The Impact of Suppressive Soils on Plant Pathogens and Agricultural Productivity

Abstract

Soil is a primal element of agricultural production. It consists of complex mix of organic and inorganic matter. Suppressive agricultural soils exist globally and the biological basis of suppressiveness has been depicted for majority of the soils. However, varied land uses and management have a great impact on them, as well as their production system sustainability. Abiotic factors have a great impact on soil suppressiveness. For instance, the soil pH, level of calcium, nitrogen form, and the availability of other nutrients in the soil play key functions in the management of diseases. Sufficient crop nutrition renders plants more resistant to or tolerant of disease. A number of commercial products consisting of beneficial, disease-suppressive organisms such as Flavobacterium spp., Trichoderma spp., Gliocladium spp., Streptomycetes spp., Pseudomonas spp., and Bacillus spp. have been reported. These products are applied through various ways including seed treatments, soil inoculation, compost inoculation, and soil drenches. They have plant growth-promoting rhizobacteria (PGPR) that colonize plant roots and trigger plant growth and/or decrease occurrence of plant disease. These PGPR serve as aggressive colonizers, plant growth stimulators, and biocontrol. This chapter describes how suppressive soils affect or influence plant pathogen suppression in the soil and how they contribute to agricultural productivity. Different types of suppressive soils which include fungi-suppressive soils, bacteria-suppressive soils, and nematode-suppressive soils have also been discussed highlighting the contribution of these types of soils to agricultural productivity.