Use of Trichoderma spp. and arbuscular mycorrhizal fungi to increase soil beneficial population of bacteria in a nectarine commercial orchard: effect on root growth, nutrient acquisition and replanting disease

The aim of the present experiment was to evaluate the effect of commercial Trichoderma and arbuscular mycorrhizal fungi (AMF)-based bio-fertilizers on nectarine root growth, nutrient acquisition and replanting disease. The experiment was performed from 2008 to 2012 in an A. mellea-infected nectarine orchard subjected to the following treatments: 1) untreated control; 2) AMF-biofertilizer applied at planting (120 kg ha-1) and every year in spring and autumn at the rate of 6 kgha-1;3)Trichoderma spp. applied at planting (5 g plant-1) and every year (in April, May and September) at 2.5 kg ha-1. AMF bio-fertilizers decreased root diameterand increased root survivorship. Leaf phosphorus concentration increased in AMF biofertilizers plots, while no significant treatments effects were observed on other leaf nutrient concentration. Although biofertilizer application did not affect soilmicrobial population, at the end of the trial (2012) the application of Trichoderma alone increased the population of the fungus.