Wheat root growth responses to horizontal stratification of fertiliser in a water-limited environment

Abstract

Background and aims: We were interested to determine the effects of horizontal stratification of nutrient-rich zones within different layers of the soil profile in water-limited environments on root growth and crop yield. This is practically relevant to large areas of China, many of which have been over-fertilized. Methods: We used soil-filled rhizotrons 1.4 m deep to grow wheat. Three different nutrient-rich horizontal stratifications were used at depths of 0–40, 60–100 and 0–140 cm. The soil was packed to a density of 1.5 g cm−3, at a matric potential of −10 kPa. The wheat was grown until it was at terminal drought. Low soil hydraulic conductance preserved the horizontal nutrient stratification. Results: Plants grown in rhizotrons with a surface layer (0–40 cm) of nutrients had the greatest root growth, water uptake and yield. When nutrients were uniformly distributed throughout the rhizotron (0–140 cm), root growth was restricted to the surface layer. Measurements of soil moisture indicate this was because the roots became impeded. Conclusions: Nutrient enrichment of the surface layer was the most effective at promoting deep roots, higher water uptake and yield under water-limited conditions. Heterogeneous nutrient distribution can modify root growth and water uptake.