Winter beans offer a flexibility that other traditional winter sown species don’t, as they don’t have a vernalisation requirement (a period of cold that they must go through in order to produce seed). This means that growers can wait to sow in optimal conditions without the looming pressure of latest safe sowing dates.
This is something that we looked into at our innovation site this year; a site which, like many, saw no drilling in the back-half of 2019 due to the adverse weather. This involved drilling Tundra, LG Raptor and LG Cartouche on two drilling dates: 28/3/20 and 23/4/20.
Crop establishment was good in both drilling dates, and the winter showed no difference from the spring in the speed of development, until the stem extension stage. After stem extension, the difference in development widened between the winter and spring varieties, with the winter varieties being later. This was shown in terms of flowering date and pod development which, in the later drilling date, showed more than 10 days between Tundra and LG Raptor.
And whilst there is no genetic reason as to why Tundra should not be drilled late into the spring, there does become a point at which the maturity of the crop becomes too late from a management point of view. So, in the instance of this demo, the end of March is as late as would be feasible for drilling Tundra. However, when drilling Tundra into the spring, there are several factors that should be considered.
• Winter beans will not branch as much if sown in the spring
• Seed rates need to be adjusted – as the drilling is pushed back, seed rates should be adjusted to optimal spring populations, towards 35-45 plants/m2
• Harvest date will be pushed back – winter beans are later than spring
• Check approval of pesticides, as it will be classified as a spring crop, not winter
So, whilst Tundra is a viable option in the spring, the autumn sowing of spring beans, such as LG Raptor and LG Cartouche, has significantly higher associated risk. This involves the increased likelihood of ascochyta and of winter damage occurring. Spring beans, when drilled in the autumn, will also increase the earliness of harvest – adding to an already strained workload around the main cereals harvest period.