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Humulus lupulus The Hidden Half
T. Graf, M. Beck, M. Mauermeier, D. Ismann, J. Portner, P. Doleschel and U. Schmidhalter

Optimising hop cultivation is a constant endeavour for the brewing industry, as it delivers one of the most important ingredients for beer production. Whereas a lot about hop production in general is known, there is only little knowledge available with regard to the morphology and extent of its root zone. However, for further improving the agricultural management, a deepened understanding of the root development and its dimensions is required for optimising irrigation, soil tillage and plant nutrition. We therefore investigated the root distribution of hop (Humulus lupulus ?Herkules?) in a sandy soil and described the spatial extension geometrically. The description is based on an excavation of the whole rootstock of a plant in the fifth year of yield. The measurements were documented by photos during the excavation procedure and subsequently illustrated by morphological drawings. The root system of hop can be subdivided into three parts: A row section with adventitious roots, a disk surrounding the rootstock with horizontally growing roots and a block of vertical roots developing downwards. Both the horizontal and the vertical part are interspersed by two types of roots (perennial and fresh ones). The total amount of the rooted soil volume was about 4.1 m3, which indicates a large potential capacity for available water. An area of around 5.0 m2 for each plant is being wetted by rainfall. These findings may contribute to optimised management decisions.

Descriptors: hop, Humulus lupulus, irrigation scheduling, root excavation, root zone

BrewingScience - Monatsschrift fr Brauwissenschaft, 67 (November/December 2014), pp. 161-166