Test the quality of retained sowing seed every year
The suitability of stored grain for sowing seed will be greatly affected by the paddock and seasonal conditions that it came from. In some instances, crop seed quality can be the difference between a successful crop or a failed crop. Many growers retain seed for sowing and by following the tips below there will be one less obstacle to a great season.
Why test your seed every year?
- A delay in germination from low quality seed is similar to delaying sowing past the optimal date. This reduces yield potential and increases the risk of hot and dry conditions reducing yield.
- Testing enables growers to accurately produce the desired plant density. Some crops like faba beans are very sensitive to plant density, and weeds get the upper hand in crops with low plant density.
- Conditions change year to year, so every batch of seed will be different. Seeds also lose vigour the longer they are stored.
There are two important tests to determine seed quality:
A germination test will tell you how many of your seeds in the bin are viable. The results will come back with the percentages that are normal, abnormal and dead. The proportion of normal germinated seeds will tell you what will happen in ideal conditions, but you will need to adjust if sowing into tougher conditions. Abnormal seeds may germinate but will have poor vigour. Seed vigour can also be tested, which will tell you the likely percentage of seed that will germinate under poor sowing conditions.
Knowing the thousand seed weight is necessary to determine an accurate sowing rate. Large seeds with higher thousand seed weights require higher sowing rates than smaller seeds (in kg of sowing seed/ha) to achieve the same population. Thousand seed weight should be measured for each seed lot as there will be large variation.
Each of these tests can be used to make informed management and financial decisions around sowing. If you have a low germination rate, it may be recommended to increase sowing rates to try to increase the number of viable seed, or to change to a better seed source.
The following formula uses both thousand seed weight and germination percentage to calculate the sowing rate that you want based on your desired plant density.
Sowing rate (kg/ha) = 1000 seed weight (g) x desired plants/m2 ÷ germination percentage
Seed cannot be tested accurately by the DIY test of wetting paper and placing it on the office windowsill. It is recommended that seed tests are undertaken in a seed laboratory. Your seed is an important starting point to the success of your new crop, and seed testing is a small cost to pay to help your crop face the season that is about to come.