Spatial distribution of apricot roots in a semi-arid environment

Information on the root system of fully mature apricot (Prunus armeniaca L.) orchards is scarce. This paper deals with the root system of apricot trees in a semi-arid region of Romania. The 15-year old orchard was established with Hungarian Best variety grafted on Constanta 14 generative rootstock. Sprinkler irrigation was applied under a mild water stress regime. The purpose of this paper was to: (1) test the hypothesis that the roots of trees planted within a certain layout occupy the whole soil space, (2) describe the spatial distribution of root density using the trench technique, and (3) emphasize the rootedness of apricot in this soil type. Soil samples were taken from both in row (IR) and inter-row (ITR) positions to determine soil properties. Some physical properties were deteriorated in ITR versus IR, mainly due to soil compaction induced by the technological traffic. The root density was almost similar in ITR and IR, decreasing with both soil depth and distance from the tree trunk, and stronger correlations were obtained with soil depth. The roots of apricot trees are mainly concentrated within 0.5 m depth and occupy the entire soil space between trees, showing the highest density at about 1 m from the tree trunk. No root avoidance for neighboring trees was found. The horizontal decrease in root density can be used in optimizing tree arrangement in orchards. Canopy shape, light penetration and groundcover management system are also important in this decision. The results could be used in countries with similar environments.