat if needed, Mr Day says. “Avoid using glyphosate as this can affect germination.”

Storage

Oilseed rape should ideally have a moisture content of 9% and be kept in half or one-tonne bags. With cereals, the ideal moisture is 15% and a trailer or bin is the best storage vessel. If grain needs to be dried following at harvest, a high volume, low temperature (less than 30C) system avoids the risk of seed damage.

Cleaning and treatment

If you keep seed over until the following year a germination test should be carried out before planting. Normally, it would be 95-99%, says Mr Day.

“Make sure the cleaning and treatment contractor is on the Verified Seed Scheme and get seed passed over a gravity separator and sieved well to get the best sample settings.”

This year, variable crops mean growers might have to remove as much as half the seed crop in screenings. This should be considered when assessing how much of a crop should be set aside for seed.

Finally, Mr Day recommends using an effective seed treatment. “At the very least protect against bunt, smut and damping off.”