| Abstract: | The advent of conservation tillage presents a need for a greater understanding of plant disease and disease interactions in temperate humid agriculture, where excessive crop residues, continuous moist soil conditions and soil compaction are potential constraints. In this review, biotic and abiotic factors, and aspects of microbial antagonism, which can influence plant disease development in the root zone, are characterized in the context of conservation tillage in humid climates.Soil densification and reduction in macroporosity can aggravate abiotic root disease. Changes in soil aeration and permeability status can alter the quantitative and qualitative differences between soil rhizofloral populations, and survival and distribution of pathogen inoculum. Further-more, anaerobic soil conditions can result in root-pathogen interactions leading to plant disease development. A good quality soil physical environment is an important indicator for root health under conservation tillage in humid climates.Conservation tillage tends to concentrate plant debris and consequently microbial biomass in the top 5 to 15 cm of soil, and thus promotes survival of pathogens. However, disease-causing microbes make up only a proportion of the rhizofloral population. Relatively high soil microbial activity can lead to competition effects that may ameliorate pathogen activity and survival, and counteract a high pathogen inoculum pressure. Microbial antagonism in the root zone can lead to the formation of disease-suppressive soils. This phenomenon, which is important for the adoption of conservation tillage in humid climates, can be influenced by soil and crop management practices, especially crop rotation. |
