Soil microbial communities and disease suppression as affected by soil compaction resulting from different management strategies

This research has examined the effects of soil compaction, and common agricultural management strategies used to overcome soil compaction, on soil bacterial and fungal activity and diversity. Soil microbial communities, bacteria and fungi in particular, play essential roles in the maintenance of soil health, where high soil microbial diversity might strongly contribute to the natural disease suppression. The activity and diversity of soil microbial communities is, however, strongly dependent on other soil characteristics, especially soil physical parameters. Soil compaction indicated by increased bulk density is the most soil physical parameter that directly modifies soil environment where crops and diseases exist in, but it might also indirectly cause more disease by affecting the composition of soil microbial communities in the soil. Many strategies have been used to attempt to overcome compaction in temperate environments, but they have been poorly studied/less successful in tropical and subtropical environments. This thesis, therefore, looks at the impact of compaction, and methods used to reduce compaction, on the soil microbial profile, and its capacity to resist introduced diseases.