The importance of seed quality for a successful season

Key messages

Rain during harvest may have led to a decline in retained seed quality

Get your seed tested as soon as possible to confirm germination and vigour

It's not recommended to plant seed with less than 70% germination

Seed quality can deteriorate rapidly in storage, depending on conditions

While agronomy, disease and seasonal conditions are big drivers of seed quality during the production phase, conditions experienced during harvest and in storage can also lead to a deterioration in seed quality over time.
Many farmers are concerned about how last year’s harvest rains may have impacted seed quality, and the flow-on effects for crop establishment this season. So, what are the best way to monitor seed quality, to avoid establishment issues?

Growing season conditions

Last year, some growers in the Riverine Plains faced a perfect storm when it came to seed production and quality, with a double whammy of dry conditions and frost during the growing season.

Dry conditions reduce overall grain yields, while a dry spring in particular can lead to smaller, shrivelled grain, with fewer stored nutrients and energy reserves.

Frost damage often also causes pinched or shrivelled grains and reduces grain numbers, sometimes with complete head abortion. Severe frosts (-2°C or lower for extended periods) will decrease yield and seed quality by lowering protein and starch levels, which are important in the germination process.

Rain during harvest

The actual impact of rain during harvest on seed quality depends on the amount of rain received and the duration of exposure of grain to moisture. Prolonged damp conditions can trigger the germination process to begin – signs can vary from mild discolouration and a loose, wrinkled coat (from swelling and drying, especially in pulses), right through to fully 'shot and sprung' grain. Once the grain has reached the stage of embryo development, seed viability is lost and the grain is often downgraded to feed quality (the seed will have used most of its energy stores, reducing its ability to complete the germination process).

While a lower falling number may indicate potential quality issues, it does not always mean seed viability has been compromised. If the seed dries out before the embryo starts to grow, it could still be viable for sowing, however testing is crucial to confirm its suitability.

Storing seed on farm

The goal of on-farm seed storage is to maintain quality from harvest through to the next season’s sowing.

For optimal storage conditions it’s recommended to:

Keep moisture levels below 12%
Maintain a storage temperature of around 20°C
Ensure seed is free from pests

If aeration cooling is unavailable, place silos in shaded areas can help regulate temperature.

Temperature plays a critical role in wheat seed germination, so proper storage conditions can make a significant difference to maintaining seed viability, as shown below.

Graph displaying influence of temperature on wheat germination

The value of seed testing

To ensure this year’s seed is of high quality, consider sending samples for laboratory testing. This will help establish:
• Germination rate
• Vigour
• Chemical resistance status (e.g. confirm canola seed is triazine tolerant)

There are several labs that complete seed quality testing including: Seed testing services (PIR SA) and Germination testing (Australian Seed Labs).

Alternatively, farmers can do a simple home germination test by counting out seeds and germinating them in damp paper towel placed in a dark place, then calculating the germination rate (be careful not to over-moisten as this can cause seed to burst). This method is less accurate than laboratory testing, but will still provide an effective indication of germination, see also GRDC's Retaining seed factsheet.

Interpreting results

You should be able to request the lab to interpret the results for you. As a general rule:

90%+ germination indicates seed is of good quality
A germination rate below 70% germination indicates seed is not recommended for sowing

Vigour is a crucial factor, as it measures a seed’s ability to establish under suboptimal conditions i.e. those that will be faced in the paddock. Seeds often lose vigour before losing germination ability, so assessing both is highly recommended.

Weather damaged seeds with low vigour will find it harder to reach the surface, so it’s important to avoid sowing too deeply, or into cold and wet soils. Consider also the effect of some seed dressings and herbicides, as well as hard-setting soils on seedling emergence.

Knowing your seed germination and vigour means you can make more informed decisions about sowing rate and sowing depth, or if you should source alternative seed.

Calculating sowing rates

Seed purchased from a retailer in bags usually states the seed’s germination percentage, vigour and thousand grain weight, as well as any seed treatments applied. The thousand grain weight is a key number to know as it will enable you to calculate the required sowing rate. If not available, working out the thousand grain weight takes just a few minutes, and a bit of concentration, using the steps below.

How to accurately determine 1000 grain weight

1. Find the right tools; use a digital electric kitchen scale with ±1g accuracy

2. Prepare seed by grading & pickling (if required)

3. Count 1000 grains, by:

Selecting a representative seed sample
Placing some seeds on an A4 sheet of paper at the table's edge
Hold an ice cream container on your knees under the table edge and use a skewer or knife to scrape 5 grains at a time into the container
Repeat 20 times (100 grains), keeping a tally of each set of 20 on the paper
Repeat this process 10 times to reach 1000 grains

4. To determine 1000 grain weight, place a small container on the kitchen scale and tare it. Then pour in the 1000 counted grains and record the weight.

5. To calculate the sowing rate, use the formula:

Sowing Rate (kg/ha) = (Target plant population/m² × Thousand grain weight (g)) ÷ (Germination % × Establishment %)

When using retained canola seed, use seed size to estimate the number of seeds per kg (see estimating size of retained canola seed, Agriculture WA ), then calculate the sowing rate using this canola seeding rate calculator, Agriculture WA

Summary

Sowing sub-optimal seed increases the risk of an establishment failure, especially in marginal conditions. A seed failure is expensive, not only in terms of the labour and inputs required (seed, chemical, fertiliser, diesel, machinery wear and tear), but also because of the yield losses associated with delayed crop establishment in resown crops.

There’s huge advantage in knowing whether your seed is suitable for sowing, or whether you should source alternative seed. By focusing on seed quality, testing, and proper storage, farmers can maximise the chances of a strong start to the season and a successful crop outcome.