The soil was a Labucheri series of the Psammentic Paleustalf (sandy,
siliceous, isohyperthermic) family. The Labucheri series is characterized by
a high sand fraction (> 90%), moderate acidity, poor water retention
(< 10%) and low nutrient status. The soil has a clear depth of 34 m,
overlying a gravelly lateritic layer [12]. Depth to water table is about 20 m.
These traits make the soil ideal for root growth studies, because roots can
grow unimpeded and are excavable to depths of 4-5 m.