Impact of Soil Structure on Root Growth Patterns– a Field Study with Rhizotron Facilities

This study compares the development of maize roots in two different types of soil by analyzing their growth over time and their vertical distribution. We further evaluated the recolonization of root-induced macropores since that can enhance the root growth into deeper soil layer and also may have influence on the nutrient and water uptake. The root monitoring was conducted in two neighboring rhizotron facilities; one with stony and one with silty soil. Maize was cultivated following winter wheat from the previous growing season. In each facility, two water treatments were considered: rainfed and irrigated.

The root growth over time and depth was observed with a minirhizotron camera via 7-m-long acrylic glass tubes installed horizontally in different soil depths (namely 10, 20, 40, 60, 80, and 120 cm). Additionally, above ground plant parameters such as crop height, leaf area index and canopy temperature were collected to be compared with the root development. The obtained images were evaluated manually using Rootfly to retrieve the density of root length and count over time and depth. To quantify the recolonization of root-induced macropores, the fraction of macropores created by the previous growing crops (winter wheat) recolonized by the subsequent roots (maize) was analyzed.

We observed that the plants growing on the soil with high gravel content had a shallower rooting depth and a higher sensitivity towards drought stress; the rainfed crops where significantly smaller than the irrigated ones and also considerably smaller than the plants growing on the silty soil, which were in their root and shoot development independent from irrigation. Furthermore, the results show higher root biomass and more frequent recolonization in the silty soil; the stony soil has sparse rooting and comparatively fewer stable channels: the recolonization of root-induced macropores is amongst others depending on soil type and soil depth.