Chicory demonstrates substantial water uptake from below 2 m depth, but still did not escape topsoil drought

Aims Deep-rooted agricultural crops can potentially utilize deep water pools and thus reduce periods where growth is water limited. Chicory ( Cichorium intybus L.) is known to be deep-rooted, but the contribution of deep roots to water uptake under well-watered and drought conditions by the deep root system has not been studied. The aim of this study was to investigate whether chicory could reach 3 m depth within a growing season and demonstrate significant water uptake from the deeper part of the root zone. Methods We tested if chicory exposed to either topsoil drought or resource competition from the shallow-rooted species ryegrass (Lolium perenne L.) and black medic ( Medicago lupulina L.) would increase deep water uptake in compensation for reduced topsoil water uptake. We grew chicory in 4 m deep soil filled rhizotrons and found that the roots reached 3 m depth within a growing season. Results Water uptake from below 1.7 m depth in 2016 and 2.3 m depth in 2017 contributed significantly to chicory water use. However, neither drought nor intercropping increased the deep water uptake. Conclusion Chicory benefits from being deep-rooted during drought events, yet deep water uptake cannot compensate for the reduced topsoil water uptake during drought.