Chicory Roots Reach Below 3 m and Acquire Water from the Lower Part of the Root Zone

Introduction

Water scarcity is a major limitation to crop production worldwide. Deep-rooted crops can potentially allow exploitation of water that more shallow-rooted crops cannot access. Several agricultural crops grow roots of several meters depth within a growing season and thereby get access to water originating from wet season surplus precipitation stored in the soil. The aim of this study was to test the hypotheses 1) that chicory roots can grow below 3 m within a growing season and 2) that chicory shifts its water uptake downwards when the topsoil dries out.

Materials and Methods

Chicory (Cichorium intybus L. cv Chicoree Zoom F1) was grown in 4 m tall rhizotrons in monoculture under dry or wet conditions and intercropped with either ryegrass (Lolium perenne L.) or black medic (Medicago lupulina cv Virgo Pajbjerg). Rhizotrons were placed outside and the growing medium was field soil. Rainout shelters and irrigation allowed controlled water supply, and water content sensors in three depths continuously logged soil water content. Depth controlled injection of ²H-enriched water was used to trace species-specific water uptake from 2.3 m. The experiment was repeated in two consecutive years.

Results and discussion

Chicory roots were observed below 3 m in July both years, which was 2 and 5 months after transplanting in the two years respectively. Root growth below 2 m was limited throughout the season both years and still, the tracer studies showed significant tracer uptake by chicory from 2.3 m. Black medic and ryegrass, which are known to be shallow rooted, did not take up ²H-enriched water tracer from 2.3 m. A significant water uptake from the lower part of the root zone was observed, but water uptake did not seem to shift downwards as the topsoil was drying out.