The enhancing effect of intercropping sugar beet with chicory on the deep root growth and nutrient uptake

Crops with deeper rooting is an emerging tool for better exploitation of soil resources. However, there is a need for more in-depth understanding on how the increased rooting depth may be achieved. In this study a novel approach for obtaining deeper rooting has been proposed. Crops with assumed similar capacity for subsoil exploration: sugar beet (Beta vulgaris) and chicory (Cichorium intybus var. foliosum) were intercropped. Repeated measurements of biomass, deep root growth, and nutrient uptake were conducted to monitor plant competitive dynamics in the intercrop and sole crops. It was found that the intercrop positively affected biomass production with Land Equivalent Ratio close to or greater than 1 (0.99 - 1.14). Similarly, the strongest root growth over time was observed for the intercrop (from 98 +/- 48 to 304 +/- 28 cm depth). Moreover, the effect from the interspecific interactions in the intercrop varied over time. In the first half of the season yield advantage and the observed enhanced contribution to the uptake of N, Mg, Mn, Zn, and Na in the intercrop were driven by the sugar beet. Later in the growing season, yield advantage, deep root growth, and contribution to the uptake of S, Fe, Cu, and Al in the intercrop were driven by the chicory. This has also been confirmed by the root quantification analysis, which showed that in the end of the season intercrop consisted of 84 % and 98 % roots from the chicory at 1 and 2.5 m depth, respectively. This study concluded that intercropping two crops with similar root characteristics, sugar beet and chicory, can still lead to complementary interactions showing potential for efficient deep soil exploration by roots and yield advantage in comparison with the sole crops.