Root Characteristics and Phosphorus Uptake of Maize Seedlings in a Bilayered Soil

Under temperate climates, no‐tillage results in cooler and denser topsoils than conventional tillage (CT) and in surface accumulation of immobile nutrients. Hence, early growth and functioning of maize ( Zea mays L.) roots may be adversely affected. These field conditions were simulated in a controlled environment system, allowing gradients in soil properties between topsoil (0–10 cm) and subsoil (10–50 cm). Combinations of topsoil temperature (Temp top ), bulk density (BD top ), and P concentration (P top ) were applied on maize seedlings grown until the three‐leaf stage. Topsoil bulk density and Temp top acted independently on shoot and root parameters but showed some interactions with P top An increase in BD top caused a linear decrease in root length, root mass, and the root/shoot ratio; an increase in root diameters in both topsoil and subsoil; and a concentration of roots in the topsoil. This resulted in a greater contribution of the topsoil roots to the nutrient supply of the shoot, as shown by 15 N labeling. Decreasing Temp top reduced shoot and root growth to a similar extent. High P top increased length, diameter, and topsoil fraction of roots, particularly at high BD top There was possibly a trade‐off between the adverse effects of low Temp top and the positive impacts of high P top on root growth. Shoot P concentration (P c ) was increased by high P top and, to a lesser degree, by increasing BD top The temperature of the topsoil had no effect on P c . It is concluded that in dense, cool soils, particular attention needs to be paid to the P supply of maize seedlings.