The Effect of Varying Cultural Practices on the Location of Mycorrhizal Infection within the Rhizosphere of Highbush Blueberry Plants

Abstract

Previous experiments in the laboratory and the field have suggested that location of mycorrhizal infection within the rhizosphere of blueberry plants may depend on cultural practices that are being used. Furthermore, we have observed that rapidly growing roots, whether in solution culture or within petri dishes, appear to be less likely to become infected when inoculated. A preliminary experiment found higher levels of mycorrhizal infection in roots growing at a 5-cm depth of soil compared to roots growing just under the mulch layer. To further test this hypothesis, an experiment was designed to evaluate the infection intensity of highbush blueberry plants (Vaccinium corymbosum L.) at different locations within the rhizosphere on plants growing under varying cultural practices. Cultural practices included mulching (mulch vs. no mulch) and nitrogen level (0 and 120 g ammonium sulfate/plant). Four-year-old `Bluecrop' highbush blueberry plants subjected to these treatments were arranged in a complete factorial design with six replications at the Russell E. Larson Agricultural Research Center at Rock Springs, Pa. Mycorrhizal infection intensity was evaluated from roots sampled nondestructively using a 2.5 cm soil corer at the interface of the mulch and soil, and at soil depths of 3 and 15 cm from two locations 15 cm from the crown of each plant. Results will be discussed.