September 20, 2013
Taking the Temperature of Better Oilseed Rape Establishment
Last season’s exceptionally challenging weather lead to a large acreage of WOSR being drilled in September. With a significant area being drilled after WW this is not unusual and in many years has resulted in high yields, sometimes higher than August drilled crops. However last year with compacted very wet soils, slugs and pigeons along with rapidly reducing soil temperatures, many crops struggled and some failed.
Soil temperature is a significant factor; it takes 160°C days (the sum of average daily temperatures) to achieve 50% establishment from the time of sowing. A crop sown in mid-August will typically take 10 days to emerge, while crops sown in the second half of September could take about 14 days. As well as this, nutrient availability, especially phosphate, will reduce in colder soils. Clearly as we move into September and it takes longer to establish, the period following emergence before the onset of winter will be shorter. Our desire is to establish a robust crop before winter ideally with a root collar diameter of approximately 10mm which will be much more tolerant to slugs, pigeons, Phoma, harsh winter weather and with the potential for reduced spring N applications with higher GAI’s if carried though.
With the high costs of establishing rape, the understandable reaction of many farmers and agronomists following last year’s experience was to say we need to have an earlier cut-off date for drilling in future. But rather than pick a “gut feel” drilling date based on last year, we have been using our network of weather stations across the UK to enable a better informed decision. Agrii agronomists have been receiving regular updates of soil temperatures in their area to aid decision making through the season.