Root Systems of Hops under Irrigated and Non-Irrigated Conditions

The examined hop fields are located in the Northern Hallertau, Bavaria, Germany, the world largest hop growing area. Sandy loamy soils are dominant for this site. Root excavations were conducted on hop plants (Humulus lupulus) cultivar Perle grown on two adjacent plots with and without sub drip irrigation, September 2015. The main intentions were: to verify if differences of the aboveground plant growth are reflected in the root development, and to demonstrate the applicability of root excavations method for relevant studies in situ. The observed differences in the aboveground hops growth were significant even at short distances. The irrigated plants were rather poorly developed having less biomass than the neighbouring non-irrigated ones. Besides, the irrigated plants had a shallow rooting depth of 1,3 m and a lateral spread of 1,6 m, while the non-irrigated larger plants developed abundant root systems down to 3,7 m depth and a spread of 3,5 m. It was also remarkable that the irrigated roots did not develop in the direction of the irrigation holes. There were also dying processes of the root ends observed at the irrigated depth of 0,3 m pointing out possible starving due to soil wetness and oxygen depletion. The results of the root excavations clearly showed that spatial extension of the root system – lateral and in-the-depth – is a good indicator for favourable aboveground growth.