Seed Rates For Winter Sown Wheat
Are you about to use overwintered seed? If so have you had the germination tested by the Official Seed Testing Station in Cambridgeshire?
Germinations can decline as illustrated by the cover photo with this blog. Here we see the use of one 500 kg bag of seed “used up” when planting this field in Autumn 2019. Survival was obviously not as good as the new seed drilled alongside it. Good job it was only one bag!
I don’t drive the tractor or operate the drill anymore but I am yet to hear of a drill that plants seed by the square meter. Which means you need to know the weight of seed to plant per ha. When you have your seed “tested” best to get a Thousand Grain Weight done at the same time. In a “normal” year it varies from 44 to 54 which means your seed rate can also vary from 140 to 170 kg/ha.
If the world record crop of 15t/ha is achieved by 470 stems per meter squared then best we target the right plant population at the beginning (and think about how we intend to manage the crop through until harvest 2021.)
According to the science, a large number of factors affect establishment
Some of the key findings are summarised below.
Soil characters affect the ability of the seed to germinate and subsequently emerge.
Germination: Seed-to-soil contact and soil water status
Emergence: Factors that influenced impedance such as clod size, distribution and sowing depth.
Rolling to improve seed-to-soil contact offers an improvement in establishment of less than 10%.
Different optimum temperatures according to sowing date due to interactions with soil moisture.
A large number of soil types were included in the data set clays and loams establishment averaging 60-65%; sands averaging nearly 90%.
Previous cropping had a significant effect on establishment; wheat crops following oats had the best establishment (79%) worst was following beans at 54%.
Over-winter survival is important as spring plant population influences yield; anticipate loosing another 15% of your autumn plant populations.