Anchorage Mechanics of the Tap Root System of Winter-sown Oilseed Rape (Brassica napus L.)

The anchorage mechanics of mature winter-sown oilseed rape (‘Envol’)were investigated by combining a morphological and mechanicalstudy of the root system with anchorage tests on real and modelplants. Oilseed rape plants were anchored by a rigid tap root;the few laterals all emerged below the centre of rotation ofthe root system (approx. 30 mm below the soil surface). Whenplants were pulled over, the tap root bent and the top 30 mmmoved in the soil towards the direction of pull, creating acrevice on the opposite side. The maximum anchorage moment was2.9 ± 0.36 N m. Two main components of anchorage wereidentified: the bending resistance of the tap root and the resistanceof the soil on the near side to compression. The relative importanceof these components was determined by measuring both the bendingresistance of the tap root, and the resistance of metal tubesof varying diameter, inserted to various depths in the soil,to being pulled over. These tests showed that the tap root bendingmoment at failure could account for around 40% of anchoragemoment, while soil resistance could account for around 60%.The model tests on the tubes also help to shed light on theway in which the dimensions of tap roots will influence theiranchorage capability. Copyright 2001 Annals of Botany Company Anchorage, lodging, root bending resistance, mechanical properties, oilseed rape, Brassica napus L