Developing Disease-Suppressive Soil Through Agronomic Management

Abstract

The ever growing human population coupled with reduced natural resources and the need for more environmentally friendly agricultural practices have highlighted the need for sustainable farming. The intricacies of the plant–microbiome interaction and its impact on plant health and productivity need to be understood for obtaining healthier and more productive plants. Suppressive soils represent an under utilised resource for the control of soil borne pathogens of food, fiber, and ornamental crops. Early research identified the characteristics of soil suppressiveness and the major groups of microorganisms involved, but in recent past due to availability of molecular tools, it has been made possible to characterize and identify the factors and mechanisms responsible for genetic and functional determinants underlying the activity of some biologically suppressive soils. Adoption of different agronomic practices by the farmers spectacularly altered the soil microbiome and considerably enhanced soil suppressiveness to various soilborne diseases. The use of organic amendments or composts for the suppression of plant pathogens could be a promising and environmentally benign alternative to chemical pesticides. The deeper understanding of microbial ecology processes could also provide directions for possible manipulations of the community, leading to a reproducible suppressive amendment. Combining measures of microbial structural diversity with functional traits should be explored in relation to soil and root health in agricultural systems. Manipulating soil quality to achieve an economic level of disease control via agronomic management has been deliberately reviewed with some skepticism. However, crop rotation, residue management practices, and various forms of organic amendments do contribute to the suppression of soil borne diseases. However, the level of understanding for the mechanisms involved in suppressive soils is still limited and not so clear. The benefits of applying organic amendments for disease control are incremental and long lasting depending upon soil ecosystems. The conventional agricultural systems need to be discouraged because of poor production efficiency due to reduced crop diversity, increased genetic uniformity, and shorter rotations. More attention is to be paid on conservation agriculture including maximum use of natural resources. Through the application of green and livestock manures, mulches, and composts, it is hoped that plant beneficial soil microbial populations will develop spontaneously. Selection of complementary rotation crops may also increase the buildup of beneficial microflora during suc- cessive field seasons. Plants can manage the development of beneficial microbial populations through the release of specific root exudates in the root zone. Recently, it has been proposed that plants may also be able to camouflage their presence to phytopathogens by blending into the soil microbial background through restricting the proliferation of root zone bacterial populations. Therefore, the future studies of biologically based soil suppressiveness will put new insights into the microbial ecology of agricultural soils and lay the foundation for the development of creative management strategies for the suppression of soilborne diseases.