Growers are still sowing oilseed rape by weight and are not taking full account of seed size and number when establishing their crops, warns ProCam Group technical manager Nick Myers.
Analysis of ProCam's 4cast data shows that the average seeding rate for oilseed rape in the last 2 years has averaged between 5-7 kg/ha regardless of establishment method.
"Assuming a typical thousand seed weight of 4-5g /1000 seeds this means that on average between 110-150 seeds/m2 were sown. Current thinking suggests that an optimum seed number for conventional varieties is 60-80 seeds/m2 to produce a final plant population of 30-40 plants/m2," Nick Myers says.
"This is all that is needed to create a crop canopy with a Green Area Index of 3.5 and means that growers could have used half the amount of seed."
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Trials in 2006 showed that lower seed numbers, even down to 40 seeds/m2, produced the best yields. ProCam's 4cast data clearly shows the trend of declining yields at higher seed rates across all soil types.
"Getting crops too thick causes problems of poor light interception and higher lodging and disease risk. Growers should check oilseed rape thousand seed weights carefully and adjust seed rates pro rata to sow the optimum number of seeds this year," Nick Myers concludes.
